checksum.c File Reference

Checksum algorithms. More...

#include <sys/types.h>
#include "rnr/rnrconfig.h"

Go to the source code of this file.

Functions
u8_t	generate_checksum8 (byte_t buf[], size_t len)
	Computes the modular 8-bit checksum over buffer. More...
u16_t	generate_checksum16 (byte_t buf[], size_t len)
	Computes the modular 16-bit checksum over buffer. More...
u32_t	generate_checksum32 (byte_t buf[], size_t len)
	Computes the modular 32-bit checksum over buffer. More...
u32_t	generate_crc32 (byte_t buf[], size_t len)
	Computes the 32-bit cyclic redundance check over buffer. More...

Variables
static u32_t	crc32tbl [256]
	CRC-32 table generated from CRC32_POLY_NORM polygon.

Detailed Description

Checksum algorithms.

Author

Daniel Packard (danie.nosp@m.l@ro.nosp@m.adnar.nosp@m.rows.nosp@m..com)

Robin Knight (robin.nosp@m..kni.nosp@m.ght@r.nosp@m.oadn.nosp@m.arrow.nosp@m.s.co.nosp@m.m)

Copyright

© 2010-2018. RoadNarrows LLC..
http://www.roadnarrows.com
All Rights Reserved

EULA

See the README and EULA files for any copyright and licensing information.

—

Definition in file checksum.c.

Function Documentation

u16_t generate_checksum16	(	byte_t	buf[],
		size_t	len
	)

Computes the modular 16-bit checksum over buffer.

The two's complitment is not taken.

Parameters

buf	Buffer to checksum.
len	Number of bytes in buf.

Returns

16-bit sum of bytes, discarding overflow.

Definition at line 113 of file checksum.c.

Referenced by profile().

{
  u16_t   sum = 0;
  size_t  i;
  
  for(i=0; i<len; ++i)
  {
    sum = (u16_t)(sum + (u16_t)buf[i]);
  }

  return sum;
}

u32_t generate_checksum32	(	byte_t	buf[],
		size_t	len
	)

Computes the modular 32-bit checksum over buffer.

The two's complitment is not taken.

Parameters

buf	Buffer to checksum
len	Number of bytes in buf.

Returns

32-bit sum of bytes, discarding overflow.

Definition at line 126 of file checksum.c.

Referenced by profile().

{
  u32_t   sum = 0;
  size_t  i;
  
  for(i=0; i<len; ++i)
  {
    sum += (u32_t)buf[i];
  }

  return sum;
}

u8_t generate_checksum8	(	byte_t	buf[],
		size_t	len
	)

Computes the modular 8-bit checksum over buffer.

The two's complitment is not taken.

Parameters

buf	Buffer to checksum.
len	Number of bytes in buf.

Returns

8-bit sum of bytes, discarding overflow.

Definition at line 100 of file checksum.c.

Referenced by profile().

{
  u8_t    sum = 0;
  size_t  i;
  
  for(i=0; i<len; ++i)
  {
    sum = (u8_t)(sum + (u8_t)buf[i]);
  }
  
  return sum;
}

u32_t generate_crc32	(	byte_t	buf[],
		size_t	len
	)

Computes the 32-bit cyclic redundance check over buffer.

CRC polynomial: 0x04C11DB7 (normal representation).

This CRC-32 is used by Ethernet, MPEG-2, gzip, gzip2, and others.

This CRC can be specified as:

width	32
poly	0x04c11db7
init	0xffffffff
refin	false
refout	false
xorout	true

Parameters

buf	Buffer to checksum
len	Number of bytes in buf.

Returns

32-bit CRC

Definition at line 139 of file checksum.c.

Referenced by profile().

{
  u32_t   crc = 0xffffffff;
  size_t  i;

  for(i=0; i<len; ++i)
  {
    crc = (crc << 8) ^ crc32tbl[((crc >> 24) ^ buf[i]) & 0xff];
  }

  return crc ^ 0xffffffff;
}