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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<keyword>clEnqueueMapBuffer</keyword>
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<year>2007-2011</year>
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<holder>The Khronos Group Inc.
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and/or associated documentation files (the
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"Materials"), to deal in the Materials without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Materials, and to
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permit persons to whom the Materials are furnished to do so, subject to
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the condition that this copyright notice and permission notice shall be included
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in all copies or substantial portions of the Materials.</holder>
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<manvolnum>3</manvolnum>
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<!-- ================================ SYNOPSIS -->
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<refnamediv id="clEnqueueMapBuffer">
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Enqueues a command to map a region of the buffer object given by <varname>buffer</varname>
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into the host address space and returns a pointer to this mapped region.
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<refsynopsisdiv xmlns:xlink="http://www.w3.org/1999/xlink"><title></title>
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<link xlink:href="scalarDataTypes.html">void</link> * <function>clEnqueueMapBuffer</function>
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<paramdef><link xlink:href="abstractDataTypes.html">cl_command_queue</link><parameter>command_queue</parameter></paramdef>
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<paramdef><link xlink:href="abstractDataTypes.html">cl_mem</link><parameter>buffer</parameter></paramdef>
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<paramdef><link xlink:href="enums.html#cl_bool">cl_bool</link><parameter>blocking_map</parameter></paramdef>
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<paramdef><link xlink:href="enums.html#cl_map_flags">cl_map_flags</link><parameter>map_flags</parameter></paramdef>
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<paramdef><link xlink:href="scalarDataTypes.html">size_t</link><parameter>offset</parameter></paramdef>
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<paramdef><link xlink:href="scalarDataTypes.html">size_t</link><parameter>size</parameter></paramdef>
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<paramdef><link xlink:href="scalarDataTypes.html">cl_uint</link><parameter>num_events_in_wait_list</parameter></paramdef>
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<paramdef>const <link xlink:href="abstractDataTypes.html">cl_event</link><parameter>*event_wait_list</parameter></paramdef>
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<paramdef><link xlink:href="abstractDataTypes.html">cl_event</link><parameter>*event</parameter></paramdef>
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<paramdef><link xlink:href="scalarDataTypes.html">cl_int</link><parameter>*errcode_ret</parameter></paramdef>
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<!-- ================================ PARAMETERS -->
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<refsect1 id="parameters">
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<title>Parameters</title>
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<term> <varname> command_queue </varname> </term>
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Must be a valid command-queue.
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<term> <varname> blocking_map </varname> </term>
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Indicates if the map operation is <varname>blocking</varname> or
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<varname>non-blocking</varname>.
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If <varname>blocking_map</varname> is <constant>CL_TRUE</constant>,
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<function>clEnqueueMapBuffer</function> does not return until the specified
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region in <varname>buffer</varname> is mapped into the host address space
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and the application can access the contents of the mapped region using
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the pointer returned by <function>clEnqueueMapBuffer</function>.
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If <varname>blocking_map</varname> is <constant>CL_FALSE</constant>
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i.e. map operation is non-blocking, the pointer to the mapped region
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returned by <function>clEnqueueMapBuffer</function> cannot be used until
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the map command has completed. The <varname>event</varname> argument
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returns an event object which can be used to query the execution status
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of the map command. When the map command is completed, the application
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can access the contents of the mapped region using the pointer returned
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by <function>clEnqueueMapBuffer</function>.
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<!-- ================================ PARAMETER TABLE (OPTIONAL) -->
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<!-- DELETE IF NOT NEEDED -->
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<!-- Use this if parameter information requires a table. Adjust the number of columns by adjusting
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<colspec /> tags. Column header goes in the <thead /> section. Delte the section if no column head needed.
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<term><varname>map_flags</varname></term>
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A bit-bield with the following supported values.
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<!-- table 5.5, also applies to clEnqueueMapImage.xml -->
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<informaltable frame="all"><tgroup cols="2" align="left" colsep="1" rowsep="1">
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<colspec colname="col1" colnum="1" />
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<colspec colname="col2" colnum="2" />
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<entry>cl_map_flags</entry>
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<entry>Description</entry>
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<entry><constant>CL_MAP_READ</constant></entry>
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This flag specifies that the region being mapped in the memory
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object is being mapped for reading.
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The pointer returned by <function>clEnqueueMapBuffer</function> or
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<citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>
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is guaranteed to contain
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the latest bits in the region being
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mapped when the <function>clEnqueueMapBuffer</function> or
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<citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>
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command has completed.
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<entry><constant>CL_MAP_WRITE</constant></entry>
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This flag specifies that the region being mapped in the memory
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object is being mapped for writing.
