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 196   <div class="section" id="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>
 200 <dl class="simple">
 201 <dt>#include &lt;libmemcached-1.0/memcached.h&gt;</dt><dd><p>Compile and link with -lmemcached</p>
 202 </dd>
 203 </dl>
 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>
 207 <dd></dd></dl>
 208
 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>
 212 <dd></dd></dl>
 213
 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>
 217 <dd></dd></dl>
 218
 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>
 234 </ul>
 235 </dd>
 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>
 238 </dd>
 239 </dl>
 240 </dd></dl>
 241
 242 </div>
 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>
 279 </div>
 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>
 285 </div>
 286 <div class="section" id="see-also">
 287 <h2>SEE ALSO<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
 288 <ul class="simple">
 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>
 293 <li><p><a class="reference internal" href="memcached_strerror.html"><span class="doc">Converting Error Codes to Messages</span></a></p></li>
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