Remi Beges / DistantIO

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crc.cpp@0:c4676d32d381, 2015-09-15 (annotated)

Committer:
Overdrivr
Date:
Tue Sep 15 15:27:55 2015 +0000
Revision:
0:c4676d32d381
Child:
1:aaffeb93f99b
Version not bug free (especially names should not be longer thant 8 characters or have spaces), but pretty reliable behavior. See github repo for tickets

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Overdrivr 0:c4676d32d381 1 // From : http://stackoverflow.com/questions/15169387/definitive-crc-for-c
Overdrivr 0:c4676d32d381 2 /* 8-bit CRC with polynomial x^8+x^6+x^3+x^2+1, 0x14D.
Overdrivr 0:c4676d32d381 3 Chosen based on Koopman, et al. (0xA6 in his notation = 0x14D >> 1):
Overdrivr 0:c4676d32d381 4 http://www.ece.cmu.edu/~koopman/roses/dsn04/koopman04_crc_poly_embedded.pdf
Overdrivr 0:c4676d32d381 5 */
Overdrivr 0:c4676d32d381 6
Overdrivr 0:c4676d32d381 7 #include "crc.h"
Overdrivr 0:c4676d32d381 8 /*
Overdrivr 0:c4676d32d381 9 static const unsigned char crc8_table[] = {
Overdrivr 0:c4676d32d381 10 0x00, 0x3e, 0x7c, 0x42, 0xf8, 0xc6, 0x84, 0xba, 0x95, 0xab, 0xe9, 0xd7,
Overdrivr 0:c4676d32d381 11 0x6d, 0x53, 0x11, 0x2f, 0x4f, 0x71, 0x33, 0x0d, 0xb7, 0x89, 0xcb, 0xf5,
Overdrivr 0:c4676d32d381 12 0xda, 0xe4, 0xa6, 0x98, 0x22, 0x1c, 0x5e, 0x60, 0x9e, 0xa0, 0xe2, 0xdc,
Overdrivr 0:c4676d32d381 13 0x66, 0x58, 0x1a, 0x24, 0x0b, 0x35, 0x77, 0x49, 0xf3, 0xcd, 0x8f, 0xb1,
Overdrivr 0:c4676d32d381 14 0xd1, 0xef, 0xad, 0x93, 0x29, 0x17, 0x55, 0x6b, 0x44, 0x7a, 0x38, 0x06,
Overdrivr 0:c4676d32d381 15 0xbc, 0x82, 0xc0, 0xfe, 0x59, 0x67, 0x25, 0x1b, 0xa1, 0x9f, 0xdd, 0xe3,
Overdrivr 0:c4676d32d381 16 0xcc, 0xf2, 0xb0, 0x8e, 0x34, 0x0a, 0x48, 0x76, 0x16, 0x28, 0x6a, 0x54,
Overdrivr 0:c4676d32d381 17 0xee, 0xd0, 0x92, 0xac, 0x83, 0xbd, 0xff, 0xc1, 0x7b, 0x45, 0x07, 0x39,
Overdrivr 0:c4676d32d381 18 0xc7, 0xf9, 0xbb, 0x85, 0x3f, 0x01, 0x43, 0x7d, 0x52, 0x6c, 0x2e, 0x10,
Overdrivr 0:c4676d32d381 19 0xaa, 0x94, 0xd6, 0xe8, 0x88, 0xb6, 0xf4, 0xca, 0x70, 0x4e, 0x0c, 0x32,
Overdrivr 0:c4676d32d381 20 0x1d, 0x23, 0x61, 0x5f, 0xe5, 0xdb, 0x99, 0xa7, 0xb2, 0x8c, 0xce, 0xf0,
Overdrivr 0:c4676d32d381 21 0x4a, 0x74, 0x36, 0x08, 0x27, 0x19, 0x5b, 0x65, 0xdf, 0xe1, 0xa3, 0x9d,
Overdrivr 0:c4676d32d381 22 0xfd, 0xc3, 0x81, 0xbf, 0x05, 0x3b, 0x79, 0x47, 0x68, 0x56, 0x14, 0x2a,
Overdrivr 0:c4676d32d381 23 0x90, 0xae, 0xec, 0xd2, 0x2c, 0x12, 0x50, 0x6e, 0xd4, 0xea, 0xa8, 0x96,
Overdrivr 0:c4676d32d381 24 0xb9, 0x87, 0xc5, 0xfb, 0x41, 0x7f, 0x3d, 0x03, 0x63, 0x5d, 0x1f, 0x21,
Overdrivr 0:c4676d32d381 25 0x9b, 0xa5, 0xe7, 0xd9, 0xf6, 0xc8, 0x8a, 0xb4, 0x0e, 0x30, 0x72, 0x4c,
