crc.c

在高通的手机平台下,一个下载手机.bin文件到手机的flash中的工具,包含PC端的程序代码和运行在基带处理器中的代码.

===========================================================================*/

word crc_16_l_calc
(
  byte *buf_ptr,
    /* Pointer to bytes containing the data to CRC.  The bit stream starts
    ** in the LS bit of the first byte.
    */

  word len
    /* Number of data bits to calculate the CRC over */
)
{
  word data, crc_16;

  /* Generate a CRC-16 by looking up the transformation in a table and
  ** XOR-ing it into the CRC, one byte at a time.
  */
  for (crc_16 = CRC_16_L_SEED ; len >= 8; len -= 8, buf_ptr++) {
    crc_16 = crc_16_l_table[ (crc_16 ^ *buf_ptr) & 0x00ff ] ^ (crc_16 >> 8);
  }

  /* Finish calculating the CRC over the trailing data bits
  **
  ** XOR the MS bit of data with the MS bit of the CRC.
  ** Shift the CRC and data left 1 bit.
  ** If the XOR result is 1, XOR the generating polynomial in with the CRC.
  */
  if (len != 0) {

    data = ((word) (*buf_ptr)) << (16-8); /* Align data MSB with CRC MSB */

    while (len-- != 0) {
      if ( ((crc_16 ^ data) & 0x01) != 0 ){   /* Is LSB of XOR a 1 */

        crc_16 >>= 1;                   /* Right shift CRC         */
        crc_16 ^= CRC_16_L_POLYNOMIAL;  /* XOR polynomial into CRC */

      } else {

        crc_16 >>= 1;                   /* Right shift CRC         */

      }

      data >>= 1;                       /* Right shift data        */
    }
  }

  return( ~crc_16 );            /* return the 1's complement of the CRC */

} /* end of crc_16_l_calc */


/*===========================================================================

FUNCTION CRC_30_CALC

DESCRIPTION
  This function calculates a 30-bit CRC over a specified number of data
  bits.  It can be used to produce a CRC and to check a CRC.

DEPENDENCIES
  None

RETURN VALUE
  Returns a double word holding 30 bits which are the contents of the
  CRC register as calculated over the specified data bits.  If this
  function is being used to check a CRC, then the return value will be
  equal to CRC_30_OK (defined in crc.h) if the CRC checks correctly.

SIDE EFFECTS
  None

===========================================================================*/

dword crc_30_calc
(
  byte *buf_ptr,
    /* Pointer to bytes containing the data to CRC.  The bit stream starts
    ** in the MS bit of the first byte.
    */

  word len
    /* Number of data bits to calculate the CRC over */
)
{
  dword data, crc_30;

  /* Generate a CRC-30 by looking up the transformation in a table and
  ** XOR-ing it into the CRC, one byte at a time.
  */
  for (crc_30 = CRC_30_SEED ; len >= 8; len -= 8, buf_ptr++) {
    crc_30 = crc30_table[ ((crc_30 >> (30 - 8)) ^ *buf_ptr) & 0xff ]
                ^ (crc_30 << 8);
  }

  /* Finish calculating the CRC over the trailing data bits
  **
  ** XOR the MS bit of data with the MS bit of the CRC.
  ** Shift the CRC and data left 1 bit.
  ** If the XOR result is 1, XOR the generating polynomial in with the CRC.
  */
  if (len != 0) {

    data = ((dword) (*buf_ptr)) << (30-8); /* Align data MSB with CRC MSB */

    while (len-- != 0) {
      if ( ((crc_30 ^ data) & (1L << 29)) != 0 ) {       /* Is MSB of XOR a 1 */

        crc_30 <<= 1;                   /* Left shift CRC          */
        crc_30 ^= CRC_30_POLYNOMIAL;    /* XOR polynomial into CRC */

      } else {

        crc_30 <<= 1;                   /* Left shift CRC          */

      }

      data <<= 1;                       /* Left shift data         */
    }
  }

  crc_30 = ~crc_30;                     /* 1's complement the CRC     */

  return( crc_30 & 0x3FFFFFFF );        /* mask the result to 30 bits */

} /* end of crc_30_calc */


/*===========================================================================

FUNCTION CRC_30_STEP

DESCRIPTION
  This function calculates a 30-bit CRC over a specified number of data
  bits.  It can be used to produce a CRC and to check a CRC.  The CRC value
  passed in is used to continue the CRC calculation from a previous call,
  this allows this routine to be used to CRC discontinuous data.

DEPENDENCIES
  None

RETURN VALUE
  Returns a double word holding 30 bits which are the contents of the
  CRC register as calculated over the specified data bits.  If this
  function is being used to check a CRC, then the return value will be
  equal to CRC_30_OK (defined in crc.h) if the CRC checks correctly.
  
