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- using System;
- using System.IO;
- using System.Text;
- using SharpCompress.Compressors.Rar;
- namespace SharpCompress.Compressors.PPMd.H
- {
- internal class RangeCoder
- {
- internal const int TOP = 1 << 24;
- internal const int BOT = 1 << 15;
- internal const long UINT_MASK = 0xFFFFffffL;
- // uint low, code, range;
- private long _low, _code, _range;
- private readonly IRarUnpack _unpackRead;
- private readonly Stream _stream;
- internal RangeCoder(IRarUnpack unpackRead)
- {
- _unpackRead = unpackRead;
- Init();
- }
- internal RangeCoder(Stream stream)
- {
- _stream = stream;
- Init();
- }
- private void Init()
- {
- SubRange = new SubRange();
- _low = _code = 0L;
- _range = 0xFFFFffffL;
- for (int i = 0; i < 4; i++)
- {
- _code = ((_code << 8) | Char) & UINT_MASK;
- }
- }
- internal int CurrentCount
- {
- get
- {
- _range = (_range / SubRange.Scale) & UINT_MASK;
- return (int)((_code - _low) / (_range));
- }
- }
- private long Char
- {
- get
- {
- if (_unpackRead != null)
- {
- return (_unpackRead.Char);
- }
- if (_stream != null)
- {
- return _stream.ReadByte();
- }
- return -1;
- }
- }
- internal SubRange SubRange { get; private set; }
- internal long GetCurrentShiftCount(int shift)
- {
- _range = Utility.URShift(_range, shift);
- return ((_code - _low) / (_range)) & UINT_MASK;
- }
- internal void Decode()
- {
- _low = (_low + (_range * SubRange.LowCount)) & UINT_MASK;
- _range = (_range * (SubRange.HighCount - SubRange.LowCount)) & UINT_MASK;
- }
- internal void AriDecNormalize()
- {
- // while ((low ^ (low + range)) < TOP || range < BOT && ((range = -low & (BOT - 1)) != 0 ? true : true))
- // {
- // code = ((code << 8) | unpackRead.getChar()&0xff)&uintMask;
- // range = (range << 8)&uintMask;
- // low = (low << 8)&uintMask;
- // }
- // Rewrote for clarity
- bool c2 = false;
- while ((_low ^ (_low + _range)) < TOP || (c2 = _range < BOT))
- {
- if (c2)
- {
- _range = (-_low & (BOT - 1)) & UINT_MASK;
- c2 = false;
- }
- _code = ((_code << 8) | Char) & UINT_MASK;
- _range = (_range << 8) & UINT_MASK;
- _low = (_low << 8) & UINT_MASK;
- }
- }
- // Debug
- public override String ToString()
- {
- StringBuilder buffer = new StringBuilder();
- buffer.Append("RangeCoder[");
- buffer.Append("\n low=");
- buffer.Append(_low);
- buffer.Append("\n code=");
- buffer.Append(_code);
- buffer.Append("\n range=");
- buffer.Append(_range);
- buffer.Append("\n subrange=");
- buffer.Append(SubRange);
- buffer.Append("]");
- return buffer.ToString();
- }
- }
- internal class SubRange
- {
- // uint LowCount, HighCount, scale;
- private long _lowCount, _highCount, _scale;
- internal void IncScale(int dScale)
- {
- Scale = Scale + dScale;
- }
- internal long HighCount { get => _highCount; set => _highCount = value & RangeCoder.UINT_MASK; }
- internal long LowCount { get => _lowCount & RangeCoder.UINT_MASK; set => _lowCount = value & RangeCoder.UINT_MASK; }
- internal long Scale { get => _scale; set => _scale = value & RangeCoder.UINT_MASK; }
- // Debug
- public override String ToString()
- {
- StringBuilder buffer = new StringBuilder();
- buffer.Append("SubRange[");
- buffer.Append("\n lowCount=");
- buffer.Append(_lowCount);
- buffer.Append("\n highCount=");
- buffer.Append(_highCount);
- buffer.Append("\n scale=");
- buffer.Append(_scale);
- buffer.Append("]");
- return buffer.ToString();
- }
- }
- }
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