func concat()

in arrow/array/concat.go [226:325]
93 lines of code
28 McCabe index (conditional complexity)

func concat(data []*Data, mem memory.Allocator) (*Data, error) {
	out := &Data{refCount: 1, dtype: data[0].dtype, nulls: 0}
	for _, d := range data {
		out.length += d.length
		if out.nulls == UnknownNullCount || d.nulls == UnknownNullCount {
			out.nulls = UnknownNullCount
			continue
		}
		out.nulls += d.nulls
	}

	out.buffers = make([]*memory.Buffer, len(data[0].buffers))
	if out.nulls != 0 && out.dtype.ID() != arrow.NULL {
		bm, err := concatBitmaps(gatherBitmaps(data, 0), mem)
		if err != nil {
			return nil, err
		}
		out.buffers[0] = bm
	}

	switch dt := out.dtype.(type) {
	case *arrow.NullType:
	case *arrow.BooleanType:
		bm, err := concatBitmaps(gatherBitmaps(data, 1), mem)
		if err != nil {
			return nil, err
		}
		out.buffers[1] = bm
	case arrow.FixedWidthDataType:
		out.buffers[1] = concatBuffers(gatherBuffersFixedWidthType(data, 1, dt), mem)
	case arrow.BinaryDataType:
		offsetBuffer, valueRanges, err := concatOffsets(gatherFixedBuffers(data, 1, arrow.Int32SizeBytes), mem)
		if err != nil {
			return nil, err
		}
		out.buffers[2] = concatBuffers(gatherBufferRanges(data, 2, valueRanges), mem)
		out.buffers[1] = offsetBuffer
	case *arrow.ListType:
		offsetBuffer, valueRanges, err := concatOffsets(gatherFixedBuffers(data, 1, arrow.Int32SizeBytes), mem)
		if err != nil {
			return nil, err
		}
		childData := gatherChildrenRanges(data, 0, valueRanges)
		for _, c := range childData {
			defer c.Release()
		}

		out.buffers[1] = offsetBuffer
		out.childData = make([]*Data, 1)
		out.childData[0], err = concat(childData, mem)
		if err != nil {
			return nil, err
		}
	case *arrow.FixedSizeListType:
		childData := gatherChildrenMultiplier(data, 0, int(dt.Len()))
		for _, c := range childData {
			defer c.Release()
		}

		children, err := concat(childData, mem)
		if err != nil {
			return nil, err
		}
		out.childData = []*Data{children}
	case *arrow.StructType:
		out.childData = make([]*Data, len(dt.Fields()))
		for i := range dt.Fields() {
			children := gatherChildren(data, i)
			for _, c := range children {
				defer c.Release()
			}

			childData, err := concat(children, mem)
			if err != nil {
				return nil, err
			}
			out.childData[i] = childData
		}
	case *arrow.MapType:
		offsetBuffer, valueRanges, err := concatOffsets(gatherFixedBuffers(data, 1, arrow.Int32SizeBytes), mem)
		if err != nil {
			return nil, err
		}
		childData := gatherChildrenRanges(data, 0, valueRanges)
		for _, c := range childData {
			defer c.Release()
		}

		out.buffers[1] = offsetBuffer
		out.childData = make([]*Data, 1)
		out.childData[0], err = concat(childData, mem)
		if err != nil {
			return nil, err
		}
	default:
		return nil, xerrors.Errorf("concatenate not implemented for type %s", dt)
	}

	return out, nil
}