  NOTE: The caller is expected to mask the bottom 30 bits from the value, 

SIDE EFFECTS
  None

===========================================================================*/

dword crc_30_step
(
  dword seed,
    /* Either the result of a previous crc_30_step() or CRC_16_STEP_SEED
    ** the first time the routine is called.  Note that the input is
    ** inverted prior to use, to counteract the inversion applied when
    ** it was returned as a result of the previous step.
    */

  byte *buf_ptr,
    /* Pointer to bytes containing the data to CRC.  The bit stream starts
    ** in the MS bit of the first byte.
    */

  word len
    /* Number of data bits to calculate the CRC over */
)
{
  dword data, crc_30;

  /* Generate a CRC-30 by looking up the transformation in a table and
  ** XOR-ing it into the CRC, one byte at a time.
  */
  for (crc_30 = ~seed & 0x3FFFFFFF; len >= 8; len -= 8, buf_ptr++) {
    crc_30 = crc30_table[ ((crc_30 >> (30 - 8)) ^ *buf_ptr) & 0xff ]
                ^ (crc_30 << 8);
  }

  /* Finish calculating the CRC over the trailing data bits
  **
  ** XOR the MS bit of data with the MS bit of the CRC.
  ** Shift the CRC and data left 1 bit.
  ** If the XOR result is 1, XOR the generating polynomial in with the CRC.
  */
  if (len != 0) {

    data = ((dword) (*buf_ptr)) << (30-8); /* Align data MSB with CRC MSB */

    while (len-- != 0) {
      if ( ((crc_30 ^ data) & (1L << 29)) != 0 ) {       /* Is MSB of XOR a 1 */

        crc_30 <<= 1;                   /* Left shift CRC          */
        crc_30 ^= CRC_30_POLYNOMIAL;    /* XOR polynomial into CRC */

      } else {

        crc_30 <<= 1;                   /* Left shift CRC          */

      }

      data <<= 1;                       /* Left shift data         */
    }
  }

  crc_30 = ~crc_30;                     /* 1's complement the CRC     */

  return( crc_30 & 0x3FFFFFFF );        /* mask the result to 30 bits */

} /* end of crc_30_calc */


/*===========================================================================

FUNCTION CRC_16_STEP

DESCRIPTION
  This function calculates a 16-bit CRC over a specified number of data
  bytes.  It can be used to produce a CRC and to check a CRC.  The CRC value
  passed in is used to continue the CRC calculation from a previous call;
  this allows this routine to be used to CRC discontinuous data.

DEPENDENCIES
  None

RETURN VALUE
  Returns a word holding 16 bits which are the contents of the CRC
  register as calculated over the specified data bits.  If this
  function is being used to check a CRC, then the return value will be
  equal to CRC_16_OK (defined in crc.h) if the CRC checks correctly.

SIDE EFFECTS
  None

===========================================================================*/

word crc_16_step
(
  word seed,
    /* Either the result of a previous crc_16_step() or CRC_16_STEP_SEED
    ** the first time the routine is called.  Note that the input is
    ** inverted prior to use, to counteract the inversion applied when
    ** it was returned as a result of the previous step.
    */

  byte *buf_ptr,
    /* Pointer to bytes containing the data to CRC.  The bit stream starts
    ** in the MS bit of the first byte.
    */

  word byte_len
    /* Number of data bytes to calculate the CRC over */
)
{
  word crc_16;

  /* Generate a CRC-16 by looking up the transformation in a table and
  ** XOR-ing it into the CRC, one byte at a time.
  **
  ** Note: complement the seed to account for it having been complemented
  ** in a previous call to crc_16_step().
  */
  for (crc_16 = ~seed ; byte_len > 0; byte_len--, buf_ptr++) {
    crc_16 = (word)(crc16_table[ (crc_16 >> (16 - 8)) ^ *buf_ptr ] ^ (crc_16 << 8));
  }

  return( ~crc_16 );            /* return the 1's complement of the CRC */

} /* end of crc_16_step */



/*===========================================================================

FUNCTION CRC_16_L_STEP

DESCRIPTION
  This function calculates a LSB-first 16-bit CRC over a specified number 
  of data bytes.  It can be used to produce a CRC and to check a CRC.  
  The CRC value passed in is used to continue the CRC calculation from a
  previous call; this allows this routine to be used to CRC discontinuous data.

DEPENDENCIES
  None

RETURN VALUE
  Returns a word holding 16 bits which are the contents of the CRC
  register as calculated over the specified data bits.  If this
  function is being used to check a CRC, then the return value will be
  equal to CRC_16_OK (defined in crc.h) if the CRC checks correctly.

SIDE EFFECTS
  None

===========================================================================*/

word crc_16_l_step
(
  word seed,

  const void *buf_ptr,
    /* Either the result of a previous crc_16_l_step() or CRC_16_L_STEP_SEED
    ** the first time the routine is called.  Note that the input is
    ** inverted prior to use, to counteract the inversion applied when
    ** it was returned as a result of the previous step.
    */

  unsigned int byte_len
    /* Number of data bytes to calculate the CRC over */
)
{
  word crc_16;
  byte *byte_ptr = (byte *) buf_ptr;

  /* Generate a CRC-16 by looking up the transformation in a table and
  ** XOR-ing it into the CRC, one byte at a time.
  */
  for (crc_16 = ~seed ; byte_len > 0; byte_len--, byte_ptr++) {
    crc_16 = crc_16_l_table[ (crc_16 ^ *byte_ptr) & 0x00ff ] ^ (crc_16 >> 8);
  }

  return( ~crc_16 );            /* return the 1's complement of the CRC */

} /* end of crc_16_l_step */