jenkins-promote-staging-trunk-libmemcached-9
[awesomized/libmemcached] / docs / man / memcached_cas.3
1 .TH "MEMCACHED_CAS" "3" "April 09, 2012" "1.0.6" "libmemcached"
2 .SH NAME
3 memcached_cas \- Working with data on the server in an atomic fashion
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33 .SH SYNOPSIS
34 .sp
35 #include <libmemcached/memcached.h>
36 .INDENT 0.0
37 .TP
38 .B memcached_return_t memcached_cas(memcached_st\fI\ *ptr\fP, const char\fI\ *key\fP, size_t\fI\ key_length\fP, const char\fI\ *value\fP, size_t\fI\ value_length\fP, time_t\fI\ expiration\fP, uint32_t\fI\ flags\fP, uint64_t\fI\ cas\fP)
39 .UNINDENT
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41 .TP
42 .B memcached_return_t memcached_cas_by_key(memcached_st\fI\ *ptr\fP, const char\fI\ *group_key\fP, size_t\fI\ group_key_length\fP, const char\fI\ *key\fP, size_t\fI\ key_length\fP, const char\fI\ *value\fP, size_t\fI\ value_length\fP, time_t\fI\ expiration\fP, uint32_t\fI\ flags\fP, uint64_t\fI\ cas\fP)
43 .UNINDENT
44 .sp
45 Compile and link with \-lmemcached
46 .SH DESCRIPTION
47 .sp
48 \fI\%memcached_cas()\fP overwrites data in the server as long as the "cas"
49 value is still the same in the server. You can get the cas value of a result
50 by calling \fBmemcached_result_cas()\fP on a memcached_result_st(3)
51 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
52 \fBmemcached_set()\fP for information on how to do this.
53 .sp
54 \fI\%memcached_cas_by_key()\fP method behaves in a similar method as the non
55 key methods. The difference is that it uses the group_key parameter
56 to map objects to particular servers.
57 .sp
58 \fI\%memcached_cas()\fP is testsed with the \fBMEMCACHED_BEHAVIOR_USE_UDP\fP behavior enabled. However, when using these operations with this behavior
59 on, there are limits to the size of the payload being sent to the server. The
60 reason for these limits is that the Memcached Server does not allow
61 multi\-datagram requests and the current server implementation sets a datagram
62 size to 1400 bytes. Due to protocol overhead, the actual limit of the user
63 supplied data is less than 1400 bytes and depends on the protocol in use as,
64 well as the operation being executed. When running with the binary protocol,
65 \fBMEMCACHED_BEHAVIOR_BINARY_PROTOCOL\fP, the size of the key,value,
66 flags and expiry combined may not exceed 1368 bytes. When running with the
67 ASCII protocol, the exact limit fluctuates depending on which function is
68 being executed and whether the function is a cas operation or not. For
69 non\-cas ASCII set operations, there are at least 1335 bytes available to
70 split among the key, key_prefix, and value; for cas ASCII operations there
71 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 \fBMEMCACHED_WRITE_FAILURE\fP will be returned.
72 .SH RETURN
73 .sp
74 All methods return a value of type \fBmemcached_return_t\fP.
75 On success the value will be \fBMEMCACHED_SUCCESS\fP.
76 Use \fBmemcached_strerror()\fP to translate this value to a printable
77 string.
78 .SH HOME
79 .sp
80 To find out more information please check:
81 \fI\%http://libmemcached.org/\fP
82 .SH SEE ALSO
83 .sp
84 \fImemcached(1)\fP \fIlibmemached(3)\fP \fImemcached_strerror(3)\fP \fImemcached_set(3)\fP \fImemcached_append(3)\fP \fImemcached_add(3)\fP \fImemcached_prepend(3)\fP \fImemcached_replace(3)\fP
85 .SH AUTHOR
86 Brian Aker
87 .SH COPYRIGHT
88 2011, Brian Aker DataDifferential, http://datadifferential.com/
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