github.com/epfl-dcsl/gotee@v0.0.0-20200909122901-014b35f5e5e9/src/strings/strings_generic.go (about)

     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  }