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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="boost_integer.mask"></a><a class="link" href="mask.html" title="Integer Masks"> Integer Masks</a> |
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| <div class="toc"><dl> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.overview">Overview</a></span></dt> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.synopsis">Synopsis</a></span></dt> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.single_bit_mask_class_template">Single |
| Bit-Mask Class Template</a></span></dt> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.group_bit_mask_class_template">Group |
| Bit-Mask Class Template</a></span></dt> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.implementation_notes">Implementation |
| Notes</a></span></dt> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.example">Example</a></span></dt> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.demonstration_program">Demonstration |
| Program</a></span></dt> |
| <dt><span class="section"><a href="mask.html#boost_integer.mask.rationale">Rationale</a></span></dt> |
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| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.overview"></a><a class="link" href="mask.html#boost_integer.mask.overview" title="Overview">Overview</a> |
| </h3></div></div></div> |
| <p> |
| The class templates in <a href="../../../../../boost/integer/integer_mask.hpp" target="_top"><boost/integer/integer_mask.hpp></a> |
| provide bit masks for a certain bit position or a contiguous-bit pack of |
| a certain size. The types of the masking constants come from the <a class="link" href="integer.html" title="Integer Type Selection">integer |
| type selection templates</a> header. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.synopsis"></a><a class="link" href="mask.html#boost_integer.mask.synopsis" title="Synopsis">Synopsis</a> |
| </h3></div></div></div> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cstddef</span><span class="special">></span> <span class="comment">// for std::size_t |
| </span> |
| <span class="keyword">namespace</span> <span class="identifier">boost</span> |
| <span class="special">{</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">Bit</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">high_bit_mask_t</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">least</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">fast</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">least</span> <span class="identifier">high_bit</span> <span class="special">=</span> <span class="emphasis"><em>implementation-defined</em></span><span class="special">;</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">fast</span> <span class="identifier">high_bit_fast</span> <span class="special">=</span> <span class="emphasis"><em>implementation-defined</em></span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bit_position</span> <span class="special">=</span> <span class="identifier">Bit</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">Bits</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">low_bits_mask_t</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">least</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">fast</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">least</span> <span class="identifier">sig_bits</span> <span class="special">=</span> <span class="emphasis"><em>implementation-defined</em></span><span class="special">;</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">fast</span> <span class="identifier">sig_bits_fast</span> <span class="special">=</span> <span class="emphasis"><em>implementation-defined</em></span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bit_count</span> <span class="special">=</span> <span class="identifier">Bits</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="comment">// Specializations for low_bits_mask_t exist for certain bit counts. |
| </span> |
| <span class="special">}</span> <span class="comment">// namespace boost |
| </span></pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.single_bit_mask_class_template"></a><a class="link" href="mask.html#boost_integer.mask.single_bit_mask_class_template" title="Single Bit-Mask Class Template">Single |
| Bit-Mask Class Template</a> |
| </h3></div></div></div> |
| <p> |
| The <code class="literal">boost::high_bit_mask_t</code> class template provides constants |
| for bit masks representing the bit at a certain position. The masks are equivalent |
| to the value 2<sup>Bit</sup>, where <code class="literal">Bit</code> is the template parameter. |
| The bit position must be a nonnegative number from zero to <span class="emphasis"><em>Max</em></span>, |
| where Max is one less than the number of bits supported by the largest unsigned |
| built-in integral type. The following table describes the members of an instantiation |
| of <code class="literal">high_bit_mask_t</code>. |
| </p> |
| <div class="table"> |
| <a name="boost_integer.mask.single_bit_mask_class_template.members_of_the__boost__high_bit_mask_t__class_template"></a><p class="title"><b>Table 2. Members of the `boost::high_bit_mask_t` Class Template</b></p> |
| <div class="table-contents"><table class="table" summary="Members of the `boost::high_bit_mask_t` Class Template"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Member |
| </p> |
| </th> |
| <th> |
| <p> |
| Meaning |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">least</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The smallest, unsigned, built-in type that supports the given bit |
| position. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">fast</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The easiest-to-manipulate analog of <code class="literal">least</code>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">high_bit</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| A <code class="literal">least</code> constant of the value 2<sup>Bit</sup>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">high_bit_fast</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| A <code class="literal">fast</code> analog of <code class="literal">high_bit</code>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">bit_position</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The value of the template parameter, in case its needed from a |
