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https://github.com/smallmain/cocos-enhance-kit.git
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162 lines
5.1 KiB
C++
162 lines
5.1 KiB
C++
/* ------------------------------------------------------------------
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* Copyright (C) 1998-2009 PacketVideo
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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* express or implied.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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* -------------------------------------------------------------------
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*/
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/*
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------------------------------------------------------------------------------
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PacketVideo Corp.
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MP3 Decoder Library
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Filename: pvmp3_crc.cpp
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Functions:
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getbits_crc
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calculate_crc
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Date: 09/21/2007
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------------------------------------------------------------------------------
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REVISION HISTORY
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Description:
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------------------------------------------------------------------------------
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INPUT AND OUTPUT DEFINITIONS
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getbits_crc
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Input
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tbits *inputStream, bit stream structure
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int32 neededBits, number of bits to read from the bit stream
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uint32 *crc, memory location holding calculated crc value
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uint32 crc_enabled flag to enable/disable crc checking
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------------------------------------------------------------------------------
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INPUT AND OUTPUT DEFINITIONS
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calculate_crc
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Input
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uint32 data, data vector
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uint32 length, number of element upon the crc will be calculated
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uint32 *crc, memory location holding calculated crc value
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------------------------------------------------------------------------------
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FUNCTION DESCRIPTION
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------------------------------------------------------------------------------
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REQUIREMENTS
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------------------------------------------------------------------------------
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REFERENCES
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[1] ISO MPEG Audio Subgroup Software Simulation Group (1996)
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ISO 13818-3 MPEG-2 Audio Decoder - Lower Sampling Frequency Extension
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------------------------------------------------------------------------------
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PSEUDO-CODE
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------------------------------------------------------------------------------
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*/
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/*----------------------------------------------------------------------------
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; INCLUDES
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----------------------------------------------------------------------------*/
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#include "pvmp3_getbits.h"
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#include "pvmp3_crc.h"
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/*----------------------------------------------------------------------------
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; MACROS
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; Define module specific macros here
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; DEFINES
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; Include all pre-processor statements here. Include conditional
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; compile variables also.
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; LOCAL FUNCTION DEFINITIONS
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; Function Prototype declaration
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; LOCAL STORE/BUFFER/POINTER DEFINITIONS
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; Variable declaration - defined here and used outside this module
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; EXTERNAL FUNCTION REFERENCES
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; Declare functions defined elsewhere and referenced in this module
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
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; Declare variables used in this module but defined elsewhere
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; FUNCTION CODE
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----------------------------------------------------------------------------*/
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uint32 getbits_crc(tmp3Bits *inputStream, /* bit stream structure */
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int32 neededBits, /* number of bits to read from the bit stream */
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uint32 *crc,
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uint32 crc_enabled)
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{
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uint32 bits = getNbits(inputStream, neededBits);
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if (crc_enabled)
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{
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calculate_crc(bits, neededBits, crc);
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}
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return(bits);
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}
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/*----------------------------------------------------------------------------
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; FUNCTION CODE
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----------------------------------------------------------------------------*/
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void calculate_crc(uint32 data,
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uint32 length,
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uint32 *crc)
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{
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uint32 carry;
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uint32 masking = 1 << length;
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while ((masking >>= 1))
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{
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carry = *crc & 0x8000;
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*crc <<= 1;
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if (!carry ^ !(data & masking))
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{
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*crc ^= CRC16_POLYNOMIAL;
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}
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}
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*crc &= 0xffff;
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}
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