Merge from Trond
[m6w6/libmemcached] / docs / memcached_callback.pod
1 =head1 NAME
2
3 memcached_callback_get, memcached_callback_set - Get and set a callback
4
5 =head1 LIBRARY
6
7 C Client Library for memcached (libmemcached, -lmemcached)
8
9 =head1 SYNOPSIS
10
11 #include <memcached.h>
12
13 memcached_return
14 memcached_callback_set (memcached_st *ptr,
15 memcached_callback flag,
16 void *data);
17
18 void *
19 memcached_callback_get (memcached_st *ptr,
20 memcached_callback flag,
21 memcached_return *error);
22
23 =head1 DESCRIPTION
24
25 libmemcached(3) can have callbacks set key execution points. These either
26 provide function calls at points in the code, or return pointers to
27 structures for particular usages.
28
29 memcached_callback_get() takes a callback flag and returns the structure or
30 function set by memcached_callback_set().
31
32 memcached_callback_set() changes the function/structure assigned by a
33 callback flag. No connections are reset.
34
35 You can use MEMCACHED_CALLBACK_USER_DATA to provide custom context if required for any
36 of the callbacks
37
38 =over 4
39
40 =item MEMCACHED_CALLBACK_CLEANUP_FUNCTION
41
42 When memcached_delete() is called this function will be excuted. At the
43 point of its execution all connections have been closed.
44
45 =item MEMCACHED_CALLBACK_CLONE_FUNCTION
46
47 When memcached_delete() is called this function will be excuted. At the
48 point of its execution all connections have been closed.
49
50 =item MEMCACHED_CALLBACK_PREFIX_KEY
51
52 You can set a value which will be used to create a domain for your keys.
53 The value specified here will be prefixed to each of your keys. The value can not
54 be greater then MEMCACHED_PREFIX_KEY_MAX_SIZE - 1 and will reduce MEMCACHED_MAX_KEY by
55 the value of your key. The prefix key is only applied to the primary key,
56 not the master key. MEMCACHED_FAILURE will be returned if no key is set. In the case
57 of a key which is too long MEMCACHED_BAD_KEY_PROVIDED will be returned.
58
59 =item MEMCACHED_CALLBACK_USER_DATA
60
61 This allows you to store a pointer to a specifc piece of data. This can be
62 retrieved from inside of memcached_fetch_execute(). Cloning a memcached_st
63 will copy the pointer to the clone.
64
65 =item MEMCACHED_CALLBACK_MALLOC_FUNCTION
66
67 DEPRECATED: use memcached_set_memory_allocators instead.
68
69 =item MEMCACHED_CALLBACK_REALLOC_FUNCTION
70
71 DEPRECATED: use memcached_set_memory_allocators instead.
72
73 =item MEMCACHED_CALLBACK_FREE_FUNCTION
74
75 DEPRECATED: use memcached_set_memory_allocators instead.
76
77 =item MEMCACHED_CALLBACK_GET_FAILURE
78
79 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
80 You are responsible for populating the result object provided. This result object will then be stored in the server and
81 returned to the calling process. You must clone the memcached_st in order to
82 make use of it. The value will be stored only if you return
83 MEMCACHED_SUCCESS or MEMCACHED_BUFFERED. Returning MEMCACHED_BUFFERED will
84 cause the object to be buffered and not sent immediatly (if this is the default behavior based on your connection setup this will happen automatically).
85
86 The prototype for this is:
87 memcached_return (*memcached_trigger_key)(memcached_st *ptr, char *key, size_t key_length, memcached_result_st *result);
88
89 =item MEMCACHED_CALLBACK_DELETE_TRIGGER
90
91 This function implements a trigger upon successful deletion of a key. The memcached_st structure will need to be cloned
92 in order to make use of it.
93
94 The prototype for this is:
95 typedef memcached_return (*memcached_trigger_delete_key)(memcached_st *ptr, char *key, size_t key_length);
96
97
98 =back
99
100 =head1 RETURN
101
102 memcached_callback_get() return the function or structure that was provided.
103 Upon error, nothing is set, null is returned, and the memcached_return
104 argument is set to MEMCACHED_FAILURE.
105
106 memcached_callback_set() returns MEMCACHED_SUCCESS upon successful setting,
107 otherwise MEMCACHED_FAILURE on error.
108
109 =head1 HOME
110
111 To find out more information please check:
112 L<http://tangent.org/552/libmemcached.html>
113
114 =head1 AUTHOR
115
116 Brian Aker, E<lt>brian@tangent.orgE<gt>
117
118 =head1 SEE ALSO
119
120 memcached(1) libmemcached(3) memcached_strerror(3)
121
122 =cut
123