| renamed instantiation of the class template. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <br class="table-break"> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.group_bit_mask_class_template"></a><a class="link" href="mask.html#boost_integer.mask.group_bit_mask_class_template" title="Group Bit-Mask Class Template">Group |
| Bit-Mask Class Template</a> |
| </h3></div></div></div> |
| <p> |
| The <code class="literal">boost::low_bits_mask_t</code> class template provides constants |
| for bit masks equivalent to the value (2<sup>Bits</sup> - 1), where <code class="literal">Bits</code> |
| is the template parameter. The parameter <code class="literal">Bits</code> must be |
| a non-negative integer from zero to <span class="emphasis"><em>Max</em></span>, where Max is |
| the number of bits supported by the largest, unsigned, built-in integral |
| type. The following table describes the members of <code class="literal">low_bits_mask_t</code>. |
| </p> |
| <div class="table"> |
| <a name="boost_integer.mask.group_bit_mask_class_template.members_of_the___boost__low_bits_mask_t__class_template"></a><p class="title"><b>Table 3. Members of the [^boost::low_bits_mask_t] Class Template</b></p> |
| <div class="table-contents"><table class="table" summary="Members of the [^boost::low_bits_mask_t] Class Template"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Member |
| </p> |
| </th> |
| <th> |
| <p> |
| Meaning |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">least</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The smallest, unsigned built-in type that supports the given bit |
| count. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">fast</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The easiest-to-manipulate analog of <code class="literal">least</code>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">sig_bits</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| A <code class="literal">least</code> constant of the desired bit-masking |
| value. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">sig_bits_fast</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| A <code class="literal">fast</code> analog of <code class="literal">sig_bits</code>. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="literal">bit_count</code> |
| </p> |
| </td> |
| <td> |
| <p> |
| The value of the template parameter, in case its needed from a |
| renamed instantiation of the class template. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <br class="table-break"> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.implementation_notes"></a><a class="link" href="mask.html#boost_integer.mask.implementation_notes" title="Implementation Notes">Implementation |
| Notes</a> |
| </h3></div></div></div> |
| <p> |
| When <code class="literal">Bits</code> is the exact size of a built-in unsigned type, |
| the implementation has to change to prevent undefined behavior. Therefore, |
| there are specializations of <code class="literal">low_bits_mask_t</code> at those |
| bit counts. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.example"></a><a class="link" href="mask.html#boost_integer.mask.example" title="Example">Example</a> |
| </h3></div></div></div> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">integer</span><span class="special">/</span><span class="identifier">integer_mask</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| |
| <span class="comment">//... |
| </span> |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">high_bit_mask_t</span><span class="special"><</span><span class="number">29</span><span class="special">></span> <span class="identifier">mask1_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">low_bits_mask_t</span><span class="special"><</span><span class="number">15</span><span class="special">></span> <span class="identifier">mask2_type</span><span class="special">;</span> |
| |
| <span class="identifier">mask1_type</span><span class="special">::</span><span class="identifier">least</span> <span class="identifier">my_var1</span><span class="special">;</span> |
| <span class="identifier">mask2_type</span><span class="special">::</span><span class="identifier">fast</span> <span class="identifier">my_var2</span><span class="special">;</span> |
| <span class="comment">//... |
| </span> |
| <span class="identifier">my_var1</span> <span class="special">|=</span> <span class="identifier">mask1_type</span><span class="special">::</span><span class="identifier">high_bit</span><span class="special">;</span> |
| <span class="identifier">my_var2</span> <span class="special">&=</span> <span class="identifier">mask2_type</span><span class="special">::</span><span class="identifier">sig_bits_fast</span><span class="special">;</span> |
| |
| <span class="comment">//... |
| </span><span class="special">}</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.demonstration_program"></a><a class="link" href="mask.html#boost_integer.mask.demonstration_program" title="Demonstration Program">Demonstration |
| Program</a> |
| </h3></div></div></div> |
| <p> |
| The program <a href="../../../test/integer_mask_test.cpp" target="_top">integer_mask_test.cpp</a> |
| is a simplistic demonstration of the results from instantiating various examples |
| of the bit mask class templates. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.rationale"></a><a class="link" href="mask.html#boost_integer.mask.rationale" title="Rationale">Rationale</a> |
| </h3></div></div></div> |
| <p> |
| The class templates in this header are an extension of the <a class="link" href="integer.html" title="Integer Type Selection">integer |
| type selection class templates</a>. The new class templates provide the |
| same sized types, but also convenient masks to use when extracting the highest |
| or all the significant bits when the containing built-in type contains more |
| bits. This prevents contamination of values by the higher, unused bits. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_integer.mask.credits"></a><a class="link" href="mask.html#boost_integer.mask.credits" title="Credits">Credits</a> |
| </h3></div></div></div> |
| <p> |
| The author of the Boost bit mask class templates is <a href="http://www.boost.org/people/daryle_walker.html" target="_top">Daryle |
| Walker</a>. |
| </p> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2001 -2009 Beman Dawes, Daryle Walker, Gennaro Prota, |
| John Maddock<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
| </div></td> |
| </tr></table> |
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