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| <title>clEnqueueReadBuffer</title> |
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| <body> |
| <div class="refentry"> |
| <a id="idm1"></a> |
| <div class="titlepage"></div> |
| <div xmlns="" class="refnamediv"> |
| <a xmlns="http://www.w3.org/1999/xhtml" id="clEnqueueReadBuffer"></a> |
| <h1> |
| clEnqueueReadBuffer |
| </h1> |
| <p> |
| Enqueue commands to read from a buffer object to host memory. |
| </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">clEnqueueReadBuffer</strong> |
| (</code> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="_top">cl_command_queue</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">command_queue</var>, </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="_top">cl_mem</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">buffer</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="enums.html#cl_bool" target="_top">cl_bool</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">blocking_read</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">size_t</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">offset</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">size_t</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">cb</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">*ptr</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">cl_uint</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">num_events_in_wait_list</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td>const <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_wait_list</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <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><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">command_queue</code> |
| </span> |
| </dt> |
| <dd> |
| <p> |
| Refers to the command-queue in which the read command will be |
| queued. <code class="varname">command_queue</code> and <code class="varname">buffer</code> must be created with the same OpenCL context. |
| </p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname">buffer</code> |
| </span> |
| </dt> |
| <dd> |
| <p>Refers to a valid buffer object.</p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname">blocking_read</code> |
| </span> |
| </dt> |
| <dd> |
| <p> |
| Indicates if the read operations are <code class="varname">blocking</code> or non-blocking. If <code class="varname">blocking_read</code> is <code class="constant">CL_TRUE</code> i.e. the read command is blocking, <code class="function">clEnqueueReadBuffer</code> does not return until the buffer data has been read and copied into memory pointed to by <code class="varname">ptr</code>. |
| </p> |
| <p> |
| If <code class="varname">blocking_read</code> is <code class="constant">CL_FALSE</code> i.e. the read command is <code class="varname">non-blocking</code>, <code class="function">clEnqueueReadBuffer</code> |
| queues a <code class="varname">non-blocking</code> read command and returns. The contents of the buffer that <code class="varname">ptr</code> points to |
| cannot be used until the read command has completed. The <code class="varname">event</code> argument returns an event |
| object which can be used to query the execution status of the read command. When the read |
| command has completed, the contents of the buffer that <code class="varname">ptr</code> points to can be used by the |
| application. |
| </p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname">offset</code> |
| </span> |
| </dt> |
| <dd> |
| <p>The offset in bytes in the buffer object to read from.</p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname">cb </code> |
| </span> |
| </dt> |
| <dd> |
| <p>The size in bytes of data being read.</p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname">ptr </code> |
| </span> |
| </dt> |
| <dd> |
| <p> |
| The pointer to buffer in host memory where data is to be read into. |
| </p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname"> |
| event_wait_list |
| </code> |
| , </span> |
| <span class="term"> |
| <code class="varname"> |
| num_events_in_wait_list |
| </code> |
| </span> |
| </dt> |
| <dd> |
| <p> |
| <code class="varname">event_wait_list</code> and <code class="varname">num_events_in_wait_list</code> specify events that need to complete before this particular command can be executed. If <code class="varname">event_wait_list</code> is NULL, then this particular command |
| does not wait on any event to complete. If <code class="varname">event_wait_list</code> is NULL, <code class="varname">num_events_in_wait_list</code> must be 0. If <code class="varname">event_wait_list</code> is not NULL, the list of events pointed to by <code class="varname">event_wait_list</code> must be valid and <code class="varname">num_events_in_wait_list</code> must be greater than 0. The events specified in <code class="varname">event_wait_list</code> act as synchronization points. The context associated with events in <code class="varname">event_wait_list</code> and <code class="varname">command_queue</code> must be the same. |
| </p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname"> |
| event |
| </code> |
| </span> |
| </dt> |
| <dd> |
| <p> |
| Returns an event object that identifies this particular read command and can be used |
| to query or queue a wait for this particular command to complete. <code class="varname">event</code> can be NULL in which |
| case it will not be possible for the application to query the status of this command or queue a |
| wait for this command to complete. |
| </p> |
| </dd> |
| </dl> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="notes"></a> |
| <h2>Notes</h2> |
| <p> |
| Calling <code class="function">clEnqueueReadBuffer</code> to read a region of the buffer object with the <code class="varname">ptr</code> argument value |
| set to <code class="varname">host_ptr</code> + <code class="varname">offset</code>, where <code class="varname">host_ptr</code> is a pointer to the memory region specified when the |
| buffer object being read is created with <code class="constant">CL_MEM_USE_HOST_PTR</code>, must meet the following |
| requirements in order to avoid undefined behavior: |
| </p> |
| <div class="itemizedlist"> |
| <ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem" style="list-style-type: disc">All commands that use this buffer object have finished execution before the read |
| command begins execution</li> |
| <li class="listitem" style="list-style-type: disc">The buffer object is not mapped</li> |
| <li class="listitem" style="list-style-type: disc">The buffer object is not used by any command-queue until the read command has |
| finished execution</li> |
| </ul> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="errors"></a> |
| <h2>Errors</h2> |
| <p> |
| <code class="function">clEnqueueReadBuffer</code> 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_COMMAND_QUEUE</span> if <code class="varname">command_queue</code> is not a valid command-queue. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_CONTEXT</span> if the context associated with <code class="varname">command_queue</code> and <code class="varname">buffer</code> are not the same or if the context associated with <code class="varname">command_queue</code> and events in |
| <code class="varname">event_wait_list</code> are not the same. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_MEM_OBJECT</span> if <code class="varname">buffer</code> is not a valid buffer object. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_VALUE</span> if the region being read specified by (<code class="varname">offset</code>, <code class="varname">cb</code>) is out of bounds or if <code class="varname">ptr</code> is a NULL value. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_EVENT_WAIT_LIST</span> if <code class="varname">event_wait_list</code> is NULL and |
| <code class="varname">num_events_in_wait_list</code> greater than 0, or <code class="varname">event_wait_list</code> is not NULL and <code class="varname">num_events_in_wait_list</code> is 0, or if event objects in <code class="varname">event_wait_list</code> are not valid events. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_MEM_OBJECT_ALLOCATION_FAILURE</span> if there is a failure to allocate memory for |
| data store associated with <code class="varname">buffer</code>. |
| </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-1.0.pdf#page=54" target="OpenCL Spec">OpenCL Specification</a> |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="seealso"></a> |
| <h2>Also see</h2> |
| <p> |
| <a class="citerefentry" href="clEnqueueCopyBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueCopyBuffer</span></span></a>, |
| <a class="citerefentry" href="clEnqueueWriteBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteBuffer</span></span></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 © 2007-2009 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 |
| permit persons to whom the Materials are furnished to do so, subject to |
| the condition that this copyright notice and permission notice shall be included |
| in all copies or substantial portions of the Materials. |
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