mirror of https://go.googlesource.com/go
1249 lines
31 KiB
Go
1249 lines
31 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package strings implements simple functions to manipulate UTF-8 encoded strings.
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//
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// For information about UTF-8 strings in Go, see https://blog.golang.org/strings.
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package strings
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import (
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"internal/bytealg"
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"internal/stringslite"
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"unicode"
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"unicode/utf8"
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)
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const maxInt = int(^uint(0) >> 1)
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// explode splits s into a slice of UTF-8 strings,
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// one string per Unicode character up to a maximum of n (n < 0 means no limit).
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// Invalid UTF-8 bytes are sliced individually.
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func explode(s string, n int) []string {
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l := utf8.RuneCountInString(s)
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if n < 0 || n > l {
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n = l
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}
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a := make([]string, n)
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for i := 0; i < n-1; i++ {
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_, size := utf8.DecodeRuneInString(s)
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a[i] = s[:size]
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s = s[size:]
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}
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if n > 0 {
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a[n-1] = s
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}
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return a
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}
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// Count counts the number of non-overlapping instances of substr in s.
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// If substr is an empty string, Count returns 1 + the number of Unicode code points in s.
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func Count(s, substr string) int {
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// special case
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if len(substr) == 0 {
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return utf8.RuneCountInString(s) + 1
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}
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if len(substr) == 1 {
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return bytealg.CountString(s, substr[0])
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}
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n := 0
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for {
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i := Index(s, substr)
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if i == -1 {
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return n
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}
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n++
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s = s[i+len(substr):]
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}
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}
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// Contains reports whether substr is within s.
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func Contains(s, substr string) bool {
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return Index(s, substr) >= 0
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}
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// ContainsAny reports whether any Unicode code points in chars are within s.
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func ContainsAny(s, chars string) bool {
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return IndexAny(s, chars) >= 0
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}
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// ContainsRune reports whether the Unicode code point r is within s.
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func ContainsRune(s string, r rune) bool {
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return IndexRune(s, r) >= 0
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}
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// ContainsFunc reports whether any Unicode code points r within s satisfy f(r).
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func ContainsFunc(s string, f func(rune) bool) bool {
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return IndexFunc(s, f) >= 0
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}
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// LastIndex returns the index of the last instance of substr in s, or -1 if substr is not present in s.
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func LastIndex(s, substr string) int {
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n := len(substr)
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switch {
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case n == 0:
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return len(s)
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case n == 1:
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return bytealg.LastIndexByteString(s, substr[0])
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case n == len(s):
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if substr == s {
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return 0
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}
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return -1
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case n > len(s):
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return -1
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}
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// Rabin-Karp search from the end of the string
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hashss, pow := bytealg.HashStrRev(substr)
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last := len(s) - n
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var h uint32
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for i := len(s) - 1; i >= last; i-- {
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h = h*bytealg.PrimeRK + uint32(s[i])
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}
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if h == hashss && s[last:] == substr {
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return last
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}
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for i := last - 1; i >= 0; i-- {
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h *= bytealg.PrimeRK
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h += uint32(s[i])
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h -= pow * uint32(s[i+n])
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if h == hashss && s[i:i+n] == substr {
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return i
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}
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}
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return -1
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}
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// IndexByte returns the index of the first instance of c in s, or -1 if c is not present in s.
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func IndexByte(s string, c byte) int {
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return stringslite.IndexByte(s, c)
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}
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// IndexRune returns the index of the first instance of the Unicode code point
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// r, or -1 if rune is not present in s.
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// If r is utf8.RuneError, it returns the first instance of any
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// invalid UTF-8 byte sequence.
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func IndexRune(s string, r rune) int {
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switch {
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case 0 <= r && r < utf8.RuneSelf:
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return IndexByte(s, byte(r))
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case r == utf8.RuneError:
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for i, r := range s {
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if r == utf8.RuneError {
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return i
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}
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}
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return -1
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case !utf8.ValidRune(r):
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return -1
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default:
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return Index(s, string(r))
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}
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}
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// IndexAny returns the index of the first instance of any Unicode code point
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// from chars in s, or -1 if no Unicode code point from chars is present in s.
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func IndexAny(s, chars string) int {
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if chars == "" {
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// Avoid scanning all of s.
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return -1
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}
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if len(chars) == 1 {
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// Avoid scanning all of s.
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r := rune(chars[0])
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if r >= utf8.RuneSelf {
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r = utf8.RuneError
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}
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return IndexRune(s, r)
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}
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if len(s) > 8 {
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if as, isASCII := makeASCIISet(chars); isASCII {
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for i := 0; i < len(s); i++ {
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if as.contains(s[i]) {
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return i
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}
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}
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return -1
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}
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}
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for i, c := range s {
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if IndexRune(chars, c) >= 0 {
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return i
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}
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}
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return -1
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}
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// LastIndexAny returns the index of the last instance of any Unicode code
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// point from chars in s, or -1 if no Unicode code point from chars is
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// present in s.
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func LastIndexAny(s, chars string) int {
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if chars == "" {
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// Avoid scanning all of s.
