BitVector Class Reference

#include <BitVector.hh>

Public Member Functions
	BitVector (unsigned char *baseBytePtr, unsigned baseBitOffset, unsigned totNumBits)
void	setup (unsigned char *baseBytePtr, unsigned baseBitOffset, unsigned totNumBits)
void	putBits (unsigned from, unsigned numBits)
void	put1Bit (unsigned bit)
unsigned	getBits (unsigned numBits)
unsigned	get1Bit ()
void	skipBits (unsigned numBits)
unsigned	curBitIndex () const
unsigned	totNumBits () const
unsigned	numBitsRemaining () const
unsigned	get_expGolomb ()
Private Attributes
unsigned char *	fBaseBytePtr
unsigned	fBaseBitOffset
unsigned	fTotNumBits
unsigned	fCurBitIndex

---

Detailed Description

Definition at line 24 of file BitVector.hh.

---

Constructor & Destructor Documentation

BitVector::BitVector	(	unsigned char *	baseBytePtr,
		unsigned	baseBitOffset,
		unsigned	totNumBits
	)

Definition at line 23 of file BitVector.cpp.

References setup().

                                          {
  setup(baseBytePtr, baseBitOffset, totNumBits);
}

---

Member Function Documentation

void BitVector::setup	(	unsigned char *	baseBytePtr,
		unsigned	baseBitOffset,
		unsigned	totNumBits
	)

Definition at line 29 of file BitVector.cpp.

References fBaseBitOffset, fBaseBytePtr, fCurBitIndex, and fTotNumBits.

Referenced by BitVector(), and MP3FrameParams::setBytePointer().

                                           {
  fBaseBytePtr = baseBytePtr;
  fBaseBitOffset = baseBitOffset;
  fTotNumBits = totNumBits;
  fCurBitIndex = 0;
}

void BitVector::putBits	(	unsigned	from,
		unsigned	numBits
	)

Definition at line 43 of file BitVector.cpp.

References fBaseBitOffset, fBaseBytePtr, fCurBitIndex, fTotNumBits, MAX_LENGTH, and shiftBits().

Referenced by putSideInfo1(), and putSideInfo2().

                                                       {
  if (numBits == 0) return; 

  unsigned char tmpBuf[4];
  unsigned overflowingBits = 0;

  if (numBits > MAX_LENGTH) {
    numBits = MAX_LENGTH;
  }

  if (numBits > fTotNumBits - fCurBitIndex) {
    overflowingBits = numBits - (fTotNumBits - fCurBitIndex);
  }

  tmpBuf[0] = (unsigned char)(from>>24);
  tmpBuf[1] = (unsigned char)(from>>16);
  tmpBuf[2] = (unsigned char)(from>>8);
  tmpBuf[3] = (unsigned char)from;

  shiftBits(fBaseBytePtr, fBaseBitOffset + fCurBitIndex, /* to */
            tmpBuf, MAX_LENGTH - numBits, /* from */
            numBits - overflowingBits /* num bits */);
  fCurBitIndex += numBits - overflowingBits;
}

void BitVector::put1Bit

(

unsigned

bit

)

Definition at line 68 of file BitVector.cpp.

References fBaseBitOffset, fBaseBytePtr, fCurBitIndex, fTotNumBits, and singleBitMask.

Referenced by putSideInfo1(), and putSideInfo2().

                                    {
  // The following is equivalent to "putBits(..., 1)", except faster:
  if (fCurBitIndex >= fTotNumBits) { /* overflow */
    return;
  } else {
    unsigned totBitOffset = fBaseBitOffset + fCurBitIndex++;
    unsigned char mask = singleBitMask[totBitOffset%8];
    if (bit) {
      fBaseBytePtr[totBitOffset/8] |= mask;
    } else {
      fBaseBytePtr[totBitOffset/8] &=~ mask;
    }
  }
}

unsigned BitVector::getBits

(

unsigned

numBits

)

Definition at line 83 of file BitVector.cpp.

References fBaseBitOffset, fBaseBytePtr, fCurBitIndex, fTotNumBits, MAX_LENGTH, and shiftBits().

Referenced by H264VideoStreamParser::analyze_seq_parameter_set_data(), H264VideoStreamParser::analyze_slice_header(), H264VideoStreamParser::analyze_vui_parameters(), get_expGolomb(), MP3FrameParams::getBits(), MPEG4GenericRTPSource::processSpecialHeader(), and rsf_huffman_decoder().

