nbitstream.h

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#ifndef N_BITSTREAM_H
#define N_BITSTREAM_H
//------------------------------------------------------------------------------
/**
    @author
    - RadonLabs GmbH 

    @since
    - 2005.6.30
    @remarks
    - 瘤肯 眠啊 
*/

#include <memory.h>
#include "../ProgramCommon/Define.h"
#include "nnode.h"

//------------------------------------------------------------------------------
class nBitStream : public nNode
{
public:
    /// standard constructor, requires separate SetSize()
    nBitStream();
    /// constructor, expects stream size in bytes
    nBitStream(int size);
    /// the destructor
    virtual ~nBitStream();

    /// directly set contents of stream
    void Set(const uchar* s, int size);
    /// directly get contents of stream
    const uchar* Get() const;
    /// Set size of stream.
    void SetSize(int size);
    /// get the byte size of the stream
    int GetSize() const;
    /// set the current bit position in the stream
    void SetPos(int pos);
    /// return the current bit position in the stream
    int GetPos() const;
    /// return the number of bits left in the stream
    int BitsLeft() const;

    /// write a bool to the stream
    void WriteBool(bool flag);
    /// read a bool from the stream
    bool ReadBool();
    /// write a compressed integer to the stream
    void WriteInt(int value, int numBits);
    /// read a compressed integer from the stream
    int ReadInt(int numBits);
    /// write a float to the stream
    void WriteFloat(float value);
    /// read a float from the stream
    float ReadFloat();
    /// write a custom byte array to the stream
    void WriteCustom(const void* ptr, int size);
    /// read a custom byte array from the stream
    void ReadCustom(void* ptr, int size);
    /// write bitstream
    void WriteBitStream(nBitStream& stream);
    /// read bitstream
    void ReadBitStream(nBitStream& stream);
    /// copy data from source stream into this stream
    void Copy(const nBitStream& source);

    /// Lock for writing.
    void BeginWrite();
    /// Unlock for writing.
    void EndWrite();
    /// Lock for reading.
    void BeginRead();
    /// Unlock for reading.
    void EndRead();
    /// Writeable?
    bool IsWriteable() const;
    /// Readable?
    bool IsReadable() const;

    /// Assignment operator.
    nBitStream& operator = (const nBitStream& s);
    /// Equality operator.
    bool operator == (const nBitStream& s) const;
    /// Inequality operator.
    bool operator != (const nBitStream& s) const;

    // output
    void Print(int lines);

protected:
    /// clear stream contents, do not rewind bit pointer
    void Clear();
    /// Write bit at current position to stream.
    void WriteBit(bool bit);
    /// Read bit at currernt position from stream.
    bool ReadBit();

private:
    unsigned char* stream;
    int streamSize;
    int currentByte;    /// Current index in the stream buffer.
    int currentBit;     /// Current bit offset int currentByte.
    bool writeable;
    bool readable;
};

//------------------------------------------------------------------------------
/**
*/
inline
nBitStream::nBitStream()
{
    streamSize  = 0;
    currentByte = 0;
    currentBit  = 0;
    writeable   = false;
    readable    = false;
    stream      = 0;
}

//------------------------------------------------------------------------------
/**
    @param  size    the byte size of the bit stream (rounded up)
*/
inline
nBitStream::nBitStream(int size)
{
    // require
    ASSERT(size > 0);

    streamSize  = size;
    currentByte = 0;
    currentBit  = 0;
    writeable   = false;
    readable    = false;

    stream = new unsigned char[size];
    if (stream != 0)
    {
        memset(stream, 0, streamSize);
    }

    // ensure
    ASSERT(stream != 0);
}

//------------------------------------------------------------------------------
/**
*/
inline
nBitStream::~nBitStream()
{
    if (stream != 0)
    {
        delete[] stream;
    }
}

//------------------------------------------------------------------------------
/**
*/
inline
void
nBitStream::Clear()
{
    // require
    ASSERT( stream != 0 );
    ASSERT( streamSize > 0 );

    memset(stream, 0, streamSize);
}

//------------------------------------------------------------------------------
/**
    Write a bool value (always encoded into 1 bit) to the current
    stream position.

