lyfz_repos/铂金版源码/7ZIP_SevenZipSharp/SevenZip/sdk/Compress/RangeCoder/RangeCoder.cs

/*  This file is part of SevenZipSharp.

    SevenZipSharp is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    SevenZipSharp is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with SevenZipSharp.  If not, see <http://www.gnu.org/licenses/>.
*/

using System;
using System.IO;

namespace SevenZip.Sdk.Compression.RangeCoder
{
    internal class Encoder
    {
        public const uint kTopValue = (1 << 24);
        private byte _cache;
        private uint _cacheSize;

        public UInt64 Low;
        public uint Range;

        private long StartPosition;
        private Stream Stream;

        public void SetStream(Stream stream)
        {
            Stream = stream;
        }

        public void ReleaseStream()
        {
            Stream = null;
        }

        public void Init()
        {
            StartPosition = Stream.Position;

            Low = 0;
            Range = 0xFFFFFFFF;
            _cacheSize = 1;
            _cache = 0;
        }

        public void FlushData()
        {
            for (int i = 0; i < 5; i++)
                ShiftLow();
        }

        public void FlushStream()
        {
            Stream.Flush();
        }

        /*public void CloseStream()
		{
			Stream.Close();
		}*/

        /*public void Encode(uint start, uint size, uint total)
		{
			Low += start * (Range /= total);
			Range *= size;
			while (Range < kTopValue)
			{
				Range <<= 8;
				ShiftLow();
			}
		}*/

        public void ShiftLow()
        {
            if ((uint) Low < 0xFF000000 || (uint) (Low >> 32) == 1)
            {
                byte temp = _cache;
                do
                {
                    Stream.WriteByte((byte) (temp + (Low >> 32)));
                    temp = 0xFF;
                } while (--_cacheSize != 0);
                _cache = (byte) (((uint) Low) >> 24);
            }
            _cacheSize++;
            Low = ((uint) Low) << 8;
        }

        public void EncodeDirectBits(uint v, int numTotalBits)
        {
            for (int i = numTotalBits - 1; i >= 0; i--)
            {
                Range >>= 1;
                if (((v >> i) & 1) == 1)
                    Low += Range;
                if (Range < kTopValue)
                {
                    Range <<= 8;
                    ShiftLow();
                }
            }
        }

        /*public void EncodeBit(uint size0, int numTotalBits, uint symbol)
		{
			uint newBound = (Range >> numTotalBits) * size0;
			if (symbol == 0)
				Range = newBound;
			else
			{
				Low += newBound;
				Range -= newBound;
			}
			while (Range < kTopValue)
			{
				Range <<= 8;
				ShiftLow();
			}
		}*/

        public long GetProcessedSizeAdd()
        {
            return _cacheSize +
                   Stream.Position - StartPosition + 4;
            // (long)Stream.GetProcessedSize();
        }
    }

    internal class Decoder
    {
        public const uint kTopValue = (1 << 24);
        public uint Code;
        public uint Range;
        // public Buffer.InBuffer Stream = new Buffer.InBuffer(1 << 16);
        public Stream Stream;

        public void Init(Stream stream)
        {
            // Stream.Init(stream);
            Stream = stream;

            Code = 0;
            Range = 0xFFFFFFFF;
            for (int i = 0; i < 5; i++)
                Code = (Code << 8) | (byte) Stream.ReadByte();
        }

        public void ReleaseStream()
        {
            // Stream.ReleaseStream();
            Stream = null;
        }

        /*public void CloseStream()
		{
			Stream.Close();
		}*/

        /*public void Normalize()
		{
			while (Range < kTopValue)
			{
				Code = (Code << 8) | (byte)Stream.ReadByte();
				Range <<= 8;
			}
		}*/

        /*public void Normalize2()
		{
			if (Range < kTopValue)
			{
				Code = (Code << 8) | (byte)Stream.ReadByte();
				Range <<= 8;
			}
		}*/

        /*public uint GetThreshold(uint total)
		{
			return Code / (Range /= total);
		}*/

        /*public void Decode(uint start, uint size, uint total)
		{
			Code -= start * Range;
			Range *= size;
			Normalize();
		}*/

        public uint DecodeDirectBits(int numTotalBits)
        {
            uint range = Range;
            uint code = Code;
            uint result = 0;
            for (int i = numTotalBits; i > 0; i--)
            {
                range >>= 1;
                /*
				result <<= 1;
				if (code >= range)
				{
					code -= range;
					result |= 1;
				}
				*/
                uint t = (code - range) >> 31;
                code -= range & (t - 1);
                result = (result << 1) | (1 - t);

                if (range < kTopValue)
                {
                    code = (code << 8) | (byte) Stream.ReadByte();
                    range <<= 8;
                }
            }
            Range = range;
            Code = code;
            return result;
        }

        /*public uint DecodeBit(uint size0, int numTotalBits)
		{
			uint newBound = (Range >> numTotalBits) * size0;
			uint symbol;
			if (Code < newBound)
			{
				symbol = 0;
				Range = newBound;
			}
			else
			{
				symbol = 1;
				Code -= newBound;
				Range -= newBound;
			}
			Normalize();
			return symbol;
		}*/

        // ulong GetProcessedSize() {return Stream.GetProcessedSize(); }
    }
}