crc.c

来自「CRC16, CRC8 source code Algorithm = tab」· C语言 代码 · 共 73 行

/**
 * \file crc.c
 * Functions and types for CRC checks.
 *
 * Generated on Thu Oct 30 15:54:49 2008,
 * by pycrc v0.6.6, http://www.tty1.net/pycrc/
 * using the configuration:
 *    Width        = 8
 *    Poly         = 0x07
 *    XorIn        = 0x00
 *    ReflectIn    = False
 *    XorOut       = 0x00
 *    ReflectOut   = False
 *    Algorithm    = table-driven
 *****************************************************************************/
#include "crc.h"

/**
 * Static table used for the table_driven implementation.
 *****************************************************************************/
uc8 crc8_table[16] =
{
  0x00, 0x07, 0x0e, 0x09, 0x1c, 0x1b, 0x12, 0x15, 0x38, 0x3f, 0x36, 0x31, 0x24, 0x23, 0x2a, 0x2d
};

uc16 crc16_table[16] =
{
  0x0000, 0xcc01, 0xd801, 0x1400, 0xf001, 0x3c00, 0x2800, 0xe401,
  0xa001, 0x6c00, 0x7800, 0xb401, 0x5000, 0x9c01, 0x8801, 0x4400
};

/**
 * Update the crc value with new data.
 *
 * \param crc      The current crc value.
 * \param data     Pointer to a buffer of \a data_len bytes.
 * \param data_len Number of bytes in the \a data buffer.
 * \return         The updated crc value.
 *****************************************************************************/
u8 crc8_update (u8 crc, u8 *data, u8 data_len)
{
  u8 tbl_idx;

  while (data_len)
  {
    tbl_idx = (crc >> 4) ^ (*data >> 4);
    crc = crc8_table[tbl_idx & 0x0f] ^ (crc << 4);
    tbl_idx = (crc >> 4) ^ (*data >> 0);
    crc = crc8_table[tbl_idx & 0x0f] ^ (crc << 4);

    data++;
    data_len--;
  }
  return crc & 0xff;
}


u16 crc16_update (u16 crc, u8 *data, u8 data_len)
{
  u8 tbl_idx;

  while (data_len--)
  {
    tbl_idx = crc ^ (*data >> (0 * 4) );
    crc = crc16_table[tbl_idx & 0x0f] ^ (crc >> 4);
    tbl_idx = crc ^ (*data >> (1 * 4) );
    crc = crc16_table[tbl_idx & 0x0f] ^ (crc >> 4);

    data++;
  }
  return crc & 0xffff;
}