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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<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>
|
