src/lib/packet.c File Reference

Packet manipulation routines. More...

#include <linux/types.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <otto/otto.h>
#include <otto/packet.h>
#include <otto/device.h>
#include <otto/control.h>

Functions
const char _ID_[]	__attribute__ ((unused))="$Id: packet.c,v 1.2 2004/07/07 22:07:12 alpha Exp $"
unsigned char	crc8 (unsigned char reg, unsigned char data)
	Calculate an 8 bit CRC.
unsigned char	compute_crc (unsigned char *bytes, int length)
	Calculate CRC for data buffer.
int	otto_crc_calc (union otto_packet *pkt)
	Calculate CRC for a packet.
int	otto_crc_valid (union otto_packet *pkt)
	Validate CRC for a packet.
int	otto_findpacket (union otto_packet *pkt, int *start, int *len)
	Find a valid packet within a packet buffer.
Variables
const unsigned char	CRC_INIT = 0xff
const unsigned char	CRC_POLY = 0x1c
const unsigned char	CRC_VALID = 0xc4

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Detailed Description

Packet manipulation routines.

See SAE J1850, 7.4.1 (HS-3000, pp. 212-213) for checksum description.

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Function Documentation

const char _ID_ [] __attribute__ (  (unused)   )  [static]

unsigned char compute_crc (  unsigned char *  bytes, int  length )  [static]

Calculate CRC for data buffer. Parameters: length  Buffer to compute CRC for Length of buffer

unsigned char crc8 (  unsigned char  reg, unsigned char  data )  [inline, static]

Calculate an 8 bit CRC. Returns: Result of CRC on indicated byte. Parameters: data  Partial product register Byte to accumulate CRC for

int otto_crc_calc (  union otto_packet *  pkt  )

Calculate CRC for a packet. Returns: Calculated checksum Parameters: pkt  Packet to compute CRC for

int otto_crc_valid (  union otto_packet *  pkt  )

Validate CRC for a packet. Returns: One if CRC is valid, zero if invalid, negative on error Parameters: pkt  Packet to validate CRC

int otto_findpacket (  union otto_packet *  pkt, int *  start, int *  len )

Find a valid packet within a packet buffer. Todo: rework without so many memcpys Parameters: pkt  Partial packet buffer to search start  [out] Start of first packet found len  [out] Length of first packet found

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Variable Documentation

const unsigned char CRC_INIT = 0xff [static]

const unsigned char CRC_POLY = 0x1c [static]

const unsigned char CRC_VALID = 0xc4 [static]

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