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 6 7 package strings 8 9 // TODO: implements short string optimization on non amd64 platforms 10 // and get rid of strings_amd64.go 11 12 // Index returns the index of the first instance of substr in s, or -1 if substr is not present in s. 13 func Index(s, substr string) int { 14 n := len(substr) 15 switch { 16 case n == 0: 17 return 0 18 case n == 1: 19 return IndexByte(s, substr[0]) 20 case n == len(s): 21 if substr == s { 22 return 0 23 } 24 return -1 25 case n > len(s): 26 return -1 27 } 28 c := substr[0] 29 i := 0 30 t := s[:len(s)-n+1] 31 fails := 0 32 for i < len(t) { 33 if t[i] != c { 34 o := IndexByte(t[i:], c) 35 if o < 0 { 36 return -1 37 } 38 i += o 39 } 40 if s[i:i+n] == substr { 41 return i 42 } 43 i++ 44 fails++ 45 if fails >= 4+i>>4 && i < len(t) { 46 // See comment in ../bytes/bytes_generic.go. 47 j := indexRabinKarp(s[i:], substr) 48 if j < 0 { 49 return -1 50 } 51 return i + j 52 } 53 } 54 return -1 55 } 56 57 // Count counts the number of non-overlapping instances of substr in s. 58 // If substr is an empty string, Count returns 1 + the number of Unicode code points in s. 59 func Count(s, substr string) int { 60 return countGeneric(s, substr) 61 } 62