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The pointer returned by <function>clEnqueueMapBuffer</function> or
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<citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>
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is guaranteed to contain the latest bits in
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the region being mapped when the <function>clEnqueueMapBuffer</function> or
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<citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>
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command has completed.
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<entry><constant>CL_MAP_WRITE_INVALIDATE_REGION</constant></entry>
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This flag specifies that the region being mapped in the memory
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object is being mapped for writing.
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The contents of the region being mapped are to be discarded.
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This is typically the case
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when the region being mapped is overwritten by the host. This
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flag allows the implementation
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to no longer guarantee that the pointer returned by
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<function>clEnqueueMapBuffer</function> or
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<citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>
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contains the latest bits in the region being
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mapped which can be a significant performance enhancement.
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<constant>CL_MAP_READ</constant> or <constant>CL_MAP_WRITE</constant>
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and <constant> CL_MAP_WRITE_INVALIDATE_REGION</constant>
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are mutually exclusive.
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</tgroup></informaltable>
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<!-- ================================ END PARAMETER TABLE -->
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<term> <varname> buffer </varname> </term>
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A valid buffer object. The OpenCL context associated with <varname>command_queue</varname>
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and <varname>buffer</varname> must be the same.
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The offset in bytes and the size of the region in the buffer object that is being mapped.
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num_events_in_wait_list
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Specify events that need to complete before this particular
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command can be executed. If <varname>event_wait_list</varname>
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is NULL, then this particular command does not wait on any
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event to complete. If <varname>event_wait_list</varname> is
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NULL, <varname>num_events_in_wait_list</varname> must be 0. If
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<varname>event_wait_list</varname> is not NULL, the list of events
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pointed to by <varname>event_wait_list</varname> must be valid
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and <varname>num_events_in_wait_list</varname> must be greater
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than 0. The events specified in <varname>event_wait_list</varname>
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act as synchronization points. The context associated with events in
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<varname>event_wait_list</varname> and <varname>command_queue</varname> must
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be the same. The memory associated with <varname>event_wait_list</varname>
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can be reused or freed after the function returns.
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<term> <varname> event </varname> </term>
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Returns an event object that identifies this particular copy command
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and can be used to query or queue a wait for this particular command
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to complete. <varname>event</varname> can be NULL in which case
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it will not be possible for the application to query the status of
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this command or queue a wait for this command to complete. If the
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<varname>event_wait_list</varname> and the <varname>event</varname>
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arguments are not NULL, the <varname>event</varname> argument should not
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refer to an element of the <varname>event_wait_list</varname> array.
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<term> <varname> errcode_ret </varname> </term>
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Returns an appropriate error code. If <varname>errcode_ret</varname>
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is NULL, no error code is returned.
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<!-- ================================ NOTES -->
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<refsect1 id="notes"><title>Notes</title>
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The returned pointer maps a region starting at <varname>offset</varname> and is at
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least <varname>size</varname> bytes in size. The result of a memory access outside
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this region is undefined.
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If the buffer object is created with <constant>CL_MEM_USE_HOST_PTR</constant> set in
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<varname>mem_flags</varname>, the following will be true:
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<itemizedlist mark="disc">
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The <varname>host_ptr</varname> specified in
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<citerefentry><refentrytitle>clCreateBuffer</refentrytitle></citerefentry>
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is guaranteed to contain the latest bits in the region being mapped when the
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<function>clEnqueueMapBuffer</function> command has completed.
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The pointer value returned by <function>clEnqueueMapBuffer</function> will be derived
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from the <varname>host_ptr</varname> specified when the buffer object is created.
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Mapped buffer objects are unmapped using
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<citerefentry><refentrytitle>clEnqueueUnmapMemObject</refentrytitle></citerefentry>.
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<!-- core spec p. 120, section 5.4.2 --> <function>clEnqueueMapBuffer</function>
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and <citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>
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increment the mapped count of the memory object. The initial mapped count value of a
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memory object is zero. Multiple calls to <function>clEnqueueMapBuffer</function> or
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<citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry> on the
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same memory object will increment this mapped count by appropriate number of calls.
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<citerefentry><refentrytitle>clEnqueueUnmapMemObject</refentrytitle></citerefentry>
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decrements the mapped count of the memory object.
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<!-- core spec p. 120, section 5.4.2 --> <function>clEnqueueMapBuffer</function>
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and <citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>
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act as synchronization points for a region of the buffer object being mapped.
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<!-- ================================ ERRORS -->
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<refsect1 id="errors"><title>Errors</title>
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<function>clEnqueueMapBuffer</function> will return a pointer to the mapped region
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if the function is executed successfully. The <varname>errcode_ret</varname> is set
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to <errorname>CL_SUCCESS</errorname>.
