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 :c:func:`memcached_callback_get()` takes a callback flag and returns the
  34 structure or function set by :c:func:`memcached_callback_set()`.
  35
  36 :c:func:`memcached_callback_set()` changes the function/structure assigned by a
  37 callback flag. No connections are reset.
  38
  39 You can use :c:type:`MEMCACHED_CALLBACK_USER_DATA` to provide custom context
  40 if required for any of the callbacks.
  41
  42
  43 .. c:var:: MEMCACHED_CALLBACK_CLEANUP_FUNCTION
  44
  45 When :c:func:`memcached_delete()` is called this function will be excuted. At
  46 the point of its execution all connections are closed.
  47
  48
  49
  50 .. c:var:: MEMCACHED_CALLBACK_CLONE_FUNCTION
  51
  52 When :c:func:`memcached_delete()` is called this function will be excuted.
  53 At the point of its execution all connections are closed.
  54
  55
  56
  57 .. c:var:: MEMCACHED_CALLBACK_PREFIX_KEY
  58
  59 You can set a value which will be used to create a domain for your keys.
  60 The value specified here will be prefixed to each of your keys. The value can
  61 not be greater then :c:type:`MEMCACHED_PREFIX_KEY_MAX_SIZE - 1` and will
  62 reduce :c:type:`MEMCACHED_MAX_KEY` by the value of your key.
  63
  64 The prefix key is only applied to the primary key, not the master key.
  65 :c:type:`MEMCACHED_FAILURE` will be returned if no key is set. In the case of
  66 a key which is too long, :c:type:`MEMCACHED_BAD_KEY_PROVIDED` will be returned.
  67
  68 If you set a value with the value being NULL then the prefix key is disabled.
  69
  70
  71 .. c:var:: MEMCACHED_CALLBACK_USER_DATA
  72
  73 This allows you to store a pointer to a specifc piece of data. This can be
  74 retrieved from inside of :c:func:`memcached_fetch_execute()`. Cloning a
  75 :c:type:`memcached_st` will copy the pointer to the clone.
  76
  77
  78
  79 .. c:var:: MEMCACHED_CALLBACK_MALLOC_FUNCTION
  80
  81 DEPRECATED: use :c:type:`memcached_set_memory_allocators` instead.
  82
  83
  84
  85 .. c:var:: MEMCACHED_CALLBACK_REALLOC_FUNCTION
  86
  87 DEPRECATED: use :c:type:`memcached_set_memory_allocators` instead.
  88
  89
  90
  91 .. c:var:: MEMCACHED_CALLBACK_FREE_FUNCTION
  92
  93 DEPRECATED: use :c:type:`memcached_set_memory_allocators` instead.
  94
  95
  96
  97 .. c:var:: MEMCACHED_CALLBACK_GET_FAILURE
  98
  99 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
 100
 101 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.
 102
 103 You must clone the :c:type:`memcached_st` in order to
 104 make use of it. The value will be stored only if you return
 105 :c:type:`MEMCACHED_SUCCESS` or :c:type:`MEMCACHED_BUFFERED`. Returning
 106 :c:type:`MEMCACHED_BUFFERED` will cause the object to be buffered and not sent
 107 immediatly (if this is the default behavior based on your connection setup
 108 this will happen automatically).
 109
 110 The prototype for this is:
 111
 112 .. c:function:: memcached_return_t (\*memcached_trigger_key)(memcached_st \*ptr, char \*key, size_t key_length, memcached_result_st \*result);
 113
 114
 115
 116 .. c:var:: MEMCACHED_CALLBACK_DELETE_TRIGGER
 117
 118 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.
 119
 120 The prototype for this is:
 121
 122 .. c:function:: typedef memcached_return_t (\*memcached_trigger_delete_key)(memcached_st \*ptr, char \*key, size_t key_length);
 123
 124
 125
 126
 127 ------
 128 RETURN
 129 ------
 130
 131
 132 :c:func:`memcached_callback_get()` return the function or structure that was
 133 provided. Upon error, nothing is set, null is returned, and the
 134 :c:type:`memcached_return_t` argument is set to :c:type:`MEMCACHED_FAILURE`.
 135
 136 :c:func:`memcached_callback_set()` returns :c:type:`MEMCACHED_SUCCESS` upon
 137 successful setting, otherwise :c:type:`MEMCACHED_FAILURE` on error.
 138
 139
 140 ----
 141 HOME
 142 ----
 143
 144
 145 To find out more information please check:
 146 `http://libmemcached.org/ <http://libmemcached.org/>`_
 147
 148
 149 ------
 150 AUTHOR
 151 ------
 152
 153
 154 Brian Aker, <brian@tangent.org>
 155
 156
 157 --------
 158 SEE ALSO
 159 --------
 160
 161
 162 :manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)`