func (s *scanner) replace(repl string) {
	s.resizeRange(s.start, s.end, len(repl))
	copy(s.b[s.start:], repl)
}
replace replaces the current token with repl.
package language
import (
	"bytes"
	"errors"
	"fmt"
	"sort"
	"golang.org/x/text/internal/tag"
)
func isAlpha(b byte) bool {
	return b > '9'
}
func isAlphaNum(s []byte) bool {
	for _, c := range s {
		if !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9') {
			return false
		}
	}
	return true
}
var ErrSyntax = errors.New("language: tag is not well-formed")
var ErrDuplicateKey = errors.New("language: different values for same key in -u extension")
type ValueError struct {
	v [8]byte
}
func NewValueError(tag []byte) ValueError {
	var e ValueError
	copy(e.v[:], tag)
	return e
}
func (e ValueError) tag() []byte {
	n := bytes.IndexByte(e.v[:], 0)
	if n == -1 {
		n = 8
	}
	return e.v[:n]
}
func (e ValueError) Error() string {
	return fmt.Sprintf("language: subtag %q is well-formed but unknown", e.tag())
}
func (e ValueError) Subtag() string {
	return string(e.tag())
}
type scanner struct {
	b     []byte
	bytes [max99thPercentileSize]byte
	token []byte
	start int  
	end   int  
	next  int  
	err   error
	done  bool
}
func makeScannerString(s string) scanner {
	scan := scanner{}
	if len(s) <= len(scan.bytes) {
		scan.b = scan.bytes[:copy(scan.bytes[:], s)]
	} else {
		scan.b = []byte(s)
	}
	scan.init()
	return scan
}
func makeScanner(b []byte) scanner {
	scan := scanner{b: b}
	scan.init()
	return scan
}
func (s *scanner) init() {
	for i, c := range s.b {
		if c == '_' {
			s.b[i] = '-'
		}
	}
	s.scan()
}
func (s *scanner) toLower(start, end int) {
	for i := start; i < end; i++ {
		c := s.b[i]
		if 'A' <= c && c <= 'Z' {
			s.b[i] += 'a' - 'A'
		}
	}
}
func (s *scanner) setError(e error) {
	if s.err == nil || (e == ErrSyntax && s.err != ErrSyntax) {
		s.err = e
	}
}
func (s *scanner) resizeRange(oldStart, oldEnd, newSize int) {
	s.start = oldStart
	if end := oldStart + newSize; end != oldEnd {
		diff := end - oldEnd
		if end < cap(s.b) {
			b := make([]byte, len(s.b)+diff)
			copy(b, s.b[:oldStart])
			copy(b[end:], s.b[oldEnd:])
			s.b = b
		} else {
			s.b = append(s.b[end:], s.b[oldEnd:]...)
		}
		s.next = end + (s.next - s.end)
		s.end = end
	}
}