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| <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN" |
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| <refentry> |
| <refentryinfo> |
| <keywordset> |
| <keyword> |
| clEnqueueReadBuffer |
| </keyword> |
| </keywordset> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle> |
| clEnqueueReadBuffer |
| </refentrytitle> |
| |
| <refmiscinfo> |
| <copyright> |
| <year>2007-2009</year> |
| <holder>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.</holder> |
| </copyright> |
| </refmiscinfo> |
| <manvolnum>2</manvolnum> |
| |
| </refmeta> |
| |
| |
| <!-- ================================ SYNOPSIS --> |
| |
| <refnamediv id="clEnqueueReadBuffer"> |
| <refname> |
| clEnqueueReadBuffer |
| </refname> |
| |
| <refpurpose> |
| Enqueue commands to read from a buffer object to host memory. |
| </refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv xmlns:xlink="http://www.w3.org/1999/xlink"><title></title> |
| <funcsynopsis> |
| <funcprototype> |
| <funcdef> |
| <link xlink:href="scalarDataTypes.html">cl_int</link> |
| <function>clEnqueueReadBuffer</function> |
| </funcdef> |
| |
| <paramdef><link xlink:href="abstractDataTypes.html">cl_command_queue</link><parameter>command_queue</parameter></paramdef> |
| <paramdef><link xlink:href="abstractDataTypes.html">cl_mem</link><parameter>buffer</parameter></paramdef> |
| <paramdef><link xlink:href="enums.html#cl_bool">cl_bool</link><parameter>blocking_read</parameter></paramdef> |
| <paramdef><link xlink:href="scalarDataTypes.html">size_t</link><parameter>offset</parameter></paramdef> |
| <paramdef><link xlink:href="scalarDataTypes.html">size_t</link><parameter>cb</parameter></paramdef> |
| <paramdef><link xlink:href="scalarDataTypes.html">void</link><parameter>*ptr</parameter></paramdef> |
| <paramdef><link xlink:href="scalarDataTypes.html">cl_uint</link><parameter>num_events_in_wait_list</parameter></paramdef> |
| <paramdef>const <link xlink:href="abstractDataTypes.html">cl_event</link><parameter>*event_wait_list</parameter></paramdef> |
| <paramdef><link xlink:href="abstractDataTypes.html">cl_event</link><parameter>*event</parameter></paramdef> |
| |
| </funcprototype> |
| </funcsynopsis> |
| </refsynopsisdiv> |
| |
| |
| <!-- ================================ PARAMETERS --> |
| |
| <refsect1 id="parameters"> |
| <title>Parameters</title> |
| <variablelist> |
| |
| <varlistentry> |
| <term><varname>command_queue</varname></term> |
| <listitem> |
| <para> <!-- parameter description --> |
| Refers to the command-queue in which the read command will be |
| queued. <varname>command_queue</varname> and <varname>buffer</varname> must be created with the same OpenCL context. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>buffer</varname></term> |
| <listitem> |
| <para>Refers to a valid buffer object.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>blocking_read</varname></term> |
| <listitem> |
| <para> <!-- parameter description --> |
| Indicates if the read operations are <varname>blocking</varname> or non-blocking. If <varname>blocking_read</varname> is <constant>CL_TRUE</constant> i.e. the read command is blocking, <function>clEnqueueReadBuffer</function> does not return until the buffer data has been read and copied into memory pointed to by <varname>ptr</varname>. |
| </para> |
| <para> |
| If <varname>blocking_read</varname> is <constant>CL_FALSE</constant> i.e. the read command is <varname>non-blocking</varname>, <function>clEnqueueReadBuffer</function> |
| queues a <varname>non-blocking</varname> read command and returns. The contents of the buffer that <varname>ptr</varname> points to |
| cannot be used until the read command has completed. The <varname>event</varname> 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 <varname>ptr</varname> points to can be used by the |
| application. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>offset</varname></term> |
| |
| <listitem> |
| <para>The offset in bytes in the buffer object to read from.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>cb </varname></term> |
| |
| <listitem> |
| <para>The size in bytes of data being read.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term> |
| <varname>ptr </varname> |
| </term> |
| |
| <listitem> |
| <para> <!-- parameter description --> |
| The pointer to buffer in host memory where data is to be read into. |
| </para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term> |
| <varname> <!-- parameter name --> |
| event_wait_list |
| </varname> |
| </term> |
| <term> |
| <varname> <!-- parameter name --> |
| num_events_in_wait_list |
| </varname> |
| </term> |
| |
| <listitem> |
| <para> <!-- parameter description --> |
| <varname>event_wait_list</varname> and <varname>num_events_in_wait_list</varname> specify events that need to complete before this particular command can be executed. If <varname>event_wait_list</varname> is NULL, then this particular command |
