﻿<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/"><channel><title>C++博客-小虎的欢乐岛-随笔分类-Algorithm</title><link>http://www.cppblog.com/wz19860913/category/12263.html</link><description>那片土在蓝天上</description><language>zh-cn</language><lastBuildDate>Tue, 10 Nov 2009 08:50:56 GMT</lastBuildDate><pubDate>Tue, 10 Nov 2009 08:50:56 GMT</pubDate><ttl>60</ttl><item><title>CRC校验算法</title><link>http://www.cppblog.com/wz19860913/archive/2009/11/10/100628.html</link><dc:creator>小虎无忧</dc:creator><author>小虎无忧</author><pubDate>Tue, 10 Nov 2009 08:06:00 GMT</pubDate><guid>http://www.cppblog.com/wz19860913/archive/2009/11/10/100628.html</guid><wfw:comment>http://www.cppblog.com/wz19860913/comments/100628.html</wfw:comment><comments>http://www.cppblog.com/wz19860913/archive/2009/11/10/100628.html#Feedback</comments><slash:comments>0</slash:comments><wfw:commentRss>http://www.cppblog.com/wz19860913/comments/commentRss/100628.html</wfw:commentRss><trackback:ping>http://www.cppblog.com/wz19860913/services/trackbacks/100628.html</trackback:ping><description><![CDATA[<p>&nbsp;　　最近搞一个协议，以实现隐蔽通道，其中需要使用CRC校验算法，由于数据位数比较少，最后决定使用位的CRC校验算法。<br>　　该算法主要就是实现一个模二运算，基本原理就是异或，移位。<br>　　模二运算的算法如下（C语言描述）：</p>
<div style="BORDER-BOTTOM: #cccccc 1px solid; BORDER-LEFT: #cccccc 1px solid; PADDING-BOTTOM: 4px; BACKGROUND-COLOR: #eeeeee; PADDING-LEFT: 4px; WIDTH: 98%; PADDING-RIGHT: 5px; FONT-SIZE: 13px; WORD-BREAK: break-all; BORDER-TOP: #cccccc 1px solid; BORDER-RIGHT: #cccccc 1px solid; PADDING-TOP: 4px"><img id=Code_Closed_Image_160328 onclick="this.style.display='none'; Code_Closed_Text_160328.style.display='none'; Code_Open_Image_160328.style.display='inline'; Code_Open_Text_160328.style.display='inline';" align=top src="http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif" width=11 height=16><img style="DISPLAY: none" id=Code_Open_Image_160328 onclick="this.style.display='none'; Code_Open_Text_160328.style.display='none'; Code_Closed_Image_160328.style.display='inline'; Code_Closed_Text_160328.style.display='inline';" align=top src="http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif" width=11 height=16><span style="BORDER-BOTTOM: #808080 1px solid; BORDER-LEFT: #808080 1px solid; BACKGROUND-COLOR: #ffffff; BORDER-TOP: #808080 1px solid; BORDER-RIGHT: #808080 1px solid" id=Code_Closed_Text_160328>模二运算</span><span style="DISPLAY: none" id=Code_Open_Text_160328><br><!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;CrcMOD2函数</span><span style="COLOR: #008000">//////////////////////////////////////////////////////</span><span style="COLOR: #008000">/<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;作用：模2运算<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;参数说明；<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;m&nbsp;——&nbsp;被除数<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;p&nbsp;——&nbsp;除数<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;返回：余数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;CrcMOD2(unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;m,&nbsp;unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;p)<br>{<br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">int</span><span style="COLOR: #000000">&nbsp;m_bits&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">,&nbsp;p_bits&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">,&nbsp;a&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">,&nbsp;bit&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">,&nbsp;flag&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">;<br>&nbsp;&nbsp;&nbsp;&nbsp;unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;m_temp&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;m,&nbsp;p_temp&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;p;<br>&nbsp;&nbsp;&nbsp;&nbsp;unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;remainder&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">,&nbsp;andData&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0x00000001</span><span style="COLOR: #000000">;<br><br>&nbsp;&nbsp;&nbsp;&nbsp;unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;dividend,&nbsp;divisor;<br><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到被除数位数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">while</span><span style="COLOR: #000000">&nbsp;(m_temp)<br>&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;m_temp&nbsp;</span><span style="COLOR: #000000">/=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">2</span><span style="COLOR: #000000">;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #000000">++</span><span style="COLOR: #000000">m_bits;<br>&nbsp;&nbsp;&nbsp;&nbsp;}<br><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到除数位数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">while</span><span style="COLOR: #000000">&nbsp;(p_temp)<br>&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;p_temp&nbsp;</span><span style="COLOR: #000000">/=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">2</span><span style="COLOR: #000000">;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #000000">++</span><span style="COLOR: #000000">p_bits;<br>&nbsp;&nbsp;&nbsp;&nbsp;}<br><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;如果被除数位数小于除数，则直接返回被除数作为余数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">if</span><span