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C/C++ Source or Header  |  1994-12-13  |  4KB  |  109 lines
  1. /*
  2.  * calculate Cyclic Redundancy Check
  3.  *
  4.  * Algorithm by: David Schwaderer, Published in PC Tech Journal April 1985.
  5.  *
  6.  * $Header: crc.c 1.5 94/12/12 $
  7.  * $Log:    crc.c,v $
  8.  * Revision 1.5  94/12/12  17:32:03  arb
  9.  * Added support for ArcFS outputsize checking
  10.  *
  11.  * Revision 1.4  92/12/07  17:17:39  duplain
  12.  * reformatted source.
  13.  * 
  14.  * Revision 1.3  92/11/06  12:05:55  duplain
  15.  * Credit author of algorithm, now I know his name.
  16.  * 
  17.  * Revision 1.2  92/11/06  11:56:47  duplain
  18.  * Slight change to CRC calculation code, no functional changes.
  19.  * 
  20.  * Revision 1.1  92/09/29  18:02:16  duplain
  21.  * Initial revision
  22.  * 
  23.  */
  24.  
  25. #include <stdio.h>
  26. #include "spark.h"
  27. #include "main.h"
  28. #include "arcfs.h"
  29.  
  30. #ifdef UNIX
  31. static char rcsid[] = "$Header: crc.c 1.5 94/12/12 $";
  32. #endif /* UNIX */
  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)
  104.     Byte byte;
  105. {
  106.     if (crcsize-- > 0)
  107.     crc = ((crc >> 8) & 0xff) ^ crctable[(crc ^ byte) & 0xff];
  108. }
  109.