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A NULL pointer is returned otherwise with one of the following error values returned
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in <varname>errcode_ret</varname>:
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<itemizedlist mark="disc">
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<errorname>CL_INVALID_COMMAND_QUEUE</errorname> if <varname>command_queue</varname>
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is not a valid command-queue.
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<errorname>CL_INVALID_CONTEXT</errorname> if the context associated with
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<varname>command_queue</varname> and <varname>image</varname>
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are not the same or if the context associated with <varname>command_queue</varname>
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and events in <varname>event_wait_list</varname> are not the same.
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<errorname>CL_INVALID_MEM_OBJECT</errorname> if <varname>image</varname> is not a valid image object.
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<errorname>CL_INVALID_VALUE</errorname> if region being mapped given by
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(<varname>offset</varname>, <varname>size</varname>)
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is out of bounds or if <varname>size</varname> is 0 or values specified in
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<varname>map_flags</varname> are not valid.
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<errorname>CL_INVALID_EVENT_WAIT_LIST</errorname>
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if <varname>event_wait_list</varname> is NULL and
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<varname>num_events_in_wait_list</varname> > 0,
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or <varname>event_wait_list</varname> is not NULL and
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<varname>num_events_in_wait_list</varname> is 0, or if event objects in
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<varname>event_wait_list</varname> are not valid events.
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<errorname>CL_MISALIGNED_SUB_BUFFER_OFFSET</errorname> if
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<varname>buffer</varname> is a sub-buffer object and <varname>offset</varname>
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specified when the sub-buffer object is created is not aligned to
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<constant>CL_DEVICE_MEM_BASE_ADDR_ALIGN</constant> value for device associated
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with <varname>queue</varname>.
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<errorname>CL_MAP_FAILURE</errorname> if there is a failure to map the
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requested region into the host address space. This error cannot occur for
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image objects created with <constant>CL_MEM_USE_HOST_PTR</constant> or
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<constant>CL_MEM_ALLOC_HOST_PTR</constant>.
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<errorname>CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST</errorname> if the
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map operation is blocking and the execution status of any of the events in
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<varname>event_wait_list</varname> is a negative integer value.
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<errorname>CL_MEM_OBJECT_ALLOCATION_FAILURE</errorname> if there is a failure to
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allocate memory for data store associated with <varname>buffer</varname>.
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<errorname>CL_INVALID_OPERATION</errorname> if <varname>buffer</varname>
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has been created with <constant>CL_MEM_HOST_WRITE_ONLY</constant> or
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<constant>CL_MEM_HOST_NO_ACCESS</constant> and <constant>CL_MAP_READ</constant>
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is set in <varname>map_flags</varname> or if <varname>buffer</varname>
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has been created with <constant>CL_MEM_HOST_READ_ONL</constant> or
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<constant>CL_MEM_HOST_NO_ACCESS</constant> and <constant>CL_MAP_WRITE</constant>
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or <constant>CL_MAP_WRITE_INVALIDATE_REGION</constant> is set in
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<varname>map_flags</varname>.
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<errorname>CL_OUT_OF_RESOURCES</errorname> if there is a failure to allocate
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resources required by the OpenCL implementation on the device.
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<errorname>CL_OUT_OF_HOST_MEMORY</errorname> if there is a failure to allocate
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resources required by the OpenCL implementation on the host.
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<!-- ================================ EXAMPLE -->
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<!-- DO NOT DELETE IN CASE AN EXAMPLE IS ADDED IN THE FUTURE -->
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<refsect2 id="example1">
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<informaltable frame="none">
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<tgroup cols="1" align="left" colsep="0" rowsep="0">
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<colspec colname="col1" colnum="1" />
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Example goes here - it will be set in "code" type with white space preserved.
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<!-- ================================ SPECIFICATION -->
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<!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page
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<refsect1 id="specification"><title>Specification</title>
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<imagedata fileref="pdficon_small1.gif" format="gif" />
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<olink uri="clEnqueueMapBuffer">OpenCL Specification</olink>
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<!-- ================================ ALSO SEE -->
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<refsect1 id="seealso"><title>Also see</title>
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<citerefentry><refentrytitle>clEnqueueMapImage</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>clEnqueueUnmapMemObject</refentrytitle></citerefentry>
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<!-- ================================ COPYRIGHT -->
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<!-- Content included from copyright.inc.xsl -->
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<refsect3 id="Copyright"><title></title>
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<imagedata fileref="KhronosLogo.jpg" format="jpg" />
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clEnqueueMapBuffer.xml
