Encoder.java

package SevenZip.Compression.RangeCoder;

import java.io.IOException;

public class Encoder
{
    static final int     kTopMask              = ~((1 << 24) - 1);
    
    static final int     kNumBitModelTotalBits = 11;
    static final int     kBitModelTotal        = 1 << kNumBitModelTotalBits;
    static final int     kNumMoveBits          = 5;
    
    java.io.OutputStream Stream;
    
    long                 Low;
    int                  Range;
    int                  _cacheSize;
    int                  _cache;
    
    long                 _position;
    
    public void SetStream(java.io.OutputStream stream)
    {
        Stream = stream;
    }
    
    public void ReleaseStream()
    {
        Stream = null;
    }
    
    public void Init()
    {
        _position = 0;
        Low = 0;
        Range = -1;
        _cacheSize = 1;
        _cache = 0;
    }
    
    public void FlushData() throws IOException
    {
        for (int i = 0; i < 5; i++)
        {
            ShiftLow();
        }
    }
    
    public void FlushStream() throws IOException
    {
        Stream.flush();
    }
    
    public void ShiftLow() throws IOException
    {
        final int LowHi = (int) (Low >>> 32);
        if (LowHi != 0 || Low < 0xFF000000L)
        {
            _position += _cacheSize;
            int temp = _cache;
            do
            {
                Stream.write(temp + LowHi);
                temp = 0xFF;
            } while (--_cacheSize != 0);
            _cache = (int) Low >>> 24;
        }
        _cacheSize++;
        Low = (Low & 0xFFFFFF) << 8;
    }
    
    public void EncodeDirectBits(int v, int numTotalBits) throws IOException
    {
        for (int i = numTotalBits - 1; i >= 0; i--)
        {
            Range >>>= 1;
            if ((v >>> i & 1) == 1)
            {
                Low += Range;
            }
            if ((Range & Encoder.kTopMask) == 0)
            {
                Range <<= 8;
                ShiftLow();
            }
        }
    }
    
    public long GetProcessedSizeAdd()
    {
        return _cacheSize + _position + 4;
    }
    
    static final int        kNumMoveReducingBits  = 2;
    public static final int kNumBitPriceShiftBits = 6;
    
    public static void InitBitModels(short[] probs)
    {
        for (int i = 0; i < probs.length; i++)
        {
            probs[i] = kBitModelTotal >>> 1;
        }
    }
    
    public void Encode(short[] probs, int index, int symbol) throws IOException
    {
        final int prob = probs[index];
        final int newBound = (Range >>> kNumBitModelTotalBits) * prob;
        if (symbol == 0)
        {
            Range = newBound;
            probs[index] = (short) (prob + (kBitModelTotal - prob >>> kNumMoveBits));
        }
        else
        {
            Low += newBound & 0xFFFFFFFFL;
            Range -= newBound;
            probs[index] = (short) (prob - (prob >>> kNumMoveBits));
        }
        if ((Range & kTopMask) == 0)
        {
            Range <<= 8;
            ShiftLow();
        }
    }
    
    private static int[] ProbPrices = new int[kBitModelTotal >>> kNumMoveReducingBits];
    
    static
    {
        final int kNumBits = kNumBitModelTotalBits - kNumMoveReducingBits;
        for (int i = kNumBits - 1; i >= 0; i--)
        {
            final int start = 1 << kNumBits - i - 1;
            final int end = 1 << kNumBits - i;
            for (int j = start; j < end; j++)
            {
                ProbPrices[j] = (i << kNumBitPriceShiftBits)
                        + (end - j << kNumBitPriceShiftBits >>> kNumBits - i
                                - 1);
            }
        }
    }
    
    static public int GetPrice(int Prob, int symbol)
    {
        return ProbPrices[((Prob - symbol ^ -symbol) & kBitModelTotal - 1) >>> kNumMoveReducingBits];
    }
    
    static public int GetPrice0(int Prob)
    {
        return ProbPrices[Prob >>> kNumMoveReducingBits];
    }
    
    static public int GetPrice1(int Prob)
    {
        return ProbPrices[kBitModelTotal - Prob >>> kNumMoveReducingBits];
    }
}