path: root/FreeRTOS-Labs/Source/FreeRTOS-IoT-Libraries/c_sdk/standard/https/src/iot_https_client.c

/*
 * Amazon FreeRTOS HTTPS Client V1.1.0
 * Copyright (C) 2019 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * http://aws.amazon.com/freertos
 * http://www.FreeRTOS.org
 */

/**
 * @file iot_https_client.c
 * @brief Implementation of the user-facing functions of the Amazon FreeRTOS HTTPS Client library.
 */

/* The config header is always included first. */
#include "iot_config.h"

/* HTTPS Client library private includes. */
#include "private/iot_https_internal.h"

/*-----------------------------------------------------------*/

/**
 * @brief Partial HTTPS request first line.
 *
 * This is used for the calculation of the requestUserBufferMinimumSize.
 * The minimum path is "/" because we cannot know how long the application requested path is is going to be.
 * CONNECT is the longest string length HTTP method according to RFC 2616.
 */
#define HTTPS_PARTIAL_REQUEST_LINE                        HTTPS_CONNECT_METHOD " " HTTPS_EMPTY_PATH " " HTTPS_PROTOCOL_VERSION

/**
 * @brief The User-Agent header line string.
 *
 * This is of the form:
 * "User-Agent: <configured-user-agent>\r\n"
 * This is used for the calculation of the requestUserBufferMinimumSize.
 */
#define HTTPS_USER_AGENT_HEADER_LINE                      HTTPS_USER_AGENT_HEADER HTTPS_HEADER_FIELD_SEPARATOR IOT_HTTPS_USER_AGENT HTTPS_END_OF_HEADER_LINES_INDICATOR

/**
 * @brief The Host header line with the field only and not the value.
 *
 * This is of the form:
 * "Host: \r\n"
 * This is used for the calculation of the requestUserBufferMinimumSize. The Host value is not specified because we
 * cannot anticipate what server the client is making requests to.
 */
#define HTTPS_PARTIAL_HOST_HEADER_LINE                    HTTPS_HOST_HEADER HTTPS_HEADER_FIELD_SEPARATOR HTTPS_END_OF_HEADER_LINES_INDICATOR

/**
 * String constants for the Connection header and possible values.
 *
 * This is used for writing headers automatically during the sending of the HTTP request.
 * "Connection: keep-alive\r\n" is written automatically for a persistent connection.
 * "Connection: close\r\n" is written automatically for a non-persistent connection.
 */
#define HTTPS_CONNECTION_KEEP_ALIVE_HEADER_LINE           HTTPS_CONNECTION_HEADER HTTPS_HEADER_FIELD_SEPARATOR HTTPS_CONNECTION_KEEP_ALIVE_HEADER_VALUE HTTPS_END_OF_HEADER_LINES_INDICATOR /**< @brief String literal for "Connection: keep-alive\r\n". */
#define HTTPS_CONNECTION_CLOSE_HEADER_LINE                HTTPS_CONNECTION_HEADER HTTPS_HEADER_FIELD_SEPARATOR HTTPS_CONNECTION_CLOSE_HEADER_VALUE HTTPS_END_OF_HEADER_LINES_INDICATOR      /**< @brief String literal for "Connection: close\r\n". */

/**
 * @brief The length of the "Connection: keep-alive\r\n" header.
 *
 * This is used for sizing a local buffer for the final headers to send that include the "Connection: keep-alive\r\n"
 * header line.
 *
 * This is used to initialize a local array for the final headers to send.
 */
#define HTTPS_CONNECTION_KEEP_ALIVE_HEADER_LINE_LENGTH    ( 24 )

/**
 * Indicates for the http-parser parsing execution function to tell it to keep parsing or to stop parsing.
 *
 * A value of 0 means the parser should keep parsing if there is more unparsed length.
 * A value greater than 0 tells the parser to stop parsing.
 */
#define KEEP_PARSING                                      ( ( int ) 0 ) /**< @brief Indicator in the http-parser callback to keep parsing when the function returns. */
#define STOP_PARSING                                      ( ( int ) 1 ) /**< @brief Indicator in the http-parser callback to stop parsing when the function returns. */

/*-----------------------------------------------------------*/

/**
 * @brief Minimum size of the request user buffer.
 *
 * The request user buffer is configured in IotHttpsClientRequestInfo_t.userBuffer. This buffer stores the internal context
 * of the request and then the request headers right after. The minimum size for the buffer is the total size of the
 * internal request context, the HTTP formatted request line, the User-Agent header line, and the part of the Host
 * header line.
 */
const uint32_t requestUserBufferMinimumSize = sizeof( _httpsRequest_t ) +
                                              sizeof( HTTPS_PARTIAL_REQUEST_LINE ) +
                                              sizeof( HTTPS_USER_AGENT_HEADER_LINE ) +
                                              sizeof( HTTPS_PARTIAL_HOST_HEADER_LINE );

/**
 * @brief Minimum size of the response user buffer.
 *
 * The response user buffer is configured in IotHttpsClientRequestInfo_t.userBuffer. This buffer stores the internal context
 * of the response and then the response headers right after. This minimum size is calculated for the case if no bytes
 * from the HTTP response headers are to be stored.
 */
const uint32_t responseUserBufferMinimumSize = sizeof( _httpsResponse_t );

/**
 * @brief Minimum size of the connection user buffer.
 *
 * The connection user buffer is configured in IotHttpsConnectionInfo_t.userBuffer. This buffer stores the internal context of the
 * connection.
 */
const uint32_t connectionUserBufferMinimumSize = sizeof( _httpsConnection_t );

/*-----------------------------------------------------------*/

/**
 * @brief Callback from http-parser to indicate the start of the HTTP response message is reached.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_message_begin.
 */
static int _httpParserOnMessageBeginCallback( http_parser * pHttpParser );

/**
 * @brief Callback from http-parser to indicate it found the HTTP response status code.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 * @param[in] pLoc - Pointer to the HTTP response status code string in the response message buffer.
 * @param[in] length - The length of the HTTP response status code string.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_status.
 */
static int _httpParserOnStatusCallback( http_parser * pHttpParser,
                                        const char * pLoc,
                                        size_t length );

/**
 * @brief Callback from http-parser to indicate it found an HTTP response header field.
 *
 * If only part of the header field was returned here in this callback, then this callback will be invoked again the
 * next time the parser executes on the next part of the header field.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 * @param[in] pLoc - Pointer to the header field string in the response message buffer.
 * @param[in] length - The length of the header field.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_header_field.
 */
static int _httpParserOnHeaderFieldCallback( http_parser * pHttpParser,
                                             const char * pLoc,
                                             size_t length );

/**
 * @brief Callback from http-parser to indicate it found an HTTP response header value.
 *
 * This value corresponds to the field that was found in the _httpParserOnHeaderFieldCallback() called immediately
 * before this callback was called.
 *
 * If only part of the header value was returned here in this callback, then this callback will be invoked again the
 * next time the parser executes on the next part of the header value.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 * @param[in] pLoc - Pointer to the header value string in the response message buffer.
 * @param[in] length - The length of the header value.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_header_value.
 */
static int _httpParserOnHeaderValueCallback( http_parser * pHttpParser,
                                             const char * pLoc,
                                             size_t length );

/**
 * @brief Callback from http-parser to indicate it reached the end of the headers in the HTTP response message.
 *
 * The end of the headers is signalled in a HTTP response message by another "\r\n" after the final header line.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_headers_complete.
 */
static int _httpParserOnHeadersCompleteCallback( http_parser * pHttpParser );

/**
 * @brief Callback from http-parser to indicate it found HTTP response body.
 *
 * This callback will be invoked multiple times if the response body is of "Transfer-Encoding: chunked".
 * _httpParserOnChunkHeaderCallback() will be invoked first, then _httpParserOnBodyCallback(), then
 * _httpParserOnChunkCompleteCallback(), then repeated back to _httpParserOnChunkHeaderCallback() if there are more
 * "chunks".
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 * @param[in] pLoc - Pointer to the body string in the response message buffer.
 * @param[in] length - The length of the body found.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_body.
 */
static int _httpParserOnBodyCallback( http_parser * pHttpParser,
                                      const char * pLoc,
                                      size_t length );

/**
 * @brief Callback from http-parser to indicate it reached the end of the HTTP response message.
 *
 * The end of the message is signalled in a HTTP response message by another "\r\n" after the final header line, with no
 * entity body; or it is signaled by "\r\n" at the end of the entity body.
 *
 * For a Transfer-Encoding: chunked type of response message, the end of the message is signalled by a terminating
 * chunk header with length zero.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_message_complete.
 */
static int _httpParserOnMessageCompleteCallback( http_parser * pHttpParser );

/* This code prints debugging information and is, therefore, compiled only when
 * log level is set to IOT_LOG_DEBUG. */
#if ( LIBRARY_LOG_LEVEL == IOT_LOG_DEBUG )

/**
 * @brief Callback from http-parser to indicate it found an HTTP Transfer-Encoding: chunked header.
 *
 * Transfer-Encoding: chunked headers are embedded in the HTTP response entity body by a "\r\n" followed by the size of
 * the chunk followed by another "\r\n".
 *
 * If only part of the header field was returned here in this callback, then this callback will be invoked again the
 * next time the parser executes on the next part of the header field.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_chunk_header.
 */
    static int _httpParserOnChunkHeaderCallback( http_parser * pHttpParser );

/**
 * @brief Callback from http-parser to indicate it reached the end of an HTTP response message "chunk".
 *
 * A chunk is complete when the chunk header size is read fully in the body.
 *
 * See https://github.com/nodejs/http-parser for more information.
 *
 * @param[in] pHttpParser - http-parser state structure.
 *
 * @return 0 to tell http-parser to keep parsing.
 *         1 to tell http-parser that parsing should stop return from http_parser_execute with error HPE_CB_chunk_complete.
 */
    static int _httpParserOnChunkCompleteCallback( http_parser * pHttpParser );
#endif

/**
 * @brief Network receive callback for the HTTPS Client library.
 *
 * This function is called by the network layer whenever data is available for the HTTP library.
 *
 * @param[in] pNetworkConnection - The network connection with the HTTPS connection, passed by the network stack.
 * @param[in] pReceiveContext - A pointer to the HTTPS Client connection handle for which the packet was received.
 */
static void _networkReceiveCallback( void * pNetworkConnection,
                                     void * pReceiveContext );

/**
 * @brief Connects to HTTPS server and initializes the connection context.
 *
 * @param[out] pConnHandle - The out parameter to return handle representing the open connection.
 * @param[in] pConnInfo - The connection configuration.
 *
 * @return #IOT_HTTPS_OK if the connection context initialization was successful.
 *         #IOT_HTTPS_CONNECTION_ERROR if the connection failed.
 *         #IOT_HTTPS_INTERNAL_ERROR if the context initialization failed.
 */
static IotHttpsReturnCode_t _createHttpsConnection( IotHttpsConnectionHandle_t * pConnHandle,
                                                    IotHttpsConnectionInfo_t * pConnInfo );

/**
 * @brief Disconnects from the network.
 *
 * @param[in] pHttpsConnection - HTTPS connection handle.
 */
static void _networkDisconnect( _httpsConnection_t * pHttpsConnection );

/**
 * @brief Destroys the network connection.
 *
 * @param[in] pHttpsConnection - HTTPS connection handle.
 */
static void _networkDestroy( _httpsConnection_t * pHttpsConnection );

/**
 * @brief Add a header to the current HTTP request.
 *
 * The headers are stored in reqHandle->pHeaders.
 *
 * @param[in] pHttpsRequest - HTTP request context.
 * @param[in] pName - The name of the header to add.
 * @param[in] nameLen - The length of the header name string.
 * @param[in] pValue - The buffer containing the value string.
 * @param[in] valueLen - The length of the header value string.
 *
 * @return #IOT_HTTPS_OK if the header was added to the request successfully.
 *         #IOT_HTTPS_INSUFFICIENT_MEMORY if there was not enough room in the IotHttpsRequestHandle_t->pHeaders.
 */
static IotHttpsReturnCode_t _addHeader( _httpsRequest_t * pHttpsRequest,
                                        const char * pName,
                                        uint32_t nameLen,
                                        const char * pValue,
                                        uint32_t valueLen );

/**
 * @brief Send data on the network.
 *
 * @param[in] pHttpsConnection - HTTP connection context.
 * @param[in] pBuf - The buffer containing the data to send.
 * @param[in] len - The length of the data to send.
 *
 * @return #IOT_HTTPS_OK if the data sent successfully.
 *         #IOT_HTTPS_NETWORK_ERROR if there was an error sending the data on the network.
 */
static IotHttpsReturnCode_t _networkSend( _httpsConnection_t * pHttpsConnection,
                                          uint8_t * pBuf,
                                          size_t len );

/**
 * @brief Receive data on the network.
 *
 * @param[in] pHttpsConnection - HTTP connection context.
 * @param[in] pBuf - The buffer to receive the data into.
 * @param[in] bufLen - The length of the data to receive.
 * @param[in] numBytesRecv - The number of bytes read from the network.
 *
 * @return #IOT_HTTPS_OK if the data was received successfully.
 *         #IOT_HTTPS_NETWORK_ERROR if we timedout trying to receive data from the network.
 */
static IotHttpsReturnCode_t _networkRecv( _httpsConnection_t * pHttpsConnection,
                                          uint8_t * pBuf,
                                          size_t bufLen,
                                          size_t * numBytesRecv );

/**
 * @brief Send all of the HTTP request headers in the pHeadersBuf and the final Content-Length and Connection headers.
 *
 * All of the headers in headerbuf are sent first followed by the computed content length and persistent connection
 * indication.
 *
 * @param[in] pHttpsConnection - HTTP connection context.
 * @param[in] pHeadersBuf - The buffer containing the request headers to send. This buffer must contain HTTP headers
 *            lines without the indicator for the the end of the HTTP headers.
 * @param[in] headersLength - The length of the request headers to send.
 * @param[in] isNonPersistent - Indicator of whether the connection is persistent or not.
 * @param[in] contentLength - The length of the request body used for automatically creating a "Content-Length" header.
 *
 * @return #IOT_HTTPS_OK if the headers were fully sent successfully.
 *         #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _sendHttpsHeaders( _httpsConnection_t * pHttpsConnection,
                                               uint8_t * pHeadersBuf,
                                               uint32_t headersLength,
                                               bool isNonPersistent,
                                               uint32_t contentLength );

/**
 * @brief Send all of the HTTP request body in pBodyBuf.
 *
 * @param[in] pHttpsConnection - HTTP connection context.
 * @param[in] pBodyBuf - Buffer of the request body to send.
 * @param[in] bodyLength - The length of the body to send.
 *
 * @return #IOT_HTTPS_OK if the body was fully sent successfully.
 *         #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _sendHttpsBody( _httpsConnection_t * pHttpsConnection,
                                            uint8_t * pBodyBuf,
                                            uint32_t bodyLength );

/**
 * @brief Parse the HTTP response message in pBuf.
 *
 * @param[in] pHttpParserInfo - Pointer to the information containing the instance of the http-parser and the execution function.
 * @param[in] pBuf - The buffer containing the data to parse.
 * @param[in] len - The length of data to parse.
 *
 * @return #IOT_HTTPS_OK if the data was parsed successfully.
 *         #IOT_HTTPS_PARSING_ERROR if there was an error with parsing the data.
 */
static IotHttpsReturnCode_t _parseHttpsMessage( _httpParserInfo_t * pHttpParserInfo,
                                                char * pBuf,
                                                size_t len );

/**
 * @brief Receive any part of an HTTP response.
 *
 * This function is used for both receiving the body into the body buffer and receiving the header into the header
 * buffer.
 *
 * @param[in] pHttpsConnection - HTTP Connection context.
 * @param[in] pParser - Pointer to the instance of the http-parser.
 * @param[in] pCurrentParserState - The current state of what has been parsed in the HTTP response.
 * @param[in] finalParserState - The final state of the parser expected after this function finishes.
 * @param[in] currentBufferProcessingState - The current buffer that is the HTTPS message is being received into.
 * @param[in] pBufCur - Pointer to the next location to write data into the buffer pBuf. This is a double pointer to update the response context buffer pointers.
 * @param[in] pBufEnd - Pointer to the end of the buffer to receive the HTTP response into.
 *
 * @return #IOT_HTTPS_OK if we received the HTTP response message part successfully.
 *         #IOT_HTTPS_PARSING_ERROR if there was an error with parsing the data.
 *         #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _receiveHttpsMessage( _httpsConnection_t * pHttpsConnection,
                                                  _httpParserInfo_t * pParser,
                                                  IotHttpsResponseParserState_t * pCurrentParserState,
                                                  IotHttpsResponseParserState_t finalParserState,
                                                  IotHttpsResponseBufferState_t currentBufferProcessingState,
                                                  uint8_t ** pBufCur,
                                                  uint8_t ** pBufEnd );

