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165 <li>Appending or Prepending Data
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168 <li class=
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184 <div itemprop=
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186 <div class=
"section" id=
"appending-or-prepending-data">
187 <h1>Appending or Prepending Data
<a class=
"headerlink" href=
"#appending-or-prepending-data" title=
"Permalink to this headline">¶
</a></h1>
188 <div class=
"section" id=
"synopsis">
189 <h2>SYNOPSIS
<a class=
"headerlink" href=
"#synopsis" title=
"Permalink to this headline">¶
</a></h2>
190 <dl class=
"docutils">
191 <dt>#include
<libmemcached-
1.0/memcached.h
></dt>
192 <dd>Compile and link with -lmemcached
</dd>
194 <dl class=
"function">
195 <dt id=
"_CPPv417memcached_prependP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t">
196 <span id=
"_CPPv317memcached_prependP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"_CPPv217memcached_prependP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"memcached_prepend__memcached_stP.cCP.s.cCP.s.time_t.uint32_t"></span><a class=
"reference internal" href=
"memcached_return_t.html#_CPPv418memcached_return_t" title=
"memcached_return_t">memcached_return_t
</a> <code class=
"descname">memcached_prepend
</code><span class=
"sig-paren">(
</span><a class=
"reference internal" href=
"memcached_create.html#_CPPv412memcached_st" title=
"memcached_st">memcached_st
</a> *
<em>ptr
</em>,
<em class=
"property">const
</em> char *
<em>key
</em>, size_t
<em>key_length
</em>,
<em class=
"property">const
</em> char *
<em>value
</em>, size_t
<em>value_length
</em>, time_t
<em>expiration
</em>, uint32_t
<em>flags
</em><span class=
"sig-paren">)
</span><a class=
"headerlink" href=
"#_CPPv417memcached_prependP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t" title=
"Permalink to this definition">¶
</a><br /></dt>
199 <dl class=
"function">
200 <dt id=
"_CPPv416memcached_appendP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t">
201 <span id=
"_CPPv316memcached_appendP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"_CPPv216memcached_appendP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"memcached_append__memcached_stP.cCP.s.cCP.s.time_t.uint32_t"></span><a class=
"reference internal" href=
"memcached_return_t.html#_CPPv418memcached_return_t" title=
"memcached_return_t">memcached_return_t
</a> <code class=
"descname">memcached_append
</code><span class=
"sig-paren">(
</span><a class=
"reference internal" href=
"memcached_create.html#_CPPv412memcached_st" title=
"memcached_st">memcached_st
</a> *
<em>ptr
</em>,
<em class=
"property">const
</em> char *
<em>key
</em>, size_t
<em>key_length
</em>,
<em class=
"property">const
</em> char *
<em>value
</em>, size_t
<em>value_length
</em>, time_t
<em>expiration
</em>, uint32_t
<em>flags
</em><span class=
"sig-paren">)
</span><a class=
"headerlink" href=
"#_CPPv416memcached_appendP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t" title=
"Permalink to this definition">¶
</a><br /></dt>
204 <dl class=
"function">
205 <dt id=
"_CPPv424memcached_prepend_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t">
206 <span id=
"_CPPv324memcached_prepend_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"_CPPv224memcached_prepend_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"memcached_prepend_by_key__memcached_stP.cCP.s.cCP.s.cCP.s.time_t.uint32_t"></span><a class=
"reference internal" href=
"memcached_return_t.html#_CPPv418memcached_return_t" title=
"memcached_return_t">memcached_return_t
</a> <code class=
"descname">memcached_prepend_by_key
</code><span class=
"sig-paren">(
</span><a class=
"reference internal" href=
"memcached_create.html#_CPPv412memcached_st" title=
"memcached_st">memcached_st
</a> *
<em>ptr
</em>,
<em class=
"property">const
</em> char *
<em>group_key
</em>, size_t
<em>group_key_length
</em>,
<em class=
"property">const
</em> char *
<em>key
</em>, size_t
<em>key_length
</em>,
<em class=
"property">const
</em> char *
<em>value
</em>, size_t
<em>value_length
</em>, time_t
<em>expiration
</em>, uint32_t
<em>flags
</em><span class=
"sig-paren">)
</span><a class=
"headerlink" href=
"#_CPPv424memcached_prepend_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t" title=
"Permalink to this definition">¶
</a><br /></dt>
209 <dl class=
"function">
210 <dt id=
"_CPPv423memcached_append_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t">
211 <span id=
