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

   1 =================
   2 Setting callbacks
   3 =================
   4
   5
   6 Get and set a callback
   7
   8 .. index:: object: memcached_st
   9
  10
  11 --------
  12 SYNOPSIS
  13 --------
  14
  15 #include <libmemcached/memcached.h>
  16
  17 .. c:function:: memcached_return_t memcached_callback_set (memcached_st *ptr, memcached_callback_t flag, void *data);
  18
  19 .. c:function:: void * memcached_callback_get (memcached_st *ptr, memcached_callback_t flag, memcached_return_t *error);
  20
  21 Compile and link with -lmemcached
  22
  23
  24 -----------
  25 DESCRIPTION
  26 -----------
  27
  28
  29 libmemcached(3) can have callbacks set key execution points. These either
  30 provide function calls at points in the code, or return pointers to
  31 structures for particular usages.
  32
  33 memcached_callback_get() takes a callback flag and returns the structure or
  34 function set by memcached_callback_set().
  35
  36 memcached_callback_set() changes the function/structure assigned by a
  37 callback flag. No connections are reset.
  38
  39 You can use MEMCACHED_CALLBACK_USER_DATA to provide custom context if required for any of the callbacks.
  40
  41
  42 .. c:var:: MEMCACHED_CALLBACK_CLEANUP_FUNCTION
  43
  44 When memcached_delete() is called this function will be excuted. At the point of its execution all connections are closed.
  45
  46
  47
  48 .. c:var:: MEMCACHED_CALLBACK_CLONE_FUNCTION
  49
  50 When memcached_delete() is called this function will be excuted. At the
  51 point of its execution all connections are closed.
  52
  53
  54
  55 .. c:var:: MEMCACHED_CALLBACK_PREFIX_KEY
  56
  57 You can set a value which will be used to create a domain for your keys.
  58 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.
  59
  60 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.
  61
  62 If you set a value with the value being NULL then the prefix key is disabled.
  63
  64
  65 .. c:var:: MEMCACHED_CALLBACK_USER_DATA
  66
  67 This allows you to store a pointer to a specifc piece of data. This can be
  68 retrieved from inside of memcached_fetch_execute(). Cloning a memcached_st
  69 will copy the pointer to the clone.
  70
  71
  72
  73 .. c:var:: MEMCACHED_CALLBACK_MALLOC_FUNCTION
  74
  75 DEPRECATED: use memcached_set_memory_allocators instead.
  76
  77
  78
  79 .. c:var:: MEMCACHED_CALLBACK_REALLOC_FUNCTION
  80
  81 DEPRECATED: use memcached_set_memory_allocators instead.
  82
  83
  84
  85 .. c:var:: MEMCACHED_CALLBACK_FREE_FUNCTION
  86
  87 DEPRECATED: use memcached_set_memory_allocators instead.
  88
  89
  90
  91 .. c:var:: MEMCACHED_CALLBACK_GET_FAILURE
  92
  93 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
  94
  95 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.
  96
  97 You must clone the memcached_st in order to
  98 make use of it. The value will be stored only if you return
  99 MEMCACHED_SUCCESS or MEMCACHED_BUFFERED. Returning MEMCACHED_BUFFERED will
 100 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).
 101
 102 The prototype for this is:
 103 memcached_return_t (\*memcached_trigger_key)(memcached_st \*ptr, char \*key, size_t key_length, memcached_result_st \*result);
 104
 105
 106
 107 .. c:var:: MEMCACHED_CALLBACK_DELETE_TRIGGER
 108
 109 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.
 110
 111 The prototype for this is: typedef memcached_return_t (\*memcached_trigger_delete_key)(memcached_st \*ptr, char \*key, size_t key_length);
 112
 113
 114
 115
 116 ------
 117 RETURN
 118 ------
 119
 120
 121 memcached_callback_get() return the function or structure that was provided.
 122 Upon error, nothing is set, null is returned, and the memcached_return_t
 123 argument is set to MEMCACHED_FAILURE.
 124
 125 memcached_callback_set() returns MEMCACHED_SUCCESS upon successful setting,
 126 otherwise MEMCACHED_FAILURE on error.
 127
 128
 129 ----
 130 HOME
 131 ----
 132
 133
 134 To find out more information please check:
 135 `http://libmemcached.org/ <http://libmemcached.org/>`_
 136
 137
 138 ------
 139 AUTHOR
 140 ------
 141
 142
 143 Brian Aker, <brian@tangent.org>
 144
 145
 146 --------
 147 SEE ALSO
 148 --------
 149
 150
 151 :manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)`