func()

in cpc/cpc_union.go [61:141]
72 lines of code
24 McCabe index (conditional complexity)

func (u *CpcUnion) Update(source *CpcSketch) error {
	if err := checkSeeds(u.seed, source.seed); err != nil {
		return err
	}

	sourceFlavorOrd := source.getFlavor()
	if sourceFlavorOrd == CpcFlavorEmpty {
		return nil
	}

	if err := u.checkUnionState(); err != nil {
		return err
	}

	// Downsample union if the source sketch has a smaller lgK.
	if source.lgK < u.lgK {
		if err := u.reduceUnionK(source.lgK); err != nil {
			return err
		}
	}

	// If the source is past SPARSE mode, ensure union is in bitMatrix mode.
	if sourceFlavorOrd > CpcFlavorSparse && u.accumulator != nil {
		bitMatrix, err := u.accumulator.bitMatrixOfSketch()
		if err != nil {
			return err
		}
		u.bitMatrix = bitMatrix
		u.accumulator = nil
	}
	state := (sourceFlavorOrd - 1) << 1
	if u.bitMatrix != nil {
		state |= 1
	}

	switch state {
	case 0: // Case A: source is SPARSE, union.accumulator valid, bitMatrix == nil.
		if u.accumulator.lgK == 0 {
			return fmt.Errorf("union accumulator cannot be nil")
		}
		// If the union is EMPTY and lgK matches, copy the source.
		if u.accumulator.getFlavor() == CpcFlavorEmpty && u.lgK == source.lgK {
			cp, err := source.Copy()
			if err != nil {
				return err
			}
			u.accumulator = cp
			break
		}
		if err := walkTableUpdatingSketch(u.accumulator, source.pairTable); err != nil {
			return err
		}
		// If accumulator has graduated beyond SPARSE, switch to bitMatrix.
		if u.accumulator.getFlavor() > CpcFlavorSparse {
			bitMatrix, err := u.accumulator.bitMatrixOfSketch()
			if err != nil {
				return err
			}
			u.bitMatrix = bitMatrix
			u.accumulator = nil
		}
	case 1: // Case B: source is SPARSE, union already in bitMatrix mode.
		u.orTableIntoMatrix(source.pairTable)
	case 3, 5: // Case C: source is HYBRID or PINNED, union in bitMatrix mode.
		if err := u.orWindowIntoMatrix(source.slidingWindow, 0, source.lgK); err != nil {
			return err
		}
		u.orTableIntoMatrix(source.pairTable)
	case 7: // Case D: source is SLIDING, union in bitMatrix mode.
		sourceMatrix, err := source.bitMatrixOfSketch()
		if err != nil {
			return err
		}
		if err := u.orMatrixIntoMatrix(sourceMatrix, source.lgK); err != nil {
			return err
		}
	default:
		return fmt.Errorf("illegal Union state: %d", state)
	}
	return nil
}