Overdrivr 0:c4676d32d381 26 0xeb, 0xd5, 0x97, 0xa9, 0x13, 0x2d, 0x6f, 0x51, 0x7e, 0x40, 0x02, 0x3c,
Overdrivr 0:c4676d32d381 27 0x86, 0xb8, 0xfa, 0xc4, 0xa4, 0x9a, 0xd8, 0xe6, 0x5c, 0x62, 0x20, 0x1e,
Overdrivr 0:c4676d32d381 28 0x31, 0x0f, 0x4d, 0x73, 0xc9, 0xf7, 0xb5, 0x8b, 0x75, 0x4b, 0x09, 0x37,
Overdrivr 0:c4676d32d381 29 0x8d, 0xb3, 0xf1, 0xcf, 0xe0, 0xde, 0x9c, 0xa2, 0x18, 0x26, 0x64, 0x5a,
Overdrivr 0:c4676d32d381 30 0x3a, 0x04, 0x46, 0x78, 0xc2, 0xfc, 0xbe, 0x80, 0xaf, 0x91, 0xd3, 0xed,
Overdrivr 0:c4676d32d381 31 0x57, 0x69, 0x2b, 0x15};
Overdrivr 0:c4676d32d381 32
Overdrivr 0:c4676d32d381 33 unsigned crc8(unsigned char *data, uint16_t len)
Overdrivr 0:c4676d32d381 34 {
Overdrivr 0:c4676d32d381 35 static unsigned char crc;
Overdrivr 0:c4676d32d381 36 unsigned char *end;
Overdrivr 0:c4676d32d381 37
Overdrivr 0:c4676d32d381 38 if (len == 0)
Overdrivr 0:c4676d32d381 39 return crc;
Overdrivr 0:c4676d32d381 40
Overdrivr 0:c4676d32d381 41 crc ^= 0xff;
Overdrivr 0:c4676d32d381 42 end = data + len;
Overdrivr 0:c4676d32d381 43 do {
Overdrivr 0:c4676d32d381 44 crc = crc8_table[crc ^ *data++];
Overdrivr 0:c4676d32d381 45 } while (data < end);
Overdrivr 0:c4676d32d381 46 return crc ^ 0xff;
Overdrivr 0:c4676d32d381 47 return 0;
Overdrivr 0:c4676d32d381 48 }*/
Overdrivr 0:c4676d32d381 49
Overdrivr 0:c4676d32d381 50 /* this was used to generate the table and to test the table-version
Overdrivr 0:c4676d32d381 51
Overdrivr 0:c4676d32d381 52 #define POLY 0xB2
Overdrivr 0:c4676d32d381 53
Overdrivr 0:c4676d32d381 54 unsigned crc8_slow(unsigned crc, unsigned char *data, size_t len)
Overdrivr 0:c4676d32d381 55 {
Overdrivr 0:c4676d32d381 56 unsigned char *end;
Overdrivr 0:c4676d32d381 57
Overdrivr 0:c4676d32d381 58 if (len == 0)
Overdrivr 0:c4676d32d381 59 return crc;
Overdrivr 0:c4676d32d381 60 crc ^= 0xff;
Overdrivr 0:c4676d32d381 61 end = data + len;
Overdrivr 0:c4676d32d381 62 do {
Overdrivr 0:c4676d32d381 63 crc ^= *data++;
Overdrivr 0:c4676d32d381 64 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 65 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 66 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 67 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 68 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 69 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 70 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 71 crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
Overdrivr 0:c4676d32d381 72 } while (data < end);
Overdrivr 0:c4676d32d381 73 return crc ^ 0xff;
Overdrivr 0:c4676d32d381 74 }
Overdrivr 0:c4676d32d381 75 */
Overdrivr 0:c4676d32d381 76 /*
Overdrivr 0:c4676d32d381 77 # From : https://en.wikipedia.org/wiki/Computation_of_cyclic_redundancy_checks
