BitTreeDecoder.java (1271B)
1 package SevenZip.Compression.RangeCoder; 2 3 public class BitTreeDecoder 4 { 5 short[] Models; 6 int NumBitLevels; 7 8 public BitTreeDecoder(int numBitLevels) 9 { 10 NumBitLevels = numBitLevels; 11 Models = new short[1 << numBitLevels]; 12 } 13 14 public void Init() 15 { 16 Decoder.InitBitModels(Models); 17 } 18 19 public int Decode(Decoder rangeDecoder) throws java.io.IOException 20 { 21 int m = 1; 22 for (int bitIndex = NumBitLevels; bitIndex != 0; bitIndex--) 23 m = (m << 1) + rangeDecoder.DecodeBit(Models, m); 24 return m - (1 << NumBitLevels); 25 } 26 27 public int ReverseDecode(Decoder rangeDecoder) throws java.io.IOException 28 { 29 int m = 1; 30 int symbol = 0; 31 for (int bitIndex = 0; bitIndex < NumBitLevels; bitIndex++) 32 { 33 int bit = rangeDecoder.DecodeBit(Models, m); 34 m <<= 1; 35 m += bit; 36 symbol |= (bit << bitIndex); 37 } 38 return symbol; 39 } 40 41 public static int ReverseDecode(short[] Models, int startIndex, 42 Decoder rangeDecoder, int NumBitLevels) throws java.io.IOException 43 { 44 int m = 1; 45 int symbol = 0; 46 for (int bitIndex = 0; bitIndex < NumBitLevels; bitIndex++) 47 { 48 int bit = rangeDecoder.DecodeBit(Models, startIndex + m); 49 m <<= 1; 50 m += bit; 51 symbol |= (bit << bitIndex); 52 } 53 return symbol; 54 } 55 }