summaryrefslogtreecommitdiffstats
path: root/CS/7zip/Compress/RangeCoder/RangeCoderBit.cs
diff options
context:
space:
mode:
Diffstat (limited to 'CS/7zip/Compress/RangeCoder/RangeCoderBit.cs')
-rwxr-xr-xCS/7zip/Compress/RangeCoder/RangeCoderBit.cs117
1 files changed, 117 insertions, 0 deletions
diff --git a/CS/7zip/Compress/RangeCoder/RangeCoderBit.cs b/CS/7zip/Compress/RangeCoder/RangeCoderBit.cs
new file mode 100755
index 0000000..000a5a0
--- /dev/null
+++ b/CS/7zip/Compress/RangeCoder/RangeCoderBit.cs
@@ -0,0 +1,117 @@
+using System;
+
+namespace SevenZip.Compression.RangeCoder
+{
+ struct BitEncoder
+ {
+ public const int kNumBitModelTotalBits = 11;
+ public const uint kBitModelTotal = (1 << kNumBitModelTotalBits);
+ const int kNumMoveBits = 5;
+ const int kNumMoveReducingBits = 2;
+ public const int kNumBitPriceShiftBits = 6;
+
+ uint Prob;
+
+ public void Init() { Prob = kBitModelTotal >> 1; }
+
+ public void UpdateModel(uint symbol)
+ {
+ if (symbol == 0)
+ Prob += (kBitModelTotal - Prob) >> kNumMoveBits;
+ else
+ Prob -= (Prob) >> kNumMoveBits;
+ }
+
+ public void Encode(Encoder encoder, uint symbol)
+ {
+ // encoder.EncodeBit(Prob, kNumBitModelTotalBits, symbol);
+ // UpdateModel(symbol);
+ uint newBound = (encoder.Range >> kNumBitModelTotalBits) * Prob;
+ if (symbol == 0)
+ {
+ encoder.Range = newBound;
+ Prob += (kBitModelTotal - Prob) >> kNumMoveBits;
+ }
+ else
+ {
+ encoder.Low += newBound;
+ encoder.Range -= newBound;
+ Prob -= (Prob) >> kNumMoveBits;
+ }
+ if (encoder.Range < Encoder.kTopValue)
+ {
+ encoder.Range <<= 8;
+ encoder.ShiftLow();
+ }
+ }
+
+ private static UInt32[] ProbPrices = new UInt32[kBitModelTotal >> kNumMoveReducingBits];
+
+ static BitEncoder()
+ {
+ const int kNumBits = (kNumBitModelTotalBits - kNumMoveReducingBits);
+ for (int i = kNumBits - 1; i >= 0; i--)
+ {
+ UInt32 start = (UInt32)1 << (kNumBits - i - 1);
+ UInt32 end = (UInt32)1 << (kNumBits - i);
+ for (UInt32 j = start; j < end; j++)
+ ProbPrices[j] = ((UInt32)i << kNumBitPriceShiftBits) +
+ (((end - j) << kNumBitPriceShiftBits) >> (kNumBits - i - 1));
+ }
+ }
+
+ public uint GetPrice(uint symbol)
+ {
+ return ProbPrices[(((Prob - symbol) ^ ((-(int)symbol))) & (kBitModelTotal - 1)) >> kNumMoveReducingBits];
+ }
+ public uint GetPrice0() { return ProbPrices[Prob >> kNumMoveReducingBits]; }
+ public uint GetPrice1() { return ProbPrices[(kBitModelTotal - Prob) >> kNumMoveReducingBits]; }
+ }
+
+ struct BitDecoder
+ {
+ public const int kNumBitModelTotalBits = 11;
+ public const uint kBitModelTotal = (1 << kNumBitModelTotalBits);
+ const int kNumMoveBits = 5;
+
+ uint Prob;
+
+ public void UpdateModel(int numMoveBits, uint symbol)
+ {
+ if (symbol == 0)
+ Prob += (kBitModelTotal - Prob) >> numMoveBits;
+ else
+ Prob -= (Prob) >> numMoveBits;
+ }
+
+ public void Init() { Prob = kBitModelTotal >> 1; }
+
+ public uint Decode(RangeCoder.Decoder rangeDecoder)
+ {
+ uint newBound = (uint)(rangeDecoder.Range >> kNumBitModelTotalBits) * (uint)Prob;
+ if (rangeDecoder.Code < newBound)
+ {
+ rangeDecoder.Range = newBound;
+ Prob += (kBitModelTotal - Prob) >> kNumMoveBits;
+ if (rangeDecoder.Range < Decoder.kTopValue)
+ {
+ rangeDecoder.Code = (rangeDecoder.Code << 8) | (byte)rangeDecoder.Stream.ReadByte();
+ rangeDecoder.Range <<= 8;
+ }
+ return 0;
+ }
+ else
+ {
+ rangeDecoder.Range -= newBound;
+ rangeDecoder.Code -= newBound;
+ Prob -= (Prob) >> kNumMoveBits;
+ if (rangeDecoder.Range < Decoder.kTopValue)
+ {
+ rangeDecoder.Code = (rangeDecoder.Code << 8) | (byte)rangeDecoder.Stream.ReadByte();
+ rangeDecoder.Range <<= 8;
+ }
+ return 1;
+ }
+ }
+ }
+}