    @param  flag    the bool value
*/
inline
void
nBitStream::WriteBool(bool flag)
{
    ASSERT(writeable);

    WriteBit(flag);
}

//------------------------------------------------------------------------------
/**
    Reads a bool value (always encoded into 1 bit) from the current
    stream position.

    @return     the bool value
*/
inline
bool
nBitStream::ReadBool()
{
    ASSERT(readable);

    return ReadBit();
}

//------------------------------------------------------------------------------
/**
    Write a signed integer clamped to numBits bits.

    @param  value       the integer value to write
    @param  numBits     number of bits to write
*/
inline
void
nBitStream::WriteInt(int value, int numBits)
{
    ASSERT(writeable);
    ASSERT((1 < numBits) && (numBits <= 32));
    ASSERT(BitsLeft() >= numBits);

    // Write sign
    int tmp = (1 << 31);
    int tmp2 = (value & tmp);
    WriteBit(tmp2 != 0);
    numBits -= 2;       // I use numBits for shifting
                        // 1 Bit less for sign
                        // 1 Bit less for shifting

    // Make absolute value;
    // write sign and value separate
    value = n_abs(value);

    // Write value
    while (numBits >= 0)
    {
        tmp = (1 << numBits);
        tmp2 = (value & tmp);
        WriteBit(tmp2 != 0);
        numBits--;
    }

    ASSERT(numBits == -1);
}

//------------------------------------------------------------------------------
/**
    Read a signed integer clamped to numBits bits, the rest of the
    32 bytes will be filled with the correct sign bit.

    @param  numBits     number of bits to read
    @return             the integer, correclty expanded to 32 bits
*/
inline
int
nBitStream::ReadInt(int numBits)
{
    ASSERT(readable);
    ASSERT((1 < numBits) && (numBits <= 32));
    ASSERT(BitsLeft() >= numBits);

    int value = 0;

    // Read sign
    bool sign = ReadBit();
    numBits -= 2;       // I use numBits for shifting
                        // 1 Bit less for sign
                        // 1 Bit less for shifting

    // Read data
    while (numBits >= 0)
    {
        int v = ReadBit() ? 1 : 0;
        value |= (v << numBits);
        numBits--;
    }

    ASSERT(numBits == -1);

    // set sign
    if (sign)
    {
        value = -value;
    }

    return value;
}

//------------------------------------------------------------------------------
/**
    Write a float value into the stream, the float value will always be
    encoded into 32 bits.

    @param  value   the float value to write
*/
inline
void
nBitStream::WriteFloat(float value)
{
    ASSERT(writeable);
    ASSERT(BitsLeft() >= 32);

    int tmp;
    memcpy(&tmp, &value, 4);
    WriteInt(tmp, 32);      // Write floats as ints; use 32 BITS
}

//------------------------------------------------------------------------------
/**
    Read a float value (encoded in 32 bit) from the stream.

    @return      the float value
*/
inline
float
nBitStream::ReadFloat()
{
    ASSERT(readable);
    ASSERT(BitsLeft() >= 32);

    int tmp = ReadInt(32);      // Read floats as int; use 32 BITS
    float value;
    memcpy(&value, &tmp, 4);

    return value;
}

//------------------------------------------------------------------------------
/**
    Write a custom byte array to the stream.

    @param  ptr     pointer to byte array to write to the stream
    @param  size    number of bytes to write
*/
inline
void
nBitStream::WriteCustom(const void* ptr, int size)
{
    ASSERT(writeable);
    ASSERT(ptr != 0);
    ASSERT(size > 0);
    ASSERT(BitsLeft() >= size * 8);

    // advance to next byte in stream
    // if current bit offset is greater 0
    if (currentBit > 0)
    {
        currentByte++;
        currentBit = 0;
    }
    memcpy(&stream[currentByte], ptr, size);
    currentByte += size;
}

//------------------------------------------------------------------------------
/**
    Read a custom byte array from the stream.

    @param  ptr     pointer to byte array
    @param  size    size in bytes to read