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authorDave Burke <daveburke@google.com>2012-04-17 09:51:45 -0700
committerDave Burke <daveburke@google.com>2012-04-17 23:04:43 -0700
commit9bf37cc9712506b2483650c82d3c41152337ef7e (patch)
tree77db44e2bae06e3d144b255628be2b7a55c581d3 /libSBRdec/src/sbr_crc.cpp
parenta37315fe10ee143d6d0b28c19d41a476a23e63ea (diff)
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Fraunhofer AAC codec.
License boilerplate update to follow. Change-Id: I2810460c11a58b6d148d84673cc031f3685e79b5
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diff --git a/libSBRdec/src/sbr_crc.cpp b/libSBRdec/src/sbr_crc.cpp
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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);
+}