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return -1
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}
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if len(s) == 1 {
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rc := rune(s[0])
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if rc >= utf8.RuneSelf {
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rc = utf8.RuneError
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}
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if IndexRune(chars, rc) >= 0 {
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return 0
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}
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return -1
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}
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if len(s) > 8 {
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if as, isASCII := makeASCIISet(chars); isASCII {
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for i := len(s) - 1; i >= 0; i-- {
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if as.contains(s[i]) {
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return i
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}
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}
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return -1
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}
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}
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if len(chars) == 1 {
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rc := rune(chars[0])
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if rc >= utf8.RuneSelf {
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rc = utf8.RuneError
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}
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for i := len(s); i > 0; {
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r, size := utf8.DecodeLastRuneInString(s[:i])
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i -= size
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if rc == r {
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return i
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}
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}
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return -1
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}
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for i := len(s); i > 0; {
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r, size := utf8.DecodeLastRuneInString(s[:i])
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i -= size
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if IndexRune(chars, r) >= 0 {
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return i
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}
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}
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return -1
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}
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// LastIndexByte returns the index of the last instance of c in s, or -1 if c is not present in s.
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func LastIndexByte(s string, c byte) int {
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return bytealg.LastIndexByteString(s, c)
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}
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// Generic split: splits after each instance of sep,
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// including sepSave bytes of sep in the subarrays.
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func genSplit(s, sep string, sepSave, n int) []string {
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if n == 0 {
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return nil
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}
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if sep == "" {
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return explode(s, n)
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}
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if n < 0 {
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n = Count(s, sep) + 1
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}
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if n > len(s)+1 {
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n = len(s) + 1
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}
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a := make([]string, n)
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n--
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i := 0
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for i < n {
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m := Index(s, sep)
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if m < 0 {
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break
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}
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a[i] = s[:m+sepSave]
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s = s[m+len(sep):]
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i++
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}
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a[i] = s
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return a[:i+1]
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}
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// SplitN slices s into substrings separated by sep and returns a slice of
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// the substrings between those separators.
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//
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// The count determines the number of substrings to return:
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//
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// n > 0: at most n substrings; the last substring will be the unsplit remainder.
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// n == 0: the result is nil (zero substrings)
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// n < 0: all substrings
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//
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// Edge cases for s and sep (for example, empty strings) are handled
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// as described in the documentation for [Split].
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//
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// To split around the first instance of a separator, see Cut.
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func SplitN(s, sep string, n int) []string { return genSplit(s, sep, 0, n) }
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// SplitAfterN slices s into substrings after each instance of sep and
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// returns a slice of those substrings.
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//
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// The count determines the number of substrings to return:
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//
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// n > 0: at most n substrings; the last substring will be the unsplit remainder.
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// n == 0: the result is nil (zero substrings)
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// n < 0: all substrings
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//
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// Edge cases for s and sep (for example, empty strings) are handled
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// as described in the documentation for SplitAfter.
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func SplitAfterN(s, sep string, n int) []string {
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return genSplit(s, sep, len(sep), n)
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}
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// Split slices s into all substrings separated by sep and returns a slice of
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// the substrings between those separators.
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//
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// If s does not contain sep and sep is not empty, Split returns a
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// slice of length 1 whose only element is s.
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//
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// If sep is empty, Split splits after each UTF-8 sequence. If both s
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// and sep are empty, Split returns an empty slice.
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//
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// It is equivalent to [SplitN] with a count of -1.
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//
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// To split around the first instance of a separator, see Cut.
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func Split(s, sep string) []string { return genSplit(s, sep, 0, -1) }
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// SplitAfter slices s into all substrings after each instance of sep and
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// returns a slice of those substrings.
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//
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// If s does not contain sep and sep is not empty, SplitAfter returns
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// a slice of length 1 whose only element is s.
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//
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// If sep is empty, SplitAfter splits after each UTF-8 sequence. If
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// both s and sep are empty, SplitAfter returns an empty slice.
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//
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// It is equivalent to [SplitAfterN] with a count of -1.
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func SplitAfter(s, sep string) []string {
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return genSplit(s, sep, len(sep), -1)
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}
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var asciiSpace = [256]uint8{'\t': 1, '\n': 1, '\v': 1, '\f': 1, '\r': 1, ' ': 1}
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// Fields splits the string s around each instance of one or more consecutive white space
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// characters, as defined by unicode.IsSpace, returning a slice of substrings of s or an
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// empty slice if s contains only white space.
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func Fields(s string) []string {
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// First count the fields.
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// This is an exact count if s is ASCII, otherwise it is an approximation.
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n := 0
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wasSpace := 1
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// setBits is used to track which bits are set in the bytes of s.
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setBits := uint8(0)
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for i := 0; i < len(s); i++ {
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r := s[i]
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setBits |= r
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isSpace := int(asciiSpace[r])
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n += wasSpace & ^isSpace
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wasSpace = isSpace
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}
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if setBits >= utf8.RuneSelf {
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// Some runes in the input string are not ASCII.
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return FieldsFunc(s, unicode.IsSpace)
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}
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// ASCII fast path
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a := make([]string, n)
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na := 0
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fieldStart := 0
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i := 0
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// Skip spaces in the front of the input.
