Updating for 1.0.2 release
[awesomized/libmemcached] / 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)`