/**
 * @brief Receive the HTTP response headers.
 *
 * Receiving the response headers is always the first step in receiving the response, therefore the
 * pHttpsResponse->httpParserInfo will be initialized to a starting state when this function is called.
 *
 * This function also sets internal states to indicate that the header buffer is being processed now for a new response.
 *
 * @param[in] pHttpsConnection - HTTP connection context.
 * @param[in] pHttpsResponse - HTTP response context.
 *
 * @return #IOT_HTTPS_OK if we received the HTTP headers successfully.
 *         #IOT_HTTPS_PARSING_ERROR if there was an error with parsing the header buffer.
 *         #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _receiveHttpsHeaders( _httpsConnection_t * pHttpsConnection,
                                                  _httpsResponse_t * pHttpsResponse );

/**
 * @brief Receive the HTTP response body.
 *
 * Sets internal states to indicate that the the body buffer is being processed now for a new response.
 *
 * @param[in] pHttpsConnection - HTTP connection context.
 * @param[in] pHttpsResponse - HTTP response context.
 *
 * @return #IOT_HTTPS_OK if we received the HTTP body successfully.
 *         #IOT_HTTPS_PARSING_ERROR if there was an error with parsing the body buffer.
 *         #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _receiveHttpsBody( _httpsConnection_t * pHttpsConnection,
                                               _httpsResponse_t * pHttpsResponse );

/**
 * @brief Read the rest of any HTTP response that may be on the network.
 *
 * This reads the rest of any left over response data that might still be on the network buffers. We do not want this
 * data left over because it will spill into the header and body buffers of next response that we try to receive.
 *
 * If we performed a request without a body and the headers received exceeds the size of the
 * pHttpsResponse->pHeaders buffer, then we need to flush the network buffer.
 *
 * If the application configured the body buffer as null in IotHttpsResponseInfo_t.syncInfo.respData and the server
 * sends body in the response, but it exceeds the size of  pHttpsResponse->pHeaders buffer, then we need to flush the
 * network buffer.
 *
 * If the amount of body received on the network does not fit into a non-null IotHttpsResponseInfo_t.syncInfo.respData,
 * then we need to flush the network buffer.
 *
 * If an asynchronous request cancels in the middle of a response process, after already sending the request message,
 * then we need to flush the network buffer.
 *
 * @param[in] pHttpsConnection - HTTP connection context.
 * @param[in] pHttpsResponse - HTTP response context.
 *
 * @return #IOT_HTTPS_OK if we successfully flushed the network data.
 *         #IOT_HTTPS_PARSING_ERROR if there was an error with parsing the data.
 *         #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _flushHttpsNetworkData( _httpsConnection_t * pHttpsConnection,
                                                    _httpsResponse_t * pHttpsResponse );

/**
 * @brief Task pool job routine to send the HTTP request within the pUserContext.
 *
 * @param[in] pTaskPool Pointer to the system task pool.
 * @param[in] pJob Pointer the to the HTTP request sending job.
 * @param[in] pUserContext Pointer to an HTTP request, passed as an opaque context.
 */
static void _sendHttpsRequest( IotTaskPool_t pTaskPool,
                               IotTaskPoolJob_t pJob,
                               void * pUserContext );


/**
 * @brief Receive the HTTPS body specific to an asynchronous type of response.
 *
 * @param[in] pHttpsResponse - HTTP response context.
 *
 * @return  #IOT_HTTPS_OK - If the the response body was received with no issues.
 *          #IOT_HTTPS_RECEIVE_ABORT - If the request was cancelled by the Application
 *          #IOT_HTTPS_PARSING_ERROR - If there was an issue parsing the HTTP response body.
 *          #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _receiveHttpsBodyAsync( _httpsResponse_t * pHttpsResponse );

/**
 * @brief Receive the HTTPS body specific to a synchronous type of response.
 *
 * @param[in] pHttpsResponse - HTTP response context.
 *
 * @return  #IOT_HTTPS_OK - If the the response body was received with no issues.
 *          #IOT_HTTPS_MESSAGE_TOO_LARGE - If the body from the network is too large to fit into the configured body buffer.
 *          #IOT_HTTPS_PARSING_ERROR - If there was an issue parsing the HTTP response body.
 *          #IOT_HTTPS_NETWORK_ERROR if there was an error receiving the data on the network.
 */
static IotHttpsReturnCode_t _receiveHttpsBodySync( _httpsResponse_t * pHttpsResponse );

/**
 * @brief Schedule the task to send the the HTTP request.
 *
 * @param[in] pHttpsRequest - HTTP request context.
 *
 * @return  #IOT_HTTPS_OK - If the task to send the HTTP request was successfully scheduled.
 *          #IOT_HTTPS_INTERNAL_ERROR - If a taskpool job could not be created.
 *          #IOT_HTTPS_ASYNC_SCHEDULING_ERROR - If there was an error scheduling the job.
 */
IotHttpsReturnCode_t _scheduleHttpsRequestSend( _httpsRequest_t * pHttpsRequest );

/**
 * @brief Add the request to the connection's request queue.
 *
 * This will schedule a task if the request is first and only request in the queue.
 *
 * @param[in] pHttpsRequest - HTTP request context.
 *
 * @return  #IOT_HTTPS_OK - If the request was successfully added to the connection's request queue.
 *          #IOT_HTTPS_INTERNAL_ERROR - If a taskpool job could not be created.
 *          #IOT_HTTPS_ASYNC_SCHEDULING_ERROR - If there was an error scheduling the job.
 */
IotHttpsReturnCode_t _addRequestToConnectionReqQ( _httpsRequest_t * pHttpsRequest );

/**
 * @brief Cancel the HTTP request's processing.
 *
 * pHttpsRequest->cancelled will be checked and the request cancelled if specified so at the following intervals:
 *  - Before sending the HTTPS headers at the start of the scheduled sending of the HTTPS request.
 *  - After Sending the HTTPS headers.
 *  - After Sending the HTTPS body.
 *
 * @param[in] pHttpsRequest - HTTP request context.
 */
static void _cancelRequest( _httpsRequest_t * pHttpsRequest );

/**
 * @brief Cancel the HTTP response's processing.
 *
 * pHttpsResponse->cancelled will be checked and the response cancelled if specified so at the following intervals:
 *  - At the start of the network receive callback.
 *  - After receiving the HTTPS headers.
 *  - After Receiving the HTTPS body.
 *
 * @param[in] pHttpsResponse - HTTP response context.
 */
static void _cancelResponse( _httpsResponse_t * pHttpsResponse );

/**
 * @brief Initialize the input pHttpsResponse with pRespInfo.
 *
 * @param[in] pRespHandle - Non-null HTTP response context.
 * @param[in] pRespInfo - Response configuration information.
 * @param[in] pHttpsRequest - HTTP request to grab async information, persistence, and method from.
 */
static IotHttpsReturnCode_t _initializeResponse( IotHttpsResponseHandle_t * pRespHandle,
                                                 IotHttpsResponseInfo_t * pRespInfo,
                                                 _httpsRequest_t * pHttpsRequest );

/**
 * @brief Increment the pointer stored in pBufCur depending on the character found in there.
 *
 * This function increments the pHeadersCur pointer further if the message ended with a header line delimiter.
 *
 * @param[in] pBufCur - Pointer to the next location to write data into the buffer pBuf. This is a double pointer to update the response context buffer pointers.
 * @param[in] pBufEnd - Pointer to the end of the buffer to receive the HTTP response into.
 */
static void _incrementNextLocationToWriteBeyondParsed( uint8_t ** pBufCur,
                                                       uint8_t ** pBufEnd );

/**
 * @brief Send the HTTPS headers and body referenced in pHttpsRequest.
 *
 * Sends both the headers and body over the network.
 *
 * @param[in] pHttpsConnection - HTTPS connection context.
 * @param[in] pHttpsRequest - HTTPS request context.
 */
static IotHttpsReturnCode_t _sendHttpsHeadersAndBody( _httpsConnection_t * pHttpsConnection,
                                                      _httpsRequest_t * pHttpsRequest );

/*-----------------------------------------------------------*/

/**
 * @brief Definition of the http-parser settings.
 *
 * The http_parser_settings holds all of the callbacks invoked by the http-parser.
 */
static http_parser_settings _httpParserSettings = { 0 };

/*-----------------------------------------------------------*/

static int _httpParserOnMessageBeginCallback( http_parser * pHttpParser )
{
    int retVal = KEEP_PARSING;

    IotLogDebug( "Parser: Start of HTTPS Response message." );

    _httpsResponse_t * pHttpsResponse = ( _httpsResponse_t * ) ( pHttpParser->data );
    /* Set the state of the parser. The headers are at the start of the message always. */
    pHttpsResponse->parserState = PARSER_STATE_IN_HEADERS;
    return retVal;
}

/*-----------------------------------------------------------*/

static int _httpParserOnStatusCallback( http_parser * pHttpParser,
                                        const char * pLoc,
                                        size_t length )
{
    _httpsResponse_t * pHttpsResponse = ( _httpsResponse_t * ) ( pHttpParser->data );

    IotLogDebug( "Parser: Status %.*s retrieved from HTTPS response.", length, pLoc );

    /* Save the status code so it can be retrieved with IotHttpsClient_ReadResponseStatus(). */
    pHttpsResponse->status = ( uint16_t ) ( pHttpParser->status_code );

    /* If we are parsing the network data received in the header buffer then we
     * increment pHttpsResponse->pHeadersCur. The status line in the response is
     * part of the data stored in header buffer _httpResponse->pHeaders. */
    if( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_FILLING_HEADER_BUFFER )
    {
        /* pHeadersCur will never exceed the pHeadersEnd here because PROCESSING_STATE_FILLING_HEADER_BUFFER
         * indicates we are currently in the header buffer and the total size of the header buffer is passed
         * into http_parser_execute() as the maximum length to parse. */
        pHttpsResponse->pHeadersCur = ( uint8_t * ) ( pLoc += length );
    }

    return KEEP_PARSING;
}

/*-----------------------------------------------------------*/

static int _httpParserOnHeaderFieldCallback( http_parser * pHttpParser,
                                             const char * pLoc,
                                             size_t length )
{
    IotLogDebug( "Parser: HTTPS header field parsed %.*s", length, pLoc );

    _httpsResponse_t * pHttpsResponse = ( _httpsResponse_t * ) ( pHttpParser->data );

    /* If we are parsing the network data received in the header buffer then we can increment
     * pHttpsResponse->pHeadersCur. */
    if( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_FILLING_HEADER_BUFFER )
    {
        pHttpsResponse->pHeadersCur = ( uint8_t * ) ( pLoc += length );
    }

    /* If the IotHttpsClient_ReadHeader() was called, then we check for the header field of interest. */
    if( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_SEARCHING_HEADER_BUFFER )
    {
        if( pHttpsResponse->readHeaderFieldLength != length )
        {
            pHttpsResponse->foundHeaderField = false;
        }
        else if( strncmp( pHttpsResponse->pReadHeaderField, pLoc, length ) == 0 )
        {
            pHttpsResponse->foundHeaderField = true;
        }
    }

    return KEEP_PARSING;
}

/*-----------------------------------------------------------*/

static int _httpParserOnHeaderValueCallback( http_parser * pHttpParser,
                                             const char * pLoc,
                                             size_t length )
{
    int retVal = KEEP_PARSING;

    IotLogDebug( "Parser: HTTPS header value parsed %.*s", length, pLoc );
    _httpsResponse_t * pHttpsResponse = ( _httpsResponse_t * ) ( pHttpParser->data );

    /* If we are parsing the network data received in the header buffer then we can increment
     * pHttpsResponse->pHeadersCur. */
    if( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_FILLING_HEADER_BUFFER )
    {
        pHttpsResponse->pHeadersCur = ( uint8_t * ) ( pLoc += length );
    }

    /* If the IotHttpsClient_ReadHeader() was called, then we check if we found the header field of interest. */
    if( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_SEARCHING_HEADER_BUFFER )
    {
        if( pHttpsResponse->foundHeaderField )
        {
            pHttpsResponse->pReadHeaderValue = ( char * ) ( pLoc );
            pHttpsResponse->readHeaderValueLength = length;
            /* We found a header field so we don't want to keep parsing.*/
            retVal = STOP_PARSING;
        }
    }

    return retVal;
}

/*-----------------------------------------------------------*/

static int _httpParserOnHeadersCompleteCallback( http_parser * pHttpParser )
{
    IotLogDebug( "Parser: End of the headers reached." );

    int retVal = KEEP_PARSING;
    _httpsResponse_t * pHttpsResponse = ( _httpsResponse_t * ) ( pHttpParser->data );
    pHttpsResponse->parserState = PARSER_STATE_HEADERS_COMPLETE;

    /* If the IotHttpsClient_ReadHeader() was called, we return after finishing looking through all of the headers.
     * Returning a non-zero value exits the http parsing. */
    if( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_SEARCHING_HEADER_BUFFER )
    {
        retVal = STOP_PARSING;
    }

    /* When in this callback the pHeaderCur pointer is at the first "\r" in the last header line. HTTP/1.1
     * headers end with another "\r\n" at the end of the last line. This means we must increment
     * the headerCur pointer to the length of "\r\n\r\n". */
    if( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_FILLING_HEADER_BUFFER )
    {
        pHttpsResponse->pHeadersCur += ( 2 * HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH );
    }

    /* This if-case is not incrementing any pHeaderCur pointers, so this case is safe to call when flushing the
     * network buffer. Flushing the network buffer needs the logic below to reach PARSER_STATE_BODY_COMPLETE if the
     * response is for a HEAD request. Before flushing the network buffer the bufferProcessingState is set to
     * PROCESSING_STATE_FINISHED so that other callback functions don't update header or body current pointers in the
     * response context. We don't want those pointers incremented because flushing the network uses a different buffer
     * to receive the rest of the response. */
    if( pHttpsResponse->bufferProcessingState <= PROCESSING_STATE_FINISHED )
    {
        /* For a HEAD method, there is no body expected in the response, so we return 1 to skip body parsing. */
        if( ( pHttpsResponse->method == IOT_HTTPS_METHOD_HEAD ) )
        {
            retVal = STOP_PARSING;

            /* Since the message is considered complete now for a HEAD response, then we set the parser state
             * to the completed state. */
            pHttpsResponse->parserState = PARSER_STATE_BODY_COMPLETE;
        }

        /* If this is NOT a HEAD method and there is body configured, but the server does not send a body in the
         * response, then the body buffer will be filled with the zeros from rest of the header buffer. http-parser
         * will invoke the on_body callback and consider the zeros following the headers as body. */

        /* If there is not body configured for a synchronous reponse, we do not stop the parser from continueing. */

        /* Skipping the body will cause the parser to invoke the _httpParserOnMessageComplete() callback. This is
         * not desired when there is actually HTTP response body sent by the server because this will set the parser
         * state to PARSER_STATE_BODY_COMPLETE. If this state is set then the rest of possible body will not be
         * flushed out. The network flush looks for the state being PARSER_STATE_BODY_COMPLETE to finish flushing. */
    }

    return retVal;
}

/*-----------------------------------------------------------*/

static int _httpParserOnBodyCallback( http_parser * pHttpParser,
                                      const char * pLoc,
                                      size_t length )
{
    IotLogDebug( "Parser: Reached the HTTPS message body. It is of length: %d", length );

    _httpsResponse_t * pHttpsResponse = ( _httpsResponse_t * ) ( pHttpParser->data );
    pHttpsResponse->parserState = PARSER_STATE_IN_BODY;

    /* If the header buffer is currently being processed, but HTTP response body was found, then for an asynchronous
     * request this if-case saves where the body is located. In the asynchronous case, the body buffer is not available
     * until the readReadyCallback is invoked, which happens after the headers are processed.  */
    if( ( pHttpsResponse->bufferProcessingState == PROCESSING_STATE_FILLING_HEADER_BUFFER ) && ( pHttpsResponse->isAsync ) )
    {
        /* For an asynchronous response, the buffer to store the body will be available after the headers
         * are read first. We may receive part of the body in the header buffer. We will want to leave this here
         * and copy it over when the body buffer is available in the _readReadyCallback().
         */
        if( pHttpsResponse->pBodyInHeaderBuf == NULL )
        {
            pHttpsResponse->pBodyInHeaderBuf = ( uint8_t * ) ( pLoc );
            pHttpsResponse->pBodyCurInHeaderBuf = pHttpsResponse->pBodyInHeaderBuf;
        }

