git.m6w6.name Git - awesomized/libmemcached/blob - 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 This alllows yout to pass in a customized version of malloc that will be used instead of the builtin malloc(3) call.
  68 The prototype for this is:
  69
  70 void *(*memcached_malloc_function)(memcached_st *ptr, const size_t size);
  71
  72 =item  MEMCACHED_CALLBACK_REALLOC_FUNCTION
  73
  74 This alllows yout to pass in a customized version of realloc that will be used instead of the builtin realloc(3) call.
  75 The prototype for this is:
  76
  77 void *(*memcached_realloc_function)(memcached_st *ptr, void *mem, const size_t size);
  78
  79 =item  MEMCACHED_CALLBACK_FREE_FUNCTION
  80
  81 This alllows yout to pass in a customized version of realloc that will be used instead of the builtin free(3) call.
  82 The prototype for this is:
  83
  84 typedef void (*memcached_free_function)(memcached_st *ptr, void *mem);
  85
  86 =item  MEMCACHED_CALLBACK_GET_FAILURE
  87
  88 This function implements the read through cache behavior. On failure of retrieval this callback will be called.
  89 You are responsible for populating the result object provided. This result object will then be stored in the server and
  90 returned to the calling process. You must clone the memcached_st in order to
  91 make use of it. The value will be stored only if you return
  92 MEMCACHED_SUCCESS or MEMCACHED_BUFFERED. Returning MEMCACHED_BUFFERED will
  93 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).
  94
  95 The prototype for this is:
  96 memcached_return (*memcached_trigger_key)(memcached_st *ptr, char *key, size_t key_length, memcached_result_st *result);
  97
  98 =item  MEMCACHED_CALLBACK_DELETE_TRIGGER
  99
 100 This function implements a trigger upon successful deletion of a key. The memcached_st structure will need to be cloned
 101 in order to make use of it.
 102
 103 The prototype for this is:
 104 typedef memcached_return (*memcached_trigger_delete_key)(memcached_st *ptr, char *key, size_t key_length);
 105
 106
 107 =back
 108
 109 =head1 RETURN
 110
 111 memcached_callback_get() return the function or structure that was provided.
 112 Upon error, nothing is set, null is returned, and the memcached_return
 113 argument is set to MEMCACHED_FAILURE.
 114
 115 memcached_callback_set() returns MEMCACHED_SUCCESS upon successful setting,
 116 otherwise MEMCACHED_FAILURE on error.
 117
 118 =head1 HOME
 119
 120 To find out more information please check:
 121 L<http://tangent.org/552/libmemcached.html>
 122
 123 =head1 AUTHOR
 124
 125 Brian Aker, E<lt>brian@tangent.orgE<gt>
 126
 127 =head1 SEE ALSO
 128
 129 memcached(1) libmemcached(3) memcached_strerror(3)
 130
 131 =cut
 132