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/****************************************************************************
(C) Copyright Fraunhofer IIS (2004)
All Rights Reserved
Please be advised that this software and/or program delivery is
Confidential Information of Fraunhofer and subject to and covered by the
Fraunhofer IIS Software Evaluation Agreement
between Google Inc. and Fraunhofer
effective and in full force since March 1, 2012.
You may use this software and/or program only under the terms and
conditions described in the above mentioned Fraunhofer IIS Software
Evaluation Agreement. Any other and/or further use requires a separate agreement.
This software and/or program is protected by copyright law and international
treaties. Any reproduction or distribution of this software and/or program,
or any portion of it, may result in severe civil and criminal penalties, and
will be prosecuted to the maximum extent possible under law.
$Id$
*******************************************************************************/
/*!
\file
\brief CRC check coutines $Revision: 36841 $
*/
#include "sbr_crc.h"
#include "FDK_bitstream.h"
#include "transcendent.h"
#define MAXCRCSTEP 16
#define MAXCRCSTEP_LD 4
/*!
\brief crc calculation
*/
static ULONG
calcCRC (HANDLE_CRC hCrcBuf, ULONG bValue, int nBits)
{
int i;
ULONG bMask = (1UL << (nBits - 1));
for (i = 0; i < nBits; i++, bMask >>= 1) {
USHORT flag = (hCrcBuf->crcState & hCrcBuf->crcMask) ? 1 : 0;
USHORT flag1 = (bMask & bValue) ? 1 : 0;
flag ^= flag1;
hCrcBuf->crcState <<= 1;
if (flag)
hCrcBuf->crcState ^= hCrcBuf->crcPoly;
}
return (hCrcBuf->crcState);
}
/*!
\brief crc
*/
static int
getCrc (HANDLE_FDK_BITSTREAM hBs, ULONG NrBits)
{
int i;
CRC_BUFFER CrcBuf;
CrcBuf.crcState = SBR_CRC_START;
CrcBuf.crcPoly = SBR_CRC_POLY;
CrcBuf.crcMask = SBR_CRC_MASK;
int CrcStep = NrBits>>MAXCRCSTEP_LD;
int CrcNrBitsRest = (NrBits - CrcStep * MAXCRCSTEP);
ULONG bValue;
for (i = 0; i < CrcStep; i++) {
bValue = FDKreadBits (hBs, MAXCRCSTEP);
calcCRC (&CrcBuf, bValue, MAXCRCSTEP);
}
bValue = FDKreadBits (hBs, CrcNrBitsRest);
calcCRC (&CrcBuf, bValue, CrcNrBitsRest);
return (CrcBuf.crcState & SBR_CRC_RANGE);
}
/*!
\brief crc interface
\return 1: CRC OK, 0: CRC check failure
*/
int
SbrCrcCheck (HANDLE_FDK_BITSTREAM hBs, /*!< handle to bit-buffer */
LONG NrBits) /*!< max. CRC length */
{
int crcResult = 1;
ULONG NrCrcBits;
ULONG crcCheckResult;
LONG NrBitsAvailable;
ULONG crcCheckSum;
crcCheckSum = FDKreadBits (hBs, 10);
NrBitsAvailable = FDKgetValidBits(hBs);
if (NrBitsAvailable <= 0){
return 0;
}
NrCrcBits = fixMin ((INT)NrBits, (INT)NrBitsAvailable);
crcCheckResult = getCrc (hBs, NrCrcBits);
FDKpushBack(hBs, (NrBitsAvailable - FDKgetValidBits(hBs)) );
if (crcCheckResult != crcCheckSum) {
crcResult = 0;
}
return (crcResult);
}
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