"_CPPv323memcached_append_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"_CPPv223memcached_append_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t"></span><span id=
"memcached_append_by_key__memcached_stP.cCP.s.cCP.s.cCP.s.time_t.uint32_t"></span><a class=
"reference internal" href=
"memcached_return_t.html#_CPPv418memcached_return_t" title=
"memcached_return_t">memcached_return_t
</a> <code class=
"descname">memcached_append_by_key
</code><span class=
"sig-paren">(
</span><a class=
"reference internal" href=
"memcached_create.html#_CPPv412memcached_st" title=
"memcached_st">memcached_st
</a> *
<em>ptr
</em>,
<em class=
"property">const
</em> char *
<em>group_key
</em>, size_t
<em>group_key_length
</em>,
<em class=
"property">const
</em> char *
<em>key
</em>, size_t
<em>key_length
</em>,
<em class=
"property">const
</em> char *
<em>value
</em>, size_t
<em>value_length
</em>, time_t
<em>expiration
</em>, uint32_t
<em>flags
</em><span class=
"sig-paren">)
</span><a class=
"headerlink" href=
"#_CPPv423memcached_append_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t" title=
"Permalink to this definition">¶
</a><br /></dt>
212 <dd><table class=
"docutils field-list" frame=
"void" rules=
"none">
213 <col class=
"field-name" />
214 <col class=
"field-body" />
216 <tr class=
"field-odd field"><th class=
"field-name">Parameters:
</th><td class=
"field-body"><ul class=
"first simple">
217 <li><strong>ptr
</strong> -- pointer to an initialized
<a class=
"reference internal" href=
"memcached_create.html#_CPPv412memcached_st" title=
"memcached_st"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_st
</span></code></a> struct
</li>
218 <li><strong>group_key
</strong> -- key namespace
</li>
219 <li><strong>group_key_length
</strong> -- length of the key namespace without any terminating zero
</li>
220 <li><strong>key
</strong> -- the key
</li>
221 <li><strong>key_length
</strong> -- length of the key without any terminating zero
</li>
222 <li><strong>value
</strong> -- the value to append/prepend
</li>
223 <li><strong>value_length
</strong> -- the length of the value without any terminating zero
</li>
224 <li><strong>expiration
</strong> -- expiration as a unix timestamp or as relative expiration time in seconds
</li>
225 <li><strong>flags
</strong> --
16 bit flags
</li>
229 <tr class=
"field-even field"><th class=
"field-name">Returns:
</th><td class=
"field-body"><p class=
"first last"><a class=
"reference internal" href=
"memcached_return_t.html#_CPPv418memcached_return_t" title=
"memcached_return_t"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_return_t
</span></code></a> indicating success
</p>
237 <div class=
"section" id=
"description">
238 <h2>DESCRIPTION
<a class=
"headerlink" href=
"#description" title=
"Permalink to this headline">¶
</a></h2>
239 <p><a class=
"reference internal" href=
"#_CPPv417memcached_prependP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t" title=
"memcached_prepend"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_prepend()
</span></code></a> and memcached_append are used to modify information on a
240 server. All methods take a
<code class=
"docutils literal notranslate"><span class=
"pre">key
</span></code>, and
<code class=
"docutils literal notranslate"><span class=
"pre">key_length
</span></code> to store the object. Keys
241 are currently limited to
250 characters when using either a version of memcached
242 which is
1.4 or below, or when using the text protocol. You must supply both a
243 value and a length. Optionally you may set an expiration time for the object
244 and a
16 bit value (it is meant to be used as a bitmap).
<code class=
"docutils literal notranslate"><span class=
"pre">flags
</span></code> is a
4 byte
245 space that is stored along the main value. Many sub libraries make use of
246 this field, so in most cases users should avoid making use of it.
</p>
247 <p><a class=
"reference internal" href=
"#_CPPv417memcached_prependP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t" title=
"memcached_prepend"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_prepend()
</span></code></a> places a segment of data before the last piece of data
248 stored. Currently expiration and key are not used in the server.
</p>
249 <p><a class=
"reference internal" href=
"#_CPPv416memcached_appendP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t" title=
"memcached_append"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_append()
</span></code></a> places a segment of data at the end of the last piece of data
250 stored. Currently expiration and key are not used in the server.