| does not wait on any event to complete. If <varname>event_wait_list</varname> is NULL, <varname>num_events_in_wait_list</varname> must be 0. If <varname>event_wait_list</varname> is not NULL, the list of events pointed to by <varname>event_wait_list</varname> must be valid and <varname>num_events_in_wait_list</varname> must be greater than 0. The events specified in <varname>event_wait_list</varname> act as synchronization points. The context associated with events in <varname>event_wait_list</varname> and <varname>command_queue</varname> must be the same. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term> |
| <varname> <!-- parameter name --> |
| event |
| </varname> |
| </term> |
| |
| <listitem> |
| <para> <!-- parameter description --> |
| 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. <varname>event</varname> 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. |
| </para> |
| </listitem> |
| </varlistentry> |
| |
| |
| |
| |
| <!-- END PARAMETER TABLE --> |
| |
| |
| |
| |
| |
| </variablelist> |
| </refsect1> |
| |
| |
| <!-- ================================ NOTES --> |
| |
| |
| <refsect1 id="notes"><title>Notes</title> |
| <para> |
| Calling <function>clEnqueueReadBuffer</function> to read a region of the buffer object with the <varname>ptr</varname> argument value |
| set to <varname>host_ptr</varname> + <varname>offset</varname>, where <varname>host_ptr</varname> is a pointer to the memory region specified when the |
| buffer object being read is created with <constant>CL_MEM_USE_HOST_PTR</constant>, must meet the following |
| requirements in order to avoid undefined behavior: |
| </para> |
| <itemizedlist mark="disc"> |
| <listitem>All commands that use this buffer object have finished execution before the read |
| command begins execution</listitem>. |
| <listitem>The buffer object is not mapped</listitem>. |
| <listitem>The buffer object is not used by any command-queue until the read command has |
| finished execution</listitem>. |
| |
| </itemizedlist> |
| </refsect1> |
| |
| |
| <!-- ================================ ERRORS --> |
| |
| |
| <refsect1 id="errors"><title>Errors</title> |
| <para> |
| <function>clEnqueueReadBuffer</function> returns <errorname>CL_SUCCESS</errorname> if the function is |
| executed successfully. Otherwise, it returns one of the following errors: |
| </para> |
| <itemizedlist mark="disc"> |
| <listitem> |
| <errorname>CL_INVALID_COMMAND_QUEUE</errorname> if <varname>command_queue</varname> is not a valid command-queue. |
| </listitem> |
| <listitem> |
| <errorname>CL_INVALID_CONTEXT</errorname> if the context associated with <varname>command_queue</varname> and <varname>buffer</varname> are not the same or if the context associated with <varname>command_queue</varname> and events in |
| <varname>event_wait_list</varname> are not the same. |
| </listitem> |
| <listitem> |
| <errorname>CL_INVALID_MEM_OBJECT</errorname> if <varname>buffer</varname> is not a valid buffer object. |
| </listitem> |
| <listitem> |
| <errorname>CL_INVALID_VALUE</errorname> if the region being read specified by (<varname>offset</varname>, <varname>cb</varname>) is out of bounds or if <varname>ptr</varname> is a NULL value. |
| </listitem> |
| <listitem> |
| <errorname>CL_INVALID_EVENT_WAIT_LIST</errorname> if <varname>event_wait_list</varname> is NULL and |
| <varname>num_events_in_wait_list</varname> greater than 0, or <varname>event_wait_list</varname> is not NULL and <varname>num_events_in_wait_list</varname> is 0, or if event objects in <varname>event_wait_list</varname> are not valid events. |
| </listitem> |
| <listitem> |
| <errorname>CL_MEM_OBJECT_ALLOCATION_FAILURE</errorname> if there is a failure to allocate memory for |
| data store associated with <varname>buffer</varname>. |
| </listitem> |
| <listitem> |
| <errorname>CL_OUT_OF_HOST_MEMORY</errorname> if there is a failure to allocate resources required by the |
| OpenCL implementation on the host. |
| </listitem> |
| |
| </itemizedlist> |
| </refsect1> |
| |
| |
| <!-- ================================ EXAMPLE --> |
| <!-- DO NOT DELETE IN CASE AN EXAMPLE IS ADDED IN THE FUTURE --> |
| <!-- |
| <refsect2 id="example1"> |
| <title> |
| Example |
| </title> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| Example goes here - it will be set in "code" type with white space preserved. |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| --> |
| |
| |
| <!-- ================================ SPECIFICATION --> |
| <!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page |
| --> |
| <refsect1 id="specification"><title>Specification</title> |
| <para> |
| <imageobject> |
| <imagedata fileref="pdficon_small1.gif" format="gif" /> |
| </imageobject> |
| |
| |
| <olink uri="clEnqueueReadBuffer">OpenCL Specification</olink> |
| </para> |
| </refsect1> |
| |
| |
| <!-- ================================ ALSO SEE --> |
| |
| |
| <refsect1 id="seealso"><title>Also see</title> |
| <para> |
| <citerefentry><refentrytitle>clEnqueueCopyBuffer</refentrytitle></citerefentry>, |
| <citerefentry><refentrytitle>clEnqueueWriteBuffer</refentrytitle></citerefentry> |
| </para> |
| </refsect1> |
| |
| <!-- ================================ COPYRIGHT --> |
| <!-- Content included from copyright.inc.xsl --> |
| |
| <refsect3 id="Copyright"><title></title> |
| <imageobject> |
| <imagedata fileref="KhronosLogo.jpg" format="jpg" /> |
| </imageobject> |
| <para /> |
| </refsect3> |
| |
| </refentry> |
| |