Method GoLineToDingoLine

pkg/sourcemap/dmap/reader.go:439–471

GoLineToDingoLine converts a Go line to Dingo line using v2 line mappings. Returns the Dingo line and kind string if a mapping is found. For unmapped lines, uses cumulative delta to compute approximate Dingo line. Uses binary search for O(log N) performance instead of O(N) linear search.

(goLine int)

// For unmapped lines, uses cumulative delta to compute approximate Dingo line.
// Uses binary search for O(log N) performance instead of O(N) linear search.
func (r *Reader) GoLineToDingoLine(goLine int) (dingoLine int, kind string) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	// If no v2 mappings available, use simple proportional fallback
	if len(r.lineMappings) == 0 {
		return r.proportionalFallback(goLine), ""
	}

	// Binary search for mapping containing goLine
	// Mappings are sorted by GoLineStart in parseLineMappings
	idx := sort.Search(len(r.lineMappings), func(i int) bool {
		return r.lineMappings[i].GoLineEnd >= uint32(goLine)
	})

	// Check if we found a valid mapping
	if idx < len(r.lineMappings) {
		entry := &r.lineMappings[idx]
		if uint32(goLine) >= entry.GoLineStart && uint32(goLine) <= entry.GoLineEnd {
			// Found mapping - return Dingo line and kind
			dingoLine = int(entry.DingoLine)
			if entry.KindIdx >= uint16(len(r.kinds)) {
				// Invalid kind index - return empty kind
				return dingoLine, ""
			}
			kind = r.kinds[entry.KindIdx]
			return dingoLine, kind
		}
	}

	// No direct mapping found - compute using cumulative delta from previous mappings
	return r.computeDeltaFallback(goLine, idx), ""
}

// proportionalFallback returns a proportionally mapped Dingo line when no v2 mappings exist.
// Uses the ratio of Dingo/Go line counts for approximate mapping.