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 201
 202   <div class="section" id="library-callbacks">
 203 <h1>Library callbacks<a class="headerlink" href="#library-callbacks" title="Permalink to this headline">¶</a></h1>
 204 <div class="section" id="synopsis">
 205 <h2>SYNOPSIS<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2>
 206 <dl class="simple">
 207 <dt>#include &lt;libmemcached/memcached.h&gt;</dt><dd><p>Compile and link with -lmemcached</p>
 208 </dd>
 209 </dl>
 210 <dl class="cpp function">
 211 <dt id="_CPPv422memcached_callback_setP12memcached_st20memcached_callback_tPKv">
 212 <span id="_CPPv322memcached_callback_setP12memcached_st20memcached_callback_tPKv"></span><span id="_CPPv222memcached_callback_setP12memcached_st20memcached_callback_tPKv"></span><span id="memcached_callback_set__memcached_stP.memcached_callback_t.voidCP"></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_callback_set</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>, <a class="reference internal" href="#_CPPv420memcached_callback_t" title="memcached_callback_t">memcached_callback_t</a> <em>flag</em>, <em class="property">const</em> void *<em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv422memcached_callback_setP12memcached_st20memcached_callback_tPKv" title="Permalink to this definition">¶</a><br /></dt>
 213 <dd><dl class="field-list simple">
 214 <dt class="field-odd">Parameters</dt>
 215 <dd class="field-odd"><ul class="simple">
 216 <li><p><strong>ptr</strong> -- pointer to 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>
 217 <li><p><strong>flag</strong> -- <a class="reference internal" href="#_CPPv420memcached_callback_t" title="memcached_callback_t"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_callback_t</span></code></a> flag to set</p></li>
 218 <li><p><strong>data</strong> -- data corresponding to <a class="reference internal" href="#_CPPv422memcached_callback_setP12memcached_st20memcached_callback_tPKv" title="memcached_callback_set::flag"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">flag</span></code></a></p></li>
 219 </ul>
 220 </dd>
 221 <dt class="field-even">Returns</dt>
 222 <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>
 223 </dd>
 224 </dl>
 225 </dd></dl>
 226
 227 <dl class="cpp function">
 228 <dt id="_CPPv422memcached_callback_getP12memcached_st20memcached_callback_tP18memcached_return_t">
 229 <span id="_CPPv322memcached_callback_getP12memcached_st20memcached_callback_tP18memcached_return_t"></span><span id="_CPPv222memcached_callback_getP12memcached_st20memcached_callback_tP18memcached_return_t"></span><span id="memcached_callback_get__memcached_stP.memcached_callback_t.memcached_return_tP"></span>void *<code class="sig-name descname">memcached_callback_get</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>, <a class="reference internal" href="#_CPPv420memcached_callback_t" title="memcached_callback_t">memcached_callback_t</a> <em>flag</em>, <a class="reference internal" href="memcached_return_t.html#_CPPv418memcached_return_t" title="memcached_return_t">memcached_return_t</a> *<em>error</em><span class="sig-paren">)</span><a class="headerlink" href="#_CPPv422memcached_callback_getP12memcached_st20memcached_callback_tP18memcached_return_t" title="Permalink to this definition">¶</a><br /></dt>
 230 <dd><dl class="field-list simple">
 231 <dt class="field-odd">Parameters</dt>
 232 <dd class="field-odd"><ul class="simple">
 233 <li><p><strong>ptr</strong> -- pointer to 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>
 234 <li><p><strong>flag</strong> -- <a class="reference internal" href="#_CPPv420memcached_callback_t" title="memcached_callback_t"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_callback_t</span></code></a> flag to query</p></li>
 235 <li><p><strong>error</strong> -- pointer to <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></li>
 236 </ul>
 237 </dd>
 238 <dt class="field-even">Returns</dt>
 239 <dd class="field-even"><p>the <code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">data</span></code> previously set</p>
 240 </dd>
 241 </dl>
 242 </dd></dl>
 243
 244 <dl class="c type">
 245 <dt id="c.memcached_callback_t">
 246 <em class="property">typedef </em><em class="property">enum</em> <a class="reference internal" href="#c.memcached_callback_t" title="memcached_callback_t">memcached_callback_t</a> <code class="sig-name descname">memcached_callback_t</code><a class="headerlink" href="#c.memcached_callback_t" title="Permalink to this definition">¶</a><br /></dt>
 247 <dd></dd></dl>
 248
 249 <dl class="cpp enum">
 250 <dt id="_CPPv420memcached_callback_t">
 251 <span id="_CPPv320memcached_callback_t"></span><span id="_CPPv220memcached_callback_t"></span><em class="property">enum </em><code class="sig-name descname">memcached_callback_t</code><a class="headerlink" href="#_CPPv420memcached_callback_t" title="Permalink to this definition">¶</a><br /></dt>
