framer_8cpp.html

计算crc校验码的程序

00152                                                                      <span class="comment">//寄存器，若为0，则无需变化</span>
00153                         }       
00154                         temp &lt;&lt;= 1;
00155 
00156                         <span class="keywordflow">if</span> ( oput )                              <span class="comment">//若输出位为1，则将crc与gx对应位取异或，</span>
00157                                                                      <span class="comment">//若为0，取异或结果不变，无需计算  </span>
00158                         {
00159                                 <a class="code" href="framer_8cpp.html#a2">crc</a> ^= gx; 
00160                         }
00161                         i=i+1;
00162                 }
00163                 
00164                 tfile.read((<span class="keywordtype">char</span>*)&amp;otemp,<span class="keyword">sizeof</span> (<span class="keywordtype">unsigned</span> <span class="keywordtype">char</span>));
00165         }
00166         
00167         ofile.put(crc);                               <span class="comment">//输出校验和数据</span>
00168         ofile.close();
00169         tfile.close();
00170         <span class="keywordflow">return</span> <span class="keyword">true</span>;
00171 }
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          <td class="md" nowrap valign="top">bool frameheader           </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="md" nowrap valign="top">char *&nbsp;</td>
          <td class="mdname" nowrap> <em>outfile</em>, </td>
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          <td class="md" nowrap align="right"></td>
          <td class="md"></td>
          <td class="md" nowrap>char *&nbsp;</td>
          <td class="mdname" nowrap> <em>tempfile</em></td>
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<p>
形成帧的前导码、帧定界符、目的地址和源地址,输出到输出文件。. 
<p>
<dl compact><dt><b>参数:</b></dt><dd>
  <table border="0" cellspacing="2" cellpadding="0">
    <tr><td valign="top"></td><td valign="top"><em>char*</em>&nbsp;</td><td>outfile 为输出文件名 </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>char*</em>&nbsp;</td><td>tempfile 临时文件名 </td></tr>
  </table>
</dl>
<dl compact><dt><b>返回:</b></dt><dd>输出成功，则返回为真 </dd></dl>
<div class="fragment"><pre class="fragment">00018 {
00019         
00020           <span class="comment">//数组存放7字节前导码、1字节帧定界符、6字节目的地址和6字节源地址。</span>
00021             
00022            
00023         <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> head[8]={0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xAB};<span class="comment">// 7字节前导码，每字节均为10101010,帧前导码10101011；</span>
00024         <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> add[12]={0x00,0x00,0xE4,0x86,0x3A,0xDC,         <span class="comment">//目标地址00-00-E4-86-3A-DC；</span>
00025                                                    0x00,0x00,0x80,0x1A,0xE6,0x65};        <span class="comment">//源地址00-00-80-1A-E6-65</span>
00026                                                         
00027    ofstream tfile( tempfile );
00028    ofstream ofile( outfile );
00029    tfile.write( (<span class="keywordtype">char</span> *) &amp;head, <span class="keyword">sizeof</span> head );
00030    tfile.write( (<span class="keywordtype">char</span> *) &amp;add, <span class="keyword">sizeof</span> add);
00031    ofile.write( (<span class="keywordtype">char</span> *) &amp;head, <span class="keyword">sizeof</span> head );
00032    tfile.close();
00033   ofile.close();
00034    <span class="keywordflow">return</span> <span class="keyword">true</span>;
00035 }
</pre></div>
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          <td class="md" valign="top">(&nbsp;</td>
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          <td class="mdname" nowrap> <em>infile</em>, </td>
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          <td class="md" nowrap align="right"></td>
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          <td class="md" nowrap>char *&nbsp;</td>
          <td class="mdname" nowrap> <em>tempfile</em></td>
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<p>
将输入文件的字节长度文件数据输出到临时文件，不足46字节的以0补齐。 
<p>
<dl compact><dt><b>参数:</b></dt><dd>
  <table border="0" cellspacing="2" cellpadding="0">
    <tr><td valign="top"></td><td valign="top"><em>char*</em>&nbsp;</td><td>infile 输入文件名 </td></tr>
    <tr><td valign="top"></td><td valign="top"><em>char*</em>&nbsp;</td><td>tempfile 临时文件名 </td></tr>
  </table>
</dl>
<dl compact><dt><b>返回:</b></dt><dd>输出成功，则返回为真 </dd></dl>
<div class="fragment"><pre class="fragment">00044 {
00045 
00046         ifstream ifile(infile,ios::binary);
00047         ofstream tfile( tempfile,ios_base::binary|ios::app );
00048 
00049         <span class="keywordflow">if</span>(!ifile)                                        <span class="comment">//输入文件无法打开，返回失败。</span>
00050         {
00051                 cout&lt;&lt;<span class="stringliteral">"cannot open"</span>&lt;&lt;infile&lt;&lt;endl;
00052                 <span class="keywordflow">return</span> <span class="keyword">false</span>;
00053         }
00054         
00055                                 
00056         
00057         <span class="keywordtype">char</span> tempchar;
00058         <span class="keywordtype">unsigned</span> <span class="keywordtype">short</span> c1,c2,bytecnt ;
00059 
00060         
00061         ifile.seekg( 0, ios_base::end );                  <span class="comment">//找到二进制文件尾</span>
00062         c1=c2=bytecnt= ifile.tellg();                     <span class="comment">//数据字段长度计数器。</span>
00063         
00064         <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> b1=c1&amp;0x00ff;                       <span class="comment">//将数据长度字段输出到临时文件</span>
00065         c2&gt;&gt;=8;
00066     <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> b2=c2;
00067         tfile.put(b2);
00068     tfile.put(b1);
00069         
00070         ifile.seekg(0);                                   <span class="comment">//开始读取数据，并输出到临时文件</span>
00071         <span class="keywordtype">int</span> cnt=bytecnt;
00072         ifile.get(tempchar);
00073         
00074         <span class="keywordflow">while</span>(cnt&gt;0)
00075         {
00076                                  
00077                 cnt--;
00078                 tfile.put(tempchar);
00079                 ifile.get(tempchar);
00080         }
00081         
00082         
00083         <span class="keywordflow">if</span>(bytecnt&gt;46)                                    <span class="comment">//数据字段大于46字节，成功返回</span>
00084         {
00085                 tfile.close();
00086                 ifile.close();
00087                 <span class="keywordflow">return</span> <span class="keyword">true</span>;
00088         }
00089         
00090         tempchar=0;
00091         <span class="keywordflow">for</span>(<span class="keywordtype">int</span> i=bytecnt;i&lt;46;i++)                      <span class="comment">//数据字段不足46字节，先用0补足46字节再返回；</span>
00092                 tfile.put(tempchar);
00093         
00094 
00095         tfile.close();
00096         ifile.close();
00097         <span class="keywordflow">return</span> <span class="keyword">true</span>;
00098 }
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