        /* If there is a chunk encoded body in the header buffer, we will want to overwrite the chunk headers with the
         * actual body. This is so that when the application calls IotHttpsClient_ReadResponseBody(), in the
         * readReadyCallback(), we can pass the body into the body buffer provided right away. */
        if( pHttpsResponse->pBodyCurInHeaderBuf != ( uint8_t * ) pLoc )
        {
            memcpy( pHttpsResponse->pBodyCurInHeaderBuf, pLoc, length );
        }

        pHttpsResponse->pBodyCurInHeaderBuf += length;
    }
    else if( pHttpsResponse->bufferProcessingState < PROCESSING_STATE_FINISHED )
    {
        /* Has the user provided a buffer and is it large enough to fit the body? The
         * case of body buffer not being large enough can happen if the body was received
         * in the header buffer and the body buffer can not fit in all the body. */
        if( ( pHttpsResponse->pBodyCur != NULL ) && ( pHttpsResponse->pBodyEnd - pHttpsResponse->pBodyCur > 0 ) )
        {
            /* There are two scenarios when we need to copy data around:
             * 1. Some or all of the response body may have been received in the header
             * buffer. If that is the case, we copy the response body received in the
             * header buffer to the user provided body buffer.
             * 2. When we receive chunked header, the actual body is separated in
             * multiple chunks which are preceeded by length. For example, a chunked
             * body may look like:
             *
             * 7\r\n
             * Mozilla\r\n
             * 9\r\n
             * Developer\r\n
             * 7\r\n
             * Network\r\n
             * 0\r\n
             * \r\n
             *
             * In this case, we want the parsed body buffer to contain actual body only
             * (MozillaDeveloperNetwork in the above example).
             */

            /* If the response body found by the parser (pLoc) is not equal to the
             * current writable location in the body buffer (_httpsResponse->pBodyCur),
             * it indicates that:
             * - Either the data is in the header buffer and needs to be copied into the
             * body buffer.
             * - Or it is a chunked response and the data needs to be moved up in the
             * body buffer. */
            if( ( pHttpsResponse->pBodyCur + length ) <= pHttpsResponse->pBodyEnd )
            {
                if( pHttpsResponse->pBodyCur != ( uint8_t * ) pLoc )
                {
                    memcpy( pHttpsResponse->pBodyCur, pLoc, length );
                }

                pHttpsResponse->pBodyCur += length;
            }
        }
    }

    return KEEP_PARSING;
}

/*-----------------------------------------------------------*/

static int _httpParserOnMessageCompleteCallback( http_parser * pHttpParser )
{
    IotLogDebug( "Parser: End of the HTTPS message reached." );

    _httpsResponse_t * pHttpsResponse = ( _httpsResponse_t * ) ( pHttpParser->data );
    pHttpsResponse->parserState = PARSER_STATE_BODY_COMPLETE;

    /* This callback is invoked when the complete HTTP response has been received.
     * We tell the parser to parse the whole body buffer as opposed to the size of
     * the response body. For example, if the size of the body buffer is 1000 but
     * the size of the actual body is 500, we tell the parser to parse the whole
     * buffer of length 1000. We do zero out the buffer in the beginning so that all
     * the buffer after the actual body contains zeros. We return greater than zero to stop parsing
     * since the end of the HTTP message has been reached. Any data beyond the end of the message is
     * ignored. */
    return STOP_PARSING;
}

/*-----------------------------------------------------------*/

/* This code prints debugging information and is, therefore, compiled only when
 * log level is set to IOT_LOG_DEBUG. */
#if ( LIBRARY_LOG_LEVEL == IOT_LOG_DEBUG )
    static int _httpParserOnChunkHeaderCallback( http_parser * pHttpParser )
    {
        ( void ) pHttpParser;
        IotLogDebug( "Parser: HTTPS message Chunked encoding header callback." );
        IotLogDebug( "Parser: HTTPS message Chunk size: %d", pHttpParser->content_length );
        return 0;
    }

/*-----------------------------------------------------------*/

    static int _httpParserOnChunkCompleteCallback( http_parser * pHttpParser )
    {
        ( void ) pHttpParser;
        IotLogDebug( "End of a HTTPS message Chunk complete callback." );
        return 0;
    }
#endif /* if ( LIBRARY_LOG_LEVEL == IOT_LOG_DEBUG ) */

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _receiveHttpsBodyAsync( _httpsResponse_t * pHttpsResponse )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    if( pHttpsResponse->pCallbacks->readReadyCallback )
    {
        /* If there is still more body that has not been passed back to the user, then this callback is invoked again. */
        do
        {
            IotLogDebug( "Invoking the readReadyCallback." );
            pHttpsResponse->pCallbacks->readReadyCallback( pHttpsResponse->pUserPrivData,
                                                           pHttpsResponse,
                                                           pHttpsResponse->bodyRxStatus,
                                                           pHttpsResponse->status );

            if( pHttpsResponse->cancelled == true )
            {
                IotLogDebug( "Cancelled HTTP response %d.", pHttpsResponse );
                status = IOT_HTTPS_RECEIVE_ABORT;

                /* We break out of the loop and do not goto clean up because we want to print debugging logs for
                 * the parser state and the networks status. */
                break;
            }
        } while( ( pHttpsResponse->parserState < PARSER_STATE_BODY_COMPLETE ) && ( pHttpsResponse->bodyRxStatus == IOT_HTTPS_OK ) );

        if( HTTPS_FAILED( pHttpsResponse->bodyRxStatus ) )
        {
            IotLogError( "Error receiving the HTTP response body for response %d. Error code: %d",
                         pHttpsResponse,
                         pHttpsResponse->bodyRxStatus );
            /* An error in the network or the parser takes precedence  */
            status = pHttpsResponse->bodyRxStatus;
        }

        if( pHttpsResponse->parserState < PARSER_STATE_BODY_COMPLETE )
        {
            IotLogDebug( "Did not receive all of the HTTP response body for response %d.",
                         pHttpsResponse );
        }
    }

    /* This GOTO cleanup is here for compiler warnings about using HTTPS_FUNCTION_EXIT_NO_CLEANUP() without a
     * corresponding goto. */
    HTTPS_GOTO_CLEANUP();
    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _receiveHttpsBodySync( _httpsResponse_t * pHttpsResponse )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );
    _httpsConnection_t * pHttpsConnection = pHttpsResponse->pHttpsConnection;

    /* The header buffer is now filled or the end of the headers has been reached already. If part of the response
     *  body was read from the network into the header buffer, then it was already copied to the body buffer in the
     *  _httpParserOnBodyCallback(). */
    if( pHttpsResponse->pBody != NULL )
    {
        /* If there is room left in the body buffer and we have not received the whole response body,
         * then try to receive more. */
        if( ( ( pHttpsResponse->pBodyEnd - pHttpsResponse->pBodyCur ) > 0 ) &&
            ( pHttpsResponse->parserState < PARSER_STATE_BODY_COMPLETE ) )
        {
            status = _receiveHttpsBody( pHttpsConnection,
                                        pHttpsResponse );

            if( HTTPS_FAILED( status ) )
            {
                IotLogError( "Error receiving the HTTPS response body for response %d. Error code: %d.",
                             pHttpsResponse,
                             status );
                HTTPS_GOTO_CLEANUP();
            }
        }
        else
        {
            IotLogDebug( "Received the maximum amount of HTTP body when filling the header buffer for response %d.",
                         pHttpsResponse );
        }

        /* If we don't reach the end of the HTTPS body in the parser, then we only received part of the body.
         *  The rest of body will be on the network socket. */
        if( HTTPS_SUCCEEDED( status ) && ( pHttpsResponse->parserState < PARSER_STATE_BODY_COMPLETE ) )
        {
            IotLogError( "HTTPS response body does not fit into application provided response buffer at location 0x%x "
                         "with length: %d",
                         pHttpsResponse->pBody,
                         pHttpsResponse->pBodyEnd - pHttpsResponse->pBody );
            HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_MESSAGE_TOO_LARGE );
        }
    }
    else
    {
        IotLogDebug( "No response body was configure for response %d.", pHttpsResponse );
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static void _networkReceiveCallback( void * pNetworkConnection,
                                     void * pReceiveContext )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    IotHttpsReturnCode_t flushStatus = IOT_HTTPS_OK;
    IotHttpsReturnCode_t disconnectStatus = IOT_HTTPS_OK;
    IotHttpsReturnCode_t scheduleStatus = IOT_HTTPS_OK;
    _httpsConnection_t * pHttpsConnection = ( _httpsConnection_t * ) pReceiveContext;
    _httpsResponse_t * pCurrentHttpsResponse = NULL;
    _httpsRequest_t * pNextHttpsRequest = NULL;
    IotLink_t * pQItem = NULL;
    bool fatalDisconnect = false;

    /* The network connection is already in the connection context. */
    ( void ) pNetworkConnection;

    /* Get the response from the response queue. */
    IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );
    pQItem = IotDeQueue_PeekHead( &( pHttpsConnection->respQ ) );
    IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

    /* If the receive callback is invoked and there is no response expected, then this a violation of the HTTP/1.1
     * protocol. */
    if( pQItem == NULL )
    {
        IotLogError( "Received data on the network, when no response was expected..." );
        fatalDisconnect = true;
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_NETWORK_ERROR );
    }

    /* Set the current HTTP response context to use. */
    pCurrentHttpsResponse = IotLink_Container( _httpsResponse_t, pQItem, link );

    /* If the receive callback has invoked, but the request associated with this response has not finished sending
     * to the server, then this is a violation of the HTTP/1.1 protocol.  */
    if( pCurrentHttpsResponse->reqFinishedSending == false )
    {
        IotLogError( "Received response data on the network when the request was not finished sending. This is unexpected." );
        fatalDisconnect = true;
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_NETWORK_ERROR );
    }

    /* If the current response was cancelled, then don't bother receiving the headers and body. */
    if( pCurrentHttpsResponse->cancelled )
    {
        IotLogDebug( "Response ID: %d was cancelled.", pCurrentHttpsResponse );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_RECEIVE_ABORT );
    }

    /* Reset the http-parser state to an initial state. This is done so that a new response can be parsed from the
     * beginning. */
    pCurrentHttpsResponse->parserState = PARSER_STATE_NONE;

    /* Receive the response from the network. */
    /* Receive the headers first. */
    status = _receiveHttpsHeaders( pHttpsConnection, pCurrentHttpsResponse );

    if( HTTPS_FAILED( status ) )
    {
        if( status == IOT_HTTPS_PARSING_ERROR )
        {
            /* There was an error parsing the HTTPS response body. This may be an indication of a server that does
             *  not adhere to protocol correctly. We should disconnect. */
            IotLogError( "Failed to parse the HTTPS headers for response %d, Error code: %d.",
                         pCurrentHttpsResponse,
                         status );
            fatalDisconnect = true;
        }
        else if( status == IOT_HTTPS_NETWORK_ERROR )
        {
            /* Given the function signature of IotNetworkInterface_t.receive, we can only receive 0 to the number of bytes
             * requested. Receiving less than the number of bytes requests is OK since we do not how much data is expected, so
             * we ask for the full size of the receive buffer. Therefore, the only error that can be returned from receiving
             * the headers or body is a timeout. We always disconnect from the network when there is a timeout because the
             * server may be slow to respond. If the server happens to send the response later at the same time another response
             * is waiting in the queue, then the workflow is corrupted. Pipelining is not current supported in this library. */
            IotLogError( "Network error receiving the HTTPS headers for response %d. Error code: %d",
                         pCurrentHttpsResponse,
                         status );
            fatalDisconnect = true;
        }
        else /* Any other error. */
        {
            IotLogError( "Failed to retrive the HTTPS body for response %d. Error code: %d", pCurrentHttpsResponse, status );
        }

        HTTPS_GOTO_CLEANUP();
    }

    /* Check if we received all of the headers into the header buffer. */
    if( pCurrentHttpsResponse->parserState < PARSER_STATE_HEADERS_COMPLETE )
    {
        IotLogDebug( "Headers received on the network did not all fit into the configured header buffer for response %d."
                     " The length of the headers buffer is: %d",
                     pCurrentHttpsResponse,
                     pCurrentHttpsResponse->pHeadersEnd - pCurrentHttpsResponse->pHeaders );
        /* It is not error if the headers did not all fit into the buffer. */
    }

    /* Receive the body. */
    if( pCurrentHttpsResponse->isAsync )
    {
        status = _receiveHttpsBodyAsync( pCurrentHttpsResponse );
    }
    else
    {
        /* Otherwise receive synchronously. */
        status = _receiveHttpsBodySync( pCurrentHttpsResponse );
    }

    if( HTTPS_FAILED( status ) )
    {
        if( status == IOT_HTTPS_RECEIVE_ABORT )
        {
            /* If the request was cancelled, this is logged, but does not close the connection. */
            IotLogDebug( "User cancelled during the async readReadyCallback() for response %d.",
                         pCurrentHttpsResponse );
        }
        else if( status == IOT_HTTPS_PARSING_ERROR )
        {
            /* There was an error parsing the HTTPS response body. This may be an indication of a server that does
             *  not adhere to protocol correctly. We should disconnect. */
            IotLogError( "Failed to parse the HTTPS body for response %d, Error code: %d.",
                         pCurrentHttpsResponse,
                         status );
            fatalDisconnect = true;
        }
        else if( status == IOT_HTTPS_NETWORK_ERROR )
        {
            /* We always disconnect for a network error because failure to receive the HTTPS body will result in a
             * corruption of the workflow. */
            IotLogError( "Network error receiving the HTTPS body for response %d. Error code: %d",
                         pCurrentHttpsResponse,
                         status );
            fatalDisconnect = true;
        }
        else /* Any other error. */
        {
            IotLogError( "Failed to retrive the HTTPS body for response %d. Error code: %d", pCurrentHttpsResponse, status );
        }

        HTTPS_GOTO_CLEANUP();
    }

    IOT_FUNCTION_CLEANUP_BEGIN();

    /* Disconnect and return in the event of an out-of-order response. If a response is received out of order
     * pCurrentHttpsResponse will be NULL because there will be no response in the connection's response queue.
     * If a response is received out of order that is an indication of a rogue server. */
    if( fatalDisconnect && !pCurrentHttpsResponse )
    {
        IotLogError( "An out-of-order response was received. The connection will be disconnected." );
        disconnectStatus = IotHttpsClient_Disconnect( pHttpsConnection );

        if( HTTPS_FAILED( disconnectStatus ) )
        {
            IotLogWarn( "Failed to disconnect after an out of order response. Error code: %d.", disconnectStatus );
        }

        /* In this case this routine returns immediately after to avoid further uses of pCurrentHttpsResponse. */
        return;
    }

    /* Report errors back to the application. */
    if( HTTPS_FAILED( status ) )
    {
        if( pCurrentHttpsResponse->isAsync && pCurrentHttpsResponse->pCallbacks->errorCallback )
        {
            pCurrentHttpsResponse->pCallbacks->errorCallback( pCurrentHttpsResponse->pUserPrivData, NULL, pCurrentHttpsResponse, status );
        }

        pCurrentHttpsResponse->syncStatus = status;
    }

    /* If this is not a persistent request, the server would have closed it after sending a response, but we
     * disconnect anyways. If we are disconnecting there is is no point in wasting time
     * flushing the network. If the network is being disconnected we also do not schedule any pending requests. */
    if( fatalDisconnect || pCurrentHttpsResponse->isNonPersistent )
    {
        IotLogDebug( "Disconnecting response %d.", pCurrentHttpsResponse );
        disconnectStatus = IotHttpsClient_Disconnect( pHttpsConnection );

        if( ( pCurrentHttpsResponse != NULL ) && pCurrentHttpsResponse->isAsync && pCurrentHttpsResponse->pCallbacks->connectionClosedCallback )
        {
            pCurrentHttpsResponse->pCallbacks->connectionClosedCallback( pCurrentHttpsResponse->pUserPrivData, pHttpsConnection, disconnectStatus );
        }

        if( HTTPS_FAILED( disconnectStatus ) )
        {
            IotLogWarn( "Failed to disconnect response %d. Error code: %d.", pCurrentHttpsResponse, disconnectStatus );
        }

        /* If we disconnect, we do not process anymore requests. */
    }
    else
    {
        /* Set the processing state of the buffer to finished for completeness. This is also to prevent the parsing of the flush
         * data from incrementing any pointer in the HTTP response context. */
        pCurrentHttpsResponse->bufferProcessingState = PROCESSING_STATE_FINISHED;

        /* Flush the socket of the rest of the data if there is data left from this response. We need to do this
         * so that for the next request on this connection, there is not left over response from this request in
         * the next response buffer.
         *
         * If a continuous stream of data is coming in from the connection, with an unknown end, we may not be able to
         * flush the network data. It may sit here forever. A continuous stream should be ingested with the async workflow.
         *
         * All network errors are ignore here because network read will have read the data from network buffer despite
         * errors. */
        flushStatus = _flushHttpsNetworkData( pHttpsConnection, pCurrentHttpsResponse );

        if( flushStatus == IOT_HTTPS_PARSING_ERROR )
        {
            IotLogWarn( "There an error parsing the network flush data. The network buffer might not be fully flushed." );
        }
        else if( flushStatus != IOT_HTTPS_OK )
        {
            IotLogDebug( "Network error when flushing the https network data: %d", flushStatus );
        }

        IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );
        /* Get the next request to process. */
        pQItem = IotDeQueue_PeekHead( &( pHttpsConnection->reqQ ) );
        IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

        /* If there is a next request to process, then create a taskpool job to send the request. */
        if( pQItem != NULL )
        {
            /* Set this next request to send. */
            pNextHttpsRequest = IotLink_Container( _httpsRequest_t, pQItem, link );

            if( pNextHttpsRequest->scheduled == false )
            {
                IotLogDebug( "Request %d is next in the queue. Now scheduling a task to send the request.", pNextHttpsRequest );
                scheduleStatus = _scheduleHttpsRequestSend( pNextHttpsRequest );

                /* If there was an error with scheduling the new task, then report it. */
                if( HTTPS_FAILED( scheduleStatus ) )
                {
                    IotLogError( "Error scheduling HTTPS request %d. Error code: %d", pNextHttpsRequest, scheduleStatus );

                    if( pNextHttpsRequest->isAsync && pNextHttpsRequest->pCallbacks->errorCallback )
                    {
                        pNextHttpsRequest->pCallbacks->errorCallback( pNextHttpsRequest->pUserPrivData, pNextHttpsRequest, NULL, scheduleStatus );
                    }
                    else
                    {
                        pNextHttpsRequest->pHttpsResponse->syncStatus = scheduleStatus;
                    }
                }
            }
        }
        else
        {
            IotLogDebug( "Network receive callback found the request queue empty. A network send task was not scheduled." );
        }
    }

    /* Dequeue response from the response queue now that it is finished. */
    IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );

    /* There could be a scenario where the request fails to send and the network server still responds,
     * In this case, the failed response will have been cancelled and removed from the queue. If the network
     * server still got a response, then the safest way to remove the current response is to remove it explicitly
     * from the queue instead of dequeuing the header of the queue which might not be the current response. */
    if( IotLink_IsLinked( &( pCurrentHttpsResponse->link ) ) )
    {
        IotDeQueue_Remove( &( pCurrentHttpsResponse->link ) );
    }

    IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

    /* The first if-case below notifies IotHttpsClient_SendSync() that the response is finished receiving. When
     * IotHttpsClient_SendSync() returns the user is allowed to modify the user buffer used for the response context.
     * In the asynchronous case, the responseCompleteCallback notifies the application that the user buffer used for the
     * response context can be modified. Posting to the respFinishedSem or calling the responseCompleteCallback MUST be
     * mutually exclusive by wrapping in an if/else. If these were separate if-cases, then there could be a context
     * switch in between where the application modifies the buffer causing the next if-case to be executed. */
    if( pCurrentHttpsResponse->isAsync == false )
    {
        IotSemaphore_Post( &( pCurrentHttpsResponse->respFinishedSem ) );
    }
    else if( pCurrentHttpsResponse->pCallbacks->responseCompleteCallback )
    {
        /* Signal to a synchronous reponse that the response is complete. */
        pCurrentHttpsResponse->pCallbacks->responseCompleteCallback( pCurrentHttpsResponse->pUserPrivData, pCurrentHttpsResponse, status, pCurrentHttpsResponse->status );
    }
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _createHttpsConnection( IotHttpsConnectionHandle_t * pConnHandle,
                                                    IotHttpsConnectionInfo_t * pConnInfo )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    IotNetworkError_t networkStatus = IOT_NETWORK_SUCCESS;

    /* The maximum string length of the ALPN protocols is configured in IOT_HTTPS_MAX_ALPN_PROTOCOLS_LENGTH.
     * The +1 is for the NULL terminator needed by IotNetworkCredentials_t.pAlpnProtos. */
    char pAlpnProtos[ IOT_HTTPS_MAX_ALPN_PROTOCOLS_LENGTH + 1 ] = { 0 };

    /* The maximum string length of the Server host name is configured in IOT_HTTPS_MAX_HOST_NAME_LENGTH.
     * This +1 is for the NULL terminator needed by IotNetworkServerInfo_t.pHostName. */
    char pHostName[ IOT_HTTPS_MAX_HOST_NAME_LENGTH + 1 ] = { 0 };
    bool connectionMutexCreated = false;
    struct IotNetworkServerInfo networkServerInfo = { 0 };
    struct IotNetworkCredentials networkCredentials = { 0 };
    _httpsConnection_t * pHttpsConnection = NULL;
    IotNetworkCredentials_t pNetworkCredentials = NULL;

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pConnInfo->userBuffer.pBuffer );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pConnInfo->pNetworkInterface );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pConnInfo->pAddress );
    HTTPS_ON_ARG_ERROR_GOTO_CLEANUP( pConnInfo->addressLen > 0 );

    /* Make sure the connection context can fit in the user buffer. */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( pConnInfo->userBuffer.bufferLen >= connectionUserBufferMinimumSize,
                                         IOT_HTTPS_INSUFFICIENT_MEMORY,
                                         "Buffer size is too small to initialize the connection context. User buffer size: %d, required minimum size; %d.",
                                         ( *pConnInfo ).userBuffer.bufferLen,
                                         connectionUserBufferMinimumSize );

    /* Make sure that the server address does not exceed the maximum permitted length. */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( pConnInfo->addressLen <= IOT_HTTPS_MAX_HOST_NAME_LENGTH,
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "IotHttpsConnectionInfo_t.addressLen has a host name length %d that exceeds maximum length %d.",
                                         pConnInfo->addressLen,
                                         IOT_HTTPS_MAX_HOST_NAME_LENGTH );

    /* Make sure that the ALPN protocols does not exceed the maximum permitted length. */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( pConnInfo->alpnProtocolsLen <= IOT_HTTPS_MAX_ALPN_PROTOCOLS_LENGTH,
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "IotHttpsConnectionInfo_t.alpnProtocolsLen of %d exceeds the configured maximum protocol length %d. See IOT_HTTPS_MAX_ALPN_PROTOCOLS_LENGTH for more information.",
                                         pConnInfo->alpnProtocolsLen,
                                         IOT_HTTPS_MAX_ALPN_PROTOCOLS_LENGTH );

    pHttpsConnection = ( _httpsConnection_t * ) ( pConnInfo->userBuffer.pBuffer );

    /* Start with the disconnected state. */
    pHttpsConnection->isConnected = false;

    /* Initialize disconnection state keeper. */
    pHttpsConnection->isDestroyed = false;

    /* Initialize the queue of responses and requests. */
    IotDeQueue_Create( &( pHttpsConnection->reqQ ) );
    IotDeQueue_Create( &( pHttpsConnection->respQ ) );

    /* This timeout is used to wait for a response on the connection as well as
     * for the timeout for the connect operation. */
    if( pConnInfo->timeout == 0 )
    {
        pHttpsConnection->timeout = IOT_HTTPS_RESPONSE_WAIT_MS;
    }
    else
    {
        pHttpsConnection->timeout = pConnInfo->timeout;
    }

    /* pNetworkInterface contains all the routines to be able to send/receive data on the network. */
    pHttpsConnection->pNetworkInterface = pConnInfo->pNetworkInterface;

    /* The address from the connection configuration information is copied to a local buffer because a NULL pointer
     * is required in IotNetworkServerInfo_t.pHostName. IotNetworkServerInfo_t contains the server information needed
     * by the network interface to create the connection. */
    memcpy( pHostName, pConnInfo->pAddress, pConnInfo->addressLen );
    pHostName[ pConnInfo->addressLen ] = '\0';
    /* Set it in the IOT network abstractions server information parameter. */
    networkServerInfo.pHostName = pHostName;
    networkServerInfo.port = pConnInfo->port;

    /* If this is TLS connection, then set the network credentials. */
    if( ( pConnInfo->flags & IOT_HTTPS_IS_NON_TLS_FLAG ) == 0 )
    {
        if( pConnInfo->flags & IOT_HTTPS_DISABLE_SNI )
        {
            networkCredentials.disableSni = true;
        }
        else
        {
            networkCredentials.disableSni = false;
        }

        if( pConnInfo->pAlpnProtocols != NULL )
        {
            /* The alpn protocol strings in IotNetworkCredentials_t require a NULL terminator, so the alpn protocol
             * string in the connection configuration information is copied to a local buffer to append the NULL
             * terminator. */
            memcpy( pAlpnProtos, pConnInfo->pAlpnProtocols, pConnInfo->alpnProtocolsLen );
            pAlpnProtos[ pConnInfo->alpnProtocolsLen ] = '\0';
            networkCredentials.pAlpnProtos = pAlpnProtos;
        }
        else
        {
            networkCredentials.pAlpnProtos = NULL;
        }

        /* If any of these are NULL a network error will result when trying to make the connection. Because there is
         * no invalid memory access resulting from these configurations being NULL, it is not check at the start
         * of the function. */
        networkCredentials.pRootCa = pConnInfo->pCaCert;
        networkCredentials.rootCaSize = pConnInfo->caCertLen;
        networkCredentials.pClientCert = pConnInfo->pClientCert;
        networkCredentials.clientCertSize = pConnInfo->clientCertLen;
        networkCredentials.pPrivateKey = pConnInfo->pPrivateKey;
        networkCredentials.privateKeySize = pConnInfo->privateKeyLen;

        pNetworkCredentials = &networkCredentials;
    }
    else
    {
        /* create() takes a NULL if there is no TLS configuration. */
        pNetworkCredentials = NULL;
    }

    /* create() will connect to the server specified in addition to creating other network layer
     *  specific resources. */
    networkStatus = pHttpsConnection->pNetworkInterface->create( &networkServerInfo,
                                                                 pNetworkCredentials,
                                                                 &( pHttpsConnection->pNetworkConnection ) );

    /* Check to see if the network connection succeeded. If it did not succeed,
     * then the output parameter pConnHandle will be used to return NULL and the
     * function returns an error. */
    if( networkStatus != IOT_NETWORK_SUCCESS )
    {
        IotLogError( "Failed to connect to the server at %.*s on port %d with error: %d",
                     pConnInfo->addressLen,
                     pConnInfo->pAddress,
                     pConnInfo->port,
                     networkStatus );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_CONNECTION_ERROR );
    }

    /* The connection succeeded so set the state to connected. */
    pHttpsConnection->isConnected = true;

    /* The receive callback is invoked by the network layer when data is ready
     * to be read from the network. */
    networkStatus = pHttpsConnection->pNetworkInterface->setReceiveCallback( pHttpsConnection->pNetworkConnection,
                                                                             _networkReceiveCallback,
                                                                             pHttpsConnection );

    if( networkStatus != IOT_NETWORK_SUCCESS )
    {
        IotLogError( "Failed to connect to set the HTTPS receive callback. " );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INTERNAL_ERROR );
    }

    /* Connection was successful, so create synchronization primitives. */

    connectionMutexCreated = IotMutex_Create( &( pHttpsConnection->connectionMutex ), false );

    if( !connectionMutexCreated )
    {
        IotLogError( "Failed to create an internal mutex." );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INTERNAL_ERROR );
    }

    /* Return the new connection information. */
    *pConnHandle = pHttpsConnection;

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    /* If we failed anywhere in the connection process, then destroy the semaphores created. */
    if( HTTPS_FAILED( status ) )
    {
        /* If there was a connect was successful, disconnect from the network.  */
        if( ( pHttpsConnection != NULL ) && ( pHttpsConnection->isConnected ) )
        {
            _networkDisconnect( pHttpsConnection );
            _networkDestroy( pHttpsConnection );
        }

        if( connectionMutexCreated )
        {
            IotMutex_Destroy( &( pHttpsConnection->connectionMutex ) );
        }

        /* Set the connection handle as NULL if everything failed. */
        *pConnHandle = NULL;
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

static void _networkDisconnect( _httpsConnection_t * pHttpsConnection )
{
    IotNetworkError_t networkStatus = IOT_NETWORK_SUCCESS;

    networkStatus = pHttpsConnection->pNetworkInterface->close( pHttpsConnection->pNetworkConnection );

    if( networkStatus != IOT_NETWORK_SUCCESS )
    {
        IotLogWarn( "Failed to shutdown the socket with error code: %d", networkStatus );
    }
}

/*-----------------------------------------------------------*/

static void _networkDestroy( _httpsConnection_t * pHttpsConnection )
{
    IotNetworkError_t networkStatus = IOT_NETWORK_SUCCESS;

    networkStatus = pHttpsConnection->pNetworkInterface->destroy( pHttpsConnection->pNetworkConnection );

    if( networkStatus != IOT_NETWORK_SUCCESS )
    {
        IotLogWarn( "Failed to shutdown the socket with error code: %d", networkStatus );
    }
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _addHeader( _httpsRequest_t * pHttpsRequest,
                                        const char * pName,
                                        uint32_t nameLen,
                                        const char * pValue,
                                        uint32_t valueLen )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    int headerFieldSeparatorLen = HTTPS_HEADER_FIELD_SEPARATOR_LENGTH;
    uint32_t additionalLength = nameLen + headerFieldSeparatorLen + valueLen + HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH;
    uint32_t possibleLastHeaderAdditionalLength = HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH;

    /* Check if there is enough space to add the header field and value
     * (name:value\r\n). We need to add a "\r\n" at the end of headers. The use of
     * possibleLastHeaderAdditionalLength is to make sure that there is always
     * space for the last "\r\n". */
    if( ( additionalLength + possibleLastHeaderAdditionalLength ) > ( ( uint32_t ) ( pHttpsRequest->pHeadersEnd - pHttpsRequest->pHeadersCur ) ) )
    {
        IotLogError( "There is %d space left in the header buffer, but we want to add %d more of header.",
                     pHttpsRequest->pHeadersEnd - pHttpsRequest->pHeadersCur,
                     additionalLength + possibleLastHeaderAdditionalLength );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INSUFFICIENT_MEMORY );
    }

    memcpy( pHttpsRequest->pHeadersCur, pName, nameLen );
    pHttpsRequest->pHeadersCur += nameLen;
    memcpy( pHttpsRequest->pHeadersCur, HTTPS_HEADER_FIELD_SEPARATOR, headerFieldSeparatorLen );
    pHttpsRequest->pHeadersCur += headerFieldSeparatorLen;
    memcpy( pHttpsRequest->pHeadersCur, pValue, valueLen );
    pHttpsRequest->pHeadersCur += valueLen;
    memcpy( pHttpsRequest->pHeadersCur, HTTPS_END_OF_HEADER_LINES_INDICATOR, HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH );
    pHttpsRequest->pHeadersCur += HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH;
    IotLogDebug( "Wrote header: \"%s: %.*s\r\n\". Space left in request user buffer: %d",
                 pName,
                 valueLen,
                 pValue,
                 pHttpsRequest->pHeadersEnd - pHttpsRequest->pHeadersCur );

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _networkSend( _httpsConnection_t * pHttpsConnection,
                                          uint8_t * pBuf,
                                          size_t len )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    size_t numBytesSent = 0;
    size_t numBytesSentTotal = 0;
    size_t sendLength = len;

    while( numBytesSentTotal < sendLength )
    {
        numBytesSent = pHttpsConnection->pNetworkInterface->send( pHttpsConnection->pNetworkConnection,
                                                                  &( pBuf[ numBytesSentTotal ] ),
                                                                  sendLength - numBytesSentTotal );

        /* pNetworkInterface->send returns 0 on error. */
        if( numBytesSent == 0 )
        {
            IotLogError( "Error in sending the HTTPS headers. Error code: %d", numBytesSent );
            break;
        }

        numBytesSentTotal += numBytesSent;
    }

    if( numBytesSentTotal != sendLength )
    {
        IotLogError( "Error sending data on the network. We sent %d but there were total %d.", numBytesSentTotal, sendLength );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_NETWORK_ERROR );
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _networkRecv( _httpsConnection_t * pHttpsConnection,
                                          uint8_t * pBuf,
                                          size_t bufLen,
                                          size_t * numBytesRecv )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    /* The HTTP server could send the header and the body in two separate TCP packets. If that is the case, then
     * receiveUpTo will return return the full headers first. Then on a second call, the body will be returned.
     * If the http parser receives just the headers despite the content length being greater than  */
    *numBytesRecv = pHttpsConnection->pNetworkInterface->receiveUpto( pHttpsConnection->pNetworkConnection,
                                                                      pBuf,
                                                                      bufLen );

    IotLogDebug( "The network interface receive returned %d.", numBytesRecv );

