📄 矛与盾的较量（2）——crc原理篇.htm
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name=L69><BR><A
name=L70> <FONT
color=#238e23>;下面赋值给寄存器ebx，以便进行crc32转换：</FONT><BR><A
name=L71> <FONT
color=#238e23>;EBX是待转换的字符串的首地址：</FONT><BR><A
name=L72> <FONT
color=#ff0000>lea</FONT> <FONT
color=#ff0000>ebx</FONT><FONT
color=#9932cd><B>,</B></FONT> szBuffer<BR><A
name=L73><BR><A
name=L74> <FONT
color=#238e23>;进行crc32转换：</FONT><BR><A
name=L75> <FONT
color=#ff0000>invoke</FONT> arraycrc32<BR><A
name=L76><BR><A
name=L77> <FONT
color=#238e23>;格式化输出：</FONT><BR><A
name=L78> <FONT
color=#ff0000>invoke</FONT> wsprintf<FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>addr</FONT> szText<FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>addr</FONT> szTemplate<FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>addr</FONT> szBuffer<FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>eax</FONT><BR><A name=L79><BR><A
name=L80> <FONT
color=#238e23>;好啦，让我们显示结果：</FONT><BR><A
name=L81> <FONT
color=#ff0000>invoke</FONT> MessageBox<FONT
color=#9932cd><B>,</B></FONT> hWnd<FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>addr</FONT> szText<FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>addr</FONT> szTitle<FONT
color=#9932cd><B>,</B></FONT> MB_OK<BR><A
name=L82> <FONT
color=#9932cd><B>.</B></FONT><FONT
color=#ff0000>ENDIF</FONT><BR><A
name=L83> <FONT
color=#9932cd><B>.</B></FONT><FONT
color=#ff0000>endif</FONT><BR><A
name=L84> <FONT
color=#9932cd><B>.</B></FONT><FONT
color=#ff0000>ELSE</FONT><BR><A
name=L85> <FONT
color=#ff0000>mov</FONT> <FONT
color=#ff0000>eax</FONT><FONT
color=#9932cd><B>,</B></FONT>FALSE<BR><A
name=L86> <FONT
color=#ff0000>ret</FONT><BR><A
name=L87> <FONT
color=#9932cd><B>.</B></FONT><FONT
color=#ff0000>ENDIF</FONT><BR><A
name=L88> <FONT
color=#ff0000>mov</FONT> <FONT
color=#ff0000>eax</FONT><FONT
color=#9932cd><B>,</B></FONT>TRUE<BR><A
name=L89> <FONT
color=#ff0000>ret</FONT><BR><A name=L90>WndProc <FONT
color=#ff0000>endp</FONT><BR><A name=L91><BR><A
name=L92><FONT
color=#238e23>;**********************************************************</FONT><BR><A
name=L93><FONT
color=#238e23>;函数功能：生成CRC-32表</FONT><BR><A
name=L94><FONT
color=#238e23>;**********************************************************</FONT><BR><A
name=L95>init_crc32table <FONT
color=#ff0000>proc</FONT><BR><A name=L96><BR><A
name=L97> <FONT
color=#238e23>;如果用C语言来表示，应该如下：</FONT><BR><A
name=L98> <FONT
color=#238e23>;</FONT><BR><A
name=L99> <FONT
color=#238e23>; for (i = 0; i
< 256; i++)</FONT><BR><A
name=L100> <FONT
color=#238e23>; {</FONT><BR><A
name=L101> <FONT
color=#238e23>; crc
= i;</FONT><BR><A
name=L102> <FONT
color=#238e23>; for
(j = 0; j < 8; j++)</FONT><BR><A
name=L103> <FONT
color=#238e23>; {</FONT><BR><A
name=L104> <FONT
color=#238e23>; if
(crc & 1)</FONT><BR><A
name=L105> <FONT
color=#238e23>; crc
= (crc >> 1) ^ 0xEDB88320;</FONT><BR><A
name=L106> <FONT
color=#238e23>; else</FONT><BR><A