style="COLOR: #000000">&nbsp;(m_bits&nbsp;</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">&nbsp;p_bits)<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">return</span><span style="COLOR: #000000">&nbsp;m;<br><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;在此开始第一次模2运算</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;m_temp&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;m&nbsp;</span><span style="COLOR: #000000">&gt;&gt;</span><span style="COLOR: #000000">&nbsp;(m_bits&nbsp;</span><span style="COLOR: #000000">-</span><span style="COLOR: #000000">&nbsp;p_bits);&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;被除数右移相应的位数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;dividend&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;m_temp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到第一次进行运算的被除数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;divisor&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到除数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;remainder&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;dividend&nbsp;</span><span style="COLOR: #000000">^</span><span style="COLOR: #000000">&nbsp;divisor;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到模2运算的结果作为余数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;m_bits&nbsp;</span><span style="COLOR: #000000">-=</span><span style="COLOR: #000000">&nbsp;p_bits;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;第一次计算完成，减去已经计算过的位数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">while</span><span style="COLOR: #000000">&nbsp;(m_bits)<br>&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">if</span><span style="COLOR: #000000">&nbsp;(</span><span style="COLOR: #000000">!</span><span style="COLOR: #000000">flag)<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dividend&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;(remainder&nbsp;</span><span style="COLOR: #000000">&lt;&lt;</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">);&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;上一次得到的余数作为这次被除数的高位</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;m_temp&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;m&nbsp;</span><span style="COLOR: #000000">&gt;&gt;</span><span style="COLOR: #000000">&nbsp;(m_bits&nbsp;</span><span style="COLOR: #000000">-</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;bit&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;andData&nbsp;</span><span style="COLOR: #000000">&amp;</span><span style="COLOR: #000000">&nbsp;m_temp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dividend&nbsp;</span><span style="COLOR: #000000">|=</span><span style="COLOR: #000000">&nbsp;bit;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;原被除数的某一位作为现在的被除数的最低位</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">else</span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dividend&nbsp;</span><span style="COLOR: #000000">&lt;&lt;=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;m_temp&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;m&nbsp;</span><span style="COLOR: #000000">&gt;&gt;</span><span style="COLOR: #000000">&nbsp;(m_bits&nbsp;</span><span style="COLOR: #000000">-</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;bit&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;andData&nbsp;</span><span style="COLOR: #000000">&amp;</span><span style="COLOR: #000000">&nbsp;m_temp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dividend&nbsp;</span><span style="COLOR: #000000">|=</span><span style="COLOR: #000000">&nbsp;bit;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;比较除数和被除数的最高位大小</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">if</span><span style="COLOR: #000000">&nbsp;((dividend&nbsp;</span><span style="COLOR: #000000">&amp;</span><span style="COLOR: #000000">&nbsp;(andData&nbsp;</span><span style="COLOR: #000000">&lt;&lt;</span><span style="COLOR: #000000">&nbsp;(p_bits&nbsp;</span><span style="COLOR: #000000">-</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">)))&nbsp;</span><span style="COLOR: #000000">&gt;=</span><span style="COLOR: #000000">&nbsp;&nbsp;(divisor&nbsp;</span><span style="COLOR: #000000">&amp;</span><span style="COLOR: #000000">&nbsp;(andData&nbsp;</span><span style="COLOR: #000000">&lt;&lt;</span><span style="COLOR: #000000">&nbsp;(p_bits&nbsp;</span><span style="COLOR: #000000">-</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">))))<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;flag&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;remainder&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;dividend&nbsp;</span><span style="COLOR: #000000">^</span><span style="COLOR: #000000">&nbsp;divisor;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到模2运算的结果作为余数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">else</span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;需要借位</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;flag&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">1</span><span style="COLOR: #000000">;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #000000">--</span><span style="COLOR: #000000">m_bits;<br>&nbsp;&nbsp;&nbsp;&nbsp;}<br><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">if</span><span style="COLOR: #000000">&nbsp;(flag)<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;remainder&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;dividend;<br><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">return</span><span style="COLOR: #000000">&nbsp;remainder;<br>}</span></span></div>
