source: MondoRescue/branches/stable/mindi-busybox/libbb/crc32.c @ 821

Last change on this file since 821 was 821, checked in by Bruno Cornec, 14 years ago

Addition of busybox 1.2.1 as a mindi-busybox new package
This should avoid delivering binary files in mindi not built there (Fedora and Debian are quite serious about that)

File size: 1.0 KB
Line 
1/* vi: set sw=4 ts=4: */
2/*
3 * CRC32 table fill function
4 * Copyright (C) 2006 by Rob Sullivan <cogito.ergo.cogito@gmail.com>
5 * (I can't really claim much credit however, as the algorithm is
6 * very well-known)
7 *
8 * The following function creates a CRC32 table depending on whether
9 * a big-endian (0x04c11db7) or little-endian (0xedb88320) CRC32 is
10 * required. Admittedly, there are other CRC32 polynomials floating
11 * around, but Busybox doesn't use them.
12 *
13 * endian = 1: big-endian
14 * endian = 0: little-endian
15 */
16
17#include <stdio.h>
18#include <stdlib.h>
19#include "libbb.h"
20
21uint32_t *bb_crc32_filltable (int endian) {
22   
23    uint32_t *crc_table = xmalloc(256 * sizeof(uint32_t));
24    uint32_t polynomial = endian ? 0x04c11db7 : 0xedb88320;
25    uint32_t c;
26    int i, j;
27   
28    for (i = 0; i < 256; i++) {
29        c = endian ? (i << 24) : i;
30        for (j = 8; j; j--) {
31            if (endian)
32                c = (c&0x80000000) ? ((c << 1) ^ polynomial) : (c << 1);
33            else
34                c = (c&1) ? ((c >> 1) ^ polynomial) : (c >> 1);
35        }
36        *crc_table++ = c;
37    }
38
39    return crc_table - 256;
40}
Note: See TracBrowser for help on using the repository browser.