SBSPSS/Utils/Libs/GLib/BITS.CPP

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2000-12-04 15:13:40 +01:00
//===========================================================================
//
// BITS.CPP
//
// Author: Graeme Webb
// Created: 3rd August 1996
// Project: General C++ Library
// Purpose: Bit stream object
//
// Copyright (c) 1996 Graeme Webb
//
//===========================================================================
// Revision history:
//===========================================================================
#include "gtypes.h"
#include "bits.hpp"
//===========================================================================
BitStream::BitStream(byte *ptr)
{
baseptr = (byte *) ptr;
currptr = (byte *) ptr;
bitpos = 0;
mask = 0x01;
}
BitStream::~BitStream()
{
}
void BitStream::IncCurPtr(void)
{
currptr++;
}
void BitStream::PutBit(uint bit)
{
if (mask == 0x01)
{
*currptr = (bit ? mask : 0);
bitpos++;
mask <<= 1;
}
else
{
*currptr |= (bit ? mask : 0);
bitpos++;
if (mask == 0x80)
{
IncCurPtr();
mask = 0x01;
}
else
{
mask <<= 1;
}
}
}
void BitStream::PutBits(ulong bits, uint len)
{
uint i;
for (i = 0; i < len; i++)
{
PutBit(bits & 1);
bits >>= 1;
}
}
uint BitStream::GetBit()
{
uint bit;
bit = (*currptr & mask) ? 1 : 0;
bitpos++;
if (mask == 0x80)
{
IncCurPtr();
mask = 0x01;
}
else
{
mask <<= 1;
}
return bit;
}
ulong BitStream::GetBits(uint len)
{
uint i;
ulong bits, mbit;
bits = 0;
mbit = 1;
for (i = 0; i < len; i++)
{
if (GetBit())
bits |= mbit;
mbit <<= 1;
}
return bits;
}
static inline ulong RoundUp(ulong value, uint align)
{
value += align - 1;
return (value - value % align);
}
void BitStream::Align(uint bytes)
{
ulong bytepos, nextpos;
bytepos = ByteLength();
nextpos = RoundUp(bytepos,bytes);
currptr = baseptr + bytepos;
while (bytepos < nextpos)
{
*currptr=0;
IncCurPtr();
bytepos++;
}
bitpos = bytepos * 8;
mask = 0x01;
}
//===========================================================================