MEMCACHED_CAS(3) libmemcached-awesome MEMCACHED_CAS(3)
NAME
memcached_cas - Atomic Compare and Swap
SYNOPSIS
#include <libmemcached/memcached.h>
Compile and link with -lmemcached
memcached_return_t memcached_cas(memcached_st *ptr, const char *key,
size_t key_length, const char *value, size_t value_length, time_t expi-
ration, 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)
Parameters
o ptr -- pointer to an initialized memcached_st struct
o group_key -- key namespace
o group_key_length -- length of the group_key without any
trailing zero
o key -- the key to check
o key_length -- the length of the key without any trail-
ing zero
o value -- the value to set
o value_length -- the length of the value without any
trailing zero
o expiration -- expiration time as unix timestamp or rel-
ative time in seconds
o flags -- 16 bit flags
o cas -- the cas value to compare
Returns
memcached_return_t indicating success
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 structure.
memcached_cas_by_key() method behaves in a similar way as the non key
methods. The difference is that it uses the group_key parameter to map
objects to particular servers.
memcached_cas() is tested 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 de-
pending 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 VALUE
All methods return a value of type memcached_return_t. On success the
value will be MEMCACHED_SUCCESS. Use memcached_strerror() to translate
this value to a printable string.
SEE ALSO
memcached(1) libmemcached(3) memcached_strerror(3) memcached_set(3)
memcached_append(3) memcached_add(3) memcached_prepend(3) memcached_re-
place(3)
1.1 Mar 06, 2023 MEMCACHED_CAS(3)
Czas wygenerowania: 0.00035 sek.
Created with the man page lookup class by Andrew Collington.
Based on a C man page viewer by Vadim Pavlov
Unicode soft-hyphen fix (as used by RedHat) by Dan Edwards
Some optimisations by Eli Argon
Caching idea and code contribution by James Richardson
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