//Java Source code for Range Coder
//By Sachin Garg, 2006
//
//This range coder is based upon the carry-less range coder 
//implementation by Dmitry Subbotin, and uses 64-bit variables 
//for improved performance.
//
//http://www.sachingarg.com/compression/entropy_coding/java_range_coder

import java.io.IOException;
import java.io.InputStream;

public final class DecompressedInputStream extends InputStream {

	public DecompressedInputStream(InputStream in) throws IOException {
		Decoder=new RangeDecoder64(in);
		Model=new Order0Model();
		read();	//Decode the first byte
	}

	public int available() {
		return (_nextByte >= 0) ? 1 : 0;
	}
    
    public void mark(int readLimit)  {
    	//not supported
    }

    public boolean markSupported() {
    	return false;
    }
    
    public void close() throws IOException {
	}

    public int read(byte[] bs) throws IOException {
    	return read(bs,0,bs.length);
    }
    
    public int read(byte[] bs, int off, int len) throws IOException {
    	for (int i = off; i < len; ++i) {
    	    int nextByte = read();
    	    if (nextByte == -1) return (i - off); // eof, return length read
    	    bs[i] = (byte)(nextByte & 0xFF);
    	}
    	return len > 0 ? len : 0;
	}

    public int read() throws IOException {
    	int result = _nextByte;
    	if (_nextByte == -1) return -1;

    	int Count = Decoder.GetCurrentCount(Model.Frequency[Model.NoOfSymbols]);
    	
    	int Symbol;
    	for(Symbol=Model.NoOfSymbols-1;Model.Frequency[Symbol]>Count;Symbol--);
    	_nextByte=Symbol==(Model.NoOfSymbols-1)?-1:Symbol;
		
    	Decoder.RemoveRange(Model.Frequency[Symbol],Model.Frequency[Symbol+1],Model.Frequency[Model.NoOfSymbols]);

    	Model.Update(Symbol);
    	
    	return result;
	}

    public long skip(long n) throws IOException {
    	for (long i = 0; i < n; ++i) 
    	    if (read() == -1) return i;
    	return n;
	}

    private Order0Model Model;
	private RangeDecoder64 Decoder;
    private int _nextByte;
}