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 7 package bytes 8 9 // Index returns the index of the first instance of sep in s, or -1 if sep is not present in s. 10 func 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. 63 func Count(s, sep []byte) int { 64 return countGeneric(s, sep) 65 } 66
