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