File size: 3,001 Bytes
e36aeda | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 | // Copyright 2024 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.
// Package stringslite implements a subset of strings,
// only using packages that may be imported by "os".
//
// Tests for these functions are in the strings package.
package stringslite
import (
"internal/bytealg"
"unsafe"
)
func HasPrefix(s, prefix string) bool {
return len(s) >= len(prefix) && s[:len(prefix)] == prefix
}
func HasSuffix(s, suffix string) bool {
return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
}
func IndexByte(s string, c byte) int {
return bytealg.IndexByteString(s, c)
}
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
case n <= bytealg.MaxLen:
// Use brute force when s and substr both are small
if len(s) <= bytealg.MaxBruteForce {
return bytealg.IndexString(s, substr)
}
c0 := substr[0]
c1 := substr[1]
i := 0
t := len(s) - n + 1
fails := 0
for i < t {
if s[i] != c0 {
// IndexByte is faster than bytealg.IndexString, so use it as long as
// we're not getting lots of false positives.
o := IndexByte(s[i+1:t], c0)
if o < 0 {
return -1
}
i += o + 1
}
if s[i+1] == c1 && s[i:i+n] == substr {
return i
}
fails++
i++
// Switch to bytealg.IndexString when IndexByte produces too many false positives.
if fails > bytealg.Cutover(i) {
r := bytealg.IndexString(s[i:], substr)
if r >= 0 {
return r + i
}
return -1
}
}
return -1
}
c0 := substr[0]
c1 := substr[1]
i := 0
t := len(s) - n + 1
fails := 0
for i < t {
if s[i] != c0 {
o := IndexByte(s[i+1:t], c0)
if o < 0 {
return -1
}
i += o + 1
}
if s[i+1] == c1 && s[i:i+n] == substr {
return i
}
i++
fails++
if fails >= 4+i>>4 && i < t {
// See comment in ../bytes/bytes.go.
j := bytealg.IndexRabinKarp(s[i:], substr)
if j < 0 {
return -1
}
return i + j
}
}
return -1
}
func Cut(s, sep string) (before, after string, found bool) {
if i := Index(s, sep); i >= 0 {
return s[:i], s[i+len(sep):], true
}
return s, "", false
}
func CutPrefix(s, prefix string) (after string, found bool) {
if !HasPrefix(s, prefix) {
return s, false
}
return s[len(prefix):], true
}
func CutSuffix(s, suffix string) (before string, found bool) {
if !HasSuffix(s, suffix) {
return s, false
}
return s[:len(s)-len(suffix)], true
}
func TrimPrefix(s, prefix string) string {
if HasPrefix(s, prefix) {
return s[len(prefix):]
}
return s
}
func TrimSuffix(s, suffix string) string {
if HasSuffix(s, suffix) {
return s[:len(s)-len(suffix)]
}
return s
}
func Clone(s string) string {
if len(s) == 0 {
return ""
}
b := make([]byte, len(s))
copy(b, s)
return unsafe.String(&b[0], len(b))
}
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