liveMedia/BitVector.hh File Reference

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Data Structures
class	BitVector
Functions
void	shiftBits (unsigned char *toBasePtr, unsigned toBitOffset, unsigned char const *fromBasePtr, unsigned fromBitOffset, unsigned numBits)

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Function Documentation

void shiftBits	(	unsigned char *	toBasePtr,
		unsigned	toBitOffset,
		unsigned char const *	fromBasePtr,
		unsigned	fromBitOffset,
		unsigned	numBits
	)

Definition at line 143 of file BitVector.cpp.

References singleBitMask.

Referenced by BitVector::getBits(), BitVector::putBits(), TranscodeMP3ADU(), and unpackBandwidthEfficientData().

                                 {
  if (numBits == 0) return;

  /* Note that from and to may overlap, if from>to */
  unsigned char const* fromBytePtr = fromBasePtr + fromBitOffset/8;
  unsigned fromBitRem = fromBitOffset%8;
  unsigned char* toBytePtr = toBasePtr + toBitOffset/8;
  unsigned toBitRem = toBitOffset%8;

  while (numBits-- > 0) {
    unsigned char fromBitMask = singleBitMask[fromBitRem];
    unsigned char fromBit = (*fromBytePtr)&fromBitMask;
    unsigned char toBitMask = singleBitMask[toBitRem];

    if (fromBit != 0) {
      *toBytePtr |= toBitMask;
    } else {
      *toBytePtr &=~ toBitMask;
    }

    if (++fromBitRem == 8) {
      ++fromBytePtr;
      fromBitRem = 0;
    }
    if (++toBitRem == 8) {
      ++toBytePtr;
      toBitRem = 0;
    }
  }
}

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