1MEMCACHED_CALLBACK(3) libmemcached-awesome MEMCACHED_CALLBACK(3)
2
6 memcached_callback - libmemcached Documentation
7
9 #include <libmemcached/memcached.h>
10 Compile and link with -lmemcached
11 memcached_return_t memcached_callback_set(memcached_st *ptr,
13 memcached_callback_t flag, const void *data)
14 Parameters
16 • ptr -- pointer to initialized memcached_st struct
18 • flag -- memcached_callback_t flag to set
20 • data -- data corresponding to flag
22 Returns
24 memcached_return_t indicating success
25 void *memcached_callback_get(memcached_st *ptr, memcached_callback_t
27 flag, memcached_return_t *error)
28 Parameters
30 • ptr -- pointer to initialized memcached_st struct
32 • flag -- memcached_callback_t flag to query
34 • error -- pointer to memcached_return_t indicating suc‐
36 cess
37 Returns
39 the data previously set
40 typedef enum memcached_callback_t memcached_callback_t
42 enum memcached_callback_t
44 enumerator MEMCACHED_CALLBACK_CLEANUP_FUNCTION
46 When memcached_free() or memcached_reset is called this
47 function will be executed. At the point of its execution
48 all connections are closed.
49 Its signature is:
51 typedef memcached_return_t (*memcached_cleanup_fn)(const
53 memcached_st *ptr)
54 enumerator MEMCACHED_CALLBACK_CLONE_FUNCTION
56 When memcached_clone() is called this function will be
57 executed.
58 Its signature is:
60 typedef memcached_return_t (*memcached_clone_fn)(‐
62 memcached_st *destination, const memcached_st *source)
63 enumerator MEMCACHED_CALLBACK_PREFIX_KEY
65 See MEMCACHED_CALLBACK_NAMESPACE.
66 enumerator MEMCACHED_CALLBACK_NAMESPACE
68 You can set a value which will be used to create a domain
69 for your keys. The value specified here will be prefixed
70 to each of your keys. The value can not be greater then
71 MEMCACHED_MAX_NAMESPACE - 1 and will reduce
72 MEMCACHED_MAX_KEY by the value of your key.
73 The prefix key is only applied to the primary key, not
75 the master key. MEMCACHED_FAILURE will be returned if no
76 key is set. In the case of a key which is too long,
77 MEMCACHED_BAD_KEY_PROVIDED will be returned.
78 If you set a value with the value being NULL then the
80 prefix key is disabled.
81 enumerator MEMCACHED_CALLBACK_USER_DATA
83 This allows you to store a pointer to a specific piece of
84 data. This can be retrieved from inside of
85 memcached_fetch_execute(). Cloning a memcached_st will
86 copy the pointer to the clone.
87 enumerator MEMCACHED_CALLBACK_MALLOC_FUNCTION
89 Deprecated since version <0.32: Use
90 memcached_set_memory_allocators() instead.
91 enumerator MEMCACHED_CALLBACK_REALLOC_FUNCTION
94 Deprecated since version <0.32: Use
95 memcached_set_memory_allocators() instead.
96 enumerator MEMCACHED_CALLBACK_FREE_FUNCTION
99 Deprecated since version <0.32: Use
100 memcached_set_memory_allocators() instead.
101 enumerator MEMCACHED_CALLBACK_GET_FAILURE
104 This function implements the read through cache behavior.
105 On failure of retrieval this callback will be called.
106 You are responsible for populating the result object pro‐
108 vided. This result object will then be stored in the
109 server and returned to the calling process.
110 You must clone the memcached_st in order to make use of
112 it. The value will be stored only if you return
113 MEMCACHED_SUCCESS or MEMCACHED_BUFFERED. Returning
114 MEMCACHED_BUFFERED will cause the object to be buffered
115 and not sent immediately (if this is the default behavior
116 based on your connection setup this will happen automati‐
117 cally).
118 The prototype for this is:
120 typedef memcached_return_t (*memcached_trigger_key)(‐
122 memcached_st *ptr, char *key, size_t key_length,
123 memcached_result_st *result)
124 enumerator MEMCACHED_CALLBACK_DELETE_TRIGGER
126 This function implements a trigger upon successful dele‐
127 tion of a key. The memcached_st structure will need to
128 be cloned in order to make use of it.
129 The prototype for this is:
131 typedef memcached_return_t
133 (*memcached_trigger_delete_key)(memcached_st *ptr, char
134 *key, size_t key_length)
135
137 libmemcached can have callbacks set key execution points. These either
138 provide function calls at points in the code, or return pointers to
139 structures for particular usages.
140 memcached_callback_get() takes a callback flag and returns the struc‐
142 ture or function set by memcached_callback_set().
143 memcached_callback_set() changes the function/structure assigned by a
145 callback flag. No connections are reset.
146 You can use MEMCACHED_CALLBACK_USER_DATA to provide custom context if
148 required for any of the callbacks.
149
151 memcached_callback_get() returns the function or structure that was
152 provided. Upon error, nothing is set, NULL is returned, and the
153 memcached_return_t argument is set to MEMCACHED_FAILURE.
154 memcached_callback_set() returns MEMCACHED_SUCCESS upon successful set‐
156 ting, otherwise MEMCACHED_FAILURE on error.
157
159 memcached(1) libmemcached(3) memcached_strerror(3)
1601.1 Jul 20, 2023 MEMCACHED_CALLBACK(3)