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      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 bytes
      8 
      9 // TODO: implements short string optimization on non amd64 platforms
     10 // and get rid of bytes_amd64.go
     11 
     12 // Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
     13 func Index(s, sep []byte) int {
     14 	n := len(sep)
     15 	if n == 0 {
     16 		return 0
     17 	}
     18 	if n > len(s) {
     19 		return -1
     20 	}
     21 	c := sep[0]
     22 	if n == 1 {
     23 		return IndexByte(s, c)
     24 	}
     25 	i := 0
     26 	t := s[:len(s)-n+1]
     27 	for i < len(t) {
     28 		if t[i] != c {
     29 			o := IndexByte(t[i:], c)
     30 			if o < 0 {
     31 				break
     32 			}
     33 			i += o
     34 		}
     35 		if Equal(s[i:i+n], sep) {
     36 			return i
     37 		}
     38 		i++
     39 	}
     40 	return -1
     41 }
     42