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 .. 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, const 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:type:: 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:type:: 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 .. c:type:: MEMCACHED_CALLBACK_PREFIX_KEY
  56
  57    See :c:type:`MEMCACHED_CALLBACK_NAMESPACE`
  58
  59 .. c:type:: MEMCACHED_CALLBACK_NAMESPACE
  60
  61 You can set a value which will be used to create a domain for your keys.
  62 The value specified here will be prefixed to each of your keys. The value can
  63 not be greater then :c:type:`MEMCACHED_PREFIX_KEY_MAX_SIZE - 1` and will
  64 reduce :c:type:`MEMCACHED_MAX_KEY` by the value of your key.
  65
  66 The prefix key is only applied to the primary key, not the master key.
  67 :c:type:`MEMCACHED_FAILURE` will be returned if no key is set. In the case of
  68 a key which is too long, :c:type:`MEMCACHED_BAD_KEY_PROVIDED` will be returned.
  69
  70 If you set a value with the value being NULL then the prefix key is disabled.
  71
  72 .. c:type:: MEMCACHED_CALLBACK_USER_DATA
  73
  74 This allows you to store a pointer to a specifc piece of data. This can be
  75 retrieved from inside of :c:func:`memcached_fetch_execute()`. Cloning a
  76 :c:type:`memcached_st` will copy the pointer to the clone.
  77
  78 .. c:type:: MEMCACHED_CALLBACK_MALLOC_FUNCTION
  79 .. deprecated:: <0.32
  80    Use :c:type:`memcached_set_memory_allocators` instead.
  81
  82 .. c:type:: MEMCACHED_CALLBACK_REALLOC_FUNCTION
  83 .. deprecated:: <0.32
  84    Use :c:type:`memcached_set_memory_allocators` instead.
  85
  86 .. c:type:: MEMCACHED_CALLBACK_FREE_FUNCTION
  87 .. deprecated:: <0.32
  88    Use :c:type:`memcached_set_memory_allocators` instead.
  89
  90 .. c:type:: MEMCACHED_CALLBACK_GET_FAILURE
  91
  92 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
  93
  94 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.
  95
  96 You must clone the :c:type:`memcached_st` in order to
  97 make use of it. The value will be stored only if you return
  98 :c:type:`MEMCACHED_SUCCESS` or :c:type:`MEMCACHED_BUFFERED`. Returning
  99 :c:type:`MEMCACHED_BUFFERED` will cause the object to be buffered and not sent
 100 immediatly (if this is the default behavior based on your connection setup
 101 this will happen automatically).
 102
 103 The prototype for this is:
 104
 105 .. c:function:: memcached_return_t (\*memcached_trigger_key)(memcached_st \*ptr, char \*key, size_t key_length, memcached_result_st \*result);
 106
 107
 108
 109 .. c:type:: MEMCACHED_CALLBACK_DELETE_TRIGGER
 110
 111 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.
 112
 113 The prototype for this is:
 114
 115 .. c:function:: typedef memcached_return_t (\*memcached_trigger_delete_key)(memcached_st \*ptr, char \*key, size_t key_length);
 116
 117
 118
 119
 120 ------
 121 RETURN
 122 ------
 123
 124
 125 :c:func:`memcached_callback_get()` return the function or structure that was
 126 provided. Upon error, nothing is set, null is returned, and the
 127 :c:type:`memcached_return_t` argument is set to :c:type:`MEMCACHED_FAILURE`.
 128
 129 :c:func:`memcached_callback_set()` returns :c:type:`MEMCACHED_SUCCESS` upon
 130 successful setting, otherwise :c:type:`MEMCACHED_FAILURE` on error.
 131
 132
 133 ----
 134 HOME
 135 ----
 136
 137
 138 To find out more information please check:
 139 `http://libmemcached.org/ <http://libmemcached.org/>`_
 140
 141
 142 ------
 143 AUTHOR
 144 ------
 145
 146
 147 Brian Aker, <brian@tangent.org>
 148
 149
 150 --------
 151 SEE ALSO
 152 --------
 153
 154
 155 :manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)`