    /* We return IOT_HTTPS_NETWORK_ERROR only if we receive nothing. Receiving less
     * data than requested is okay because it is not known in advance how much data
     * we are going to receive and therefore we request for the available buffer
     * size. */
    if( *numBytesRecv == 0 )
    {
        IotLogError( "Error in receiving the HTTPS response message. Socket Error code %d", *numBytesRecv );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_NETWORK_ERROR );

        /* A network error is returned when zero is received because that would indicate that either there
        * was a network error or there was a timeout reading data. If there was timeout reading data, then
        * the server was too slow to respond. If the server is too slow to respond, then a network error must
        * be returned to trigger a connection close. The connection must close after the network error so
        * that the response from this request does not piggyback on the response from the next request. */
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _sendHttpsHeaders( _httpsConnection_t * pHttpsConnection,
                                               uint8_t * pHeadersBuf,
                                               uint32_t headersLength,
                                               bool isNonPersistent,
                                               uint32_t contentLength )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    const char * connectionHeader = NULL;
    int numWritten = 0;
    int connectionHeaderLen = 0;
    /* The Content-Length header of the form "Content-Length: N\r\n" with a NULL terminator for snprintf. */
    char contentLengthHeaderStr[ HTTPS_MAX_CONTENT_LENGTH_LINE_LENGTH + 1 ];

    /* The HTTP headers to send after the headers in pHeadersBuf are the Content-Length and the Connection type and
     * the final "\r\n" to indicate the end of the the header lines. Note that we are using
     * HTTPS_CONNECTION_KEEP_ALIVE_HEADER_LINE_LENGTH because length of "Connection: keep-alive\r\n" is
     * more than "Connection: close\r\n". Creating a buffer of bigger size ensures that
     * both the connection type strings will fit in the buffer. */
    char finalHeaders[ HTTPS_MAX_CONTENT_LENGTH_LINE_LENGTH + HTTPS_CONNECTION_KEEP_ALIVE_HEADER_LINE_LENGTH + HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH ] = { 0 };

    /* Send the headers passed into this function first. These headers are not terminated with a second set of "\r\n". */
    status = _networkSend( pHttpsConnection, pHeadersBuf, headersLength );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error sending the HTTPS headers in the request user buffer. Error code: %d", status );
        HTTPS_GOTO_CLEANUP();
    }

    /* If there is a Content-Length, then write that to the finalHeaders to send. */
    if( contentLength > 0 )
    {
        numWritten = snprintf( contentLengthHeaderStr,
                               sizeof( contentLengthHeaderStr ),
                               "%s: %u\r\n",
                               HTTPS_CONTENT_LENGTH_HEADER,
                               ( unsigned int ) contentLength );
    }

    if( ( numWritten < 0 ) || ( numWritten >= sizeof( contentLengthHeaderStr ) ) )
    {
        IotLogError( "Internal error in snprintf() in _sendHttpsHeaders(). Error code %d.", numWritten );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INTERNAL_ERROR );
    }

    /* snprintf() succeeded so copy that to the finalHeaders. */
    memcpy( finalHeaders, contentLengthHeaderStr, numWritten );

    /* Write the connection persistence type to the final headers. */
    if( isNonPersistent )
    {
        connectionHeader = HTTPS_CONNECTION_CLOSE_HEADER_LINE;
        connectionHeaderLen = FAST_MACRO_STRLEN( HTTPS_CONNECTION_CLOSE_HEADER_LINE );
    }
    else
    {
        connectionHeader = HTTPS_CONNECTION_KEEP_ALIVE_HEADER_LINE;
        connectionHeaderLen = FAST_MACRO_STRLEN( HTTPS_CONNECTION_KEEP_ALIVE_HEADER_LINE );
    }

    memcpy( &finalHeaders[ numWritten ], connectionHeader, connectionHeaderLen );
    numWritten += connectionHeaderLen;
    memcpy( &finalHeaders[ numWritten ], HTTPS_END_OF_HEADER_LINES_INDICATOR, HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH );
    numWritten += HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH;

    status = _networkSend( pHttpsConnection, ( uint8_t * ) finalHeaders, numWritten );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error sending final HTTPS Headers \r\n%s. Error code: %d", finalHeaders, status );
        HTTPS_GOTO_CLEANUP();
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _sendHttpsBody( _httpsConnection_t * pHttpsConnection,
                                            uint8_t * pBodyBuf,
                                            uint32_t bodyLength )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    status = _networkSend( pHttpsConnection, pBodyBuf, bodyLength );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error sending final HTTPS body at location 0x%x. Error code: %d", pBodyBuf, status );
        HTTPS_GOTO_CLEANUP();
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _parseHttpsMessage( _httpParserInfo_t * pHttpParserInfo,
                                                char * pBuf,
                                                size_t len )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    size_t parsedBytes = 0;
    const char * pHttpParserErrorDescription = NULL;
    http_parser * pHttpParser = &( pHttpParserInfo->responseParser );

    IotLogDebug( "Now parsing HTTP message buffer to process a response." );
    parsedBytes = pHttpParserInfo->parseFunc( pHttpParser, &_httpParserSettings, pBuf, len );
    IotLogDebug( "http-parser parsed %d bytes out of %d specified.", parsedBytes, len );

    /* If the parser fails with HPE_CLOSED_CONNECTION or HPE_INVALID_CONSTANT that simply means there
     * was data beyond the end of the message. We do not fail in this case because we give the whole
     * header buffer or body buffer to the parser even if it is only partly filled with data.
     * Errors <= HPE_CB_chunk_complete means that a non-zero number was returned from some callback.
     * A nonzero number is returned from some callbacks when we want to stop the parser early
     * for example - a HEAD request or the user explicitly asked to ignore the body by not
     * providing the body buffer. */
    if( ( pHttpParser->http_errno != 0 ) &&
        ( HTTP_PARSER_ERRNO( pHttpParser ) != HPE_CLOSED_CONNECTION ) &&
        ( HTTP_PARSER_ERRNO( pHttpParser ) != HPE_INVALID_CONSTANT ) &&
        ( HTTP_PARSER_ERRNO( pHttpParser ) > HPE_CB_chunk_complete ) )
    {
        pHttpParserErrorDescription = http_errno_description( HTTP_PARSER_ERRNO( pHttpParser ) );
        IotLogError( "http_parser failed on the http response with error: %s", pHttpParserErrorDescription );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_PARSING_ERROR );
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static void _incrementNextLocationToWriteBeyondParsed( uint8_t ** pBufCur,
                                                       uint8_t ** pBufEnd )
{
    /* There is an edge case where the final one or two character received in the header buffer is part of
     * the header field separator ": " or part of the header line end "\r\n" delimiters. When this
     * happens, pHeadersCur in the response will point not the end of the buffer, but to a character in
     * the delimiter. For example:
     * Let's say this is our current header buffer after receiving and parsing:
     * ["HTTP/1.1 200 OK\r\n\header0: value0\r\nheader1: value1\r\n"]
     * pHeadersCur will point to \r because the http-parser does not invoke a callback on the
     * delimiters. Since no callback is invoked, pHeadersCur is not incremented. pHeadersEnd points to
     * the end of the header buffer which is the unwritable memory location right after the final '\n'.
     * Because pHeadersCur is less than pHeaderEnd we loop again and receive on the network causing the
     * buffer to look like this:
     * ["HTTP/1.1 200 OK\r\n\header0: value0\r\nheader1: value1he"]
     * Which will cause an incorrect header1 value to be read if the application decides to read it with
     * IotHttpsClient_ReadHeader().
     *
     * If our header buffer looks like:
     * ["HTTP/1.1 200 OK\r\n\header0: value0\r\nheader1: "]
     * then pHeaderCur will point to the colon.
     *
     * If our header buffer looks like:
     * ["HTTP/1.1 200 OK\r\n\header0: value0\r\nheader1:"]
     * then pHeaderCur will point to the colon.
     *
     * If our header buffer looks like
     * ["HTTP/1.1 200 OK\r\n\header0: value0\r\nheader1: value1 "]
     * then http-parser will consider that space as part of value1.
     *
     * If our header buffer looks like
     * ["HTTP/1.1 200 OK\r\n\header0: value0\r\nheader1: value1\r"]
     * then pHeaderCur will point to the carriage return.
     *
     * If our header buffer looks like
     * ["HTTP/1.1 200 OK\r\n\header0: value0\r\nheader1: value1\r\n"]
     * As explained in the example above, pHeaderCur will point to the carriage return.
     *
     * If we somehow receive a partial HTTP response message in our zeroed-out header buffer:
     * case 1: ["HTTP/1.1 200 OK\r\nheader0: value0\r\nheader1: value1\r\0\0\0\0\0\0\0"]
     * case 2: ["HTTP/1.1 200 OK\r\nheader0: value0\r\nheader1: value1\r\n\0\0\0\0\0\0"]
     * case 3: ["HTTP/1.1 200 OK\r\nheader0: value0\r\nheader1:\0\0\0\0\0\0\0\0\0\0\0"]
     * case 4: ["HTTP/1.1 200 OK\r\nheader0: value0\r\nheader1: \0\0\0\0\0\0\0\0\0\0\0"]
     * then parser may fail or append all of the NULL characters to a header field name or value. */
    while( *pBufCur < *pBufEnd )
    {
        if( **pBufCur == CARRIAGE_RETURN_CHARACTER )
        {
            ( *pBufCur )++;
        }
        else if( **pBufCur == NEWLINE_CHARACTER )
        {
            ( *pBufCur )++;
            break;
        }
        else if( **pBufCur == COLON_CHARACTER )
        {
            ( *pBufCur )++;
        }
        else if( ( **pBufCur == SPACE_CHARACTER ) && ( *( *pBufCur - 1 ) == COLON_CHARACTER ) )
        {
            ( *pBufCur )++;
            break;
        }
        else
        {
            break;
        }
    }
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _receiveHttpsMessage( _httpsConnection_t * pHttpsConnection,
                                                  _httpParserInfo_t * pHttpParserInfo,
                                                  IotHttpsResponseParserState_t * pCurrentParserState,
                                                  IotHttpsResponseParserState_t finalParserState,
                                                  IotHttpsResponseBufferState_t currentBufferProcessingState,
                                                  uint8_t ** pBufCur,
                                                  uint8_t ** pBufEnd )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    size_t numBytesRecv = 0;

    /* The final parser state is either the end of the header lines or the end of the entity body. This state is set in
     * the http-parser callbacks. */
    while( ( *pCurrentParserState < finalParserState ) && ( *pBufEnd - *pBufCur > 0 ) )
    {
        status = _networkRecv( pHttpsConnection,
                               *pBufCur,
                               *pBufEnd - *pBufCur,
                               &numBytesRecv );

        /* A network error in _networkRecv is returned only when we received zero bytes. In that case, there is
         * no point in parsing we return immediately with the network error. */
        if( HTTPS_FAILED( status ) )
        {
            IotLogError( "Network error receiving the HTTPS response headers. Error code: %d", status );
            break;
        }

        status = _parseHttpsMessage( pHttpParserInfo, ( char * ) ( *pBufCur ), numBytesRecv );

        if( HTTPS_FAILED( status ) )
        {
            IotLogError( "Failed to parse the message buffer with error: %d", pHttpParserInfo->responseParser.http_errno );
            break;
        }

        /* If the current buffer being filled is the header buffer, then \r\n header line separators should not get
         * overwritten on the next network read. See _incrementNextLocationToWriteBeyondParsed() for more
         * information. */
        if( currentBufferProcessingState == PROCESSING_STATE_FILLING_HEADER_BUFFER )
        {
            _incrementNextLocationToWriteBeyondParsed( pBufCur, pBufEnd );
        }

        /* The _httpsResponse->pHeadersCur pointer is updated in the http_parser callbacks. */
        IotLogDebug( "There is %d of space left in the buffer.", *pBufEnd - *pBufCur );
    }

    /* If we did not reach the end of the headers or body in the parser callbacks, then the buffer configured does not
     * fit all of that part of the HTTP message. */
    if( *pCurrentParserState < finalParserState )
    {
        IotLogDebug( "There are still more data on the network. It could not fit into the specified length %d.",
                     *pBufEnd - *pBufCur );
    }

    HTTPS_GOTO_CLEANUP();
    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _receiveHttpsHeaders( _httpsConnection_t * pHttpsConnection,
                                                  _httpsResponse_t * pHttpsResponse )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    pHttpsResponse->bufferProcessingState = PROCESSING_STATE_FILLING_HEADER_BUFFER;

    IotLogDebug( "Now attempting to receive the HTTP response headers into a buffer with length %d.",
                 pHttpsResponse->pHeadersEnd - pHttpsResponse->pHeadersCur );

    status = _receiveHttpsMessage( pHttpsConnection,
                                   &( pHttpsResponse->httpParserInfo ),
                                   &( pHttpsResponse->parserState ),
                                   PARSER_STATE_HEADERS_COMPLETE,
                                   PROCESSING_STATE_FILLING_HEADER_BUFFER,
                                   &( pHttpsResponse->pHeadersCur ),
                                   &( pHttpsResponse->pHeadersEnd ) );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error receiving the HTTP headers. Error code %d", status );
        HTTPS_GOTO_CLEANUP();
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

/* _receiveHttpsHeaders() must be called first before this function is called. */
static IotHttpsReturnCode_t _receiveHttpsBody( _httpsConnection_t * pHttpsConnection,
                                               _httpsResponse_t * pHttpsResponse )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    IotLogDebug( "Now attempting to receive the HTTP response body into a buffer with length %d.",
                 pHttpsResponse->pBodyEnd - pHttpsResponse->pBodyCur );

    pHttpsResponse->bufferProcessingState = PROCESSING_STATE_FILLING_BODY_BUFFER;

    status = _receiveHttpsMessage( pHttpsConnection,
                                   &( pHttpsResponse->httpParserInfo ),
                                   &( pHttpsResponse->parserState ),
                                   PARSER_STATE_BODY_COMPLETE,
                                   PROCESSING_STATE_FILLING_BODY_BUFFER,
                                   &( pHttpsResponse->pBodyCur ),
                                   &( pHttpsResponse->pBodyEnd ) );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error receiving the HTTP body. Error code %d", status );
        HTTPS_GOTO_CLEANUP();
    }

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    IotLogDebug( "The remaining content length on the network is %d.",
                 pHttpsResponse->httpParserInfo.responseParser.content_length );

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _flushHttpsNetworkData( _httpsConnection_t * pHttpsConnection,
                                                    _httpsResponse_t * pHttpsResponse )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    static uint8_t flushBuffer[ IOT_HTTPS_MAX_FLUSH_BUFFER_SIZE ] = { 0 };
    const char * pHttpParserErrorDescription = NULL;
    IotHttpsReturnCode_t parserStatus = IOT_HTTPS_OK;
    IotHttpsReturnCode_t networkStatus = IOT_HTTPS_OK;
    size_t numBytesRecv = 0;

    /* Even if there is not body, the parser state will become body complete after the headers finish. */
    while( pHttpsResponse->parserState < PARSER_STATE_BODY_COMPLETE )
    {
        IotLogDebug( "Now clearing the rest of the response data on the socket. " );
        networkStatus = _networkRecv( pHttpsConnection, flushBuffer, IOT_HTTPS_MAX_FLUSH_BUFFER_SIZE, &numBytesRecv );

        /* Run this through the parser so that we can get the end of the HTTP message, instead of simply timing out the socket to stop.
         * If we relied on the socket timeout to stop reading the network socket, then the server may close the connection. */
        parserStatus = _parseHttpsMessage( &( pHttpsResponse->httpParserInfo ), ( char * ) flushBuffer, numBytesRecv );

        if( HTTPS_FAILED( parserStatus ) )
        {
            pHttpParserErrorDescription = http_errno_description( HTTP_PARSER_ERRNO( &pHttpsResponse->httpParserInfo.responseParser ) );
            IotLogError( "Network Flush: Failed to parse the response body buffer with error: %d, %s",
                         pHttpsResponse->httpParserInfo.responseParser.http_errno,
                         pHttpParserErrorDescription );
            break;
        }

        /* If there is a network error then we want to stop clearing out the buffer. */
        if( HTTPS_FAILED( networkStatus ) )
        {
            IotLogWarn( "Network Flush: Error receiving the rest of the HTTP response. Error code: %d",
                        networkStatus );
            break;
        }
    }

    /* All network errors except timeouts are returned. */
    if( HTTPS_FAILED( networkStatus ) )
    {
        status = networkStatus;
    }
    else
    {
        status = parserStatus;
    }

    HTTPS_GOTO_CLEANUP();

