func ContainsFunc(b []byte, f func(rune) bool) bool {
	return IndexFunc(b, f) >= 0
}

// IndexByte returns the index of the first instance of c in b, or -1 if c is not present in b.
func IndexByte(b []byte, c byte) int {
	return bytealg.IndexByte(b, c)
}

func indexBytePortable(s []byte, c byte) int {
	for i, b := range s {
		if b == c {
			return i
		}
	}
	return -1

	fmt.Println(bytes.Index([]byte("chicken"), []byte("dmr")))
	// Output:
	// 4
	// -1
}

func ExampleIndexByte() {
	fmt.Println(bytes.IndexByte([]byte("chicken"), byte('k')))
	fmt.Println(bytes.IndexByte([]byte("chicken"), byte('g')))
	// Output:
	// 4
	// -1
}

func ExampleIndexFunc() {
	f := func(c rune) bool {
		return unicode.Is(unicode.Han, c)
	}

		forward := ""
		if len(opts.ForwardTo) > 0 && strings.HasPrefix(opts.ForwardTo, current) {
			forward = strings.TrimPrefix(opts.ForwardTo, current)
			// Trim further directories and trailing slash.
			if idx := strings.IndexByte(forward, '/'); idx > 0 {
				forward = forward[:idx]
			}
		}
		if contextCanceled(ctx) {
			return ctx.Err()
		}
		if opts.Limit > 0 && objsReturned >= opts.Limit {
			return nil
		}

			// if the revision is "default", render templates with an empty revision
			if rev == util.DefaultRevisionName {
				rev = ""
			}
			injectorAddress := centralOpts.Xds
			index := strings.IndexByte(injectorAddress, ':')
			if index != -1 {
				injectorAddress = injectorAddress[:index]
			}
			injector, meshConfig, err := setupKubeInjectParameters(cliContext, &sidecarTemplate, &valuesConfig, rev, injectorAddress)

// fail.
func DecryptETag(key crypto.ObjectKey, object ObjectInfo) (string, error) {
	if n := strings.Count(object.ETag, "-"); n > 0 {
		if n != 1 {
			return "", errObjectTampered
		}
		i := strings.IndexByte(object.ETag, '-')
		if len(object.ETag[:i]) != 32 {
			return "", errObjectTampered
		}
		if _, err := hex.DecodeString(object.ETag[:32]); err != nil {
			return "", errObjectTampered
		}