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<title>accessQualifiers</title>
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<a id="id-1"></a>
<div class="titlepage"></div>
<div xmlns="" class="refnamediv">
<a xmlns="http://www.w3.org/1999/xhtml" id="accessQualifiers"></a>
<h1>Access Qualifiers</h1>
<p>
Access Qualifiers for image memory objects.
</p>
</div>
<div class="refsect2">
<a id="synopsis"></a>
<h3>
</h3>
<div class="informaltable">
<table class="informaltable" border="0">
<colgroup>
<col align="left" class="col1" />
</colgroup>
<tbody>
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<td align="left">
__read_only
__write_only
__read_write
read_only
write_only
read_write
</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="refsect1">
<a id="description"></a>
<h2>Description</h2>
<p>
Image objects specified as arguments to a
kernel can be declared to be read-only, write-only or
read-write. The <code class="function">__read_only</code>
(or <code class="function">read_only</code>) and
<code class="function">__write_only</code>
(or <code class="function">write_only</code>) qualifiers must be used with
image object arguments to declare if the image
object is being read or written by a kernel or function. The
<code class="function">__read_write</code> (or <code class="function">read_write</code>)
qualifier must be used with image object arguments
of kernels and of user-defined functions to
declare if the image object is being both read and
written by the kernel. If no qualifier is provided,
<code class="function">read_only</code> is assumed.
</p>
<p>
In the following example
</p>
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<div class="literallayout"><p>kernel void<br />
foo (read_only image2d_t imageA, <br />
    write_only image2d_t imageB)<br />
{<br />
    ...<br />
}<br />
</p></div>
</td>
</tr>
</tbody>
</table>
</div>
<p>
<code class="code">imageA</code> is a read-only 2D image object, and
<code class="code">imageB</code> is a write-only 2D image object.
</p>
<p>
The sampler-less read image and write image built-ins
can be used with image declared with the
<code class="function">__read_write</code> (or <code class="function">read_write</code>) qualifier.
Calls to built-ins that read from an image
using a sampler for images declared with the
<code class="function">__read_write</code> (or <code class="function">read_write</code>) qualifier
will be a compilation error.
</p>
<p>
Pipe objects specified as arguments to a kernel
also use these access qualifiers. Refer to
section 6.13.16 for a detailed description on
how these access qualifiers can be used with pipes.
</p>
</div>
<div class="refsect1">
<a id="notes"></a>
<h2>Notes</h2>
<p>
The <code class="function">__read_only</code>, <code class="function">__write_only</code>,
<code class="function">__read_write</code>, <code class="function">read_only</code>,
<code class="function">write_only</code> and <code class="function">read_write</code> names are reserved
for use as access qualifiers and shall not be used otherwise.
</p>
</div>
<div class="refsect1">
<a id="specification"></a>
<h2>Specification</h2>
<p>
<img src="pdficon_small1.gif" />
<a href="https://www.khronos.org/registry/cl/specs/opencl-2.1-openclc.pdf#page=46" target="OpenCL Spec">OpenCL Specification</a>
</p>
</div>
<div class="refsect1">
<a id="seealso"></a>
<h2>Also see</h2>
<p>
<a class="citerefentry" href="qualifiers.html"><span class="citerefentry"><span class="refentrytitle">qualifiers</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 © 2007-2015 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,
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