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/* $Id$ */
/** @file
* IPRT - Adler-32
*/
/*
* Copyright (C) 2010 Oracle Corporation
*
* This file is part of VirtualBox Open Source Edition (OSE), as
* available from http://www.virtualbox.org. This file is free software;
* you can redistribute it and/or modify it under the terms of the GNU
* General Public License (GPL) as published by the Free Software
* Foundation, in version 2 as it comes in the "COPYING" file of the
* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL) only, as it comes in the "COPYING.CDDL" file of the
* VirtualBox OSE distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*/
/*******************************************************************************
* Header Files *
*******************************************************************************/
#include <iprt/crc.h>
#include "internal/iprt.h"
#include <iprt/asm.h>
#include <iprt/assert.h>
/*******************************************************************************
* Defined Constants And Macros *
*******************************************************************************/
#define RTCRC_ADLER_32_NUMBER 65521
RTDECL(uint32_t) RTCrcAdler32(void const *pv, size_t cb)
{
/* Don't want to do the unrolling twice. */
return RTCrcAdler32Process(RTCrcAdler32Start(), pv, cb);
}
RTDECL(uint32_t) RTCrcAdler32Start(void)
{
return 1;
}
RTDECL(uint32_t) RTCrcAdler32Process(uint32_t u32Crc, void const *pv, size_t cb)
{
uint8_t const *pbSrc = (uint8_t const *)pv;
uint32_t a = u32Crc & 0xffff;
uint32_t b = u32Crc >> 16;
if (cb < 64 /* randomly selected number */)
{
while (cb-- > 0)
{
a += *pbSrc++;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
}
}
else
{
switch (((uintptr_t)pbSrc & 0x3))
{
case 0:
break;
case 1:
a += *pbSrc++;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
cb--;
/* fall thru */
case 2:
a += *pbSrc++;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
cb--;
/* fall thru */
case 3:
a += *pbSrc++;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
cb--;
break;
}
while (cb >= 4)
{
uint32_t u32 = *(uint32_t const *)pbSrc;
pbSrc += 4;
a += u32 & 0xff;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
a += (u32 >> 8) & 0xff;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
a += (u32 >> 16) & 0xff;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
a += (u32 >> 24) & 0xff;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
cb -= 4;
}
switch (cb)
{
case 0:
break;
case 3:
a += *pbSrc++;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
cb--;
/* fall thru */
case 2:
a += *pbSrc++;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
cb--;
/* fall thru */
case 1:
a += *pbSrc++;
a %= RTCRC_ADLER_32_NUMBER;
b += a;
b %= RTCRC_ADLER_32_NUMBER;
cb--;
break;
}
}
return a | (b << 16);
}
RTDECL(uint32_t) RTCrcAdler32Finish(uint32_t u32Crc)
{
return u32Crc;
}
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