Method addOffset

bitmapcontainer.go:1310–1366

(x uint16)

}

func (bc *bitmapContainer) addOffset(x uint16) (container, container) {
	var low, high *bitmapContainer

	if bc.cardinality == 0 {
		return nil, nil
	}

	b := uint32(x) >> 6
	i := uint32(x) % 64
	end := uint32(1024) - b

	low = newBitmapContainer()
	if i == 0 {
		copy(low.bitmap[b:], bc.bitmap[:end])
	} else {
		low.bitmap[b] = bc.bitmap[0] << i
		for k := uint32(1); k < end; k++ {
			newval := bc.bitmap[k] << i
			newval |= bc.bitmap[k-1] >> (64 - i)
			low.bitmap[b+k] = newval
		}
	}
	low.computeCardinality()

	if low.cardinality == bc.cardinality {
		// All elements from bc ended up in low, meaning high will be empty.
		return low, nil
	}

	if low.cardinality == 0 {
		// low is empty, let's reuse the container for high.
		high = low
		low = nil
	} else {
		// None of the containers will be empty, so allocate both.
		high = newBitmapContainer()
	}

	if i == 0 {
		copy(high.bitmap[:b], bc.bitmap[end:])
	} else {
		for k := end; k < 1024; k++ {
			newval := bc.bitmap[k] << i
			newval |= bc.bitmap[k-1] >> (64 - i)
			high.bitmap[k-end] = newval
		}
		high.bitmap[b] = bc.bitmap[1023] >> (64 - i)
	}
	high.computeCardinality()

	// Ensure proper nil interface.
	if low == nil {
		return nil, high
	}

	return low, high
}