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package SevenZip.Compression.RangeCoder;
public class BitTreeDecoder
{
short[] Models;
int NumBitLevels;
public BitTreeDecoder(int numBitLevels)
{
NumBitLevels = numBitLevels;
Models = new short[1 << numBitLevels];
}
public void Init()
{
Decoder.InitBitModels(Models);
}
public int Decode(Decoder rangeDecoder) throws java.io.IOException
{
int m = 1;
for (int bitIndex = NumBitLevels; bitIndex != 0; bitIndex--)
m = (m << 1) + rangeDecoder.DecodeBit(Models, m);
return m - (1 << NumBitLevels);
}
public int ReverseDecode(Decoder rangeDecoder) throws java.io.IOException
{
int m = 1;
int symbol = 0;
for (int bitIndex = 0; bitIndex < NumBitLevels; bitIndex++)
{
int bit = rangeDecoder.DecodeBit(Models, m);
m <<= 1;
m += bit;
symbol |= (bit << bitIndex);
}
return symbol;
}
public static int ReverseDecode(short[] Models, int startIndex,
Decoder rangeDecoder, int NumBitLevels) throws java.io.IOException
{
int m = 1;
int symbol = 0;
for (int bitIndex = 0; bitIndex < NumBitLevels; bitIndex++)
{
int bit = rangeDecoder.DecodeBit(Models, startIndex + m);
m <<= 1;
m += bit;
symbol |= (bit << bitIndex);
}
return symbol;
}
}
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