Go: Reverse a UTF-8 encoded string

This function returns a string with the UTF-8 encoded characters of s in reverse order. Invalid UTF-8 sequences, if any, will be reversed byte by byte.

func ReverseUTF8(s string) string {
	res := make([]byte, len(s))
	prevPos, resPos := 0, len(s)
	for pos := range s {
		resPos -= pos - prevPos
		copy(res[resPos:], s[prevPos:pos])
		prevPos = pos
	copy(res[0:], s[prevPos:])
	return string(res)

Example usage:

for _, s := range []string{
	"Hello, 世界",
	"\xff\xfe\xfd", // invalid UTF-8
} {
	fmt.Printf("%q\n", ReverseUTF8(s))
"界世 ,olleH"


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