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</a></li>
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</a></li>
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196 <div class=
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"appending-or-prepending-data">
197 <h1>Appending or Prepending Data
<a class=
"headerlink" href=
"#appending-or-prepending-data" title=
"Permalink to this headline">¶
</a></h1>
198 <div class=
"section" id=
"synopsis">
199 <h2>SYNOPSIS
<a class=
"headerlink" href=
"#synopsis" title=
"Permalink to this headline">¶
</a></h2>
201 <dt>#include
<libmemcached-
1.0/memcached.h
></dt><dd><p>Compile and link with -lmemcached
</p>
204 <dl class=
"cpp function">
205 <dt id=
"_CPPv417memcached_prependP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t">
206 <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=
"sig-name 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>
209 <dl class=
"cpp function">
210 <dt id=
"_CPPv416memcached_appendP12memcached_stPKc6size_tPKc6size_t6time_t8uint32_t">
211 <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=
"sig-name 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>
214 <dl class=
"cpp function">
215 <dt id=
"_CPPv424memcached_prepend_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t">
216 <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=
"sig-name 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>
219 <dl class=
"cpp function">
220 <dt id=
"_CPPv423memcached_append_by_keyP12memcached_stPKc6size_tPKc6size_tPKc6size_t6time_t8uint32_t">
221 <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=
"sig-name 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>
222 <dd><dl class=
"field-list simple">
223 <dt class=
"field-odd">Parameters
</dt>
224 <dd class=
"field-odd"><ul class=
"simple">
225 <li><p><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
</p></li>
226 <li><p><strong>group_key
</strong> -- key namespace
</p></li>
227 <li><p><strong>group_key_length
</strong> -- length of the key namespace without any terminating zero
</p></li>
228 <li><p><strong>key
</strong> -- the key
</p></li>
229 <li><p><strong>key_length
</strong> -- length of the key without any terminating zero
</p></li>
230 <li><p><strong>value
</strong> -- the value to append/prepend
</p></li>
231 <li><p><strong>value_length
</strong> -- the length of the value without any terminating zero
</p></li>
232 <li><p><strong>expiration
</strong> -- expiration as a unix timestamp or as relative expiration time in seconds
</p></li>
233 <li><p><strong>flags
</strong> --
16 bit flags
</p></li>
236 <dt class=
"field-even">Returns
</dt>
237 <dd class=
"field-even"><p><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>
243 <div class=
"section" id=
"description">
244 <h2>DESCRIPTION
<a class=
"headerlink" href=
"#description" title=
"Permalink to this headline">¶
</a></h2>
245 <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
246 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
247 are currently limited to
250 characters when using either a version of memcached
248 which is
1.4 or below, or when using the text protocol. You must supply both a
249 value and a length. Optionally you may set an expiration time for the object
250 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
251 space that is stored along the main value. Many sub libraries make use of
252 this field, so in most cases users should avoid making use of it.
</p>
253 <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
254 stored. Currently expiration and key are not used in the server.
</p>
255 <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
256 stored. Currently expiration and key are not used in the server.
</p>
257 <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
258 a similar manner as the non key methods. The difference is that they use their
259 group_key parameter to map objects to particular servers.
</p>
260 <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
261 fastest way to store data on the server.
</p>
262 <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>
263 behavior enabled. However, when using these operations with this behavior on,
264 there are limits to the size of the payload being sent to the server. The
265 reason for these limits is that the Memcached Server does not allow
266 multi-datagram requests and the current server implementation sets a datagram
267 size to
1400 bytes. Due to protocol overhead, the actual limit of the user
268 supplied data is less than
1400 bytes and depends on the protocol in use as,
269 well as the operation being executed. When running with the binary protocol,
270 <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
271 expiry combined may not exceed
1368 bytes. When running with the ASCII protocol,
272 the exact limit fluctuates depending on which function is being executed and
273 whether the function is a cas operation or not. For non-cas ASCII set
274 operations, there are at least
1335 bytes available to split among the key,
275 key_prefix, and value; for cas ASCII operations there are at least
1318 bytes
276 available to split among the key, key_prefix and value. If the total size of the
277 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>
278 will be returned.
</p>
280 <div class=
"section" id=
"return-value">
281 <h2>RETURN VALUE
<a class=
"headerlink" href=
"#return-value" title=
"Permalink to this headline">¶
</a></h2>
282 <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
283 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>
284 <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>
286 <div class=
"section" id=
"see-also">
287 <h2>SEE ALSO
<a class=
"headerlink" href=
"#see-also" title=
"Permalink to this headline">¶
</a></h2>
289 <li><p><em class=
"manpage"><a class=
"manpage reference external" href=
"https://linux.die.net/man/1/memcached">memcached(
1)
</a></em></p></li>
290 <li><p><a class=
"reference internal" href=
"../libmemcached.html"><span class=
"doc">C/C++ Client Library for memcached
</span></a></p></li>
291 <li><p><a class=
"reference internal" href=
"memcached_set.html"><span class=
"doc">Storing data on the server
</span></a></p></li>
292 <li><p><a class=
"reference internal" href=
"memcached_cas.html"><span class=
"doc">Working with data on the server in an atomic fashion
</span></a></p></li>
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