</p>
251 <p><a class=
"reference internal" href=
"#_CPPv424memcached_prepend_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t" title=
"memcached_prepend_by_key"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_prepend_by_key()
</span></code></a> and
<a class=
"reference internal" href=
"#_CPPv423memcached_append_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t" title=
"memcached_append_by_key"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_append_by_key()
</span></code></a> methods both behave in
252 a similar manner as the non key methods. The difference is that they use their
253 group_key parameter to map objects to particular servers.
</p>
254 <p>If you are looking for performance,
<a class=
"reference internal" href=
"memcached_set.html#_CPPv413memcached_setP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t" title=
"memcached_set"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_set()
</span></code></a> with non-blocking IO is the
255 fastest way to store data on the server.
</p>
256 <p>All of the above functions are tested with the
<a class=
"reference internal" href=
"memcached_behavior.html#_CPPv4N20memcached_behavior_t26MEMCACHED_BEHAVIOR_USE_UDPE" title=
"MEMCACHED_BEHAVIOR_USE_UDP"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">MEMCACHED_BEHAVIOR_USE_UDP
</span></code></a>
257 behavior enabled. However, when using these operations with this behavior on,
258 there are limits to the size of the payload being sent to the server. The
259 reason for these limits is that the Memcached Server does not allow
260 multi-datagram requests and the current server implementation sets a datagram
261 size to
1400 bytes. Due to protocol overhead, the actual limit of the user
262 supplied data is less than
1400 bytes and depends on the protocol in use as,
263 well as the operation being executed. When running with the binary protocol,
264 <a class=
"reference internal" href=
"memcached_behavior.html#_CPPv4N20memcached_behavior_t34MEMCACHED_BEHAVIOR_BINARY_PROTOCOLE" title=
"MEMCACHED_BEHAVIOR_BINARY_PROTOCOL"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">MEMCACHED_BEHAVIOR_BINARY_PROTOCOL
</span></code></a>, the size of the key,value, flags and
265 expiry combined may not exceed
1368 bytes. When running with the ASCII protocol,
266 the exact limit fluctuates depending on which function is being executed and
267 whether the function is a cas operation or not. For non-cas ASCII set
268 operations, there are at least
1335 bytes available to split among the key,
269 key_prefix, and value; for cas ASCII operations there are at least
1318 bytes
270 available to split among the key, key_prefix and value. If the total size of the
271 command, including overhead, exceeds
1400 bytes, a
<a class=
"reference internal" href=
"memcached_return_t.html#_CPPv4N18memcached_return_t23MEMCACHED_WRITE_FAILUREE" title=
"MEMCACHED_WRITE_FAILURE"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">MEMCACHED_WRITE_FAILURE
</span></code></a>
272 will be returned.
</p>
274 <div class=
"section" id=
"return-value">
275 <h2>RETURN VALUE
<a class=
"headerlink" href=
"#return-value" title=
"Permalink to this headline">¶
</a></h2>
276 <p>All methods return a value of type
<a class=
"reference internal" href=
"memcached_return_t.html#_CPPv418memcached_return_t" title=
"memcached_return_t"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_return_t
</span></code></a>. On success the value
277 will be
<a class=
"reference internal" href=
"memcached_return_t.html#_CPPv4N18memcached_return_t17MEMCACHED_SUCCESSE" title=
"MEMCACHED_SUCCESS"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">MEMCACHED_SUCCESS
</span></code></a>.
</p>
278 <p>Use
<a class=
"reference internal" href=
"memcached_strerror.html#_CPPv418memcached_strerrorP12memcached_st18memcached_return_t" title=
"memcached_strerror"><code class=
"xref cpp cpp-any docutils literal notranslate"><span class=
"pre">memcached_strerror()
</span></code></a> to translate this value to a printable string.
</p>
280 <div class=
"section" id=
"see-also">
281 <h2>SEE ALSO
<a class=
"headerlink" href=
"#see-also" title=
"Permalink to this headline">¶
</a></h2>
283 <li><em class=
"manpage"><a class=
"manpage reference external" href=
"https://linux.die.net/man/1/memcached">memcached(
1)
</a></em></li>
284 <li><a class=
"reference internal" href=
"../libmemcached.html"><span class=
"doc">C/C++ Client Library for memcached
</span></a></li>
285 <li><a class=
"reference internal" href=
"memcached_set.html"><span class=
"doc">Storing data on the server
</span></a></li>
286 <li><a class=
"reference internal" href=
"memcached_cas.html"><span class=
"doc">Working with data on the server in an atomic fashion
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