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diff --git a/docs/source/memcached_cas.rst b/docs/source/memcached_cas.rst new file mode 100644 index 00000000..a796f303 --- /dev/null +++ b/docs/source/memcached_cas.rst @@ -0,0 +1,78 @@ +==================================================== +Working with data on the server in an atomic fashion +==================================================== + +.. index:: object: memcached_st + + +-------- +SYNOPSIS +-------- + + +#include <libmemcached/memcached.h> + +.. c:function:: 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) + +.. c:function:: 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 +----------- + +:c:func:`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 :c:func:`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 +:c:func:`memcached_set` for information on how to do this. + +:c:func:`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. + +:c:func:`memcached_cas` is testsed with the :c:type:`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, +:c:type:`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 :c:type:`MEMCACHED_WRITE_FAILURE` will be returned. + + +------ +RETURN +------ + + +All methods return a value of type :c:type:`memcached_return_t`. +On success the value will be :c:type:`MEMCACHED_SUCCESS`. +Use :c:func:`memcached_strerror` to translate this value to a printable +string. + + +---- +HOME +---- + + +To find out more information please check: +`http://libmemcached.org/ <http://libmemcached.org/>`_ + + +-------- +SEE ALSO +-------- + + +:manpage:`memcached(1)` :manpage:`libmemached(3)` :manpage:`memcached_strerror(3)` :manpage:`memcached_set(3)` :manpage:`memcached_append(3)` :manpage:`memcached_add(3)` :manpage:`memcached_prepend(3)` :manpage:`memcached_replace(3)` + |