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Source file src/strings/strings_generic.go

Documentation: strings

  // Copyright 2015 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // +build !amd64,!s390x
  
  package strings
  
  // TODO: implements short string optimization on non amd64 platforms
  // and get rid of strings_amd64.go
  
  // Index returns the index of the first instance of substr in s, or -1 if substr is not present in s.
  func Index(s, substr string) int {
  	n := len(substr)
  	switch {
  	case n == 0:
  		return 0
  	case n == 1:
  		return IndexByte(s, substr[0])
  	case n == len(s):
  		if substr == s {
  			return 0
  		}
  		return -1
  	case n > len(s):
  		return -1
  	}
  	c := substr[0]
  	i := 0
  	t := s[:len(s)-n+1]
  	fails := 0
  	for i < len(t) {
  		if t[i] != c {
  			o := IndexByte(t[i:], c)
  			if o < 0 {
  				return -1
  			}
  			i += o
  		}
  		if s[i:i+n] == substr {
  			return i
  		}
  		i++
  		fails++
  		if fails >= 4+i>>4 && i < len(t) {
  			// See comment in ../bytes/bytes_generic.go.
  			j := indexRabinKarp(s[i:], substr)
  			if j < 0 {
  				return -1
  			}
  			return i + j
  		}
  	}
  	return -1
  }
  
  // Count counts the number of non-overlapping instances of substr in s.
  // If substr is an empty string, Count returns 1 + the number of Unicode code points in s.
  func Count(s, substr string) int {
  	return countGeneric(s, substr)
  }
  

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