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diff --git a/docs/source/memcached_get.rst b/docs/source/memcached_get.rst new file mode 100644 index 00000000..59309669 --- /dev/null +++ b/docs/source/memcached_get.rst @@ -0,0 +1,131 @@ +=============================== +Retrieving data from the server +=============================== + +.. index:: object: memcached_st + +-------- +SYNOPSIS +-------- + + +#include <libmemcached/memcached.h> + +.. c:function:: memcached_result_st * memcached_fetch_result (memcached_st *ptr, memcached_result_st *result, memcached_return_t *error) + +.. c:function:: char * memcached_get (memcached_st *ptr, const char *key, size_t key_length, size_t *value_length, uint32_t *flags, memcached_return_t *error) + +.. c:function:: memcached_return_t memcached_mget (memcached_st *ptr, const char * const *keys, const size_t *key_length, size_t number_of_keys) + +.. c:function:: char * memcached_get_by_key (memcached_st *ptr, const char *group_key, size_t group_key_length, const char *key, size_t key_length, size_t *value_length, uint32_t *flags, memcached_return_t *error) + +.. c:function:: memcached_return_t memcached_mget_by_key (memcached_st *ptr, const char *group_key, size_t group_key_length, const char * const *keys, const size_t *key_length, size_t number_of_keys) + +.. c:function:: memcached_return_t memcached_fetch_execute (memcached_st *ptr, memcached_execute_fn *callback, void *context, uint32_t number_of_callbacks) + +.. c:function:: memcached_return_t memcached_mget_execute (memcached_st *ptr, const char * const *keys, const size_t *key_length, size_t number_of_keys, memcached_execute_fn *callback, void *context, uint32_t number_of_callbacks) + +.. c:function:: memcached_return_t memcached_mget_execute_by_key (memcached_st *ptr, const char *group_key, size_t group_key_length, const char * const *keys, const size_t *key_length, size_t number_of_keys, memcached_execute_fn *callback, void *context, uint32_t number_of_callbacks) + +.. c:type:: memcached_return_t (*memcached_execute_fn)(const memcached_st *ptr, memcached_result_st *result, void *context) + +Compile and link with -lmemcached + + +----------- +DESCRIPTION +----------- + + +:c:func:`memcached_get` is used to fetch an individual value from the server. +You must pass in a key and its length to fetch the object. You must supply +three pointer variables which will give you the state of the returned +object. A :c:type:`uint32_t` pointer to contain whatever flags you stored with the value, a :c:type:`size_t` pointer which will be filled with size of of +the object, and a :c:type:`memcached_return_t` pointer to hold any error. The +object will be returned upon success and NULL will be returned on failure. Any +object returned by :c:func:`memcached_get` must be released by the caller +application. + +:c:func:`memcached_mget` is used to select multiple keys at once. For +multiple key operations it is always faster to use this function. This function always works asynchronously. + +To retrieve data after a successful execution of :c:func:`memcached_mget`, you will need to +call :c:func:`memcached_fetch_result`. You should continue to call this function until +it returns a NULL (i.e. no more values). If you need to quit in the middle of a +:c:func:`memcached_mget` call, you can execute a :c:func:`memcached_quit`, those this is not required. + +:c:func:`memcached_fetch_result` is used to fetch an individual value from the server. :c:func:`memcached_mget` must always be called before using this method. +You must pass in a key and its length to fetch the object. You must supply +three pointer variables which will give you the state of the returned +object. A :c:type:`uint32_t` pointer to contain whatever flags you stored with the value, a :c:type:`size_t` pointer which will be filled with size of of the +object, and a :c:type:`memcached_return_t` pointer to hold any error. The +object will be returned upon success and NULL will be returned on failure. :c:type:`MEMCACHED_END` is returned by the \*error value when all objects that have been found are returned. The final value upon :c:type:`MEMCACHED_END` is null. + +:c:func:`memcached_fetch_result` is used to return a :c:type:`memcached_result_st` structure from a memcached server. The result object is forward compatible +with changes to the server. For more information please refer to the +:c:type:`memcached_result_st` help. This function will dynamically allocate a +result structure for you if you do not pass one to the function. + +:c:func:`memcached_fetch_execute` is a callback function for result sets. +Instead of returning the results to you for processing, it passes each of the +result sets to the list of functions you provide. It passes to the function +a :c:type:`memcached_st` that can be cloned for use in the called +function (it can not be used directly). It also passes a result set which does +not need to be freed. Finally it passes a "context". This is just a pointer to +a memory reference you supply the calling function. Currently only one value +is being passed to each function call. In the future there will be an option +to allow this to be an array. + +:c:func:`memcached_mget_execute` and :c:func:`memcached_mget_execute_by_key` +is similar to :c:func:`memcached_mget`, but it may trigger the supplied +callbacks with result sets while sending out the queries. If you try to +perform a really large multiget with :c:func:`memcached_mget` you may +encounter a deadlock in the OS kernel (it will fail to write data to the +socket because the input buffer is full). :c:func:`memcached_mget_execute` +solves this problem by processing some of the results before continuing +sending out requests. Please note that this function is only available in +the binary protocol. + +:c:func:`memcached_get_by_key` and :c:func:`memcached_mget_by_key` behave +in a similar nature as :c:func:`memcached_get` and :c:func:`memcached_mget`. +The difference is that they take a master key that is used for determining +which server an object was stored if key partitioning was used for storage. + +All of the above functions are not tested when the +:c:type:`MEMCACHED_BEHAVIOR_USE_UDP` has been set. Executing any of these +functions with this behavior on will result in :c:type:`MEMCACHED_NOT_SUPPORTED` being returned, or for those functions which do not return a :c:type:`memcached_return_t`, the error function parameter will be set to :c:type:`MEMCACHED_NOT_SUPPORTED`. + + +------ +RETURN +------ + + +All objects retrieved via :c:func:`memcached_get` or :c:func:`memcached_get_by_key` must be freed with :manpage:`free(3)`. + +:c:func:`memcached_get` will return NULL on +error. You must look at the value of error to determine what the actual error +was. + +:c:func:`memcached_fetch_execute` return :c:type:`MEMCACHED_SUCCESS` if +all keys were successful. :c:type:`MEMCACHED_NOTFOUND` will be return if no +keys at all were found. + +:c:func:`memcached_fetch_result` sets error +to :c:type:`MEMCACHED_END` upon successful conclusion. +:c:type:`MEMCACHED_NOTFOUND` will be return if no keys at all were found. + +---- +HOME +---- + + +To find out more information please check: +`http://libmemcached.org/ <http://libmemcached.org/>`_ + + +-------- +SEE ALSO +-------- + +:manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)` |