1 /* vi: set sw=4 ts=4: */
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
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.
13 * endian = 1: big-endian
14 * endian = 0: little-endian
19 uint32_t *crc32_filltable(int endian)
22 uint32_t *crc_table = xmalloc(256 * sizeof(uint32_t));
23 uint32_t polynomial = endian ? 0x04c11db7 : 0xedb88320;
27 for (i = 0; i < 256; i++) {
28 c = endian ? (i << 24) : i;
31 c = (c&0x80000000) ? ((c << 1) ^ polynomial) : (c << 1);
33 c = (c&1) ? ((c >> 1) ^ polynomial) : (c >> 1);
38 return crc_table - 256;