4.44 beta

CPP/7zip/Common/LSBFDecoder.h

@@ -0,0 +1,127 @@
+// LSBFDecoder.h
+
+#ifndef __STREAM_LSBFDECODER_H
+#define __STREAM_LSBFDECODER_H
+
+#include "../IStream.h"
+
+namespace NStream {
+namespace NLSBF {
+
+const int kNumBigValueBits = 8 * 4;
+
+const int kNumValueBytes = 3;
+const int kNumValueBits = 8  * kNumValueBytes;
+
+const UInt32 kMask = (1 << kNumValueBits) - 1;
+
+extern Byte kInvertTable[256];
+// the Least Significant Bit of byte is First
+
+template<class TInByte>
+class CBaseDecoder
+{
+protected:
+  int m_BitPos;
+  UInt32 m_Value;
+  TInByte m_Stream;
+public:
+  UInt32 NumExtraBytes;
+  bool Create(UInt32 bufferSize) { return m_Stream.Create(bufferSize); }
+  void SetStream(ISequentialInStream *inStream) { m_Stream.SetStream(inStream); }
+  void ReleaseStream() { m_Stream.ReleaseStream(); }
+  void Init()
+  {
+    m_Stream.Init();
+    m_BitPos = kNumBigValueBits; 
+    m_Value = 0;
+    NumExtraBytes = 0;
+  }
+  UInt64 GetProcessedSize() const 
+    { return m_Stream.GetProcessedSize() - (kNumBigValueBits - m_BitPos) / 8; }
+  UInt64 GetProcessedBitsSize() const 
+    { return (m_Stream.GetProcessedSize() << 3) - (kNumBigValueBits - m_BitPos); }
+  int GetBitPosition() const { return (m_BitPos & 7); }
+
+  void Normalize()
+  {
+    for (;m_BitPos >= 8; m_BitPos -= 8)
+    {
+      Byte b = 0;
+      if (!m_Stream.ReadByte(b))
+      {
+        b = 0xFF; // check it
+        NumExtraBytes++;
+      }
+      m_Value = (b << (kNumBigValueBits - m_BitPos)) | m_Value;
+    }
+  }
+  
+  UInt32 ReadBits(int numBits)
+  {
+    Normalize();
+    UInt32 res = m_Value & ((1 << numBits) - 1);
+    m_BitPos += numBits;
+    m_Value >>= numBits;
+    return res;
+  }
+
+  bool ExtraBitsWereRead() const
+  {
+    if (NumExtraBytes == 0)
+      return false;
+    return ((UInt32)(kNumBigValueBits - m_BitPos) < (NumExtraBytes << 3));
+  }
+};
+
+template<class TInByte>
+class CDecoder: public CBaseDecoder<TInByte>
+{
+  UInt32 m_NormalValue;
+
+public:
+  void Init()
+  {
+    CBaseDecoder<TInByte>::Init();
+    m_NormalValue = 0;
+  }
+
+  void Normalize()
+  {
+    for (; this->m_BitPos >= 8; this->m_BitPos -= 8)
+    {
+      Byte b = 0;
+      if (!this->m_Stream.ReadByte(b))
+      {
+        b = 0xFF; // check it
+        this->NumExtraBytes++;
+      }
+      m_NormalValue = (b << (kNumBigValueBits - this->m_BitPos)) | m_NormalValue;
+      this->m_Value = (this->m_Value << 8) | kInvertTable[b];
+    }
+  }
+  
+  UInt32 GetValue(int numBits)
+  {
+    Normalize();
+    return ((this->m_Value >> (8 - this->m_BitPos)) & kMask) >> (kNumValueBits - numBits);
+  }
+
+  void MovePos(int numBits)
+  {
+    this->m_BitPos += numBits;
+    m_NormalValue >>= numBits;
+  }
+  
+  UInt32 ReadBits(int numBits)
+  {
+    Normalize();
+    UInt32 res = m_NormalValue & ( (1 << numBits) - 1);
+    MovePos(numBits);
+    return res;
+  }
+};
+
+}}
+
+#endif