/* crc32.c -- compute the CRC-32 of a data stream
 * Copyright (C) 1995-2006, 2010, 2011, 2012 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 *
 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
 * tables for updating the shift register in one step with three exclusive-ors
 * instead of four steps with four exclusive-ors.  This results in about a
 * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
 */

/* @(#) $Id$ */

#include "zutil.h"      /* for STDC and FAR definitions */

#define local static

#define TBLS 1

/* ========================================================================
 * Tables of CRC-32s of all single-byte values, made by make_crc_table().
 */
#include "crc32.h"

/* =========================================================================
 * This function can be used by asm versions of crc32()
 */
const z_crc_t FAR * ZEXPORT get_crc_table()
{
    return (const z_crc_t FAR *)crc_table;
}

/* ========================================================================= */
#define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
#define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1

/* ========================================================================= */
unsigned long ZEXPORT crc32(crc, buf, len)
    unsigned long crc;
    const unsigned char FAR *buf;
    uInt len;
{
    if (buf == Z_NULL) return 0UL;

    crc = crc ^ 0xffffffffUL;
    while (len >= 8) {
        DO8;
        len -= 8;
    }
    if (len) do {
        DO1;
    } while (--len);
    return crc ^ 0xffffffffUL;
}