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| <refentry> |
| <refentryinfo> |
| <keywordset> |
| <keyword>clEnqueueReadBuffer</keyword> |
| </keywordset> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle> |
| clEnqueueReadBuffer |
| </refentrytitle> |
| |
| <refmiscinfo> |
| <copyright> |
| <year>2007-2010</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>3</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>size</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. |
| </para> |
| |
| <para> |
| 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>size</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. The memory associated with <varname>event_wait_list</varname> |
| can be reused or freed after the function returns. |
| </para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term> <varname> 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. |
| If the <varname>event_wait_list</varname> and the event arguments are |
| not NULL, the <varname>event</varname> argument should not refer to an |
| element of the <varname>event_wait_list</varname> array. |
| </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 or a memory object (buffer or image) |
| created from this buffer object have finished execution before the read command |
| begins execution. |
| </listitem> |
| |
| <listitem> |
| The buffer object or memory objects created from this buffer object are not mapped. |
| </listitem> |
| |
| <listitem> |
| The buffer object or memory objects created from this buffer object are 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>size</varname>) is out of bounds or if |
| <varname>ptr</varname> is a NULL value or if size is 0. |
| </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_MISALIGNED_SUB_BUFFER_OFFSET</errorname> if |
| <varname>buffer</varname> is a sub-buffer object and <varname>offset</varname> |
| specified when the sub-buffer object is created is not aligned to |
| <constant>CL_DEVICE_MEM_BASE_ADDR_ALIGN</constant> value for device associated |
| with <varname>queue</varname>. |
| </listitem> |
| |
| <listitem> |
| <errorname>CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST</errorname> if the read |
| and write operations are blocking and the execution status of any of the events |
| in <varname>event_wait_list</varname> is a negative integer value. |
| </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_INVALID_OPERATION</errorname> if |
| <function>clEnqueueReadBuffer</function> is called on <varname>buffer</varname> |
| which has been created with <constant>CL_MEM_HOST_WRITE_ONLY</constant> or |
| <constant>CL_MEM_HOST_NO_ACCESS</constant>. |
| </listitem> |
| |
| <listitem> |
| <errorname>CL_OUT_OF_RESOURCES</errorname> if there is a failure to allocate |
| resources required by the OpenCL implementation on the device. |
| </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>, |
| <citerefentry><refentrytitle>clEnqueueWriteBufferRect</refentrytitle></citerefentry>, |
| <citerefentry><refentrytitle>clEnqueueReadBufferRect</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> |
| |
| <!-- 20-Oct-2011 --> |
| </refentry> |
| |
