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); | |
} | |
} |