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crc.c
266 lines (260 loc) · 9.82 KB
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crc.c
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/*
* Copyright (c) 2005, Daniel C. Newman <dan.newman@mtbaldy.us>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* + Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* + Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* + Neither the name of mtbaldy.us nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* *******************************************************
* Code to generate the CRC16 algorithm table
* *******************************************************
* #include <stdio.h>
* #define CRC16 0xA001 // X^16 + X^15 + X^2 + 1
*
* static unsigned short compute_crc(unsigned short data)
* {
* unsigned short crc;
* int i;
*
* crc = 0;
* for (i = 8; i; --i)
* {
* if ((data ^ crc) & 0x0001)
* crc = (crc >> 1) ^ CRC16;
* else
* crc >>= 1;
* data >>= 1;
* }
* return(crc);
* }
*
* int main(void)
* {
* int i;
*
* printf( "static const unsigned int table[256] = {\n" );
*
* for ( i = 0; i < 256; i++ )
* {
* printf("0x%04X%s", compute_crc(i), (i < 255) ? ", " : "};\n");
* if (i < 255 && 7 == (i % 8))
* printf("\n");
* }
* }
* *******************************************************
*
* *******************************************************
* A non-table driven version of the CRC16 algorithm
* *******************************************************
* int
* crc16(int crc, int ch)
* {
* static short has_odd_parity[16] = {
* 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0};
*
* ch = (ch ^ (crc & 0xFF)) & 0xFF;
* crc = (crc & 0xFFFF) >> 8;
* if (1 == (has_odd_parity[ch & 0x0F] ^ has_odd_parity[ch >> 4]))
* crc = crc ^ 0xC001;
* ch = (ch << 6);
* crc = crc ^ ch;
* ch = ch << 1;
* crc = crc ^ ch;
* return(crc);
* }
* *******************************************************
*/
/*
* int crc16(int crc, int ch)
*
* Compute the CRC-16 of the byte ch using the short crc as the seed.
* The result of the computation is the return value.
*
* For example, to compute the CRC-16 of the bytes 0x01 0x02 0x03,
* one would.
*
* int crc = 0;
* crc = crc16(crc, 0x01);
* crc = crc16(crc, 0x02);
* crc = crc16(crc, 0x03);
*
* Note that the CRC-16 has two useful properties. For n > 0 bytes
* data[1], ..., data[n-1] compute the CRC-16 over the data as
* follows.
*
* crc = 0;
* for (i = 0; i < n; i++)
* crc = crc16(crc, data[i]);
*
* Then, the two properties are
*
* 0x0000 == crc16(crc16(crc, 0xff & crc), 0xff & (crc >> 8));
* 0xb001 == crc16(crc16(crc, 0xff & ~crc), 0xff & (~crc >> 8)));
*
* These properties allow us to compare an expected CRC-16 or it's
* one's complement with the received data by computing the CRC-16 over
* the received data AND the expected CRC-16 [or 1's complement] and then
* seeing if the result is 0x0000 [or 0xb001].
*
*
* Call arguments:
*
* int crc
* The 16-bit seed to combine with the low 8 bits of ch. Used
* for input only.
*
* int ch
* The byte to compute the CRC of. Only the low 8 bits are used.
* Used for input only.
*
* Return values:
*
* 16 bit CRC computation.
*/
int
crc16(int crc, int ch)
{
static const unsigned int table[256] = {
0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040};
return((crc >> 8) ^ table[(crc & 0xff) ^ ch]);
}
/*
* unsigned char crc8(unsigned char crc, unsigned char ch)
*
* Compute the 8-bit DOW CRC of the byte ch using the byte crc
* as the seed. The result of the computation is the return value.
*
* For example, to compute the DOW CRC of the bytes 0x01 0x02 0x03,
* one would use the following code:
*
* unsigned char crc = 0x00;
* crc = crc8(crc, 0x01);
* crc = crc8(crc, 0x02);
* crc = crc8(crc, 0x03);
*
* Note that the DOW CRC has two useful properties. For n > 0 bytes
* data[1], ..., data[n-1] compute the DOW CRC over the data as
* follows.