name=L107> <FONT
color=#238e23>; crc
>>= 1;</FONT><BR><A
name=L108> <FONT
color=#238e23>; }</FONT><BR><A
name=L109> <FONT
color=#238e23>; crc32tbl[i]
= crc;</FONT><BR><A
name=L110> <FONT
color=#238e23>; }</FONT><BR><A
name=L111> <FONT
color=#238e23>;</FONT><BR><A
name=L112> <FONT
color=#238e23>;呵呵，让我们把上面的语句改成assembly的：</FONT><BR><A
name=L113><BR><A
name=L114> <FONT
color=#ff0000>mov</FONT> <FONT
color=#ff0000>ecx</FONT><FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#802000>256</FONT> <FONT
color=#238e23>; repeat for every DWORD in
table</FONT><BR><A
name=L115> <FONT
color=#ff0000>mov</FONT> <FONT
color=#ff0000>edx</FONT><FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#802000>0EDB88320h</FONT><BR><A name=L116><FONT
color=#802000>$BigLoop</FONT><FONT
color=#3080ca>:</FONT><BR><A
name=L117> <FONT
color=#ff0000>lea</FONT> <FONT
color=#ff0000>eax</FONT><FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#871f78>[</FONT><FONT
color=#ff0000>ecx</FONT><FONT
color=#3080ca>-</FONT><FONT color=#802000>1</FONT><FONT
color=#871f78>]</FONT><BR><A
name=L118> <FONT
color=#ff0000>push</FONT> <FONT
color=#ff0000>ecx</FONT><BR><A
name=L119> <FONT
color=#ff0000>mov</FONT> <FONT
color=#ff0000>ecx</FONT><FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#802000>8</FONT><BR><A name=L120><FONT
color=#802000>$SmallLoop</FONT><FONT
color=#3080ca>:</FONT><BR><A
name=L121> <FONT
color=#ff0000>shr</FONT> <FONT
color=#ff0000>eax</FONT><FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#802000>1</FONT><BR><A
name=L122> <FONT
color=#ff0000>jnc</FONT>
@F<BR><A
name=L123> <FONT
color=#ff0000>xor</FONT> <FONT
color=#ff0000>eax</FONT><FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>edx</FONT><BR><A name=L124>@@<FONT
color=#3080ca>:</FONT><BR><A
name=L125> <FONT
color=#ff0000>dec</FONT> <FONT
color=#ff0000>ecx</FONT><BR><A
name=L126> <FONT
color=#ff0000>jne</FONT> <FONT
color=#802000>$SmallLoop</FONT><BR><A
name=L127> <FONT
color=#ff0000>pop</FONT> <FONT
color=#ff0000>ecx</FONT><BR><A
name=L128> <FONT
color=#ff0000>mov</FONT> <FONT
color=#871f78>[</FONT>crc32tbl<FONT
color=#3080ca>+</FONT><FONT
color=#ff0000>ecx</FONT><FONT
color=#3080ca>*</FONT><FONT color=#802000>4</FONT><FONT
color=#3080ca>-</FONT><FONT color=#802000>4</FONT><FONT
color=#871f78>]</FONT><FONT
color=#9932cd><B>,</B></FONT> <FONT
color=#ff0000>eax</FONT><BR><A
name=L129> <FONT
color=#ff0000>dec</FONT> <FONT
color=#ff0000>ecx</FONT><BR><A
name=L130> <FONT
color=#ff0000>jne</FONT> <FONT
color=#802000>$BigLoop</FONT><BR><A name=L131><BR><A
name=L132> <FONT
color=#ff0000>ret</FONT><BR><A
name=L133>init_crc32table <FONT
color=#ff0000>endp</FONT><BR><A name=L134><BR><A
name=L135><BR><A name=L136><FONT
color=#238e23>;**************************************************************</FONT><BR><A
name=L137><FONT
color=#238e23>;函数功能：计算CRC-32</FONT><BR><A
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