crc.c

   1
   2 /*
   3  * calculate Cyclic Redundancy Check
   4  *
   5  * Algorithm by: David Schwaderer, Published in PC Tech Journal April 1985.
   6  *
   7  * $Header: crc.c 1.6 95/07/13 $
   8  * $Log:        crc.c,v $
   9  * Revision 1.6  95/07/13  xx:xx:xx  BB
  10  * Minor change for use with Borland C/C++ 1,3 and 4
  11  *
  12  * Revision 1.5  94/12/12  17:32:03  arb
  13  * Added support for ArcFS outputsize checking
  14  *
  15  * Revision 1.4  92/12/07  17:17:39  duplain
  16  * reformatted source.
  17  *
  18  * Revision 1.3  92/11/06  12:05:55  duplain
  19  * Credit author of algorithm, now I know his name.
  20  *
  21  * Revision 1.2  92/11/06  11:56:47  duplain
  22  * Slight change to CRC calculation code, no functional changes.
  23  *
  24  * Revision 1.1  92/09/29  18:02:16  duplain
  25  * Initial revision
  26  *
  27  */
  28
  29 #include <stdio.h>
  30 #include "spark.h"
  31 #include "main.h"
  32 #include "arcfs.h"
  33
  34 Word crc;
  35 static Word crctable[256] = {
  36         0x00000000, 0x0000c0c1, 0x0000c181, 0x00000140,
  37         0x0000c301, 0x000003c0, 0x00000280, 0x0000c241,
  38         0x0000c601, 0x000006c0, 0x00000780, 0x0000c741,
  39         0x00000500, 0x0000c5c1, 0x0000c481, 0x00000440,
  40         0x0000cc01, 0x00000cc0, 0x00000d80, 0x0000cd41,
  41         0x00000f00, 0x0000cfc1, 0x0000ce81, 0x00000e40,
  42         0x00000a00, 0x0000cac1, 0x0000cb81, 0x00000b40,
  43         0x0000c901, 0x000009c0, 0x00000880, 0x0000c841,
  44         0x0000d801, 0x000018c0, 0x00001980, 0x0000d941,
  45         0x00001b00, 0x0000dbc1, 0x0000da81, 0x00001a40,
  46         0x00001e00, 0x0000dec1, 0x0000df81, 0x00001f40,
  47         0x0000dd01, 0x00001dc0, 0x00001c80, 0x0000dc41,
  48         0x00001400, 0x0000d4c1, 0x0000d581, 0x00001540,
  49         0x0000d701, 0x000017c0, 0x00001680, 0x0000d641,
  50         0x0000d201, 0x000012c0, 0x00001380, 0x0000d341,
  51         0x00001100, 0x0000d1c1, 0x0000d081, 0x00001040,
  52         0x0000f001, 0x000030c0, 0x00003180, 0x0000f141,
  53         0x00003300, 0x0000f3c1, 0x0000f281, 0x00003240,
  54         0x00003600, 0x0000f6c1, 0x0000f781, 0x00003740,
  55         0x0000f501, 0x000035c0, 0x00003480, 0x0000f441,
  56         0x00003c00, 0x0000fcc1, 0x0000fd81, 0x00003d40,
  57         0x0000ff01, 0x00003fc0, 0x00003e80, 0x0000fe41,
  58         0x0000fa01, 0x00003ac0, 0x00003b80, 0x0000fb41,
  59         0x00003900, 0x0000f9c1, 0x0000f881, 0x00003840,
  60         0x00002800, 0x0000e8c1, 0x0000e981, 0x00002940,
  61         0x0000eb01, 0x00002bc0, 0x00002a80, 0x0000ea41,
  62         0x0000ee01, 0x00002ec0, 0x00002f80, 0x0000ef41,
  63         0x00002d00, 0x0000edc1, 0x0000ec81, 0x00002c40,
  64         0x0000e401, 0x000024c0, 0x00002580, 0x0000e541,
  65         0x00002700, 0x0000e7c1, 0x0000e681, 0x00002640,
  66         0x00002200, 0x0000e2c1, 0x0000e381, 0x00002340,
  67         0x0000e101, 0x000021c0, 0x00002080, 0x0000e041,
  68         0x0000a001, 0x000060c0, 0x00006180, 0x0000a141,
  69         0x00006300, 0x0000a3c1, 0x0000a281, 0x00006240,
  70         0x00006600, 0x0000a6c1, 0x0000a781, 0x00006740,
  71         0x0000a501, 0x000065c0, 0x00006480, 0x0000a441,
  72         0x00006c00, 0x0000acc1, 0x0000ad81, 0x00006d40,
  73         0x0000af01, 0x00006fc0, 0x00006e80, 0x0000ae41,
  74         0x0000aa01, 0x00006ac0, 0x00006b80, 0x0000ab41,
  75         0x00006900, 0x0000a9c1, 0x0000a881, 0x00006840,
  76         0x00007800, 0x0000b8c1, 0x0000b981, 0x00007940,
  77         0x0000bb01, 0x00007bc0, 0x00007a80, 0x0000ba41,
  78         0x0000be01, 0x00007ec0, 0x00007f80, 0x0000bf41,
  79         0x00007d00, 0x0000bdc1, 0x0000bc81, 0x00007c40,
  80         0x0000b401, 0x000074c0, 0x00007580, 0x0000b541,
  81         0x00007700, 0x0000b7c1, 0x0000b681, 0x00007640,
  82         0x00007200, 0x0000b2c1, 0x0000b381, 0x00007340,
  83         0x0000b101, 0x000071c0, 0x00007080, 0x0000b041,
  84         0x00005000, 0x000090c1, 0x00009181, 0x00005140,
  85         0x00009301, 0x000053c0, 0x00005280, 0x00009241,
  86         0x00009601, 0x000056c0, 0x00005780, 0x00009741,
  87         0x00005500, 0x000095c1, 0x00009481, 0x00005440,
  88         0x00009c01, 0x00005cc0, 0x00005d80, 0x00009d41,
  89         0x00005f00, 0x00009fc1, 0x00009e81, 0x00005e40,
  90         0x00005a00, 0x00009ac1, 0x00009b81, 0x00005b40,
  91         0x00009901, 0x000059c0, 0x00005880, 0x00009841,
  92         0x00008801, 0x000048c0, 0x00004980, 0x00008941,
  93         0x00004b00, 0x00008bc1, 0x00008a81, 0x00004a40,
  94         0x00004e00, 0x00008ec1, 0x00008f81, 0x00004f40,
  95         0x00008d01, 0x00004dc0, 0x00004c80, 0x00008c41,
  96         0x00004400, 0x000084c1, 0x00008581, 0x00004540,
  97         0x00008701, 0x000047c0, 0x00004680, 0x00008641,
  98         0x00008201, 0x000042c0, 0x00004380, 0x00008341,
  99         0x00004100, 0x000081c1, 0x00008081, 0x00004040
 100 };
 101
 102 void
 103 calccrc(Byte byte)
 104 {
 105         if (crcsize-- > 0)
 106                 /* BB added cast to next line to stop Borland compiler
 107                    from complaining */
 108                 /* crc = ((crc >> 8) & 0xff) ^ crctable[(crc ^ byte) & 0xff]; */
 109 #ifdef __MSDOS__
 110                 crc = ((crc >> 8) & 0xff) ^ crctable[(int) ((crc ^ byte) & 0xff)];
 111 #else
 112                 crc = ((crc >> 8) & 0xff) ^ crctable[(crc ^ byte) & 0xff];
 113 #endif                                                  /* __MSDOS__ */
 114 }