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _sendHttpsHeadersAndBody( _httpsConnection_t * pHttpsConnection,
                                                      _httpsRequest_t * pHttpsRequest )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    /* Send the HTTP headers. */
    status = _sendHttpsHeaders( pHttpsConnection,
                                pHttpsRequest->pHeaders,
                                pHttpsRequest->pHeadersCur - pHttpsRequest->pHeaders,
                                pHttpsRequest->isNonPersistent,
                                pHttpsRequest->bodyLength );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error sending the HTTPS headers with error code: %d", status );
        HTTPS_GOTO_CLEANUP();
    }

    if( ( pHttpsRequest->pBody != NULL ) && ( pHttpsRequest->bodyLength > 0 ) )
    {
        status = _sendHttpsBody( pHttpsConnection, pHttpsRequest->pBody, pHttpsRequest->bodyLength );

        if( HTTPS_FAILED( status ) )
        {
            IotLogError( "Error sending final HTTPS body. Return code: %d", status );
            HTTPS_GOTO_CLEANUP();
        }
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static void _sendHttpsRequest( IotTaskPool_t pTaskPool,
                               IotTaskPoolJob_t pJob,
                               void * pUserContext )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    _httpsRequest_t * pHttpsRequest = ( _httpsRequest_t * ) ( pUserContext );
    _httpsConnection_t * pHttpsConnection = pHttpsRequest->pHttpsConnection;
    _httpsResponse_t * pHttpsResponse = pHttpsRequest->pHttpsResponse;
    IotHttpsReturnCode_t disconnectStatus = IOT_HTTPS_OK;
    IotHttpsReturnCode_t scheduleStatus = IOT_HTTPS_OK;
    IotLink_t * pQItem = NULL;
    _httpsRequest_t * pNextHttpsRequest = NULL;

    ( void ) pTaskPool;
    ( void ) pJob;

    IotLogDebug( "Task with request ID: %d started.", pHttpsRequest );

    if( pHttpsRequest->cancelled == true )
    {
        IotLogDebug( "Request ID: %d was cancelled.", pHttpsRequest );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_SEND_ABORT );
    }

    /* To protect against out of order network data from a rouge server, signal that the request is
     * not finished sending. */
    pHttpsResponse->reqFinishedSending = false;

    /* Queue the response to expect from the network. */
    IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );
    IotDeQueue_EnqueueTail( &( pHttpsConnection->respQ ), &( pHttpsResponse->link ) );
    IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

    /* Get the headers from the application. For a synchronous request the application should have appended extra
     * headers before this point. */
    if( pHttpsRequest->isAsync && pHttpsRequest->pCallbacks->appendHeaderCallback )
    {
        pHttpsRequest->pCallbacks->appendHeaderCallback( pHttpsRequest->pUserPrivData, pHttpsRequest );
    }

    if( pHttpsRequest->cancelled == true )
    {
        IotLogDebug( "Request ID: %d was cancelled.", pHttpsRequest );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_SEND_ABORT );
    }

    /* Ask the user for data to write body to the network. We only ask the user once. This is so that
     * we can calculate the Content-Length to send.*/
    if( pHttpsRequest->isAsync && pHttpsRequest->pCallbacks->writeCallback )
    {
        /* If there is data, then a Content-Length header value will be provided and we send the headers
         * before that user data. */
        pHttpsRequest->pCallbacks->writeCallback( pHttpsRequest->pUserPrivData, pHttpsRequest );
    }

    if( HTTPS_FAILED( pHttpsRequest->bodyTxStatus ) )
    {
        IotLogError( "Failed to send the headers and body over the network during the writeCallback. Error code: %d.",
                     status );
        HTTPS_SET_AND_GOTO_CLEANUP( pHttpsRequest->bodyTxStatus );
    }

    if( pHttpsRequest->cancelled == true )
    {
        IotLogDebug( "Request ID: %d was cancelled.", pHttpsRequest );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_SEND_ABORT );
    }

    /* If this is a synchronous request then the header and body were configured beforehand. The header and body
     * are sent now. For an asynchronous request, the header and body are sent in IotHttpsClient_WriteRequestBody()
     * which is to be invoked in #IotHttpsClientCallbacks_t.writeCallback(). If the application never invokes
     * IotHttpsClient_WriteRequestBody(), then pHttpsRequest->pBody will be NULL. In this case we still want to
     * send whatever headers we have.  */
    if( ( pHttpsRequest->isAsync == false ) ||
        ( ( pHttpsRequest->isAsync ) && ( pHttpsRequest->pBody == NULL ) ) )
    {
        status = _sendHttpsHeadersAndBody( pHttpsConnection, pHttpsRequest );

        if( HTTPS_FAILED( status ) )
        {
            IotLogError( "Failed to send the headers and body on the network. Error code: %d", status );
            HTTPS_GOTO_CLEANUP();
        }
    }

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    /* The request has finished sending. This indicates to the network receive callback that the request was
     * finished, so a response received on the network is valid. This also lets a possible application called
     * IotHttpsClient_Disconnect() know that the connection is not busy, so the connection can be destroyed. */
    pHttpsResponse->reqFinishedSending = true;

    if( HTTPS_FAILED( status ) )
    {
        /* If the headers or body failed to send, then there should be no response expected from the server. */
        /* Cancel the response incase there is a response from the server. */
        _cancelResponse( pHttpsResponse );
        IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );

        if( IotLink_IsLinked( &( pHttpsResponse->link ) ) )
        {
            IotDeQueue_Remove( &( pHttpsResponse->link ) );
        }

        IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

        /* Set the error status in the sync workflow. */
        pHttpsResponse->syncStatus = status;

        /* Return the error status or cancel status to the application for an asynchronous workflow. */
        if( pHttpsRequest->isAsync && pHttpsRequest->pCallbacks->errorCallback )
        {
            pHttpsRequest->pCallbacks->errorCallback( pHttpsRequest->pUserPrivData, pHttpsRequest, NULL, status );
        }

        /* We close the connection on all network errors. All network errors in receiving the response, close the
         * connection. For consistency in behavior, if there is a network error in send, the connection should also be
         * closed. */
        if( status == IOT_HTTPS_NETWORK_ERROR )
        {
            IotLogDebug( "Disconnecting request %d.", pHttpsRequest );
            disconnectStatus = IotHttpsClient_Disconnect( pHttpsConnection );

            if( pHttpsRequest->isAsync && pHttpsRequest->pCallbacks->connectionClosedCallback )
            {
                pHttpsRequest->pCallbacks->connectionClosedCallback( pHttpsRequest->pUserPrivData,
                                                                     pHttpsConnection,
                                                                     disconnectStatus );
            }

            if( HTTPS_FAILED( disconnectStatus ) )
            {
                IotLogWarn( "Failed to disconnect request %d. Error code: %d.", pHttpsRequest, disconnectStatus );
            }
        }
        else
        {
            /* Because this request failed, the network receive callback may never be invoked to schedule other possible
             * requests in the queue. In order to avoid requests never getting scheduled on a connected connection,
             * the first item in the queue is scheduled if it can be. */
            IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );

            /* Get the next item in the queue by removing this current (which is the first) and peeking at the head
             * again. */
            IotDeQueue_Remove( &( pHttpsRequest->link ) );
            pQItem = IotDeQueue_PeekHead( &( pHttpsConnection->reqQ ) );
            /* This current request is put back because it is removed again for all cases at the end of this routine. */
            IotDeQueue_EnqueueHead( &( pHttpsConnection->reqQ ), &( pHttpsRequest->link ) );
            IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

            if( pQItem != NULL )
            {
                /* Set this next request to send. */
                pNextHttpsRequest = IotLink_Container( _httpsRequest_t, pQItem, link );

                if( pNextHttpsRequest->scheduled == false )
                {
                    IotLogDebug( "Request %d is next in the queue. Now scheduling a task to send the request.", pNextHttpsRequest );
                    scheduleStatus = _scheduleHttpsRequestSend( pNextHttpsRequest );

                    /* If there was an error with scheduling the new task, then report it. */
                    if( HTTPS_FAILED( scheduleStatus ) )
                    {
                        IotLogError( "Error scheduling HTTPS request %d. Error code: %d", pNextHttpsRequest, scheduleStatus );

                        if( pNextHttpsRequest->isAsync && pNextHttpsRequest->pCallbacks->errorCallback )
                        {
                            pNextHttpsRequest->pCallbacks->errorCallback( pNextHttpsRequest->pUserPrivData, pNextHttpsRequest, NULL, scheduleStatus );
                        }
                        else
                        {
                            pNextHttpsRequest->pHttpsResponse->syncStatus = scheduleStatus;
                        }
                    }
                }
            }
        }

        /* Post to the response finished semaphore to unlock the application waiting on a synchronous request. */
        if( pHttpsRequest->isAsync == false )
        {
            IotSemaphore_Post( &( pHttpsResponse->respFinishedSem ) );
        }
        else if( pHttpsRequest->pCallbacks->responseCompleteCallback )
        {
            /* Call the response complete callback. We always call this even if we did not receive the response to
             * let the application know that the request has completed. */
            pHttpsRequest->pCallbacks->responseCompleteCallback( pHttpsRequest->pUserPrivData, NULL, status, 0 );
        }
    }

    IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );
    /* Now that the current request is finished, we dequeue the current request from the queue. */
    IotDeQueue_DequeueHead( &( pHttpsConnection->reqQ ) );
    IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

    /* This routine returns a void so there is no HTTPS_FUNCTION_CLEANUP_END();. */
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t _scheduleHttpsRequestSend( _httpsRequest_t * pHttpsRequest )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    IotTaskPoolError_t taskPoolStatus = IOT_TASKPOOL_SUCCESS;
    _httpsConnection_t * pHttpsConnection = pHttpsRequest->pHttpsConnection;

    /* Set the request to scheduled even if scheduling fails. */
    pHttpsRequest->scheduled = true;

    taskPoolStatus = IotTaskPool_CreateJob( _sendHttpsRequest,
                                            ( void * ) ( pHttpsRequest ),
                                            &( pHttpsConnection->taskPoolJobStorage ),
                                            &( pHttpsConnection->taskPoolJob ) );

    /* Creating a task pool job should never fail when parameters are valid. */
    if( taskPoolStatus != IOT_TASKPOOL_SUCCESS )
    {
        IotLogError( "Error creating a taskpool job for request servicing. Error code: %d", taskPoolStatus );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INTERNAL_ERROR );
    }

    taskPoolStatus = IotTaskPool_Schedule( IOT_SYSTEM_TASKPOOL, pHttpsConnection->taskPoolJob, 0 );

    if( taskPoolStatus != IOT_TASKPOOL_SUCCESS )
    {
        IotLogError( "Failed to schedule taskpool job. Error code: %d", taskPoolStatus );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_ASYNC_SCHEDULING_ERROR );
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t _addRequestToConnectionReqQ( _httpsRequest_t * pHttpsRequest )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    _httpsConnection_t * pHttpsConnection = pHttpsRequest->pHttpsConnection;
    bool scheduleRequest = false;

    /* Log information about the request*/
    IotLogDebug( "Now queueing request %d.", pHttpsRequest );

    if( pHttpsRequest->isNonPersistent )
    {
        IotLogDebug( "Request %d is non-persistent.", pHttpsRequest );
    }
    else
    {
        IotLogDebug( "Request %d is persistent. ", pHttpsRequest );
    }

    if( pHttpsRequest->isAsync )
    {
        IotLogDebug( " Request %d is asynchronous.", pHttpsRequest );
    }
    else
    {
        IotLogDebug( " Request %d is synchronous.", pHttpsRequest );
    }

    /* This is a new request and has not been scheduled if this routine is called. */
    pHttpsRequest->scheduled = false;

    /* Place the request into the queue. */
    IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );

    /* If there is an active response, scheduling the next request at the same time may corrupt the workflow. Part of
     * the next response for the next request may be present in the currently receiving response's buffers. To avoid
     * this, check if there are pending responses to determine if this request should be scheduled right away or not.
     *
     * If there are other requests in the queue, and there are responses in the queue, then the network receive callback
     * will handle scheduling the next requests (or is already scheduled and currently sending). */
    if( ( IotDeQueue_IsEmpty( &( pHttpsConnection->reqQ ) ) ) &&
        ( IotDeQueue_IsEmpty( &( pHttpsConnection->respQ ) ) ) )
    {
        scheduleRequest = true;
    }

    /* Place into the connection's request to have a taskpool worker schedule to serve it later. */
    IotDeQueue_EnqueueTail( &( pHttpsConnection->reqQ ), &( pHttpsRequest->link ) );
    IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

    if( scheduleRequest )
    {
        /* This routine schedules a task pool worker to send the request. If a worker is available immediately, then
         * the request is sent right away. */
        status = _scheduleHttpsRequestSend( pHttpsRequest );

        if( HTTPS_FAILED( status ) )
        {
            IotLogError( "Failed to schedule the request in the queue for request %d. Error code: %d", pHttpsRequest, status );

            /* If we fail to schedule the only request in the queue we should remove it. */
            IotMutex_Lock( &( pHttpsConnection->connectionMutex ) );
            IotDeQueue_Remove( &( pHttpsRequest->link ) );
            IotMutex_Unlock( &( pHttpsConnection->connectionMutex ) );

            HTTPS_GOTO_CLEANUP();
        }
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static void _cancelRequest( _httpsRequest_t * pHttpsRequest )
{
    pHttpsRequest->cancelled = true;
}

/*-----------------------------------------------------------*/

static void _cancelResponse( _httpsResponse_t * pHttpsResponse )
{
    pHttpsResponse->cancelled = true;
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_Init( void )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    /* This sets all member in the _httpParserSettings to zero. It does not return any errors. */
    http_parser_settings_init( &_httpParserSettings );

    /* Set the http-parser callbacks. */
    _httpParserSettings.on_message_begin = _httpParserOnMessageBeginCallback;
    _httpParserSettings.on_status = _httpParserOnStatusCallback;
    _httpParserSettings.on_header_field = _httpParserOnHeaderFieldCallback;
    _httpParserSettings.on_header_value = _httpParserOnHeaderValueCallback;
    _httpParserSettings.on_headers_complete = _httpParserOnHeadersCompleteCallback;
    _httpParserSettings.on_body = _httpParserOnBodyCallback;
    _httpParserSettings.on_message_complete = _httpParserOnMessageCompleteCallback;

/* This code prints debugging information and is, therefore, compiled only when
 * log level is set to IOT_LOG_DEBUG. */
    #if ( LIBRARY_LOG_LEVEL == IOT_LOG_DEBUG )
        _httpParserSettings.on_chunk_header = _httpParserOnChunkHeaderCallback;
        _httpParserSettings.on_chunk_complete = _httpParserOnChunkCompleteCallback;
    #endif
    HTTPS_GOTO_CLEANUP();
    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

static IotHttpsReturnCode_t _initializeResponse( IotHttpsResponseHandle_t * pRespHandle,
                                                 IotHttpsResponseInfo_t * pRespInfo,
                                                 _httpsRequest_t * pHttpsRequest )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    _httpsResponse_t * pHttpsResponse = NULL;

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pRespInfo->userBuffer.pBuffer );

    /* Check of the user buffer is large enough for the response context + default headers. */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( pRespInfo->userBuffer.bufferLen >= responseUserBufferMinimumSize,
                                         IOT_HTTPS_INSUFFICIENT_MEMORY,
                                         "Buffer size is too small to initialize the response context. User buffer size: %d, required minimum size; %d.",
                                         pRespInfo->userBuffer.bufferLen,
                                         responseUserBufferMinimumSize );

    /* Initialize the corresponding response to this request. */
    pHttpsResponse = ( _httpsResponse_t * ) ( pRespInfo->userBuffer.pBuffer );

    /* Clear out the response user buffer. This is important because we
     * give the whole buffer to the parser as opposed to the actual content
     * length and rely on the parser to stop when a complete HTTP response
     * is found. To make sure that any data in the buffer which is not part
     * of the received HTTP response, does not get interpreted as part of
     * the HTTP repose, we zero out the buffer here. */
    memset( pRespInfo->userBuffer.pBuffer, 0, pRespInfo->userBuffer.bufferLen );

    pHttpsResponse->pHeaders = ( uint8_t * ) ( pHttpsResponse ) + sizeof( _httpsResponse_t );
    pHttpsResponse->pHeadersEnd = ( uint8_t * ) ( pHttpsResponse ) + pRespInfo->userBuffer.bufferLen;
    pHttpsResponse->pHeadersCur = pHttpsResponse->pHeaders;

    if( pHttpsRequest->isAsync )
    {
        pHttpsResponse->isAsync = true;