 252 <dd><dl class="cpp enumerator">
 253 <dt id="_CPPv4N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTIONE">
 254 <span id="_CPPv3N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTIONE"></span><span id="_CPPv2N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTIONE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_CLEANUP_FUNCTION</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTIONE" title="Permalink to this definition">¶</a><br /></dt>
 255 <dd><p>When <a class="reference internal" href="memcached_create.html#_CPPv414memcached_freeP12memcached_st" title="memcached_free"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_free()</span></code></a> or <code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_reset</span></code> is called this function
 256 will be executed. At the point of its execution all connections are closed.</p>
 257 <p>Its signature is:</p>
 258 <dl class="cpp type">
 259 <dt id="_CPPv4N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTION20memcached_cleanup_fnE">
 260 <span id="_CPPv3N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTION20memcached_cleanup_fnE"></span><span id="_CPPv2N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTION20memcached_cleanup_fnE"></span><span id="memcached_callback_t::MEMCACHED_CALLBACK_CLEANUP_FUNCTION::memcached_cleanup_fn"></span><em class="property">typedef </em><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_cleanup_fn</code>)<span class="sig-paren">(</span><em class="property">const</em> <a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *ptr<span class="sig-paren">)</span><a class="headerlink" href="#_CPPv4N20memcached_callback_t35MEMCACHED_CALLBACK_CLEANUP_FUNCTION20memcached_cleanup_fnE" title="Permalink to this definition">¶</a><br /></dt>
 261 <dd></dd></dl>
 262
 263 </dd></dl>
 264
 265 <dl class="cpp enumerator">
 266 <dt id="_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTIONE">
 267 <span id="_CPPv3N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTIONE"></span><span id="_CPPv2N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTIONE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_CLONE_FUNCTION</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTIONE" title="Permalink to this definition">¶</a><br /></dt>
 268 <dd><p>When <a class="reference internal" href="memcached_create.html#_CPPv415memcached_cloneP12memcached_stP12memcached_st" title="memcached_clone"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_clone()</span></code></a> is called this function will be executed.</p>
 269 <p>Its signature is:</p>
 270 <dl class="cpp type">
 271 <dt id="_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTION18memcached_clone_fnE">
 272 <span id="_CPPv3N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTION18memcached_clone_fnE"></span><span id="_CPPv2N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTION18memcached_clone_fnE"></span><span id="memcached_callback_t::MEMCACHED_CALLBACK_CLONE_FUNCTION::memcached_clone_fn"></span><em class="property">typedef </em><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_clone_fn</code>)<span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *destination, <em class="property">const</em> <a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *source<span class="sig-paren">)</span><a class="headerlink" href="#_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_CLONE_FUNCTION18memcached_clone_fnE" title="Permalink to this definition">¶</a><br /></dt>
 273 <dd></dd></dl>
 274
 275 </dd></dl>
 276
 277 <dl class="cpp enumerator">
 278 <dt id="_CPPv4N20memcached_callback_t29MEMCACHED_CALLBACK_PREFIX_KEYE">
 279 <span id="_CPPv3N20memcached_callback_t29MEMCACHED_CALLBACK_PREFIX_KEYE"></span><span id="_CPPv2N20memcached_callback_t29MEMCACHED_CALLBACK_PREFIX_KEYE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_PREFIX_KEY</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t29MEMCACHED_CALLBACK_PREFIX_KEYE" title="Permalink to this definition">¶</a><br /></dt>
 280 <dd><p>See <a class="reference internal" href="#_CPPv4N20memcached_callback_t28MEMCACHED_CALLBACK_NAMESPACEE" title="memcached_callback_t::MEMCACHED_CALLBACK_NAMESPACE"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_CALLBACK_NAMESPACE</span></code></a>.</p>
 281 </dd></dl>
 282
 283 <dl class="cpp enumerator">
 284 <dt id="_CPPv4N20memcached_callback_t28MEMCACHED_CALLBACK_NAMESPACEE">
 285 <span id="_CPPv3N20memcached_callback_t28MEMCACHED_CALLBACK_NAMESPACEE"></span><span id="_CPPv2N20memcached_callback_t28MEMCACHED_CALLBACK_NAMESPACEE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_NAMESPACE</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t28MEMCACHED_CALLBACK_NAMESPACEE" title="Permalink to this definition">¶</a><br /></dt>
 286 <dd><p>You can set a value which will be used to create a domain for your keys.
