package SevenZip.Compression.RangeCoder; import java.io.IOException; public class Decoder { static final int kTopMask = ~((1 << 24) - 1); static final int kNumBitModelTotalBits = 11; static final int kBitModelTotal = (1 << kNumBitModelTotalBits); static final int kNumMoveBits = 5; int Range; int Code; java.io.InputStream Stream; public final void SetStream(java.io.InputStream stream) { Stream = stream; } public final void ReleaseStream() { Stream = null; } public final void Init() throws IOException { Code = 0; Range = -1; for (int i = 0; i < 5; i++) Code = (Code << 8) | Stream.read(); } public final int DecodeDirectBits(int numTotalBits) throws IOException { int result = 0; for (int i = numTotalBits; i != 0; i--) { Range >>>= 1; int t = ((Code - Range) >>> 31); Code -= Range & (t - 1); result = (result << 1) | (1 - t); if ((Range & kTopMask) == 0) { Code = (Code << 8) | Stream.read(); Range <<= 8; } } return result; } public int DecodeBit(short []probs, int index) throws IOException { int prob = probs[index]; int newBound = (Range >>> kNumBitModelTotalBits) * prob; if ((Code ^ 0x80000000) < (newBound ^ 0x80000000)) { Range = newBound; probs[index] = (short)(prob + ((kBitModelTotal - prob) >>> kNumMoveBits)); if ((Range & kTopMask) == 0) { Code = (Code << 8) | Stream.read(); Range <<= 8; } return 0; } else { Range -= newBound; Code -= newBound; probs[index] = (short)(prob - ((prob) >>> kNumMoveBits)); if ((Range & kTopMask) == 0) { Code = (Code << 8) | Stream.read(); Range <<= 8; } return 1; } } public static void InitBitModels(short []probs) { for (int i = 0; i < probs.length; i++) probs[i] = (kBitModelTotal >>> 1); } }