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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// The wire protocol for HTTP's "chunked" Transfer-Encoding.
// This code is duplicated in httputil/chunked.go.
// Please make any changes in both files.
package http
import (
"bufio"
"bytes"
"errors"
"io"
"strconv"
)
const maxLineLength = 4096 // assumed <= bufio.defaultBufSize
var ErrLineTooLong = errors.New("header line too long")
// newChunkedReader returns a new chunkedReader that translates the data read from r
// out of HTTP "chunked" format before returning it.
// The chunkedReader returns io.EOF when the final 0-length chunk is read.
//
// newChunkedReader is not needed by normal applications. The http package
// automatically decodes chunking when reading response bodies.
func newChunkedReader(r io.Reader) io.Reader {
br, ok := r.(*bufio.Reader)
if !ok {
br = bufio.NewReader(r)
}
return &chunkedReader{r: br}
}
type chunkedReader struct {
r *bufio.Reader
n uint64 // unread bytes in chunk
err error
}
func (cr *chunkedReader) beginChunk() {
// chunk-size CRLF
var line string
line, cr.err = readLine(cr.r)
if cr.err != nil {
return
}
cr.n, cr.err = strconv.ParseUint(line, 16, 64)
if cr.err != nil {
return
}
if cr.n == 0 {
cr.err = io.EOF
}
}
func (cr *chunkedReader) Read(b []uint8) (n int, err error) {
if cr.err != nil {
return 0, cr.err
}
if cr.n == 0 {
cr.beginChunk()
if cr.err != nil {
return 0, cr.err
}
}
if uint64(len(b)) > cr.n {
b = b[0:cr.n]
}
n, cr.err = cr.r.Read(b)
cr.n -= uint64(n)
if cr.n == 0 && cr.err == nil {
// end of chunk (CRLF)
b := make([]byte, 2)
if _, cr.err = io.ReadFull(cr.r, b); cr.err == nil {
if b[0] != '\r' || b[1] != '\n' {
cr.err = errors.New("malformed chunked encoding")
}
}
}
return n, cr.err
}
// Read a line of bytes (up to \n) from b.
// Give up if the line exceeds maxLineLength.
// The returned bytes are a pointer into storage in
// the bufio, so they are only valid until the next bufio read.
func readLineBytes(b *bufio.Reader) (p []byte, err error) {
if p, err = b.ReadSlice('\n'); err != nil {
// We always know when EOF is coming.
// If the caller asked for a line, there should be a line.
if err == io.EOF {
err = io.ErrUnexpectedEOF
} else if err == bufio.ErrBufferFull {
err = ErrLineTooLong
}
return nil, err
}
if len(p) >= maxLineLength {
return nil, ErrLineTooLong
}
// Chop off trailing white space.
p = bytes.TrimRight(p, " \r\t\n")
return p, nil
}
// readLineBytes, but convert the bytes into a string.
func readLine(b *bufio.Reader) (s string, err error) {
p, e := readLineBytes(b)
if e != nil {
return "", e
}
return string(p), nil
}
// newChunkedWriter returns a new chunkedWriter that translates writes into HTTP
// "chunked" format before writing them to w. Closing the returned chunkedWriter
// sends the final 0-length chunk that marks the end of the stream.
//
// newChunkedWriter is not needed by normal applications. The http
// package adds chunking automatically if handlers don't set a
// Content-Length header. Using newChunkedWriter inside a handler
// would result in double chunking or chunking with a Content-Length
// length, both of which are wrong.
func newChunkedWriter(w io.Writer) io.WriteCloser {
return &chunkedWriter{w}
}
// Writing to chunkedWriter translates to writing in HTTP chunked Transfer
// Encoding wire format to the underlying Wire chunkedWriter.
type chunkedWriter struct {
Wire io.Writer
}
// Write the contents of data as one chunk to Wire.
// NOTE: Note that the corresponding chunk-writing procedure in Conn.Write has
// a bug since it does not check for success of io.WriteString
func (cw *chunkedWriter) Write(data []byte) (n int, err error) {
// Don't send 0-length data. It looks like EOF for chunked encoding.
if len(data) == 0 {
return 0, nil
}
head := strconv.FormatInt(int64(len(data)), 16) + "\r\n"
if _, err = io.WriteString(cw.Wire, head); err != nil {
return 0, err
}
if n, err = cw.Wire.Write(data); err != nil {
return
}
if n != len(data) {
err = io.ErrShortWrite
return
}
_, err = io.WriteString(cw.Wire, "\r\n")
return
}
func (cw *chunkedWriter) Close() error {
_, err := io.WriteString(cw.Wire, "0\r\n")
return err
}
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