import "math"

var optimize = true // set to false to force slow-path conversions for testing

// commonPrefixLenIgnoreCase returns the length of the common
// prefix of s and prefix, with the character case of s ignored.
// The prefix argument must be all lower-case.
func commonPrefixLenIgnoreCase(s, prefix string) int {
	n := len(prefix)
	if n > len(s) {
		n = len(s)
	}
	for i := 0; i < n; i++ {
		c := s[i]