1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// -build !amd64,!s390x,!arm64
6
7package bytes
8
9// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
10func Index(s, sep []byte) int {
11	n := len(sep)
12	switch {
13	case n == 0:
14		return 0
15	case n == 1:
16		return IndexByte(s, sep[0])
17	case n == len(s):
18		if Equal(sep, s) {
19			return 0
20		}
21		return -1
22	case n > len(s):
23		return -1
24	}
25	c := sep[0]
26	i := 0
27	fails := 0
28	t := s[:len(s)-n+1]
29	for i < len(t) {
30		if t[i] != c {
31			o := IndexByte(t[i:], c)
32			if o < 0 {
33				break
34			}
35			i += o
36		}
37		if Equal(s[i:i+n], sep) {
38			return i
39		}
40		i++
41		fails++
42		if fails >= 4+i>>4 && i < len(t) {
43			// Give up on IndexByte, it isn't skipping ahead
44			// far enough to be better than Rabin-Karp.
45			// Experiments (using IndexPeriodic) suggest
46			// the cutover is about 16 byte skips.
47			// TODO: if large prefixes of sep are matching
48			// we should cutover at even larger average skips,
49			// because Equal becomes that much more expensive.
50			// This code does not take that effect into account.
51			j := indexRabinKarp(s[i:], sep)
52			if j < 0 {
53				return -1
54			}
55			return i + j
56		}
57	}
58	return -1
59}
60
61// Count counts the number of non-overlapping instances of sep in s.
62// If sep is an empty slice, Count returns 1 + the number of UTF-8-encoded code points in s.
63func Count(s, sep []byte) int {
64	return countGeneric(s, sep)
65}
66