git.m6w6.name Git - m6w6/libmemcached/blob - docs/memcached_get.pod

   1 =head1 NAME
   2
   3 memcached_get, memcached_mget, memcached_fetch - Get a value
   4
   5 =head1 LIBRARY
   6
   7 C Client Library for memcached (libmemcached, -lmemcached)
   8
   9 =head1 SYNOPSIS
  10
  11   #include <memcached.h>
  12
  13   memcached_result_st *
  14   memcached_fetch_result(memcached_st *ptr,
  15                        memcached_result_st *result,
  16                        memcached_return *error);
  17
  18   char *memcached_get (memcached_st *ptr,
  19                        const char *key, size_t key_length,
  20                        size_t *value_length,
  21                        uint32_t *flags,
  22                        memcached_return *error);
  23
  24   memcached_return
  25   memcached_mget (memcached_st *ptr,
  26                   char **keys, size_t *key_length,
  27                   size_t number_of_keys);
  28   char *
  29   memcached_get_by_key(memcached_st *ptr,
  30                        const char *master_key, size_t master_key_length,
  31                        const char *key, size_t key_length,
  32                        size_t *value_length,
  33                        uint32_t *flags,
  34                        memcached_return *error);
  35
  36   memcached_return
  37   memcached_mget_by_key(memcached_st *ptr,
  38                         const char *master_key, size_t master_key_length,
  39                         char **keys, size_t *key_length,
  40                         size_t number_of_keys);
  41
  42   char *memcached_fetch (memcached_st *ptr,
  43                          char *key, size_t *key_length,
  44                          size_t *value_length,
  45                          uint32_t *flags,
  46                          memcached_return *error);
  47   memcached_return
  48   memcached_fetch_execute(memcached_st *ptr,
  49                           memcached_return (*callback[])(memcached_st *ptr, memcached_result_st *result, void *context),
  50                           void *context,
  51                           unsigned int number_of_callbacks);
  52
  53 =head1 DESCRIPTION
  54
  55 memcached_get() is used to fetch an individual value from the server. You
  56 must pass in a key and its length to fetch the object. You must supply
  57 three pointer variables which will give you the state of the returned
  58 object.  A uint32_t pointer to contain whatever flags you stored with the value,
  59 a size_t pointer which will be filled with size of of the object, and a
  60 memcached_return pointer to hold any error. The object will be returned
  61 upon success and NULL will be returned on failure. Any object returned by
  62 memcached_get() must be released by the caller application.
  63
  64 memcached_mget() is used to select multiple keys at once. For multiple key
  65 operations it is always faster to use this function. This function always
  66 works asynchronously. memcached_fetch() is then used to retrieve any keys
  67 found. No error is given on keys that are not found. You must call either
  68 memcached_fetch() or memcached_fetch_result() after a successful call to
  69 memcached_mget(). You should continue to call these functions until they
  70 return NULL (aka no more values). If you need to quit in the middle of a
  71 memcached_get() call, execute a memcached_quit(). After you do this, you can
  72 issue new queries against the server.
  73
  74 memcached_fetch() is used to fetch an individual value from the server.
  75 memcached_mget() must always be called before using this method.  You
  76 must pass in a key and its length to fetch the object. You must supply
  77 three pointer variables which will give you the state of the returned
  78 object.  A uint32_t pointer to contain whatever flags you stored with the value,
  79 a size_t pointer which will be filled with size of of the object, and a
  80 memcached_return pointer to hold any error. The object will be returned
  81 upon success and NULL will be returned on failure. MEMCACHD_END is returned
  82 by the *error value when all objects that have been found are returned.
  83 The final value upon MEMCACHED_END is null. Values returned by
  84 memcached_fetch() musted be free'ed by the caller.
  85
  86 memcached_fetch_result() is used to return a memcached_result_st(3) structure
  87 from a memcached server. The result object is forward compatible with changes
  88 to the server. For more information please refer to the memcached_result_st(3)
  89 help. This function will dynamically allocate a result structure for you
  90 if you do not pass one to the function.
  91
  92 memcached_fetch_execute() is a callback function for result sets. Instead
  93 of returning the results to you for processing, it passes each of the
  94 result sets to the list of functions you provide. It passes to the function
  95 a memcached_st that can be cloned for use in the called function (it can not
  96 be used directly). It also passes a result set which does not need to be freed.
  97 Finally it passes a "context". This is just a pointer to a memory reference
  98 you supply the calling function. Currently only one value is being passed
  99 to each function call. In the future there will be an option to allow this
 100 to be an array.
 101
 102 memcached_get_by_key() and memcached_mget_by_key() behave in a similar nature
 103 as memcached_get() and memcached_mget(). The difference is that they take
 104 a master key that is used for determining which server an object was stored
 105 if key partitioning was used for storage.
 106
 107 All of the above functions are not supported when the C<MEMCACHED_BEHAVIOR_USE_UDP>
 108 has been set. Executing any of these functions with this behavior on will result in
 109 C<MEMCACHED_NOT_SUPPORTED> being returned or, for those functions which do not return
 110 a C<memcached_return>, the error function parameter will be set to
 111 C<MEMCACHED_NOT_SUPPORTED>.
 112
 113 =head1 RETURN
 114
 115 All objects returned must be freed by the calling application.
 116 memcached_get() and memcached_fetch() will return NULL on error. You must
 117 look at the value of error to determine what the actual error was.
 118
 119 =head1 HOME
 120
 121 To find out more information please check:
 122 L<http://tangent.org/552/libmemcached.html>
 123
 124 =head1 AUTHOR
 125
 126 Brian Aker, E<lt>brian@tangent.orgE<gt>
 127
 128 =head1 SEE ALSO
 129
 130 memcached(1) libmemcached(3) memcached_strerror(3)
 131
 132 =cut
 133