crc_byte.c

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/* file: crc_byte.c
   purpose: generate 3GPP LTE CRCs. Byte-oriented implementation of CRC's
   author: raymond.knopp@eurecom.fr
   date: 21.10.2009

   Original UMTS version by
   P. Humblet
   May 10, 2001
   Modified in June, 2001, to include  the length non multiple of 8
*/


#include "coding_defs.h"

/*ref 36-212 v8.6.0 , pp 8-9 */
/* the highest degree is set by default */

unsigned int             poly24a = 0x864cfb00;   // 1000 0110 0100 1100 1111 1011
												 // D^24 + D^23 + D^18 + D^17 + D^14 + D^11 + D^10 + D^7 + D^6 + D^5 + D^4 + D^3 + D + 1
unsigned int             poly24b = 0x80006300;   // 1000 0000 0000 0000 0110 0011
											     // D^24 + D^23 + D^6 + D^5 + D + 1
unsigned int             poly24c = 0xb2b11700;   // 1011 0010 1011 0001 0001 0111
												 // D^24+D^23+D^21+D^20+D^17+D^15+D^13+D^12+D^8+D^4+D^2+D+1

unsigned int             poly16 = 0x10210000;    // 0001 0000 0010 0001            D^16 + D^12 + D^5 + 1
unsigned int             poly12 = 0x80F00000;    // 1000 0000 1111                 D^12 + D^11 + D^3 + D^2 + D + 1
unsigned int             poly8 = 0x9B000000;     // 1001 1011                      D^8  + D^7  + D^4 + D^3 + D + 1
uint32_t poly6 = 0x84000000; // 10000100000... -> D^6+D^5+1
uint32_t poly11 = 0xc4200000; //11000100001000... -> D^11+D^10+D^9+D^5+1

/*********************************************************

For initialization && verification purposes,
   bit by bit implementation with any polynomial

The first bit is in the MSB of each byte

*********************************************************/
unsigned int crcbit (unsigned char * inputptr,
					 int octetlen,
					 unsigned int poly)
{
  unsigned int i, crc = 0, c;

  while (octetlen-- > 0) {
    c = (*inputptr++) << 24;

    for (i = 8; i != 0; i--) {
      if ((1 << 31) & (c ^ crc))
        crc = (crc << 1) ^ poly;
      else
        crc <<= 1;

      c <<= 1;
    }
  }

  return crc;
}

/*********************************************************

crc table initialization

*********************************************************/
static unsigned int        crc24aTable[256];
static unsigned int        crc24bTable[256];
static unsigned int        crc24cTable[256];
static unsigned short      crc16Table[256];
static unsigned short      crc12Table[256];
static unsigned char       crc8Table[256];

void crcTableInit (void)
{
  unsigned char c = 0;

  do {
    crc24aTable[c] = crcbit (&c, 1, poly24a);
    crc24bTable[c] = crcbit (&c, 1, poly24b);
    crc24cTable[c] = crcbit (&c, 1, poly24c);
    crc16Table[c] = (unsigned short) (crcbit (&c, 1, poly16) >> 16);
    crc12Table[c] = (unsigned short) (crcbit (&c, 1, poly12) >> 16);
    crc8Table[c] = (unsigned char) (crcbit (&c, 1, poly8) >> 24);
  } while (++c);
}

//Generic version
void crcTable256Init (uint32_t poly, uint32_t* crc256Table)
{
        unsigned char c = 0;

        do {
                crc256Table[c] = crcbit(&c, 1, poly);
        } while (++c);

}

/*********************************************************

Byte by byte implementations,
assuming initial byte is 0 padded (in MSB) if necessary

*********************************************************/
unsigned int crc24a (unsigned char * inptr,
					 int bitlen)
{

  int             octetlen, resbit;
  unsigned int             crc = 0;
  octetlen = bitlen / 8;        /* Change in octets */
  resbit = (bitlen % 8);

  while (octetlen-- > 0) {
    //   printf("crc24a: in %x => crc %x\n",crc,*inptr);
    crc = (crc << 8) ^ crc24aTable[(*inptr++) ^ (crc >> 24)];
  }

  if (resbit > 0)
    crc = (crc << resbit) ^ crc24aTable[((*inptr) >> (8 - resbit)) ^ (crc >> (32 - resbit))];

  return crc;
}

unsigned int crc24b (unsigned char * inptr,
					 int bitlen)
{
  int octetlen, resbit;
  unsigned int crc = 0;
  octetlen = bitlen / 8;        /* Change in octets */
  resbit = (bitlen % 8);

  while (octetlen-- > 0) {
    //    printf("crc24b: in %x => crc %x (%x)\n",crc,*inptr,crc24bTable[(*inptr) ^ (crc >> 24)]);
    crc = (crc << 8) ^ crc24bTable[(*inptr++) ^ (crc >> 24)];
  }

  if (resbit > 0)
    crc = (crc << resbit) ^ crc24bTable[((*inptr) >> (8 - resbit)) ^ (crc >> (32 - resbit))];

  return crc;
}

unsigned int crc24c (unsigned char * inptr,
					 int bitlen)
{
  int octetlen, resbit;
  unsigned int crc = 0;
  octetlen = bitlen / 8;        /* Change in octets */
  resbit = (bitlen % 8);

