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

   1 =head1 NAME
   2
   3 memcached_callback_get, memcached_callback_set - Get and set a callback
   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_return_t
  14     memcached_callback_set (memcached_st *ptr,
  15                             memcached_callback_t flag,
  16                             void *data);
  17
  18   void *
  19     memcached_callback_get (memcached_st *ptr,
  20                             memcached_callback_t flag,
  21                             memcached_return_t *error);
  22
  23 =head1 DESCRIPTION
  24
  25 libmemcached(3) can have callbacks set key execution points. These either
  26 provide function calls at points in the code, or return pointers to
  27 structures for particular usages.
  28
  29 memcached_callback_get() takes a callback flag and returns the structure or
  30 function set by memcached_callback_set().
  31
  32 memcached_callback_set() changes the function/structure assigned by a
  33 callback flag. No connections are reset.
  34
  35 You can use MEMCACHED_CALLBACK_USER_DATA to provide custom context if required for any
  36 of the callbacks
  37
  38 =over 4
  39
  40 =item MEMCACHED_CALLBACK_CLEANUP_FUNCTION
  41
  42 When memcached_delete() is called this function will be excuted. At the
  43 point of its execution all connections have been closed.
  44
  45 =item MEMCACHED_CALLBACK_CLONE_FUNCTION
  46
  47 When memcached_delete() is called this function will be excuted. At the
  48 point of its execution all connections have been closed.
  49
  50 =item MEMCACHED_CALLBACK_PREFIX_KEY
  51
  52 You can set a value which will be used to create a domain for your keys.
  53 The value specified here will be prefixed to each of your keys. The value can not
  54 be greater then MEMCACHED_PREFIX_KEY_MAX_SIZE - 1 and will reduce MEMCACHED_MAX_KEY by
  55 the value of your key. The prefix key is only applied to the primary key,
  56 not the master key. MEMCACHED_FAILURE will be returned if no key is set. In the case
  57 of a key which is too long MEMCACHED_BAD_KEY_PROVIDED will be returned.
  58
  59 =item MEMCACHED_CALLBACK_USER_DATA
  60
  61 This allows you to store a pointer to a specifc piece of data. This can be
  62 retrieved from inside of memcached_fetch_execute(). Cloning a memcached_st
  63 will copy the pointer to the clone.
  64
  65 =item  MEMCACHED_CALLBACK_MALLOC_FUNCTION
  66
  67 DEPRECATED: use memcached_set_memory_allocators instead.
  68
  69 =item  MEMCACHED_CALLBACK_REALLOC_FUNCTION
  70
  71 DEPRECATED: use memcached_set_memory_allocators instead.
  72
  73 =item  MEMCACHED_CALLBACK_FREE_FUNCTION
  74
  75 DEPRECATED: use memcached_set_memory_allocators instead.
  76
  77 =item  MEMCACHED_CALLBACK_GET_FAILURE
  78
  79 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
  80 You are responsible for populating the result object provided. This result object will then be stored in the server and
  81 returned to the calling process. You must clone the memcached_st in order to
  82 make use of it. The value will be stored only if you return
  83 MEMCACHED_SUCCESS or MEMCACHED_BUFFERED. Returning MEMCACHED_BUFFERED will
  84 cause the object to be buffered and not sent immediatly (if this is the default behavior based on your connection setup this will happen automatically).
  85
  86 The prototype for this is:
  87 memcached_return_t (*memcached_trigger_key)(memcached_st *ptr, char *key, size_t key_length, memcached_result_st *result);
  88
  89 =item  MEMCACHED_CALLBACK_DELETE_TRIGGER
  90
  91 This function implements a trigger upon successful deletion of a key. The memcached_st structure will need to be cloned
  92 in order to make use of it.
  93
  94 The prototype for this is:
  95 typedef memcached_return_t (*memcached_trigger_delete_key)(memcached_st *ptr, char *key, size_t key_length);
  96
  97
  98 =back
  99
 100 =head1 RETURN
 101
 102 memcached_callback_get() return the function or structure that was provided.
 103 Upon error, nothing is set, null is returned, and the memcached_return_t
 104 argument is set to MEMCACHED_FAILURE.
 105
 106 memcached_callback_set() returns MEMCACHED_SUCCESS upon successful setting,
 107 otherwise MEMCACHED_FAILURE on error.
 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