libgo/go/strings/strings_generic.go

   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 }