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:type:: memcached_callback_t
  18
  19 .. c:function:: memcached_return_t memcached_callback_set (memcached_st *ptr, memcached_callback_t flag, const void *data)
  20
  21 .. c:function:: void * memcached_callback_get (memcached_st *ptr, memcached_callback_t flag, memcached_return_t *error)
  22
  23 Compile and link with -lmemcached
  24
  25
  26 -----------
  27 DESCRIPTION
  28 -----------
  29
  30
  31 libmemcached(3) can have callbacks set key execution points. These either
  32 provide function calls at points in the code, or return pointers to
  33 structures for particular usages.
  34
  35 :c:func:`memcached_callback_get` takes a callback flag and returns the
  36 structure or function set by :c:func:`memcached_callback_set`.
  37
  38 :c:func:`memcached_callback_set` changes the function/structure assigned by a
  39 callback flag. No connections are reset.
  40
  41 You can use :c:type:`MEMCACHED_CALLBACK_USER_DATA` to provide custom context
  42 if required for any of the callbacks.
  43
  44
  45 .. c:type:: MEMCACHED_CALLBACK_CLEANUP_FUNCTION
  46
  47 When :c:func:`memcached_delete` is called this function will be excuted. At
  48 the point of its execution all connections are closed.
  49
  50
  51
  52 .. c:type:: MEMCACHED_CALLBACK_CLONE_FUNCTION
  53
  54 When :c:func:`memcached_delete` is called this function will be excuted.
  55 At the point of its execution all connections are closed.
  56
  57 .. c:type:: MEMCACHED_CALLBACK_PREFIX_KEY
  58
  59    See :c:type:`MEMCACHED_CALLBACK_NAMESPACE`
  60
  61 .. c:type:: MEMCACHED_CALLBACK_NAMESPACE
  62
  63 You can set a value which will be used to create a domain for your keys.
  64 The value specified here will be prefixed to each of your keys. The value can
  65 not be greater then :c:macro:`MEMCACHED_PREFIX_KEY_MAX_SIZE` - 1 and will
  66 reduce :c:macro:`MEMCACHED_MAX_KEY` by the value of your key.
  67
  68 The prefix key is only applied to the primary key, not the master key.
  69 :c:type:`MEMCACHED_FAILURE` will be returned if no key is set. In the case of
  70 a key which is too long, :c:type:`MEMCACHED_BAD_KEY_PROVIDED` will be returned.
  71
  72 If you set a value with the value being NULL then the prefix key is disabled.
  73
  74 .. c:type:: MEMCACHED_CALLBACK_USER_DATA
  75
  76 This allows you to store a pointer to a specifc piece of data. This can be
  77 retrieved from inside of :c:func:`memcached_fetch_execute`. Cloning a
  78 :c:type:`memcached_st` will copy the pointer to the clone.
  79
  80 .. c:type:: MEMCACHED_CALLBACK_MALLOC_FUNCTION
  81 .. deprecated:: <0.32
  82    Use :c:type:`memcached_set_memory_allocators` instead.
  83
  84 .. c:type:: MEMCACHED_CALLBACK_REALLOC_FUNCTION
  85 .. deprecated:: <0.32
  86    Use :c:type:`memcached_set_memory_allocators` instead.
  87
  88 .. c:type:: MEMCACHED_CALLBACK_FREE_FUNCTION
  89 .. deprecated:: <0.32
  90    Use :c:type:`memcached_set_memory_allocators` instead.
  91
  92 .. c:type:: MEMCACHED_CALLBACK_GET_FAILURE
  93
  94 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
  95
  96 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.
  97
  98 You must clone the :c:type:`memcached_st` in order to
  99 make use of it. The value will be stored only if you return
 100 :c:type:`MEMCACHED_SUCCESS` or :c:type:`MEMCACHED_BUFFERED`. Returning
 101 :c:type:`MEMCACHED_BUFFERED` will cause the object to be buffered and not sent
 102 immediatly (if this is the default behavior based on your connection setup
 103 this will happen automatically).
 104
 105 The prototype for this is:
 106
 107 .. c:function:: memcached_return_t (\*memcached_trigger_key)(memcached_st \*ptr, char \*key, size_t key_length, memcached_result_st \*result);
 108
 109
 110
 111 .. c:type:: MEMCACHED_CALLBACK_DELETE_TRIGGER
 112
 113 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.
 114
 115 The prototype for this is:
 116
 117 .. c:function:: typedef memcached_return_t (\*memcached_trigger_delete_key)(memcached_st \*ptr, char \*key, size_t key_length);
 118
 119
 120
 121
 122 ------
 123 RETURN
 124 ------
 125
 126
 127 :c:func:`memcached_callback_get` return the function or structure that was
 128 provided. Upon error, nothing is set, null is returned, and the
 129 :c:type:`memcached_return_t` argument is set to :c:type:`MEMCACHED_FAILURE`.
 130
 131 :c:func:`memcached_callback_set` returns :c:type:`MEMCACHED_SUCCESS` upon
 132 successful setting, otherwise :c:type:`MEMCACHED_FAILURE` on error.
 133
 134
 135 ----
 136 HOME
 137 ----
 138
 139
 140 To find out more information please check:
 141 `http://libmemcached.org/ <http://libmemcached.org/>`_
 142
 143
 144 ------
 145 AUTHOR
 146 ------
 147
 148
 149 Brian Aker, <brian@tangent.org>
 150
 151
 152 --------
 153 SEE ALSO
 154 --------
 155
 156
 157 :manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)`