        /* For an asynchronous request the response body is provided by the application in the
         * IotHttpsCallbacks_t.readReadyCallback(). These pointers will be updated when IotHttpsClient_ReadResponseBody()
         * is invoked. */
        pHttpsResponse->pBody = NULL;
        pHttpsResponse->pBodyCur = NULL;
        pHttpsResponse->pBodyEnd = NULL;

        pHttpsResponse->pCallbacks = pHttpsRequest->pCallbacks;
        pHttpsResponse->pUserPrivData = pHttpsRequest->pUserPrivData;
    }
    else
    {
        pHttpsResponse->isAsync = false;
        /* The request body pointer is allowed to be NULL. u.pSyncInfo was checked for NULL earlier in this function. */
        pHttpsResponse->pBody = pRespInfo->pSyncInfo->pBody;
        pHttpsResponse->pBodyCur = pHttpsResponse->pBody;
        pHttpsResponse->pBodyEnd = pHttpsResponse->pBody + pRespInfo->pSyncInfo->bodyLen;

        /* Clear out the body bufffer. This is important because we give the
         * whole buffer to the parser as opposed to the actual content length and
         * rely on the parser to stop when a complete HTTP response is found. To
         * make sure that any data in the buffer which is not part of the received
         * HTTP response, does not get interpreted as part of the HTTP repose, we
         * zero out the buffer here. */
        memset( pRespInfo->pSyncInfo->pBody, 0, pRespInfo->pSyncInfo->bodyLen );
    }

    /* Reinitialize the parser and set the fill buffer state to empty. This does not return any errors. */
    http_parser_init( &( pHttpsResponse->httpParserInfo.responseParser ), HTTP_RESPONSE );
    http_parser_init( &( pHttpsResponse->httpParserInfo.readHeaderParser ), HTTP_RESPONSE );
    /* Set the third party http parser function. */
    pHttpsResponse->httpParserInfo.parseFunc = http_parser_execute;
    pHttpsResponse->httpParserInfo.readHeaderParser.data = ( void * ) ( pHttpsResponse );
    pHttpsResponse->httpParserInfo.responseParser.data = ( void * ) ( pHttpsResponse );

    pHttpsResponse->status = 0;
    pHttpsResponse->method = pHttpsRequest->method;
    pHttpsResponse->parserState = PARSER_STATE_NONE;
    pHttpsResponse->bufferProcessingState = PROCESSING_STATE_NONE;
    pHttpsResponse->pReadHeaderField = NULL;
    pHttpsResponse->readHeaderFieldLength = 0;
    pHttpsResponse->pReadHeaderValue = NULL;
    pHttpsResponse->readHeaderValueLength = 0;
    pHttpsResponse->foundHeaderField = 0;
    pHttpsResponse->pHttpsConnection = NULL;

    pHttpsResponse->pBodyInHeaderBuf = NULL;
    pHttpsResponse->pBodyCurInHeaderBuf = NULL;
    pHttpsResponse->bodyRxStatus = IOT_HTTPS_OK;
    pHttpsResponse->cancelled = false;
    pHttpsResponse->syncStatus = IOT_HTTPS_OK;
    /* There is no request associated with this response right now, so it is finished sending. */
    pHttpsResponse->reqFinishedSending = true;
    pHttpsResponse->isNonPersistent = pHttpsRequest->isNonPersistent;

    /* Set the response handle to return. */
    *pRespHandle = pHttpsResponse;

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    if( HTTPS_FAILED( status ) )
    {
        pRespHandle = NULL;
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

void IotHttpsClient_Cleanup( void )
{
    /* There is nothing to clean up here as of now. */
}

/* --------------------------------------------------------- */

IotHttpsReturnCode_t IotHttpsClient_Connect( IotHttpsConnectionHandle_t * pConnHandle,
                                             IotHttpsConnectionInfo_t * pConnInfo )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    /* Check for NULL parameters in a public API. */
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pConnHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pConnInfo );

    /* If a valid connection handle is passed in. */
    if( *pConnHandle != NULL )
    {
        /* If the handle in a connected state, then we want to disconnect before reconnecting. The ONLY way to put the
         * handle is a disconnect state is to call IotHttpsClient_Disconnect(). */
        if( ( *pConnHandle )->isConnected )
        {
            status = IotHttpsClient_Disconnect( *pConnHandle );

            if( HTTPS_FAILED( status ) )
            {
                IotLogError( "Error disconnecting a connected *pConnHandle passed to IotHttpsClient_Connect().Error code %d", status );
                *pConnHandle = NULL;
                HTTPS_GOTO_CLEANUP();
            }
        }
    }

    /* Connect to the server now. Initialize all resources needed for the connection context as well here. */
    status = _createHttpsConnection( pConnHandle, pConnInfo );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error in IotHttpsClient_Connect(). Error code %d.", status );
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_Disconnect( IotHttpsConnectionHandle_t connHandle )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    _httpsRequest_t * pHttpsRequest = NULL;
    _httpsResponse_t * pHttpsResponse = NULL;
    IotLink_t * pRespItem = NULL;
    IotLink_t * pReqItem = NULL;

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( connHandle );

    /* If this routine is currently is progress by another thread, for instance the taskpool worker that received a
     * network error after sending, then return right away because connection resources are being used. */
    if( IotMutex_TryLock( &( connHandle->connectionMutex ) ) == false )
    {
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_BUSY );
    }

    /* Do not attempt to disconnect an already disconnected connection.
     * It can happen when a user calls this functions and we return IOT_HTTPS_BUSY. */
    if( connHandle->isConnected )
    {
        /* Mark the network as disconnected whether the disconnect passes or not. */
        connHandle->isConnected = false;
        _networkDisconnect( connHandle );
    }

    /* If there is a response in the connection's response queue and the associated request has not finished sending,
     * then we cannot destroy the connection until it finishes. */
    pRespItem = IotDeQueue_DequeueHead( &( connHandle->respQ ) );

    if( pRespItem != NULL )
    {
        pHttpsResponse = IotLink_Container( _httpsResponse_t, pRespItem, link );

        if( pHttpsResponse->reqFinishedSending == false )
        {
            IotLogError( "Connection is in use. Disconnected, but cannot destroy the connection." );
            status = IOT_HTTPS_BUSY;

            /* The request is busy, to as quickly as possible allow a successful retry call of this function we must
             * cancel the busy request which is the first in the queue. */
            pReqItem = IotDeQueue_PeekHead( &( connHandle->reqQ ) );

            if( pReqItem != NULL )
            {
                pHttpsRequest = IotLink_Container( _httpsRequest_t, pReqItem, link );
                _cancelRequest( pHttpsRequest );
            }

            /* We set the status as busy, but we do not goto the cleanup right away because we still want to remove
             * all pending requests. */
        }

        /* Delete all possible pending responses. (This is defensive.) */
        IotDeQueue_RemoveAll( &( connHandle->respQ ), NULL, 0 );

        /* Put the response that was dequeued back so that the application can call this function again to check later
         * that is exited and marked itself as finished sending.
         * If during the last check and this check reqFinishedSending gets set to true, that is OK because on the next
         * call to this routine, the disconnect will succeed. */
        if( pHttpsResponse->reqFinishedSending == false )
        {
            IotDeQueue_EnqueueHead( &( connHandle->respQ ), pRespItem );
        }
    }

    /* Remove all pending requests. If this routine is called from the application context and there is a
     * network receive callback in process, this routine will wait in _networkDestroy until that routine returns.
     * If this is routine is called from the network receive callback context, then the destroy happens after the
     * network receive callback context returns. */
    IotDeQueue_RemoveAll( &( connHandle->reqQ ), NULL, 0 );

    /* Do not attempt to destroy an already destroyed connection. This can happen when the user calls this function and
     * IOT_HTTPS_BUSY is returned. */
    if( HTTPS_SUCCEEDED( status ) )
    {
        if( connHandle->isDestroyed == false )
        {
            connHandle->isDestroyed = true;
            _networkDestroy( connHandle );
        }
    }

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    /* This function is no longer in process, so disconnecting is no longer in process. This signals to the retry
     * on this function that it can proceed with the disconnecting activities. */
    if( connHandle != NULL )
    {
        IotMutex_Unlock( &( connHandle->connectionMutex ) );
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_InitializeRequest( IotHttpsRequestHandle_t * pReqHandle,
                                                       IotHttpsRequestInfo_t * pReqInfo )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    _httpsRequest_t * pHttpsRequest = NULL;
    size_t additionalLength = 0;
    size_t spaceLen = 1;
    char * pSpace = " ";
    size_t httpsMethodLen = 0;
    size_t httpsProtocolVersionLen = FAST_MACRO_STRLEN( HTTPS_PROTOCOL_VERSION );

    /* Check for NULL parameters in the public API. */
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pReqHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pReqInfo );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pReqInfo->userBuffer.pBuffer );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pReqInfo->pHost );

    if( pReqInfo->isAsync )
    {
        HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pReqInfo->u.pAsyncInfo );
    }
    else
    {
        HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pReqInfo->u.pSyncInfo );
    }

    /* Check of the user buffer is large enough for the request context + default headers. */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( pReqInfo->userBuffer.bufferLen >= requestUserBufferMinimumSize,
                                         IOT_HTTPS_INSUFFICIENT_MEMORY,
                                         "Buffer size is too small to initialize the request context. User buffer size: %d, required minimum size; %d.",
                                         pReqInfo->userBuffer.bufferLen,
                                         requestUserBufferMinimumSize );

    /* Set the request contet to the start of the userbuffer. */
    pHttpsRequest = ( _httpsRequest_t * ) ( pReqInfo->userBuffer.pBuffer );
    /* Clear out the user buffer. */
    memset( pReqInfo->userBuffer.pBuffer, 0, pReqInfo->userBuffer.bufferLen );

    /* Set the start of the headers to the end of the request context in the user buffer. */
    pHttpsRequest->pHeaders = ( uint8_t * ) pHttpsRequest + sizeof( _httpsRequest_t );
    pHttpsRequest->pHeadersEnd = ( uint8_t * ) pHttpsRequest + pReqInfo->userBuffer.bufferLen;
    pHttpsRequest->pHeadersCur = pHttpsRequest->pHeaders;

    /* Get the length of the HTTP method. */
    httpsMethodLen = strlen( _pHttpsMethodStrings[ pReqInfo->method ] );

    /* Add the request line to the header buffer. */
    additionalLength = httpsMethodLen +          \
                       spaceLen +                \
                       pReqInfo->pathLen +       \
                       spaceLen +                \
                       httpsProtocolVersionLen + \
                       HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH;

    if( ( additionalLength + pHttpsRequest->pHeadersCur ) > ( pHttpsRequest->pHeadersEnd ) )
    {
        IotLogError( "Request line does not fit into the request user buffer: \"%s %.*s HTTP/1.1\\r\\n\" . ",
                     _pHttpsMethodStrings[ pReqInfo->method ],
                     pReqInfo->pathLen,
                     pReqInfo->pPath );
        IotLogError( "The length needed is %d and the space available is %d.", additionalLength, pHttpsRequest->pHeadersEnd - pHttpsRequest->pHeadersCur );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INSUFFICIENT_MEMORY );
    }

    /* Write "<METHOD> <PATH> HTTP/1.1\r\n" to the start of the header space. */
    memcpy( pHttpsRequest->pHeadersCur, _pHttpsMethodStrings[ pReqInfo->method ], httpsMethodLen );
    pHttpsRequest->pHeadersCur += httpsMethodLen;
    memcpy( pHttpsRequest->pHeadersCur, pSpace, spaceLen );
    pHttpsRequest->pHeadersCur += spaceLen;

    if( pReqInfo->pPath == NULL )
    {
        pReqInfo->pPath = HTTPS_EMPTY_PATH;
        pReqInfo->pathLen = FAST_MACRO_STRLEN( HTTPS_EMPTY_PATH );
    }

    memcpy( pHttpsRequest->pHeadersCur, pReqInfo->pPath, pReqInfo->pathLen );
    pHttpsRequest->pHeadersCur += pReqInfo->pathLen;
    memcpy( pHttpsRequest->pHeadersCur, pSpace, spaceLen );
    pHttpsRequest->pHeadersCur += spaceLen;
    memcpy( pHttpsRequest->pHeadersCur, HTTPS_PROTOCOL_VERSION, httpsProtocolVersionLen );
    pHttpsRequest->pHeadersCur += httpsProtocolVersionLen;
    memcpy( pHttpsRequest->pHeadersCur, HTTPS_END_OF_HEADER_LINES_INDICATOR, HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH );
    pHttpsRequest->pHeadersCur += HTTPS_END_OF_HEADER_LINES_INDICATOR_LENGTH;

    /* Add the User-Agent header. */
    status = _addHeader( pHttpsRequest, HTTPS_USER_AGENT_HEADER, FAST_MACRO_STRLEN( HTTPS_USER_AGENT_HEADER ), IOT_HTTPS_USER_AGENT, FAST_MACRO_STRLEN( IOT_HTTPS_USER_AGENT ) );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Failed to write header to the request user buffer: \"User-Agent: %s\\r\\n\" . Error code: %d",
                     IOT_HTTPS_USER_AGENT,
                     status );
        HTTPS_GOTO_CLEANUP();
    }

    status = _addHeader( pHttpsRequest, HTTPS_HOST_HEADER, FAST_MACRO_STRLEN( HTTPS_HOST_HEADER ), pReqInfo->pHost, pReqInfo->hostLen );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Failed to write \"Host: %.*s\\r\\n\" to the request user buffer. Error code: %d",
                     pReqInfo->hostLen,
                     pReqInfo->pHost,
                     status );
        HTTPS_GOTO_CLEANUP();
    }

    if( pReqInfo->isAsync )
    {
        pHttpsRequest->isAsync = true;
        /* If this is an asynchronous request then save the callbacks to use. */
        pHttpsRequest->pCallbacks = &( pReqInfo->u.pAsyncInfo->callbacks );
        pHttpsRequest->pUserPrivData = pReqInfo->u.pAsyncInfo->pPrivData;
        /* The body pointer and body length will be filled in when the application sends data in the writeCallback. */
        pHttpsRequest->pBody = NULL;
        pHttpsRequest->bodyLength = 0;
    }
    else
    {
        pHttpsRequest->isAsync = false;
        /* Set the HTTP request entity body. This is allowed to be NULL for no body like for a GET request. */
        pHttpsRequest->pBody = pReqInfo->u.pSyncInfo->pBody;
        pHttpsRequest->bodyLength = pReqInfo->u.pSyncInfo->bodyLen;
    }

    /* Save the method of this request. */
    pHttpsRequest->method = pReqInfo->method;
    /* Set the connection persistence flag for keeping the connection open after receiving a response. */
    pHttpsRequest->isNonPersistent = pReqInfo->isNonPersistent;
    /* Initialize the request cancellation. */
    pHttpsRequest->cancelled = false;
    /* Initialize the status of sending the body over the network in a possible asynchronous request. */
    pHttpsRequest->bodyTxStatus = IOT_HTTPS_OK;
    /* This is a new request and therefore not scheduled yet. */
    pHttpsRequest->scheduled = false;

    /* Set the request handle to return. */
    *pReqHandle = pHttpsRequest;

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    if( HTTPS_FAILED( status ) && ( pReqHandle != NULL ) )
    {
        /* Set the request handle to return to NULL, if we failed anywhere. */
        *pReqHandle = NULL;
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_AddHeader( IotHttpsRequestHandle_t reqHandle,
                                               char * pName,
                                               uint32_t nameLen,
                                               char * pValue,
                                               uint32_t valueLen )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    /* Check for NULL pointer paramters. */
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pName );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pValue );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( reqHandle );

    /* Check for name long enough for header length calculation to overflow */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( nameLen <= ( UINT32_MAX >> 2 ),
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "Attempting to generate headers with name length %d > %d. This is not allowed.",
                                         nameLen, UINT32_MAX >> 2 );

    /* Check for value long enough for header length calculation to overflow */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( valueLen <= ( UINT32_MAX >> 2 ),
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "Attempting to generate headers with value length %d > %d. This is not allowed.",
                                         valueLen, UINT32_MAX >> 2 );

    /* Check for auto-generated header "Content-Length". This header is created and send automatically when right before
     * request body is sent on the network. */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( strncmp( pName, HTTPS_CONTENT_LENGTH_HEADER, FAST_MACRO_STRLEN( HTTPS_CONTENT_LENGTH_HEADER ) ) != 0,
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "Attempting to add auto-generated header %s. This is not allowed.",
                                         HTTPS_CONTENT_LENGTH_HEADER );

    /* Check for auto-generated header "Connection". This header is created and send automatically when right before
     * request body is sent on the network. */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( strncmp( pName, HTTPS_CONNECTION_HEADER, FAST_MACRO_STRLEN( HTTPS_CONNECTION_HEADER ) ) != 0,
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "Attempting to add auto-generated header %s. This is not allowed.",
                                         HTTPS_CONNECTION_HEADER );

