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

   1 =================
   2 Setting callbacks
   3 =================
   4
   5
   6 Get and set a callback
   7
   8
   9 -------
  10 LIBRARY
  11 -------
  12
  13
  14 C Client Library for memcached (libmemcached, -lmemcached)
  15
  16
  17 --------
  18 SYNOPSIS
  19 --------
  20
  21 #include <libmemcached/memcached.h>
  22
  23 .. c:function:: memcached_return_t memcached_callback_set (memcached_st *ptr, memcached_callback_t flag, void *data);
  24
  25 .. c:function:: void * memcached_callback_get (memcached_st *ptr, memcached_callback_t flag, memcached_return_t *error);
  26
  27
  28
  29 -----------
  30 DESCRIPTION
  31 -----------
  32
  33
  34 libmemcached(3) can have callbacks set key execution points. These either
  35 provide function calls at points in the code, or return pointers to
  36 structures for particular usages.
  37
  38 memcached_callback_get() takes a callback flag and returns the structure or
  39 function set by memcached_callback_set().
  40
  41 memcached_callback_set() changes the function/structure assigned by a
  42 callback flag. No connections are reset.
  43
  44 You can use MEMCACHED_CALLBACK_USER_DATA to provide custom context if required for any of the callbacks.
  45
  46
  47 .. c:var:: MEMCACHED_CALLBACK_CLEANUP_FUNCTION
  48
  49 When memcached_delete() is called this function will be excuted. At the point of its execution all connections are closed.
  50
  51
  52
  53 .. c:var:: MEMCACHED_CALLBACK_CLONE_FUNCTION
  54
  55 When memcached_delete() is called this function will be excuted. At the
  56 point of its execution all connections are closed.
  57
  58
  59
  60 .. c:var:: MEMCACHED_CALLBACK_PREFIX_KEY
  61
  62 You can set a value which will be used to create a domain for your keys.
  63 The value specified here will be prefixed to each of your keys. The value can not be greater then MEMCACHED_PREFIX_KEY_MAX_SIZE - 1 and will reduce MEMCACHED_MAX_KEY by the value of your key.
  64
  65 The prefix key is only applied to the primary key, not the master key. MEMCACHED_FAILURE will be returned if no key is set. In the case of a key which is too long, MEMCACHED_BAD_KEY_PROVIDED will be returned.
  66
  67 If you set a value with the value being NULL then the prefix key is disabled.
  68
  69
  70 .. c:var:: MEMCACHED_CALLBACK_USER_DATA
  71
  72 This allows you to store a pointer to a specifc piece of data. This can be
  73 retrieved from inside of memcached_fetch_execute(). Cloning a memcached_st
  74 will copy the pointer to the clone.
  75
  76
  77
  78 .. c:var:: MEMCACHED_CALLBACK_MALLOC_FUNCTION
  79
  80 DEPRECATED: use memcached_set_memory_allocators instead.
  81
  82
  83
  84 .. c:var:: MEMCACHED_CALLBACK_REALLOC_FUNCTION
  85
  86 DEPRECATED: use memcached_set_memory_allocators instead.
  87
  88
  89
  90 .. c:var:: MEMCACHED_CALLBACK_FREE_FUNCTION
  91
  92 DEPRECATED: use memcached_set_memory_allocators instead.
  93
  94
  95
  96 .. c:var:: MEMCACHED_CALLBACK_GET_FAILURE
  97
  98 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
  99
 100 You are responsible for populating the result object provided. This result object will then be stored in the server and returned to the calling process.
 101
 102 You must clone the memcached_st in order to
 103 make use of it. The value will be stored only if you return
 104 MEMCACHED_SUCCESS or MEMCACHED_BUFFERED. Returning MEMCACHED_BUFFERED will
 105 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).
 106
 107 The prototype for this is:
 108 memcached_return_t (\*memcached_trigger_key)(memcached_st \*ptr, char \*key, size_t key_length, memcached_result_st \*result);
 109
 110
 111
 112 .. c:var:: MEMCACHED_CALLBACK_DELETE_TRIGGER
 113
 114 This function implements a trigger upon successful deletion of a key. The memcached_st structure will need to be cloned in order to make use of it.
 115
 116 The prototype for this is: typedef memcached_return_t (\*memcached_trigger_delete_key)(memcached_st \*ptr, char \*key, size_t key_length);
 117
 118
 119
 120
 121 ------
 122 RETURN
 123 ------
 124
 125
 126 memcached_callback_get() return the function or structure that was provided.
 127 Upon error, nothing is set, null is returned, and the memcached_return_t
 128 argument is set to MEMCACHED_FAILURE.
 129
 130 memcached_callback_set() returns MEMCACHED_SUCCESS upon successful setting,
 131 otherwise MEMCACHED_FAILURE on error.
 132
 133
 134 ----
 135 HOME
 136 ----
 137
 138
 139 To find out more information please check:
 140 `http://libmemcached.org/ <http://libmemcached.org/>`_
 141
 142
 143 ------
 144 AUTHOR
 145 ------
 146
 147
 148 Brian Aker, <brian@tangent.org>
 149
 150
 151 --------
 152 SEE ALSO
 153 --------
 154
 155
 156 :manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)`