crcutil.c

sdcc是为51等小型嵌入式cpu设计的c语言编译器支持数种不同类型的cpu

//---------------------------------------------------------------------------
// Copyright (C) 2000 Dallas Semiconductor Corporation, All Rights Reserved.
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
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// OTHER DEALINGS IN THE SOFTWARE.
// 
// Except as contained in this notice, the name of Dallas Semiconductor 
// shall not be used except as stated in the Dallas Semiconductor 
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//--------------------------------------------------------------------------
//
//  crcutil.c - Keeps track of the CRC for 16 and 8 bit operations
//  version 2.00
//
//  Badly abused by Kevin Vigor, 11/20/2000

// Include files
#include "crcutil.h"

// Local global variables
#ifdef WANT_CRC_16
static short oddparity[16] = { 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
#endif
static unsigned char dscrc_table[] = {
        0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
      157,195, 33,127,252,162, 64, 30, 95,  1,227,189, 62, 96,130,220,
       35,125,159,193, 66, 28,254,160,225,191, 93,  3,128,222, 60, 98,
      190,224,  2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
       70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89,  7,
      219,133,103, 57,186,228,  6, 88, 25, 71,165,251,120, 38,196,154,
      101, 59,217,135,  4, 90,184,230,167,249, 27, 69,198,152,122, 36,
      248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91,  5,231,185,
      140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
       17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
      175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
       50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
      202,148,118, 40,171,245, 23, 73,  8, 86,180,234,105, 55,213,139,
       87,  9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
      233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
      116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};

#ifdef WANT_CRC_16
//--------------------------------------------------------------------------
// Calculate a new CRC16 from the input data shorteger.  Return the current
// CRC16.
//
// Returns: the current CRC16
//

unsigned int docrc16(unsigned int oldCrc, 
		     unsigned int byte)
{
   byte = (byte ^ (oldCrc & 0xff)) & 0xff;
   oldCrc >>= 8;

   if (oddparity[byte & 0xf] ^ oddparity[byte >> 4])
   {
     oldCrc ^= 0xc001;
   }

   byte <<= 6;
   oldCrc ^= byte;
   byte <<= 1;
   oldCrc ^= byte;

   return oldCrc;
}
#endif

unsigned char docrc8(unsigned char oldCrc, unsigned char x)
{
   return dscrc_table[oldCrc ^ x];
}