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