 287 The value specified here will be prefixed to each of your keys. The
 288 value can not be greater then <a class="reference internal" href="constants.html#c.MEMCACHED_MAX_NAMESPACE" title="MEMCACHED_MAX_NAMESPACE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">MEMCACHED_MAX_NAMESPACE</span></code></a> - 1 and
 289 will reduce <a class="reference internal" href="constants.html#c.MEMCACHED_MAX_KEY" title="MEMCACHED_MAX_KEY"><code class="xref c c-macro docutils literal notranslate"><span class="pre">MEMCACHED_MAX_KEY</span></code></a> by the value of your key.</p>
 290 <p>The prefix key is only applied to the primary key, not the master key.
 291 <a class="reference internal" href="memcached_return_t.html#_CPPv4N18memcached_return_t17MEMCACHED_FAILUREE" title="MEMCACHED_FAILURE"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_FAILURE</span></code></a> will be returned if no key is set. In the case of a
 292 key which is too long, <a class="reference internal" href="memcached_return_t.html#_CPPv4N18memcached_return_t26MEMCACHED_BAD_KEY_PROVIDEDE" title="MEMCACHED_BAD_KEY_PROVIDED"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_BAD_KEY_PROVIDED</span></code></a> will be returned.</p>
 293 <p>If you set a value with the value being NULL then the prefix key is
 294 disabled.</p>
 295 </dd></dl>
 296
 297 <dl class="cpp enumerator">
 298 <dt id="_CPPv4N20memcached_callback_t28MEMCACHED_CALLBACK_USER_DATAE">
 299 <span id="_CPPv3N20memcached_callback_t28MEMCACHED_CALLBACK_USER_DATAE"></span><span id="_CPPv2N20memcached_callback_t28MEMCACHED_CALLBACK_USER_DATAE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_USER_DATA</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t28MEMCACHED_CALLBACK_USER_DATAE" title="Permalink to this definition">¶</a><br /></dt>
 300 <dd><p>This allows you to store a pointer to a specific piece of data. This can
 301 be retrieved from inside of <a class="reference internal" href="memcached_get.html#_CPPv423memcached_fetch_executeP12memcached_stP20memcached_execute_fnPv8uint32_t" title="memcached_fetch_execute"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_fetch_execute()</span></code></a>. Cloning a
 302 <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> will copy the pointer to the clone.</p>
 303 </dd></dl>
 304
 305 <dl class="cpp enumerator">
 306 <dt id="_CPPv4N20memcached_callback_t34MEMCACHED_CALLBACK_MALLOC_FUNCTIONE">
 307 <span id="_CPPv3N20memcached_callback_t34MEMCACHED_CALLBACK_MALLOC_FUNCTIONE"></span><span id="_CPPv2N20memcached_callback_t34MEMCACHED_CALLBACK_MALLOC_FUNCTIONE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_MALLOC_FUNCTION</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t34MEMCACHED_CALLBACK_MALLOC_FUNCTIONE" title="Permalink to this definition">¶</a><br /></dt>
 308 <dd><div class="deprecated">
 309 <p><span class="versionmodified deprecated">Deprecated since version &lt;0.32: </span>Use <a class="reference internal" href="memcached_memory_allocators.html#_CPPv431memcached_set_memory_allocatorsP12memcached_st19memcached_malloc_fn17memcached_free_fn20memcached_realloc_fn19memcached_calloc_fnPv" title="memcached_set_memory_allocators"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_set_memory_allocators()</span></code></a> instead.</p>
 310 </div>
 311 </dd></dl>
 312
 313 <dl class="cpp enumerator">
 314 <dt id="_CPPv4N20memcached_callback_t35MEMCACHED_CALLBACK_REALLOC_FUNCTIONE">
 315 <span id="_CPPv3N20memcached_callback_t35MEMCACHED_CALLBACK_REALLOC_FUNCTIONE"></span><span id="_CPPv2N20memcached_callback_t35MEMCACHED_CALLBACK_REALLOC_FUNCTIONE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_REALLOC_FUNCTION</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t35MEMCACHED_CALLBACK_REALLOC_FUNCTIONE" title="Permalink to this definition">¶</a><br /></dt>
 316 <dd><div class="deprecated">
 317 <p><span class="versionmodified deprecated">Deprecated since version &lt;0.32: </span>Use <a class="reference internal" href="memcached_memory_allocators.html#_CPPv431memcached_set_memory_allocatorsP12memcached_st19memcached_malloc_fn17memcached_free_fn20memcached_realloc_fn19memcached_calloc_fnPv" title="memcached_set_memory_allocators"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_set_memory_allocators()</span></code></a> instead.</p>
 318 </div>
