Setting callbacks¶
Get and set a callback
SYNOPSIS¶
#include <libmemcached/memcached.h>
-
memcached_callback_t
¶
-
memcached_return_t
memcached_callback_set
(memcached_st *ptr, memcached_callback_t flag, const void *data)¶
-
void *
memcached_callback_get
(memcached_st *ptr, memcached_callback_t flag, memcached_return_t *error)¶
Compile and link with -lmemcached
DESCRIPTION¶
libmemcached(3) can have callbacks set key execution points. These either provide function calls at points in the code, or return pointers to structures for particular usages.
memcached_callback_get()
takes a callback flag and returns the
structure or function set by memcached_callback_set()
.
memcached_callback_set()
changes the function/structure assigned by a
callback flag. No connections are reset.
You can use MEMCACHED_CALLBACK_USER_DATA
to provide custom context
if required for any of the callbacks.
-
MEMCACHED_CALLBACK_CLEANUP_FUNCTION
¶
When memcached_delete()
is called this function will be excuted. At
the point of its execution all connections are closed.
-
MEMCACHED_CALLBACK_CLONE_FUNCTION
¶
When memcached_delete()
is called this function will be excuted.
At the point of its execution all connections are closed.
-
MEMCACHED_CALLBACK_PREFIX_KEY
¶
-
MEMCACHED_CALLBACK_NAMESPACE
¶
You can set a value which will be used to create a domain for your keys.
The value specified here will be prefixed to each of your keys. The value can
not be greater then MEMCACHED_PREFIX_KEY_MAX_SIZE
- 1 and will
reduce MEMCACHED_MAX_KEY
by the value of your key.
The prefix key is only applied to the primary key, not the master key.
MEMCACHED_FAILURE
will be returned if no key is set. In the case of
a key which is too long, MEMCACHED_BAD_KEY_PROVIDED
will be returned.
If you set a value with the value being NULL then the prefix key is disabled.
-
MEMCACHED_CALLBACK_USER_DATA
¶
This allows you to store a pointer to a specifc piece of data. This can be
retrieved from inside of memcached_fetch_execute()
. Cloning a
memcached_st
will copy the pointer to the clone.
-
MEMCACHED_CALLBACK_MALLOC_FUNCTION
¶
Deprecated since version <0.32: Use memcached_set_memory_allocators
instead.
-
MEMCACHED_CALLBACK_REALLOC_FUNCTION
¶
Deprecated since version <0.32: Use memcached_set_memory_allocators
instead.
-
MEMCACHED_CALLBACK_FREE_FUNCTION
¶
Deprecated since version <0.32: Use memcached_set_memory_allocators
instead.
-
MEMCACHED_CALLBACK_GET_FAILURE
¶
This function implements the read through cache behavior. On failure of retrieval this callback will be called.
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.
You must clone the memcached_st
in order to
make use of it. The value will be stored only if you return
MEMCACHED_SUCCESS
or MEMCACHED_BUFFERED
. Returning
MEMCACHED_BUFFERED
will 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).
The prototype for this is:
-
memcached_return_t (*memcached_trigger_key)(memcached_st *ptr, char *key, size_t key_length, memcached_result_st *result);
-
MEMCACHED_CALLBACK_DELETE_TRIGGER
¶
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.
The prototype for this is:
-
typedef memcached_return_t (*memcached_trigger_delete_key)(memcached_st *ptr, char *key, size_t key_length);
RETURN¶
memcached_callback_get()
return the function or structure that was
provided. Upon error, nothing is set, null is returned, and the
memcached_return_t
argument is set to MEMCACHED_FAILURE
.
memcached_callback_set()
returns MEMCACHED_SUCCESS
upon
successful setting, otherwise MEMCACHED_FAILURE
on error.
HOME¶
To find out more information please check: http://libmemcached.org/
AUTHOR¶
Brian Aker, <brian@tangent.org>
SEE ALSO¶
memcached(1) libmemcached(3) memcached_strerror(3)