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    <title>clSetEventCallback</title>
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    <div class="refentry">
      <a id="id-1"></a>
      <div class="titlepage"></div>
      <div xmlns="" class="refnamediv">
        <a xmlns="http://www.w3.org/1999/xhtml" id="clSetEventCallback"></a>
        <h1>     
            clSetEventCallback
        </h1>
        <p>          
            Registers a user callback function for a specific command execution status.
        </p>
      </div>
      <div class="refsynopsisdiv">
        <h2></h2>
        <div class="funcsynopsis">
          <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
            <tr valign="bottom">
              <td>
                <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef">              
                    <a class="link" href="scalarDataTypes.html" target="_top">cl_int</a> <strong class="fsfunc">clSetEventCallback</strong>
                (</code>
                <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="_top">cl_event</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">event</var>, </td>
              </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td>
                    <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">cl_int</a>
                     <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">command_exec_callback_type</var>
                , </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">void</a> (CL_CALLBACK  <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*pfn_event_notify) 
                (<a class="link" href="abstractDataTypes.html" target="_top">cl_event</a> event, <a class="link" href="scalarDataTypes.html" target="_top">cl_int</a> event_command_exec_status,
                 <a class="link" href="scalarDataTypes.html" target="_top">void</a> *user_data</var>), </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">void</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*user_data</var><code>)</code></td>
            </tr>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="parameters"></a>
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <code class="varname">event</code>
              </span>
            </dt>
            <dd>
              <p>A valid event object.</p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">command_exec_callback_type</code>
              </span>
            </dt>
            <dd>
              <p> 
                        The command execution status for which the callback is registered. The command execution callback 
                        value for which a callback can be registered is CL_COMPLETE. There is no guarantee that the callback
                        functions registered for various execution status values for an event will be called in the exact 
                        order that the execution status of a command changes.
                    </p>
              <p>
                        The callback function registered for a <code class="varname">command_exec_callback_type</code> value of 
                        CL_COMPLETE will be called when the command has completed successfully or is abnormally terminated.
                    </p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">pfn_event_notify</code>
              </span>
            </dt>
            <dd>
              <p> 
                        The event callback function that can be registered by the application. 
                        This callback function may be called asynchronously by the OpenCL 
                        implementation. It is the application's responsibility to ensure 
                        that the callback function is thread-safe. The parameters to this callback function are:
                    </p>
              <div class="itemizedlist">
                <ul class="itemizedlist" style="list-style-type: disc; ">
                  <li class="listitem" style="list-style-type: disc"><code class="varname">event</code>: the event object for which the callback function is invoked.
                        </li>
                  <li class="listitem" style="list-style-type: disc"><code class="varname">event_command_exec_status</code>: the execution status of command for which 
                            this callback function is invoked. See the table of values for 
                            <a class="citerefentry" href="clGetEventInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetEventInfo</span></span></a><code class="varname">param_value</code> for the command execution status values. If the callback 
                             is 
                            called as the result of the command associated with event being abnormally terminated, an 
                            appropriate error code for the error that caused the termination will be passed to 
                            <code class="varname">event_command_exec_status</code> instead.
                        </li>
                  <li class="listitem" style="list-style-type: disc"><code class="varname">user_data</code>: a pointer to user supplied data.
                        </li>
                </ul>
              </div>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">user_data</code>
              </span>
            </dt>
            <dd>
              <p> 
                        Will be passed as the <code class="varname">user_data</code> argument when <code class="varname">pfn_notify</code> 
                        is called. <code class="varname">user_data</code> can be NULL.
                    </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
            The registered callback function will be called when the execution status of command associated with 
            <code class="varname">event</code> changes to the execution status specified by <code class="varname">command_exec_status</code>.
        </p>
        <p>
            Each call to <code class="function">clSetEventCallback</code> registers the specified user callback function on a 
            callback stack associated with <code class="varname">event</code>. The order in which the registered user callback 
            functions are called is undefined.
        </p>
        <p>
            All callbacks registered for an event object must be called. All enqueued 
            callbacks shall be called before the event object is destroyed. Callbacks must 
            return promptly. The behavior of calling expensive system routines, OpenCL API 
            calls to create contexts or command-queues, or blocking OpenCL operations from 
            the following list below, in a callback is undefined.
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc">
              <a class="citerefentry" href="clFinish.html">
                <span class="citerefentry">
                  <span class="refentrytitle">clFinish</span>
                </span>
              </a>
            </li>
            <li class="listitem" style="list-style-type: disc">
              <a class="citerefentry" href="clWaitForEvents.html">
                <span class="citerefentry">
                  <span class="refentrytitle">clWaitForEvents</span>
                </span>
              </a>
            </li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to <a class="citerefentry" href="clEnqueueReadBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadBuffer</span></span></a>, 
                <a class="citerefentry" href="clEnqueueReadBufferRect.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadBufferRect</span></span></a>, <a class="citerefentry" href="clEnqueueWriteBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteBuffer</span></span></a>, and  <a class="citerefentry" href="clEnqueueWriteBufferRect.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteBufferRect</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to <a class="citerefentry" href="clEnqueueReadImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadImage</span></span></a> and <a class="citerefentry" href="clEnqueueWriteImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteImage</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to <a class="citerefentry" href="clEnqueueMapBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueMapBuffer</span></span></a> and <a class="citerefentry" href="clEnqueueMapImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueMapImage</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
                blocking calls to <a class="citerefentry" href="clBuildProgram.html"><span class="citerefentry"><span class="refentrytitle">clBuildProgram</span></span></a></li>
          </ul>
        </div>
        <p>
            If an application needs to wait for completion of a routine from the above l
            ist in a callback, please use the non-blocking form of the function, and assign 
            a completion callback to it to do the remainder of your work. Note that when a 
            callback (or other code) enqueues commands to a command-queue, the commands are 
            not required to begin execution until the queue is flushed. In standard usage, 
            blocking enqueue calls serve this role by implicitly flushing the queue. Since 
            blocking calls are not permitted in callbacks, those callbacks that enqueue 
            commands on a command queue should either call 
             <a class="citerefentry" href="clFlush.html"><span class="citerefentry"><span class="refentrytitle">clFlush</span></span></a> on the queue 
             before returning or arrange for 
             <a class="citerefentry" href="clFlush.html"><span class="citerefentry"><span class="refentrytitle">clFlush</span></span></a> to be 
             called later on another thread.
            </p>
      </div>
      <div class="refsect1">
        <a id="errors"></a>
        <h2>Errors</h2>
        <p>
            Returns <span class="errorname">CL_SUCCESS</span> if the function is executed successfully. Otherwise, it returns 
            one of the following errors:
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_EVENT</span> if <code class="varname">event</code> is not a valid event object.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_VALUE</span> if <code class="varname">pfn_event_notify</code> is NULL or if 
                <code class="varname">command_exec_callback_type</code> is not CL_COMPLETE.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_RESOURCES</span> if there is a failure to allocate resources required 
                by the OpenCL implementation on the device.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_HOST_MEMORY</span> if there is a failure to allocate resources 
                required by the OpenCL implementation on the host.
            </li>
          </ul>
        </div>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p>
            <img src="pdficon_small1.gif" />
            
                      
            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.1.pdf#page=144" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2010 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
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