8 .. index:: object: memcached_st
15 #include <libmemcached/memcached.h>
17 .. c:function:: memcached_return_t memcached_callback_set (memcached_st *ptr, memcached_callback_t flag, void *data);
19 .. c:function:: void * memcached_callback_get (memcached_st *ptr, memcached_callback_t flag, memcached_return_t *error);
21 Compile and link with -lmemcached
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.
33 :c:func:`memcached_callback_get()` takes a callback flag and returns the
34 structure or function set by :c:func:`memcached_callback_set()`.
36 :c:func:`memcached_callback_set()` changes the function/structure assigned by a
37 callback flag. No connections are reset.
39 You can use :c:type:`MEMCACHED_CALLBACK_USER_DATA` to provide custom context
40 if required for any of the callbacks.
43 .. c:type:: MEMCACHED_CALLBACK_CLEANUP_FUNCTION
45 When :c:func:`memcached_delete()` is called this function will be excuted. At
46 the point of its execution all connections are closed.
50 .. c:type:: MEMCACHED_CALLBACK_CLONE_FUNCTION
52 When :c:func:`memcached_delete()` is called this function will be excuted.
53 At the point of its execution all connections are closed.
55 .. c:type:: MEMCACHED_CALLBACK_PREFIX_KEY
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
59 not be greater then :c:type:`MEMCACHED_PREFIX_KEY_MAX_SIZE - 1` and will
60 reduce :c:type:`MEMCACHED_MAX_KEY` by the value of your key.
62 The prefix key is only applied to the primary key, not the master key.
63 :c:type:`MEMCACHED_FAILURE` will be returned if no key is set. In the case of
64 a key which is too long, :c:type:`MEMCACHED_BAD_KEY_PROVIDED` will be returned.
66 If you set a value with the value being NULL then the prefix key is disabled.
68 .. c:type:: MEMCACHED_CALLBACK_USER_DATA
70 This allows you to store a pointer to a specifc piece of data. This can be
71 retrieved from inside of :c:func:`memcached_fetch_execute()`. Cloning a
72 :c:type:`memcached_st` will copy the pointer to the clone.
74 .. c:type:: MEMCACHED_CALLBACK_MALLOC_FUNCTION
76 Use :c:type:`memcached_set_memory_allocators` instead.
78 .. c:type:: MEMCACHED_CALLBACK_REALLOC_FUNCTION
80 Use :c:type:`memcached_set_memory_allocators` instead.
82 .. c:type:: MEMCACHED_CALLBACK_FREE_FUNCTION
84 Use :c:type:`memcached_set_memory_allocators` instead.
86 .. c:type:: MEMCACHED_CALLBACK_GET_FAILURE
88 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
90 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.
92 You must clone the :c:type:`memcached_st` in order to
93 make use of it. The value will be stored only if you return
94 :c:type:`MEMCACHED_SUCCESS` or :c:type:`MEMCACHED_BUFFERED`. Returning
95 :c:type:`MEMCACHED_BUFFERED` will cause the object to be buffered and not sent
96 immediatly (if this is the default behavior based on your connection setup
97 this will happen automatically).
99 The prototype for this is:
101 .. c:function:: memcached_return_t (\*memcached_trigger_key)(memcached_st \*ptr, char \*key, size_t key_length, memcached_result_st \*result);
105 .. c:type:: MEMCACHED_CALLBACK_DELETE_TRIGGER
107 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.
109 The prototype for this is:
111 .. c:function:: typedef memcached_return_t (\*memcached_trigger_delete_key)(memcached_st \*ptr, char \*key, size_t key_length);
121 :c:func:`memcached_callback_get()` return the function or structure that was
122 provided. Upon error, nothing is set, null is returned, and the
123 :c:type:`memcached_return_t` argument is set to :c:type:`MEMCACHED_FAILURE`.
125 :c:func:`memcached_callback_set()` returns :c:type:`MEMCACHED_SUCCESS` upon
126 successful setting, otherwise :c:type:`MEMCACHED_FAILURE` on error.
134 To find out more information please check:
135 `http://libmemcached.org/ <http://libmemcached.org/>`_
143 Brian Aker, <brian@tangent.org>
151 :manpage:`memcached(1)` :manpage:`libmemcached(3)` :manpage:`memcached_strerror(3)`