<br>　　CrcGetCode函数获原始数据和CRC生成多项式，利用模二运算得到新的数据。算法如下：<br>
<div style="BORDER-BOTTOM: #cccccc 1px solid; BORDER-LEFT: #cccccc 1px solid; PADDING-BOTTOM: 4px; BACKGROUND-COLOR: #eeeeee; PADDING-LEFT: 4px; WIDTH: 98%; PADDING-RIGHT: 5px; FONT-SIZE: 13px; WORD-BREAK: break-all; BORDER-TOP: #cccccc 1px solid; BORDER-RIGHT: #cccccc 1px solid; PADDING-TOP: 4px"><img id=Code_Closed_Image_160538 onclick="this.style.display='none'; Code_Closed_Text_160538.style.display='none'; Code_Open_Image_160538.style.display='inline'; Code_Open_Text_160538.style.display='inline';" align=top src="http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif" width=11 height=16><img style="DISPLAY: none" id=Code_Open_Image_160538 onclick="this.style.display='none'; Code_Open_Text_160538.style.display='none'; Code_Closed_Image_160538.style.display='inline'; Code_Closed_Text_160538.style.display='inline';" align=top src="http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif" width=11 height=16><span style="BORDER-BOTTOM: #808080 1px solid; BORDER-LEFT: #808080 1px solid; BACKGROUND-COLOR: #ffffff; BORDER-TOP: #808080 1px solid; BORDER-RIGHT: #808080 1px solid" id=Code_Closed_Text_160538>给数据加上校验码</span><span style="DISPLAY: none" id=Code_Open_Text_160538><br><!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;CrcGetCode函数</span><span style="COLOR: #008000">//////////////////////////////////////////////////</span><span style="COLOR: #008000">/<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;作用：通过原始数据与CRC多项式，得到整个数据的编码<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;参数说明：<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;originalData&nbsp;——&nbsp;原始数据<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;crcPolynomial&nbsp;——&nbsp;CRC生成多项式<br></span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;返回：原始数据&nbsp;+&nbsp;校验码</span><span style="COLOR: #008000"><br></span><span style="COLOR: #0000ff">int</span><span style="COLOR: #000000">&nbsp;CrcGetCode(unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;originalData,&nbsp;unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;crcPolynomial)<br>{<br>&nbsp;&nbsp;&nbsp;&nbsp;unsigned&nbsp;</span><span style="COLOR: #0000ff">long</span><span style="COLOR: #000000">&nbsp;checkBits&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">,&nbsp;temp&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;crcPolynomial,&nbsp;m&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;originalData,&nbsp;fcs;<br><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">while</span><span style="COLOR: #000000">&nbsp;(temp)<br>&nbsp;&nbsp;&nbsp;&nbsp;{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;temp&nbsp;</span><span style="COLOR: #000000">/=</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">2</span><span style="COLOR: #000000">;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #000000">++</span><span style="COLOR: #000000">checkBits;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;校验位个数加一</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;}<br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #000000">--</span><span style="COLOR: #000000">&nbsp;checkBits;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到校验位个数（比生成多项式少1位）</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;m&nbsp;</span><span style="COLOR: #000000">&lt;&lt;=</span><span style="COLOR: #000000">&nbsp;checkBits;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;得到模二运算的被除数</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">if</span><span style="COLOR: #000000">&nbsp;(checkBits&nbsp;</span><span style="COLOR: #000000">==</span><span style="COLOR: #000000">&nbsp;</span><span style="COLOR: #000000">0</span><span style="COLOR: #000000">)<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">return</span><span style="COLOR: #000000">&nbsp;m;<br><br>&nbsp;&nbsp;&nbsp;&nbsp;fcs&nbsp;</span><span style="COLOR: #000000">=</span><span style="COLOR: #000000">&nbsp;CrcMOD2(m,&nbsp;crcPolynomial);<br><br>&nbsp;&nbsp;&nbsp;&nbsp;m&nbsp;</span><span style="COLOR: #000000">|=</span><span style="COLOR: #000000">&nbsp;fcs;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;加上FCS校验子</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000"><br>&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #0000ff">return</span><span style="COLOR: #000000">&nbsp;m;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="COLOR: #008000">//</span><span style="COLOR: #008000">&nbsp;返回整个编码</span><span style="COLOR: #008000"><br></span><span style="COLOR: #000000">}</span></span></div>
<img src ="http://www.cppblog.com/wz19860913/aggbug/100628.html" width = "1" height = "1" /><br><br><div align=right><a style="text-decoration:none;" href="http://www.cppblog.com/wz19860913/" target="_blank">小虎无忧</a> 2009-11-10 16:06 <a href="http://www.cppblog.com/wz19860913/archive/2009/11/10/100628.html#Feedback" target="_blank" style="text-decoration:none;">发表评论</a></div>]]></description></item></channel></rss>