Method UTF16ToUTF8

internal/ast/positionmap.go:91–111

UTF16ToUTF8 converts a UTF-16 code unit offset to a UTF-8 byte offset.

(utf16Offset int)

// UTF16ToUTF8 converts a UTF-16 code unit offset to a UTF-8 byte offset.
func (pm *PositionMap) UTF16ToUTF8(utf16Offset int) int {
	if pm.asciiOnly {
		return utf16Offset
	}
	// We need the last entry where (utf8Pos - delta) <= utf16Offset.
	// (utf8Pos - delta) is the UTF-16 offset of that entry's character.
	lo, hi := 0, len(pm.entries)
	for lo < hi {
		mid := lo + (hi-lo)/2
		utf16Pos := pm.entries[mid].utf8Pos - pm.entries[mid].delta
		if utf16Pos <= utf16Offset {
			lo = mid + 1
		} else {
			hi = mid
		}
	}
	if lo == 0 {
		return utf16Offset
	}
	return utf16Offset + pm.entries[lo-1].delta
}