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 {
        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 {
        int prob = probs[index];
        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 {
        int kNumBits = (kNumBitModelTotalBits-kNumMoveReducingBits);
        for (int i = kNumBits-1; i>=0; i--) {
            int start = 1<<(kNumBits-i-1);
            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];
    }

}