  while (octetlen-- > 0) {
/*#ifdef DEBUG_CRC24C
	  printf("crc24c: in %x => crc %x (%x)\n",crc,*inptr,crc24cTable[(*inptr) ^ (crc >> 24)]);
#endif*/
    crc = (crc << 8) ^ crc24cTable[(*inptr++) ^ (crc >> 24)];
  }

  if (resbit > 0)
    crc = (crc << resbit) ^ crc24cTable[((*inptr) >> (8 - resbit)) ^ (crc >> (32 - resbit))];

  return crc;
}

unsigned int
crc16 (unsigned char * inptr, int bitlen)
{
  int             octetlen, resbit;
  unsigned int             crc = 0;
  octetlen = bitlen / 8;        /* Change in octets */
  resbit = (bitlen % 8);

  while (octetlen-- > 0) {

    crc = (crc << 8) ^ (crc16Table[(*inptr++) ^ (crc >> 24)] << 16);
  }

  if (resbit > 0)
    crc = (crc << resbit) ^ (crc16Table[((*inptr) >> (8 - resbit)) ^ (crc >> (32 - resbit))] << 16);

  return crc;
}

unsigned int
crc12 (unsigned char * inptr, int bitlen)
{
  int             octetlen, resbit;
  unsigned int             crc = 0;
  octetlen = bitlen / 8;        /* Change in octets */
  resbit = (bitlen % 8);

  while (octetlen-- > 0) {
    crc = (crc << 8) ^ (crc12Table[(*inptr++) ^ (crc >> 24)] << 16);
  }

  if (resbit > 0)
    crc = (crc << resbit) ^ (crc12Table[((*inptr) >> (8 - resbit)) ^ (crc >> (32 - resbit))] << 16);

  return crc;
}

unsigned int
crc8 (unsigned char * inptr, int bitlen)
{
  int             octetlen, resbit;
  unsigned int             crc = 0;
  octetlen = bitlen / 8;        /* Change in octets */
  resbit = (bitlen % 8);

  while (octetlen-- > 0) {
    crc = crc8Table[(*inptr++) ^ (crc >> 24)] << 24;
  }

  if (resbit > 0)
    crc = (crc << resbit) ^ (crc8Table[((*inptr) >> (8 - resbit)) ^ (crc >> (32 - resbit))] << 24);

  return crc;
}

//Generic version
unsigned int crcPayload(unsigned char * inptr, int bitlen, uint32_t* crc256Table)
{
        int octetlen, resbit;
        unsigned int crc = 0;
        octetlen = bitlen/8; // Change in bytes
        resbit = (bitlen % 8);

        while (octetlen-- > 0)
        {
                crc = (crc << 8) ^ crc256Table[(*inptr++) ^ (crc >> 24)];
        }

        if (resbit > 0)
        {
                crc = (crc << resbit) ^ crc256Table[((*inptr) >> (8 - resbit)) ^ (crc >> (32 - resbit))];
        }
        return crc;
}

int check_crc(uint8_t* decoded_bytes, uint32_t n, uint32_t F, uint8_t crc_type)
{
  uint32_t crc,oldcrc;
  uint8_t crc_len,temp;

  switch (crc_type) {
  case CRC24_A:
  case CRC24_B:
    crc_len=3;
    break;

  case CRC16:
    crc_len=2;
    break;

  case CRC8:
    crc_len=1;
    break;

  default:
    crc_len=3;
  }

  oldcrc= *((unsigned int *)(&decoded_bytes[(n>>3)-crc_len]));

  switch (crc_type) {
    
  case CRC24_A:
    oldcrc&=0x00ffffff;
    crc = crc24a(&decoded_bytes[F>>3],
		 n-24-F)>>8;
    temp=((uint8_t *)&crc)[2];
    ((uint8_t *)&crc)[2] = ((uint8_t *)&crc)[0];
    ((uint8_t *)&crc)[0] = temp;
    
    break;
    
  case CRC24_B:
      oldcrc&=0x00ffffff;
      crc = crc24b(decoded_bytes,
                   n-24)>>8;
      temp=((uint8_t *)&crc)[2];
      ((uint8_t *)&crc)[2] = ((uint8_t *)&crc)[0];
      ((uint8_t *)&crc)[0] = temp;
      
      break;

    case CRC16:
      oldcrc&=0x0000ffff;
      crc = crc16(decoded_bytes,
                  n-16)>>16;
      
      break;

    case CRC8:
      oldcrc&=0x000000ff;
      crc = crc8(decoded_bytes,
                 n-8)>>24;
      break;
    }

    if (crc == oldcrc)
      return(1);
    else
      return(0);

}


#ifdef DEBUG_CRC
/*******************************************************************/
/**
   Test code
********************************************************************/

#include <stdio.h>

main()
{
  unsigned char test[] = "Thebigredfox";
  crcTableInit();
  printf("%x\n", crcbit(test, sizeof(test) - 1, poly24));
  printf("%x\n", crc24(test, (sizeof(test) - 1)*8));
  printf("%x\n", crcbit(test, sizeof(test) - 1, poly8));
  printf("%x\n", crc8(test, (sizeof(test) - 1)*8));
}
#endif