4.44 beta

CPP/7zip/Common/MSBFDecoder.h

@@ -0,0 +1,69 @@
+// MSBFDecoder.h
+// the Most Significant Bit of byte is First
+
+#ifndef __STREAM_MSBFDECODER_H
+#define __STREAM_MSBFDECODER_H
+
+#include "../../Common/Types.h"
+#include "../IStream.h"
+
+namespace NStream {
+namespace NMSBF {
+
+const int kNumBigValueBits = 8 * 4;
+const int kNumValueBytes = 3;
+const int kNumValueBits = 8  * kNumValueBytes;
+
+const UInt32 kMask = (1 << kNumValueBits) - 1;
+
+template<class TInByte>
+class CDecoder
+{
+  UInt32 m_BitPos;
+  UInt32 m_Value;
+public:
+  TInByte m_Stream;
+  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; 
+    Normalize();
+  }
+  
+  UInt64 GetProcessedSize() const 
+    { return m_Stream.GetProcessedSize() - (kNumBigValueBits - m_BitPos) / 8; }
+  UInt32 GetBitPosition() const { return (m_BitPos & 7); }
+  
+  void Normalize()
+  {
+    for (;m_BitPos >= 8; m_BitPos -= 8)
+      m_Value = (m_Value << 8) | m_Stream.ReadByte();
+  }
+
+  UInt32 GetValue(UInt32 numBits) const
+  {
+    // return (m_Value << m_BitPos) >> (kNumBigValueBits - numBits);
+    return ((m_Value >> (8 - m_BitPos)) & kMask) >> (kNumValueBits - numBits);
+  }
+  
+  void MovePos(UInt32 numBits)
+  {
+    m_BitPos += numBits;
+    Normalize();
+  }
+  
+  UInt32 ReadBits(UInt32 numBits)
+  {
+    UInt32 res = GetValue(numBits);
+    MovePos(numBits);
+    return res;
+  }
+};
+
+}}
+
+#endif