*
* crc = 0x00;
* for (i = 0; i < n; i++)
* crc = crc8(crc, data[i]);
*
* Then, the two properties are
*
* 0x00 == crc8(crc, crc);
* 0x35 == crc8(crc, ~crc);
*
* These properties allow us to compare an expected DOW CRC or it's
* one's complement with the received data by computing the CRC over
* the received data AND the expected CRC [or 1's complement] and then
* seeing if the result is 0x00 [or 0x35].
*
* Call arguments:
*
* unsigned char crc
* The seed to combine with ch. Used for input only.
*
* unsigned char ch
* The byte to compute the CRC of. Used for input only.
*
* Return values:
*
* 8 bit CRC computation.
*/
unsigned char
crc8(unsigned char crc, unsigned char ch)
{
static const unsigned char table[256] = {
0x00, 0x5E, 0xBC, 0xE2, 0x61, 0x3F, 0xDD, 0x83,
0xC2, 0x9C, 0x7E, 0x20, 0xA3, 0xFD, 0x1F, 0x41,
0x9D, 0xC3, 0x21, 0x7F, 0xFC, 0xA2, 0x40, 0x1E,
0x5F, 0x01, 0xE3, 0xBD, 0x3E, 0x60, 0x82, 0xDC,
0x23, 0x7D, 0x9F, 0xC1, 0x42, 0x1C, 0xFE, 0xA0,
0xE1, 0xBF, 0x5D, 0x03, 0x80, 0xDE, 0x3C, 0x62,
0xBE, 0xE0, 0x02, 0x5C, 0xDF, 0x81, 0x63, 0x3D,
0x7C, 0x22, 0xC0, 0x9E, 0x1D, 0x43, 0xA1, 0xFF,
0x46, 0x18, 0xFA, 0xA4, 0x27, 0x79, 0x9B, 0xC5,
0x84, 0xDA, 0x38, 0x66, 0xE5, 0xBB, 0x59, 0x07,
0xDB, 0x85, 0x67, 0x39, 0xBA, 0xE4, 0x06, 0x58,
0x19, 0x47, 0xA5, 0xFB, 0x78, 0x26, 0xC4, 0x9A,
0x65, 0x3B, 0xD9, 0x87, 0x04, 0x5A, 0xB8, 0xE6,
0xA7, 0xF9, 0x1B, 0x45, 0xC6, 0x98, 0x7A, 0x24,
0xF8, 0xA6, 0x44, 0x1A, 0x99, 0xC7, 0x25, 0x7B,
0x3A, 0x64, 0x86, 0xD8, 0x5B, 0x05, 0xE7, 0xB9,
0x8C, 0xD2, 0x30, 0x6E, 0xED, 0xB3, 0x51, 0x0F,
0x4E, 0x10, 0xF2, 0xAC, 0x2F, 0x71, 0x93, 0xCD,
0x11, 0x4F, 0xAD, 0xF3, 0x70, 0x2E, 0xCC, 0x92,
0xD3, 0x8D, 0x6F, 0x31, 0xB2, 0xEC, 0x0E, 0x50,
0xAF, 0xF1, 0x13, 0x4D, 0xCE, 0x90, 0x72, 0x2C,
0x6D, 0x33, 0xD1, 0x8F, 0x0C, 0x52, 0xB0, 0xEE,
0x32, 0x6C, 0x8E, 0xD0, 0x53, 0x0D, 0xEF, 0xB1,
0xF0, 0xAE, 0x4C, 0x12, 0x91, 0xCF, 0x2D, 0x73,
0xCA, 0x94, 0x76, 0x28, 0xAB, 0xF5, 0x17, 0x49,
0x08, 0x56, 0xB4, 0xEA, 0x69, 0x37, 0xD5, 0x8B,
0x57, 0x09, 0xEB, 0xB5, 0x36, 0x68, 0x8A, 0xD4,
0x95, 0xCB, 0x29, 0x77, 0xF4, 0xAA, 0x48, 0x16,
0xE9, 0xB7, 0x55, 0x0B, 0x88, 0xD6, 0x34, 0x6A,
0x2B, 0x75, 0x97, 0xC9, 0x4A, 0x14, 0xF6, 0xA8,
0x74, 0x2A, 0xC8, 0x96, 0x15, 0x4B, 0xA9, 0xF7,
0xB6, 0xE8, 0x0A, 0x54, 0xD7, 0x89, 0x6B, 0x35};
return(table[crc ^ ch]);
}