 319 </dd></dl>
 320
 321 <dl class="cpp enumerator">
 322 <dt id="_CPPv4N20memcached_callback_t32MEMCACHED_CALLBACK_FREE_FUNCTIONE">
 323 <span id="_CPPv3N20memcached_callback_t32MEMCACHED_CALLBACK_FREE_FUNCTIONE"></span><span id="_CPPv2N20memcached_callback_t32MEMCACHED_CALLBACK_FREE_FUNCTIONE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_FREE_FUNCTION</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t32MEMCACHED_CALLBACK_FREE_FUNCTIONE" title="Permalink to this definition">¶</a><br /></dt>
 324 <dd><div class="deprecated">
 325 <p><span class="versionmodified deprecated">Deprecated since version &lt;0.32: </span>Use <a class="reference internal" href="memcached_memory_allocators.html#_CPPv431memcached_set_memory_allocatorsP12memcached_st19memcached_malloc_fn17memcached_free_fn20memcached_realloc_fn19memcached_calloc_fnPv" title="memcached_set_memory_allocators"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_set_memory_allocators()</span></code></a> instead.</p>
 326 </div>
 327 </dd></dl>
 328
 329 <dl class="cpp enumerator">
 330 <dt id="_CPPv4N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILUREE">
 331 <span id="_CPPv3N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILUREE"></span><span id="_CPPv2N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILUREE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_GET_FAILURE</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILUREE" title="Permalink to this definition">¶</a><br /></dt>
 332 <dd><p>This function implements the read through cache behavior. On failure of
 333 retrieval this callback will be called.</p>
 334 <p>You are responsible for populating the result object provided. This
 335 result object will then be stored in the server and returned to the
 336 calling process.</p>
 337 <p>You must clone the <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> in order to make use of it. The value
 338 will be stored only if you return <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> or
 339 <a class="reference internal" href="memcached_return_t.html#_CPPv4N18memcached_return_t18MEMCACHED_BUFFEREDE" title="MEMCACHED_BUFFERED"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_BUFFERED</span></code></a>. Returning <a class="reference internal" href="memcached_return_t.html#_CPPv4N18memcached_return_t18MEMCACHED_BUFFEREDE" title="MEMCACHED_BUFFERED"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_BUFFERED</span></code></a> will cause the
 340 object to be buffered and not sent immediately (if this is the default
 341 behavior based on your connection setup this will happen automatically).</p>
 342 <p>The prototype for this is:</p>
 343 <dl class="cpp type">
 344 <dt id="_CPPv4N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILURE21memcached_trigger_keyE">
 345 <span id="_CPPv3N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILURE21memcached_trigger_keyE"></span><span id="_CPPv2N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILURE21memcached_trigger_keyE"></span><span id="memcached_callback_t::MEMCACHED_CALLBACK_GET_FAILURE::memcached_trigger_key"></span><em class="property">typedef </em><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_trigger_key</code>)<span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *ptr, char *key, size_t key_length, <a class="reference internal" href="memcached_result_st.html#_CPPv419memcached_result_st" title="memcached_result_st">memcached_result_st</a> *result<span class="sig-paren">)</span><a class="headerlink" href="#_CPPv4N20memcached_callback_t30MEMCACHED_CALLBACK_GET_FAILURE21memcached_trigger_keyE" title="Permalink to this definition">¶</a><br /></dt>
 346 <dd></dd></dl>
 347
 348 </dd></dl>
 349
 350 <dl class="cpp enumerator">
 351 <dt id="_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGERE">
 352 <span id="_CPPv3N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGERE"></span><span id="_CPPv2N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGERE"></span><em class="property">enumerator </em><code class="sig-name descname">MEMCACHED_CALLBACK_DELETE_TRIGGER</code><a class="headerlink" href="#_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGERE" title="Permalink to this definition">¶</a><br /></dt>
 353 <dd><p>This function implements a trigger upon successful deletion of a key.
