139 lines
1.9 KiB
C++
139 lines
1.9 KiB
C++
//===========================================================================
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//
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// BITS.CPP
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//
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// Author: Graeme Webb
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// Created: 3rd August 1996
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// Project: General C++ Library
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// Purpose: Bit stream object
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//
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// Copyright (c) 1996 Graeme Webb
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//
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//===========================================================================
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// Revision history:
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//===========================================================================
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#include "gtypes.h"
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#include "bits.hpp"
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//===========================================================================
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BitStream::BitStream(byte *ptr)
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{
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baseptr = (byte *) ptr;
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currptr = (byte *) ptr;
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bitpos = 0;
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mask = 0x01;
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}
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BitStream::~BitStream()
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{
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}
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void BitStream::IncCurPtr(void)
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{
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currptr++;
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}
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void BitStream::PutBit(uint bit)
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{
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if (mask == 0x01)
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{
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*currptr = (bit ? mask : 0);
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bitpos++;
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mask <<= 1;
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}
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else
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{
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*currptr |= (bit ? mask : 0);
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bitpos++;
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if (mask == 0x80)
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{
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IncCurPtr();
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mask = 0x01;
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}
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else
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{
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mask <<= 1;
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}
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}
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}
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void BitStream::PutBits(ulong bits, uint len)
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{
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uint i;
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for (i = 0; i < len; i++)
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{
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PutBit(bits & 1);
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bits >>= 1;
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}
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}
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uint BitStream::GetBit()
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{
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uint bit;
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bit = (*currptr & mask) ? 1 : 0;
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bitpos++;
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if (mask == 0x80)
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{
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IncCurPtr();
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mask = 0x01;
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}
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else
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{
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mask <<= 1;
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}
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return bit;
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}
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ulong BitStream::GetBits(uint len)
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{
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uint i;
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ulong bits, mbit;
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bits = 0;
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mbit = 1;
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for (i = 0; i < len; i++)
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{
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if (GetBit())
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bits |= mbit;
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mbit <<= 1;
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}
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return bits;
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}
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static inline ulong RoundUp(ulong value, uint align)
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{
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value += align - 1;
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return (value - value % align);
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}
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void BitStream::Align(uint bytes)
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{
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ulong bytepos, nextpos;
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bytepos = ByteLength();
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nextpos = RoundUp(bytepos,bytes);
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currptr = baseptr + bytepos;
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while (bytepos < nextpos)
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{
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*currptr=0;
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IncCurPtr();
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bytepos++;
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}
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bitpos = bytepos * 8;
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mask = 0x01;
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}
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//===========================================================================
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