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90 lines
3.1 KiB
C
90 lines
3.1 KiB
C
13 years ago
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/*
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** Copyright 2003-2010, VisualOn, Inc.
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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 express or implied.
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** See the License for the specific language governing permissions and
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** limitations under the License.
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*/
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/*******************************************************************************
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File: bitbuffer.h
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Content: Bit Buffer Management structure and functions
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*******************************************************************************/
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#ifndef BITBUFFER_H
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#define BITBUFFER_H
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#include "typedef.h"
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enum direction
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{
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forwardDirection,
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backwardDirection
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};
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/*!
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The pointer 'pReadNext' points to the next available word, where bits can be read from. The pointer
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'pWriteNext' points to the next available word, where bits can be written to. The pointer pBitBufBase
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points to the start of the bitstream buffer and the pointer pBitBufEnd points to the end of the bitstream
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buffer. The two pointers are used as lower-bound respectively upper-bound address for the modulo addressing
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mode.
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The element cntBits contains the currently available bits in the bit buffer. It will be incremented when
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bits are written to the bitstream buffer and decremented when bits are read from the bitstream buffer.
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*/
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struct BIT_BUF
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{
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UWord8 *pBitBufBase; /*!< pointer points to first position in bitstream buffer */
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UWord8 *pBitBufEnd; /*!< pointer points to last position in bitstream buffer */
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UWord8 *pWriteNext; /*!< pointer points to next available word in bitstream buffer to write */
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UWord32 cache;
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Word16 wBitPos; /*!< 31<=wBitPos<=0*/
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Word16 cntBits; /*!< number of available bits in the bitstream buffer
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write bits to bitstream buffer => increment cntBits
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read bits from bitstream buffer => decrement cntBits */
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Word16 size; /*!< size of bitbuffer in bits */
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Word16 isValid; /*!< indicates whether the instance has been initialized */
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}; /* size Word16: 8 */
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/*! Define pointer to bit buffer structure */
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typedef struct BIT_BUF *HANDLE_BIT_BUF;
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HANDLE_BIT_BUF CreateBitBuffer(HANDLE_BIT_BUF hBitBuf,
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UWord8 *pBitBufBase,
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Word16 bitBufSize);
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void DeleteBitBuffer(HANDLE_BIT_BUF *hBitBuf);
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Word16 GetBitsAvail(HANDLE_BIT_BUF hBitBuf);
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Word16 WriteBits(HANDLE_BIT_BUF hBitBuf,
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UWord32 writeValue,
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Word16 noBitsToWrite);
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void ResetBitBuf(HANDLE_BIT_BUF hBitBuf,
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UWord8 *pBitBufBase,
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Word16 bitBufSize);
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#define GetNrBitsAvailable(hBitBuf) ( (hBitBuf)->cntBits)
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#define GetNrBitsRead(hBitBuf) ((hBitBuf)->size-(hBitBuf)->cntBits)
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#endif /* BITBUFFER_H */
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