 354 The <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> structure will need to be cloned in order to make use
 355 of it.</p>
 356 <p>The prototype for this is:</p>
 357 <dl class="cpp type">
 358 <dt id="_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGER28memcached_trigger_delete_keyE">
 359 <span id="_CPPv3N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGER28memcached_trigger_delete_keyE"></span><span id="_CPPv2N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGER28memcached_trigger_delete_keyE"></span><span id="memcached_callback_t::MEMCACHED_CALLBACK_DELETE_TRIGGER::memcached_trigger_delete_key"></span><em class="property">typedef </em><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_trigger_delete_key</code>)<span class="sig-paren">(</span><a class="reference internal" href="memcached_create.html#_CPPv412memcached_st" title="memcached_st">memcached_st</a> *ptr, char *key, size_t key_length<span class="sig-paren">)</span><a class="headerlink" href="#_CPPv4N20memcached_callback_t33MEMCACHED_CALLBACK_DELETE_TRIGGER28memcached_trigger_delete_keyE" title="Permalink to this definition">¶</a><br /></dt>
 360 <dd></dd></dl>
 361
 362 </dd></dl>
 363
 364 </dd></dl>
 365
 366 </div>
 367 <div class="section" id="description">
 368 <h2>DESCRIPTION<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
 369 <p><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">libmemcached</span></code> can have callbacks set key execution points. These either provide
 370 function calls at points in the code, or return pointers to structures for
 371 particular usages.</p>
 372 <p><a class="reference internal" href="#_CPPv422memcached_callback_getP12memcached_st20memcached_callback_tP18memcached_return_t" title="memcached_callback_get"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_callback_get()</span></code></a> takes a callback flag and returns the structure or
 373 function set by <a class="reference internal" href="#_CPPv422memcached_callback_setP12memcached_st20memcached_callback_tPKv" title="memcached_callback_set"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_callback_set()</span></code></a>.</p>
 374 <p><a class="reference internal" href="#_CPPv422memcached_callback_setP12memcached_st20memcached_callback_tPKv" title="memcached_callback_set"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_callback_set()</span></code></a> changes the function/structure assigned by a callback
 375 flag. No connections are reset.</p>
 376 <p>You can use <a class="reference internal" href="#_CPPv4N20memcached_callback_t28MEMCACHED_CALLBACK_USER_DATAE" title="MEMCACHED_CALLBACK_USER_DATA"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_CALLBACK_USER_DATA</span></code></a> to provide custom context if required
 377 for any of the callbacks.</p>
 378 </div>
 379 <div class="section" id="return-value">
 380 <h2>RETURN VALUE<a class="headerlink" href="#return-value" title="Permalink to this headline">¶</a></h2>
 381 <p><a class="reference internal" href="#_CPPv422memcached_callback_getP12memcached_st20memcached_callback_tP18memcached_return_t" title="memcached_callback_get"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_callback_get()</span></code></a> returns the function or structure that was provided.
 382 Upon error, nothing is set, NULL is returned, and the <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>
 383 argument is set to <a class="reference internal" href="memcached_return_t.html#_CPPv4N18memcached_return_t17MEMCACHED_FAILUREE" title="MEMCACHED_FAILURE"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_FAILURE</span></code></a>.</p>
 384 <p><a class="reference internal" href="#_CPPv422memcached_callback_setP12memcached_st20memcached_callback_tPKv" title="memcached_callback_set"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">memcached_callback_set()</span></code></a> returns <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> upon successful setting,
 385 otherwise <a class="reference internal" href="memcached_return_t.html#_CPPv4N18memcached_return_t17MEMCACHED_FAILUREE" title="MEMCACHED_FAILURE"><code class="xref cpp cpp-any docutils literal notranslate"><span class="pre">MEMCACHED_FAILURE</span></code></a> on error.</p>
 386 </div>
 387 <div class="section" id="see-also">
 388 <h2>SEE ALSO<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
 389 <ul class="simple">
 390 <li><p><em class="manpage"><a class="manpage reference external" href="https://linux.die.net/man/1/memcached">memcached(1)</a></em></p></li>
 391 <li><p><a class="reference internal" href="../libmemcached.html"><span class="doc">C/C++ Client Library for memcached</span></a></p></li>
 392 <li><p><a class="reference internal" href="memcached_strerror.html"><span class="doc">Converting Error Codes to Messages</span></a></p></li>
 393 </ul>
 394 </div>
 395 </div>
 396
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 398            </div>
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