MEMCACHED_CAS(3)						   libmemcached 						  MEMCACHED_CAS(3)

NAME

       memcached_cas - Working with data on the server in an atomic fashion

SYNOPSIS

       #include <libmemcached/memcached.h>

       memcached_return_t   memcached_cas(memcached_st *ptr,   const   char *key,   size_t key_length,	 const	char *value,  size_t value_length,
       time_t expiration, uint32_t flags, uint64_t cas)

       memcached_return_t   memcached_cas_by_key(memcached_st *ptr,   const    char *group_key,    size_t group_key_length,    const	char *key,
       size_t key_length, const char *value, size_t value_length, time_t expiration, uint32_t flags, uint64_t cas)

       Compile and link with -lmemcached

DESCRIPTION

       memcached_cas()	overwrites  data  in the server as long as the "cas" value is still the same in the server. You can get the cas value of a
       result by calling memcached_result_cas() on a memcached_result_st(3) structure. At the point that this note was written cas is still  buggy
       in memached. Turning on tests for it in libmemcached(3) is optional. Please see memcached_set() for information on how to do this.

       memcached_cas_by_key() method behaves in a similar method as the non key methods. The difference is that it uses the group_key parameter to
       map objects to particular servers.

       memcached_cas() is testsed with the MEMCACHED_BEHAVIOR_USE_UDP behavior enabled. However, when using these operations  with  this  behavior
       on,  there  are	limits to the size of the payload being sent to the server.  The reason for these limits is that the Memcached Server does
       not allow multi-datagram requests and the current server implementation sets a datagram size to 1400 bytes. Due to protocol  overhead,  the
       actual limit of the user supplied data is less than 1400 bytes and depends on the protocol in use as, well as the operation being executed.
       When running with the binary protocol, MEMCACHED_BEHAVIOR_BINARY_PROTOCOL, the size of the key,value, flags and	expiry	combined  may  not
       exceed  1368  bytes.  When  running  with  the ASCII protocol, the exact limit fluctuates depending on which function is being executed and
       whether the function is a cas operation or not. For non-cas ASCII set operations, there are at least 1335 bytes available  to  split  among
       the  key,  key_prefix,  and  value; for cas ASCII operations there are at least 1318 bytes available to split among the key, key_prefix and
       value. If the total size of the command, including overhead, exceeds 1400 bytes, a MEMCACHED_WRITE_FAILURE will be returned.

RETURN

       All methods return a value of type memcached_return_t.  On success the value will be MEMCACHED_SUCCESS.	Use memcached_strerror() to trans-
       late this value to a printable string.

HOME

       To find out more information please check: http://libmemcached.org/

SEE ALSO

       memcached(1)   libmemached(3)   memcached_strerror(3)   memcached_set(3)  memcached_append(3)  memcached_add(3)	memcached_prepend(3)  mem-
       cached_replace(3)

AUTHOR

       Brian Aker

COPYRIGHT

       2011, Brian Aker DataDifferential, http://datadifferential.com/

1.0.8								   May 22, 2012 						  MEMCACHED_CAS(3)