    /* Check for auto-generated header "Host". This header is created and placed into the header buffer space
     * in IotHttpsClient_InitializeRequest(). */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( strncmp( pName, HTTPS_HOST_HEADER, FAST_MACRO_STRLEN( HTTPS_HOST_HEADER ) ) != 0,
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "Attempting to add auto-generated header %s. This is not allowed.",
                                         HTTPS_HOST_HEADER );

    /* Check for auto-generated header "User-Agent". This header is created and placed into the header buffer space
     * in IotHttpsClient_InitializeRequest(). */
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( strncmp( pName, HTTPS_USER_AGENT_HEADER, FAST_MACRO_STRLEN( HTTPS_USER_AGENT_HEADER ) ) != 0,
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "Attempting to add auto-generated header %s. This is not allowed.",
                                         HTTPS_USER_AGENT_HEADER );


    status = _addHeader( reqHandle, pName, nameLen, pValue, valueLen );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Error in IotHttpsClient_AddHeader(), error code %d.", status );
        HTTPS_GOTO_CLEANUP();
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_SendSync( IotHttpsConnectionHandle_t connHandle,
                                              IotHttpsRequestHandle_t reqHandle,
                                              IotHttpsResponseHandle_t * pRespHandle,
                                              IotHttpsResponseInfo_t * pRespInfo,
                                              uint32_t timeoutMs )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    bool respFinishedSemCreated = false;
    _httpsResponse_t * pHttpsResponse = NULL;

    /* Parameter checks. */
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( connHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( reqHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pRespHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pRespInfo );
    /* Stop the application from scheduling requests on a closed connection. */
    HTTPS_ON_ARG_ERROR_GOTO_CLEANUP( connHandle->isConnected );

    /* If an asynchronous request/response is configured, that is invalid for this API. */
    if( reqHandle->isAsync )
    {
        IotLogError( "Called IotHttpsClient_SendSync on an asynchronous configured request." );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INVALID_PARAMETER );
    }

    /* Initialize the response handle to return. */
    status = _initializeResponse( pRespHandle, pRespInfo, reqHandle );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Failed to initialize the response on the synchronous request %d.", reqHandle );
        HTTPS_GOTO_CLEANUP();
    }

    /* Set the internal response to use. */
    pHttpsResponse = *pRespHandle;

    /* The implicit connection passed and we need to the set the connection handle in the request and response. */
    reqHandle->pHttpsConnection = connHandle;
    pHttpsResponse->pHttpsConnection = connHandle;

    /* Create the semaphore used to wait on the response to finish being received. */
    respFinishedSemCreated = IotSemaphore_Create( &( pHttpsResponse->respFinishedSem ), 0 /* initialValue */, 1 /* maxValue */ );

    if( respFinishedSemCreated == false )
    {
        IotLogError( "Failed to create an internal semaphore." );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INTERNAL_ERROR );
    }

    /* Associate the response to the request so that we can schedule it to be received when the request gets scheduled to send. */
    reqHandle->pHttpsResponse = pHttpsResponse;

    /* Schedule this request to be sent by adding it to the connection's request queue. */
    status = _addRequestToConnectionReqQ( reqHandle );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Failed to schedule the synchronous request. Error code: %d", status );
        HTTPS_GOTO_CLEANUP();
    }

    /* Wait for the request to finish. */
    if( timeoutMs == 0 )
    {
        IotSemaphore_Wait( &( pHttpsResponse->respFinishedSem ) );
    }
    else
    {
        if( IotSemaphore_TimedWait( &( pHttpsResponse->respFinishedSem ), timeoutMs ) == false )
        {
            IotLogError( "Timed out waiting for the synchronous request to finish. Timeout ms: %d", timeoutMs );
            _cancelRequest( reqHandle );
            HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_TIMEOUT_ERROR );
        }
    }

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    if( respFinishedSemCreated )
    {
        IotSemaphore_Destroy( &( pHttpsResponse->respFinishedSem ) );
    }

    /* If the syncStatus is anything other than IOT_HTTPS_OK, then the request was scheduled. */
    if( ( pHttpsResponse != NULL ) && HTTPS_FAILED( pHttpsResponse->syncStatus ) )
    {
        status = pHttpsResponse->syncStatus;
    }

    if( HTTPS_FAILED( status ) )
    {
        if( pRespHandle != NULL )
        {
            *pRespHandle = NULL;
        }

        IotLogError( "IotHttpsClient_SendSync() failed." );
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_WriteRequestBody( IotHttpsRequestHandle_t reqHandle,
                                                      uint8_t * pBuf,
                                                      uint32_t len,
                                                      int isComplete )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( reqHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pBuf );

    /* This function is not valid for a synchronous response. Applications need to configure the request body in
     * IotHttpsRequestInfo_t.pSyncInfo_t.reqData before calling IotHttpsClient_SendSync(). */
    HTTPS_ON_ARG_ERROR_GOTO_CLEANUP( reqHandle->isAsync );
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( isComplete == 1,
                                         IOT_HTTPS_NOT_SUPPORTED,
                                         "isComplete must be 1 in IotHttpsClient_WriteRequestBody() for the current version of the HTTPS Client library." );

    /* If the bodyLength is greater than 0, then we already called this function and we need to enforce that this
     * function must only be called once. We only call this function once so that we can calculate the Content-Length. */
    if( reqHandle->bodyLength > 0 )
    {
        IotLogError( "Error this function must be called once with the data needed to send. Variable length HTTP "
                     "request body is not supported in this library." );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_MESSAGE_FINISHED );
    }

    /* Set the pointer to the body and the length for the content-length calculation. */
    reqHandle->pBody = ( uint8_t * ) pBuf;
    reqHandle->bodyLength = len;

    /* We send the HTTPS headers and body in this function so that the application has the freedom to specify a body
     * that may be buffer on stack. */
    status = _sendHttpsHeadersAndBody( reqHandle->pHttpsConnection, reqHandle );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Failed to send the headers and body. Error code %d.", status );
        HTTPS_GOTO_CLEANUP();
    }

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    if( reqHandle != NULL )
    {
        reqHandle->bodyTxStatus = status;
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_ReadResponseBody( IotHttpsResponseHandle_t respHandle,
                                                      uint8_t * pBuf,
                                                      uint32_t * pLen )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    uint32_t bodyLengthInHeaderBuf = 0;

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( respHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pBuf );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pLen );
    HTTPS_ON_ARG_ERROR_GOTO_CLEANUP( respHandle->isAsync );

    /* Set the current body in the respHandle to use in _receiveHttpsBody(). _receiveHttpsBody is generic
     *  to both async and sync request/response handling. In the sync version the body is configured during
     *  initializing the request. In the async version the body is given in this function on the fly. */
    respHandle->pBody = pBuf;
    respHandle->pBodyCur = respHandle->pBody;
    respHandle->pBodyEnd = respHandle->pBodyCur + *pLen;

    /* When there is part of the body in the header pBuffer. We need to move that data to this body pBuffer
     * provided in this function. */
    bodyLengthInHeaderBuf = respHandle->pBodyCurInHeaderBuf - respHandle->pBodyInHeaderBuf;

    if( bodyLengthInHeaderBuf > 0 )
    {
        uint32_t copyLength = bodyLengthInHeaderBuf > *pLen ? *pLen : bodyLengthInHeaderBuf;
        memcpy( respHandle->pBodyCur, respHandle->pBodyInHeaderBuf, copyLength );
        respHandle->pBodyCur += copyLength;

        /* This function may be called multiple times until all of the body that may be present in the header buffer is
         * moved out. */
        respHandle->pBodyInHeaderBuf += copyLength;
    }

    /* If there is room in the body buffer just provided by the application and we have not completed the current
     * HTTP response message, then try to receive more body. */
    if( ( ( respHandle->pBodyEnd - respHandle->pBodyCur ) > 0 ) && ( respHandle->parserState < PARSER_STATE_BODY_COMPLETE ) )
    {
        status = _receiveHttpsBody( respHandle->pHttpsConnection, respHandle );

        if( HTTPS_FAILED( status ) )
        {
            IotLogError( "Failed to receive the HTTP response body on the network. Error code: %d.", status );
            HTTPS_GOTO_CLEANUP();
        }
    }

    *pLen = respHandle->pBodyCur - respHandle->pBody;

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    if( respHandle != NULL )
    {
        respHandle->bodyRxStatus = status;
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_CancelRequestAsync( IotHttpsRequestHandle_t reqHandle )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( reqHandle );

    _cancelRequest( reqHandle );

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_CancelResponseAsync( IotHttpsResponseHandle_t respHandle )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( respHandle );

    _cancelResponse( respHandle );

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}


/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_SendAsync( IotHttpsConnectionHandle_t connHandle,
                                               IotHttpsRequestHandle_t reqHandle,
                                               IotHttpsResponseHandle_t * pRespHandle,
                                               IotHttpsResponseInfo_t * pRespInfo )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( connHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( reqHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pRespHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pRespInfo );
    HTTPS_ON_ARG_ERROR_GOTO_CLEANUP( reqHandle->isAsync );
    /* Stop the application from scheduling requests on a closed connection. */
    HTTPS_ON_ARG_ERROR_GOTO_CLEANUP( connHandle->isConnected );

    /* Initialize the response handle to return. */
    status = _initializeResponse( pRespHandle, pRespInfo, reqHandle );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Failed to initialize the response on the synchronous request %d.", reqHandle );
        HTTPS_GOTO_CLEANUP();
    }

    /* Set the connection handle in the request handle so that we can use it in the _writeRequestBody() callback. */
    reqHandle->pHttpsConnection = connHandle;

    /* Set the connection handle in the response handle sp that we can use it in the _readReadyCallback() callback. */
    ( *pRespHandle )->pHttpsConnection = connHandle;

    /* Associate the response to the request so that we can schedule it to be received when the request gets scheduled to send. */
    reqHandle->pHttpsResponse = *pRespHandle;

    /* Add the request to the connection's request queue. */
    status = _addRequestToConnectionReqQ( reqHandle );

    if( HTTPS_FAILED( status ) )
    {
        IotLogError( "Failed to add request %d to the connection's request queue. Error code: %d.", reqHandle, status );
        HTTPS_GOTO_CLEANUP();
    }

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_ReadResponseStatus( IotHttpsResponseHandle_t respHandle,
                                                        uint16_t * pStatus )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( respHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pStatus );

    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( respHandle->status != 0,
                                         IOT_HTTPS_NOT_FOUND,
                                         "The HTTP response status was not found in the HTTP response header buffer." );

    *pStatus = respHandle->status;

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_ReadHeader( IotHttpsResponseHandle_t respHandle,
                                                char * pName,
                                                uint32_t nameLen,
                                                char * pValue,
                                                uint32_t valueLen )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    const char * pHttpParserErrorDescription = NULL;
    IotHttpsResponseBufferState_t savedBufferState = PROCESSING_STATE_NONE;
    IotHttpsResponseParserState_t savedParserState = PARSER_STATE_NONE;
    size_t numParsed = 0;

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( respHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pName );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pValue );
    HTTPS_ON_ARG_ERROR_MSG_GOTO_CLEANUP( valueLen > 0,
                                         IOT_HTTPS_INVALID_PARAMETER,
                                         "pValue has insufficient space to store a value string (length is 0)" );

    /* The buffer processing state is changed to searching the header buffer in this function. The parser state is
    * changed in the response to wherever the parser is currently located in the response. If this function is called
    * in the middle of processing a response (for example in readReadyCallback() routine of an asynchronous response),
    * then parsing the response need to be able to start at the same place it was before calling this function. */
    savedBufferState = respHandle->bufferProcessingState;
    savedParserState = respHandle->parserState;

    /* The header search parameters in the response handle are used as context in the http-parser callbacks. During
     * the callback, pReadHeaderField is checked against the currently parsed header name. foundHeaderField is set to
     * true when the pReadHeaderField is found in a header field callback. The bufferProcessingState tells the callback
     * to skip the logic pertaining to when the response is being parsed for the first time. pReadHeaderValue will store
     * the header value found. readHeaderValueLength will store the length of the header value found from within the
     * response headers. */
    respHandle->pReadHeaderField = pName;
    respHandle->readHeaderFieldLength = nameLen;
    respHandle->foundHeaderField = false;
    respHandle->bufferProcessingState = PROCESSING_STATE_SEARCHING_HEADER_BUFFER;
    respHandle->pReadHeaderValue = NULL;
    respHandle->readHeaderValueLength = 0;

    /* Start over the HTTP parser so that it will parser from the beginning of the message. */
    http_parser_init( &( respHandle->httpParserInfo.readHeaderParser ), HTTP_RESPONSE );

    IotLogDebug( "Now parsing HTTP Message buffer to read a header." );
    numParsed = respHandle->httpParserInfo.parseFunc( &( respHandle->httpParserInfo.readHeaderParser ), &_httpParserSettings, ( char * ) ( respHandle->pHeaders ), respHandle->pHeadersCur - respHandle->pHeaders );
    IotLogDebug( "Parsed %d characters in IotHttpsClient_ReadHeader().", numParsed );

    /* There shouldn't be any errors parsing the response body given that the handle is from a validly
     * received response, so this check is defensive. If there were errors parsing the original response headers, then
     * the response handle would have been invalidated and the connection closed. */
    if( ( respHandle->httpParserInfo.readHeaderParser.http_errno != 0 ) &&
        ( HTTP_PARSER_ERRNO( &( respHandle->httpParserInfo.readHeaderParser ) ) > HPE_CB_chunk_complete ) )
    {
        pHttpParserErrorDescription = http_errno_description( HTTP_PARSER_ERRNO( &( respHandle->httpParserInfo.readHeaderParser ) ) );
        IotLogError( "http_parser failed on the http response with error: %s", pHttpParserErrorDescription );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_PARSING_ERROR );
    }

    /* Not only do we need an indication that the header field was found, but also that the value was found as well.
     * The value is found when it is non-NULL. The case where the header field is found, but the value is not found
     * occurs when there are incomplete headers stored in the header buffer. The header buffer could end with a header
     * field name. */
    if( respHandle->foundHeaderField && ( respHandle->pReadHeaderValue != NULL ) )
    {
        /* The len of the pValue buffer must account for the NULL terminator. */
        if( respHandle->readHeaderValueLength > ( valueLen - 1 ) )
        {
            IotLogError( "IotHttpsClient_ReadHeader(): The length of the pValue buffer specified is less than the actual length of the pValue. " );
            HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_INSUFFICIENT_MEMORY );
        }
        else
        {
            memcpy( pValue, respHandle->pReadHeaderValue, respHandle->readHeaderValueLength );
            pValue[ respHandle->readHeaderValueLength ] = '\0';
        }
    }
    else
    {
        IotLogWarn( "IotHttpsClient_ReadHeader(): The header field %s was not found.", pName );
        HTTPS_SET_AND_GOTO_CLEANUP( IOT_HTTPS_NOT_FOUND );
    }

    HTTPS_FUNCTION_CLEANUP_BEGIN();

    /* Always restore the state back to what it was before entering this function. */
    if( respHandle != NULL )
    {
        respHandle->bufferProcessingState = savedBufferState;
        respHandle->parserState = savedParserState;
    }

    HTTPS_FUNCTION_CLEANUP_END();
}

/*-----------------------------------------------------------*/

IotHttpsReturnCode_t IotHttpsClient_ReadContentLength( IotHttpsResponseHandle_t respHandle,
                                                       uint32_t * pContentLength )
{
    HTTPS_FUNCTION_ENTRY( IOT_HTTPS_OK );

    const int CONTENT_LENGTH_NUMBERIC_BASE = 10;
    char pContentLengthStr[ HTTPS_MAX_CONTENT_LENGTH_LINE_LENGTH ] = { 0 };

    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( respHandle );
    HTTPS_ON_NULL_ARG_GOTO_CLEANUP( pContentLength );

    /* If there is no content-length header or if we were not able to store it in the header buffer this will be
     * invalid. We do not use the content-length member of the http-parser state structure to get the content
     * length as this is a PRIVATE member. Because it is a PRIVATE member it can be any value. */
    status = IotHttpsClient_ReadHeader( respHandle, HTTPS_CONTENT_LENGTH_HEADER, FAST_MACRO_STRLEN( HTTPS_CONTENT_LENGTH_HEADER ), pContentLengthStr, HTTPS_MAX_CONTENT_LENGTH_LINE_LENGTH );

    if( HTTPS_FAILED( status ) )
    {
        *pContentLength = 0;
        IotLogError( "Could not read the Content-Length for the response." );
        HTTPS_GOTO_CLEANUP();
    }

    *pContentLength = strtoul( pContentLengthStr, NULL, CONTENT_LENGTH_NUMBERIC_BASE );

    HTTPS_FUNCTION_EXIT_NO_CLEANUP();
}

/*-----------------------------------------------------------*/

/* Provide access to internal functions and variables if testing. */
#if IOT_BUILD_TESTS == 1
    #include "iot_test_access_https_client.c"
#endif