crc16.c File Reference

#include "crc16.h"

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Macros
#define	CRC_INIT   0xFFFF
#define	CRC(crcval, newchar)

Functions
unsigned short	crcsum (const unsigned char *message, unsigned long length, unsigned short crc)
int	crcverify (const unsigned char *message, unsigned long length)
void	crcappend (unsigned char *message, unsigned long length)

Variables
static const unsigned short	crc_table [256]

Macro Definition Documentation

CRC

#define CRC	(		crcval,
			newchar
	)

Value:

  crcval = (crcval >> 8) ^ \
  crc_table[(crcval ^ newchar) & 0x00ff]

CRC_INIT

#define CRC_INIT   0xFFFF

Function Documentation

crcappend()

void crcappend	(	unsigned char *	message,
		unsigned long	length
	)

{
  unsigned long crc;
 
  crc = crcsum(message, length, CRC_INIT);
  message[length] = (unsigned char)(crc & 0xff);
  message[length+1] = (unsigned char)((crc >> 8) & 0xff);
}

References CRC_INIT, and crcsum().

Referenced by jtagmkII_send().

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crcsum()

unsigned short crcsum	(	const unsigned char *	message,
		unsigned long	length,
		unsigned short	crc
	)

{
  unsigned long i;
 
  for(i = 0; i < length; i++)
    {
      CRC(crc, message[i]);
    }
  return crc;
}

References CRC.

Referenced by crcappend(), and crcverify().

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crcverify()

int crcverify	(	const unsigned char *	message,
		unsigned long	length
	)

{
  /*
   * Returns true if the last two bytes in a message is the crc of the
   * preceding bytes.
   */
  unsigned short expected;
 
  expected = crcsum(message, length - 2, CRC_INIT);
  return (expected & 0xff) == message[length - 2] &&
    ((expected >> 8) & 0xff) == message[length - 1];
}

References CRC_INIT, and crcsum().

Referenced by jtagmkII_recv_frame().

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Variable Documentation

crc_table

const unsigned short crc_table[256]

static