# -*- coding: utf-8 -*-
"""This is a Python implementation of the bsd 16 bit checksum algorithm.
The original code and license is listed at the end of this file, and
was fetched from revision 225736.
Listed in its own file to preserve original copyright statement and
conditions.
"""
[docs]def bsd_checksum(data):
"""Implementation of the bsd 16-bit checksum algorithm.
"""
if not isinstance(data, bytearray):
data = bytearray(data) # pragma: no cover
r = 0
for ch in data:
if r & 1:
r |= 0x10000
r = ((r >> 1) + ch) & 0xffff
return r
"""
/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
#if 0
static char sccsid[] = "@(#)sum1.c 8.1 (Berkeley) 6/6/93";
#endif
#endif /* not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <unistd.h>
#include <stdint.h>
#include "extern.h"
int
csum1(int fd, uint32_t *cval, off_t *clen)
{
int nr;
u_int lcrc;
off_t total;
u_char *p;
u_char buf[8192];
/*
* 16-bit checksum, rotating right before each addition;
* overflow is discarded.
*/
lcrc = total = 0;
while ((nr = read(fd, buf, sizeof(buf))) > 0)
for (total += nr, p = buf; nr--; ++p) {
if (lcrc & 1)
lcrc |= 0x10000;
lcrc = ((lcrc >> 1) + *p) & 0xffff;
}
if (nr < 0)
return (1);
*cval = lcrc;
*clen = total;
return (0);
}
"""