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

   1 =head1 NAME
   2
   3 memcached_get, memcached_mget, memcached_fetch
   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                        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                   unsigned int number_of_keys);
  28   char *
  29   memcached_get_by_key(memcached_st *ptr,
  30                        char *master_key, size_t master_key_length,
  31                        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                         char *master_key, size_t master_key_length,
  39                         char **keys, size_t *key_length,
  40                         unsigned int 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                           unsigned int (*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.
  62
  63 memcached_mget() is used to select multiple keys at once. For multiple key
  64 operations it is always faster to use this function. This function always
  65 works asynchronously. memcached_fetch() is then used to retrieve any keys
  66 found. No error is given on keys that are not found. You must call either
  67 memcached_fetch() or memcached_fetch_result() after a successful call to
  68 memcached_mget(). You should continue to call these functions until they
  69 return NULL (aka no more values). If you need to quit in the middle of a
  70 memcached_get() call, execute a memcached_quit(). After you do this, you can
  71 issue new queries against the server.
  72
  73 memcached_fetch() is used to fetch an individual value from the server.
  74 memcached_mget() must always be called before using this method.  You
  75 must pass in a key and its length to fetch the object. You must supply
  76 three pointer variables which will give you the state of the returned
  77 object.  A uint32_t pointer to contain whatever flags you stored with the value,
  78 a size_t pointer which will be filled with size of of the object, and a
  79 memcached_return pointer to hold any error. The object will be returned
  80 upon success and NULL will be returned on failure.
  81
  82 memcached_fetch_result() is used to return a memcached_result_st(3) structure
  83 from a memcached server. The result object is forward compatible with changes
  84 to the server. For more information please refer to the memcached_result_st(3)
  85 help. This function will dynamically allocate a result structure for you
  86 if you do not pass one to the function.
  87
  88 memcached_fetch_execute() is a callback function for result sets. Instead
  89 of returning the results to you for processing, it passes each of the
  90 result sets to the list of functions you provide. It passes to the function
  91 a memcached_st that can be cloned for use in called the cluster (it can not
  92 be used directly). It also passed a result set which does not need to be freed.
  93 Finally it passes a "context". This is just a pointer to a memory reference
  94 you supply the calling function. Currently only one value is being passed
  95 to each function call. In the future there will be an option to allow this
  96 to be an array.
  97
  98 memcached_get_by_key() and memcached_mget_by_key() behave in a similar nature
  99 as memcached_get() and memcached_mget(). The difference is that they take
 100 a master key that is used for determining which server an object was stored
 101 if key partitioning was used for storage.
 102
 103 =head1 RETURN
 104
 105 All objects returned must be freed by the calling application.
 106 memcached_get() and memcached_fetch() will return NULL on error. You must
 107 look at the value of error to determine what the actual error was.
 108
 109 =head1 HOME
 110
 111 To find out more information please check:
 112 L<http://tangent.org/552/libmemcached.html>
 113
 114 =head1 AUTHOR
 115
 116 Brian Aker, E<lt>brian@tangent.orgE<gt>
 117
 118 =head1 SEE ALSO
 119
 120 memcached(1) libmemcached(3) memcached_strerror(3)
 121
 122 =cut
 123