                                            {
  if (numBits == 0) return 0;

  unsigned char tmpBuf[4];
  unsigned overflowingBits = 0;

  if (numBits > MAX_LENGTH) {
    numBits = MAX_LENGTH;
  }

  if (numBits > fTotNumBits - fCurBitIndex) {
    overflowingBits = numBits - (fTotNumBits - fCurBitIndex);
  }

  shiftBits(tmpBuf, 0, /* to */
            fBaseBytePtr, fBaseBitOffset + fCurBitIndex, /* from */
            numBits - overflowingBits /* num bits */);
  fCurBitIndex += numBits - overflowingBits;

  unsigned result
    = (tmpBuf[0]<<24) | (tmpBuf[1]<<16) | (tmpBuf[2]<<8) | tmpBuf[3];
  result >>= (MAX_LENGTH - numBits); // move into low-order part of word
  result &= (0xFFFFFFFF << overflowingBits); // so any overflow bits are 0
  return result;
}

unsigned BitVector::get1Bit

(

)

Definition at line 109 of file BitVector.cpp.

References fBaseBitOffset, fBaseBytePtr, fCurBitIndex, and fTotNumBits.

Referenced by H264VideoStreamParser::analyze_seq_parameter_set_data(), H264VideoStreamParser::analyze_slice_header(), H264VideoStreamParser::analyze_vui_parameters(), MP3FrameParams::get1Bit(), get_expGolomb(), and rsf_huffman_decoder().

                            {
  // The following is equivalent to "getBits(1)", except faster:

  if (fCurBitIndex >= fTotNumBits) { /* overflow */
    return 0;
  } else {
    unsigned totBitOffset = fBaseBitOffset + fCurBitIndex++;
    unsigned char curFromByte = fBaseBytePtr[totBitOffset/8];
    unsigned result = (curFromByte >> (7-(totBitOffset%8))) & 0x01;
    return result;
  }
}

void BitVector::skipBits

(

unsigned

numBits

)

Definition at line 122 of file BitVector.cpp.

References fCurBitIndex, and fTotNumBits.

Referenced by H264VideoStreamParser::analyze_seq_parameter_set_data(), H264VideoStreamParser::analyze_slice_header(), H264VideoStreamParser::analyze_vui_parameters(), and MP3HuffmanDecode().

                                         {
  if (numBits > fTotNumBits - fCurBitIndex) { /* overflow */
    fCurBitIndex = fTotNumBits;
  } else {
    fCurBitIndex += numBits;
  }
}

unsigned BitVector::curBitIndex

(

)

const [inline]

Definition at line 42 of file BitVector.hh.

References fCurBitIndex.

Referenced by MP3HuffmanDecode().

{ return fCurBitIndex; }

unsigned BitVector::totNumBits

(

)

const [inline]

Definition at line 43 of file BitVector.hh.

References fTotNumBits.

{ return fTotNumBits; }

unsigned BitVector::numBitsRemaining

(

)

const [inline]

Definition at line 44 of file BitVector.hh.

References fCurBitIndex, and fTotNumBits.

{ return fTotNumBits - fCurBitIndex; }

unsigned BitVector::get_expGolomb

(

)

Definition at line 130 of file BitVector.cpp.

References fCurBitIndex, fTotNumBits, get1Bit(), and getBits().

Referenced by H264VideoStreamParser::analyze_seq_parameter_set_data(), H264VideoStreamParser::analyze_slice_header(), and H264VideoStreamParser::analyze_vui_parameters().

                                  {
  unsigned numLeadingZeroBits = 0;
  unsigned codeStart = 1;

  while (get1Bit() == 0 && fCurBitIndex < fTotNumBits) {
    ++numLeadingZeroBits;
    codeStart *= 2;
  }

  return codeStart -1 + getBits(numLeadingZeroBits);
}

---

Field Documentation

unsigned char* BitVector::fBaseBytePtr [private]

Definition at line 50 of file BitVector.hh.

Referenced by get1Bit(), getBits(), put1Bit(), putBits(), and setup().

unsigned BitVector::fBaseBitOffset [private]

Definition at line 51 of file BitVector.hh.

Referenced by get1Bit(), getBits(), put1Bit(), putBits(), and setup().

unsigned BitVector::fTotNumBits [private]

Definition at line 52 of file BitVector.hh.

Referenced by get1Bit(), get_expGolomb(), getBits(), numBitsRemaining(), put1Bit(), putBits(), setup(), skipBits(), and totNumBits().

unsigned BitVector::fCurBitIndex [private]

Definition at line 53 of file BitVector.hh.

Referenced by curBitIndex(), get1Bit(), get_expGolomb(), getBits(), numBitsRemaining(), put1Bit(), putBits(), setup(), and skipBits().

---

The documentation for this class was generated from the following files:

• liveMedia/BitVector.hh
• liveMedia/BitVector.cpp

---