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这是一本关于verilog编程语言的教程,对学习verilog语言有帮助

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解压缩操作在右侧可以接受任何位流类型，包括一个流。右侧的数据可以具有比解压缩操作所能容纳的位数更多的位数。然而，如果需要的位数比右侧表达式所能提供的位数更多的话，则会产生一个错误。&nbsp;</p>
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例如： </p><div class="Element170">
<a href="#" onclick="CopyElementToClipboard('code00247');">Copy Code</a></div>
<div class="Element13"><div class="Element12" id="code00247"><pre class="Element12"><span style="color: #0000FF">int</span> a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">;</span>
<span style="color: #0000FF">logic</span> <span style="color: #800080">[</span><span style="color: #FF0000">10</span><span style="color: #800080">:</span><span style="color: #FF0000">0</span><span style="color: #800080">]</span> up<span style="color: #800080">[</span><span style="color: #FF0000">3</span><span style="color: #800080">:</span><span style="color: #FF0000">0</span><span style="color: #800080">];</span>
<span style="color: #0000FF">logic</span> <span style="color: #800080">[</span><span style="color: #FF0000">11</span><span style="color: #800080">:</span><span style="color: #FF0000">1</span><span style="color: #800080">]</span> p1<span style="color: #800080">,</span> p2<span style="color: #800080">,</span> p3<span style="color: #800080">,</span> p4<span style="color: #800080">;</span>

<span style="color: #0000FF">bit</span> <span style="color: #800080">[</span><span style="color: #FF0000">96</span><span style="color: #800080">:</span><span style="color: #FF0000">1</span><span style="color: #800080">]</span> y <span style="color: #800080">=</span> <span style="color: #800080">{&gt;&gt;{</span>a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">}};</span>  <span style="color: #008000">// 正确：压缩a, b, c</span>
<span style="color: #0000FF">int</span> j <span style="color: #800080">=</span> <span style="color: #800080">{&gt;&gt;{</span>a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">}};</span>         <span style="color: #008000">// 错误：j具有32位 &lt; 96位</span>
<span style="color: #0000FF">bit</span> <span style="color: #800080">[</span><span style="color: #FF0000">99</span><span style="color: #800080">:</span><span style="color: #FF0000">0</span><span style="color: #800080">]</span> d <span style="color: #800080">=</span> <span style="color: #800080">{&gt;&gt;{</span>a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">}};</span>  <span style="color: #008000">// 正确：d被填充4位</span>
<span style="color: #800080">{&gt;&gt;{</span>a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">}}</span> <span style="color: #800080">=</span> <span style="color: #FF0000">23</span><span style="color: #800080">'</span><span style="color: #0000FF">b</span><span style="color: #FF0000">1</span><span style="color: #800080">;</span>         <span style="color: #008000">// 错误：流中的位数太少</span>
<span style="color: #800080">{&gt;&gt;{</span>a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">}}</span> <span style="color: #800080">=</span> 96<span style="color: #800080">'</span><span style="color: #0000FF">b</span><span style="color: #FF0000">1</span><span style="color: #800080">;</span>         <span style="color: #008000">// 正确：解压缩后a = 0, b = 0, c = 1</span>
<span style="color: #800080">{&gt;&gt;{</span>a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">}}</span> <span style="color: #800080">=</span> 100<span style="color: #800080">'</span><span style="color: #0000FF">b</span><span style="color: #FF0000">1</span><span style="color: #800080">;</span>        <span style="color: #008000">// 正确：结果与上一个例子相同（有四位未读）</span>
<span style="color: #800080">{&gt;&gt;{</span>p1<span style="color: #800080">,</span> p2<span style="color: #800080">,</span> p3<span style="color: #800080">,</span> p4<span style="color: #800080">}} =</span> up<span style="color: #800080">;</span>     <span style="color: #008000">// 正确：解压缩后 p1 = up[3], p2 = up[2],</span>
                               <span style="color: #008000">//                p3 = up[1], p4 = up[0]</span></pre></div></div>
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<a href="00860.html" target="topic">第七章 操作符与表达式</a></p></div>
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描述&nbsp;</div></td></tr><tr>
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<a href="00565.html" target="topic">7.18.1 将动态尺寸的数据位流化</a>&nbsp;</div></td><td class="Element206" valign="top" width="50%">
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如果解压缩操作包含了庞大的动态尺寸类型，那么解压缩过程是很复杂的（就像强制类型转换中一样）：第一个动态尺寸条目被重新调整尺寸以便容纳流中所有的有效数据（排除了后续的固定尺寸条目）。对于仅仅包含了一个动态尺寸数据条目的流来说，采用这种机制来实现解压缩操作是足够的。然而，当流中包含了多个可变尺寸的数据包，或者每一个数据包包含了多个可变尺寸的数据条目、或者解压缩的数据的尺寸存储与一个流的中间部分，那么这种机制是很麻烦的并且容易引入错误。为了解决这些问题，解压缩操作允许使用一个<span style="color: #0000FF">with</span>表达式来显式地指明解压缩操作中可变尺寸域的范围。<br><br><span style="color: #0000FF">with</span>表达式的语法如下： &nbsp;</div></td></tr></table></div></div>
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<a href="00860.html" target="topic">第七章 操作符与表达式</a>, <a href="00912.html" target="topic">主题</a></div>
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