Function stitch

vector/apply.go:86–131

stitch returns a Dynamic for tags and vecs. If vecs contains any Dynamics, stitch flattens them and returns a value containing no nested Dynamics.

(tags []uint32, vecs []Any)

// stitch returns a Dynamic for tags and vecs.  If vecs contains any Dynamics,
// stitch flattens them and returns a value containing no nested Dynamics.
func stitch(tags []uint32, vecs []Any) Any {
	var foundDynamic bool
	var newVecsLen int
	for _, vec := range vecs {
		if d, ok := vec.(*Dynamic); ok {
			foundDynamic = true
			newVecsLen += len(d.Values)
		} else if o, ok := vec.(*Optional); ok {
			foundDynamic = true
			newVecsLen += len(o.Dynamic.Values)
		} else {
			newVecsLen++
		}
	}
	if !foundDynamic {
		return NewDynamic(tags, vecs)
	}
	newVecs := make([]Any, 0, newVecsLen)     // vecs but with nested Dynamics replaced by their values
	nestedTags := make([][]uint32, len(vecs)) // tags from nested Dynamics (nil for non-Dynamics)
	shifts := make([]uint32, len(vecs))       // tag + shift[tag] translates tag to newVecs
	var lastShift uint32
	for i, vec := range vecs {
		shifts[i] = lastShift
		if d, ok := vec.(*Dynamic); ok {
			newVecs = append(newVecs, d.Values...)
			nestedTags[i] = d.Tags
			lastShift += uint32(len(d.Values)) - 1
		} else if o, ok := vec.(*Optional); ok {
			newVecs = append(newVecs, o.Dynamic.Values...)
			nestedTags[i] = o.Dynamic.Tags
			lastShift += uint32(len(o.Dynamic.Values)) - 1
		} else {
			newVecs = append(newVecs, vec)
		}
	}
	newTags := make([]uint32, len(tags))
	for i, t := range tags {
		newTag := t + shifts[t]
		if nested := nestedTags[t]; len(nested) > 0 {
			newTag += nested[0]
			nestedTags[t] = nested[1:]
		}
		newTags[i] = newTag
	}
	return NewDynamic(newTags, newVecs)
}