Overdrivr 0:c4676d32d381 78
Overdrivr 0:c4676d32d381 79 # Most significant bit first (big-endian)
Overdrivr 0:c4676d32d381 80 # x^16+x^12+x^5+1 = (1) 0001 0000 0010 0001 = 0x1021
Overdrivr 0:c4676d32d381 81
Overdrivr 0:c4676d32d381 82 def crc16(data):
Overdrivr 0:c4676d32d381 83 rem = 0
Overdrivr 0:c4676d32d381 84 n = 16
Overdrivr 0:c4676d32d381 85 # A popular variant complements rem here
Overdrivr 0:c4676d32d381 86 for d in data:
Overdrivr 0:c4676d32d381 87 rem = rem ^ (d << (n-8)) # n = 16 in this example
Overdrivr 0:c4676d32d381 88 for j in range(1,8):
Overdrivr 0:c4676d32d381 89 # Assuming 8 bits per byte
Overdrivr 0:c4676d32d381 90 if rem & 0x8000:
Overdrivr 0:c4676d32d381 91 # if leftmost (most significant) bit is set
Overdrivr 0:c4676d32d381 92 rem = (rem << 1) ^ 0x1021
Overdrivr 0:c4676d32d381 93 else:
Overdrivr 0:c4676d32d381 94 rem = rem << 1
Overdrivr 0:c4676d32d381 95 rem = rem & 0xffff # Trim remainder to 16 bits
Overdrivr 0:c4676d32d381 96 # A popular variant complements rem here
Overdrivr 0:c4676d32d381 97 return rem
Overdrivr 0:c4676d32d381 98 */
Overdrivr 0:c4676d32d381 99 // Most significant bit first (big-endian)
Overdrivr 0:c4676d32d381 100 // x^16+x^12+x^5+1 = (1) 0001 0000 0010 0001 = 0x1021
Overdrivr 0:c4676d32d381 101
Overdrivr 0:c4676d32d381 102 uint16_t crc16(uint8_t* data, uint16_t len)
Overdrivr 0:c4676d32d381 103 {
Overdrivr 0:c4676d32d381 104 uint16_t rem = 0;
Overdrivr 0:c4676d32d381 105 uint16_t n = 16;
Overdrivr 0:c4676d32d381 106 // A popular variant complements rem here
Overdrivr 0:c4676d32d381 107 for(uint16_t i = 0 ; i < len ; i++)
Overdrivr 0:c4676d32d381 108 {
Overdrivr 0:c4676d32d381 109 rem = rem ^ (data[i] << (n-8)); // n = 16 in this example
Overdrivr 0:c4676d32d381 110
Overdrivr 0:c4676d32d381 111 for(uint16_t j = 1 ; j < 8 ; j++) // Assuming 8 bits per byte
Overdrivr 0:c4676d32d381 112 {
Overdrivr 0:c4676d32d381 113
Overdrivr 0:c4676d32d381 114 if(rem & 0x8000)
Overdrivr 0:c4676d32d381 115 {
Overdrivr 0:c4676d32d381 116 // if leftmost (most significant) bit is set
Overdrivr 0:c4676d32d381 117 rem = (rem << 1) ^ 0x1021;
Overdrivr 0:c4676d32d381 118 }
Overdrivr 0:c4676d32d381 119 else
Overdrivr 0:c4676d32d381 120 {
Overdrivr 0:c4676d32d381 121 rem = rem << 1;
Overdrivr 0:c4676d32d381 122 }
Overdrivr 0:c4676d32d381 123 rem &= 0xffff; // Trim remainder to 16 bits
Overdrivr 0:c4676d32d381 124 }
Overdrivr 0:c4676d32d381 125 }
Overdrivr 0:c4676d32d381 126 // A popular variant complements rem here
Overdrivr 0:c4676d32d381 127 return rem;
Overdrivr 0:c4676d32d381 128 }
Overdrivr 0:c4676d32d381 129
Overdrivr 0:c4676d32d381 130