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for i < len(s) && asciiSpace[s[i]] != 0 {
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i++
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}
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fieldStart = i
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for i < len(s) {
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if asciiSpace[s[i]] == 0 {
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i++
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continue
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}
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a[na] = s[fieldStart:i]
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na++
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i++
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// Skip spaces in between fields.
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for i < len(s) && asciiSpace[s[i]] != 0 {
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i++
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}
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fieldStart = i
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}
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if fieldStart < len(s) { // Last field might end at EOF.
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a[na] = s[fieldStart:]
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}
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return a
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}
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// FieldsFunc splits the string s at each run of Unicode code points c satisfying f(c)
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// and returns an array of slices of s. If all code points in s satisfy f(c) or the
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// string is empty, an empty slice is returned.
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//
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// FieldsFunc makes no guarantees about the order in which it calls f(c)
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// and assumes that f always returns the same value for a given c.
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func FieldsFunc(s string, f func(rune) bool) []string {
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// A span is used to record a slice of s of the form s[start:end].
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// The start index is inclusive and the end index is exclusive.
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type span struct {
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start int
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end int
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}
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spans := make([]span, 0, 32)
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// Find the field start and end indices.
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// Doing this in a separate pass (rather than slicing the string s
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// and collecting the result substrings right away) is significantly
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// more efficient, possibly due to cache effects.
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start := -1 // valid span start if >= 0
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for end, rune := range s {
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if f(rune) {
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if start >= 0 {
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spans = append(spans, span{start, end})
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// Set start to a negative value.
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// Note: using -1 here consistently and reproducibly
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// slows down this code by a several percent on amd64.
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start = ^start
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}
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} else {
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if start < 0 {
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start = end
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}
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}
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}
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// Last field might end at EOF.
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if start >= 0 {
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spans = append(spans, span{start, len(s)})
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}
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// Create strings from recorded field indices.
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a := make([]string, len(spans))
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for i, span := range spans {
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a[i] = s[span.start:span.end]
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}
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return a
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}
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// Join concatenates the elements of its first argument to create a single string. The separator
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// string sep is placed between elements in the resulting string.
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func Join(elems []string, sep string) string {
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switch len(elems) {
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case 0:
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return ""
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case 1:
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return elems[0]
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}
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var n int
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if len(sep) > 0 {
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if len(sep) >= maxInt/(len(elems)-1) {
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panic("strings: Join output length overflow")
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}
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n += len(sep) * (len(elems) - 1)
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}
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for _, elem := range elems {
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if len(elem) > maxInt-n {
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panic("strings: Join output length overflow")
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}
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n += len(elem)
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}
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var b Builder
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b.Grow(n)
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b.WriteString(elems[0])
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for _, s := range elems[1:] {
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b.WriteString(sep)
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b.WriteString(s)
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}
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return b.String()
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}
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// HasPrefix reports whether the string s begins with prefix.
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func HasPrefix(s, prefix string) bool {
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return stringslite.HasPrefix(s, prefix)
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}
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// HasSuffix reports whether the string s ends with suffix.
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func HasSuffix(s, suffix string) bool {
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return stringslite.HasSuffix(s, suffix)
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}
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// Map returns a copy of the string s with all its characters modified
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// according to the mapping function. If mapping returns a negative value, the character is
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// dropped from the string with no replacement.
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func Map(mapping func(rune) rune, s string) string {
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// In the worst case, the string can grow when mapped, making
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// things unpleasant. But it's so rare we barge in assuming it's
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// fine. It could also shrink but that falls out naturally.
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// The output buffer b is initialized on demand, the first
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// time a character differs.
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var b Builder
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for i, c := range s {
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r := mapping(c)
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if r == c && c != utf8.RuneError {
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continue
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}
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var width int
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if c == utf8.RuneError {
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c, width = utf8.DecodeRuneInString(s[i:])
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if width != 1 && r == c {
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continue
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}
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} else {
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width = utf8.RuneLen(c)
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}
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b.Grow(len(s) + utf8.UTFMax)
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b.WriteString(s[:i])
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if r >= 0 {
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b.WriteRune(r)
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}
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s = s[i+width:]
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break
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}
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// Fast path for unchanged input
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if b.Cap() == 0 { // didn't call b.Grow above
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return s
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}
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for _, c := range s {
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r := mapping(c)
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if r >= 0 {
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// common case
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// Due to inlining, it is more performant to determine if WriteByte should be
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// invoked rather than always call WriteRune
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if r < utf8.RuneSelf {
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b.WriteByte(byte(r))
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} else {
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// r is not an ASCII rune.
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b.WriteRune(r)
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}
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}
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}
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return b.String()
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}
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// According to static analysis, spaces, dashes, zeros, equals, and tabs
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// are the most commonly repeated string literal,
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// often used for display on fixed-width terminal windows.
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// Pre-declare constants for these for O(1) repetition in the common-case.
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const (
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repeatedSpaces = "" +
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" " +
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" "
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repeatedDashes = "" +
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"----------------------------------------------------------------" +
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"----------------------------------------------------------------"
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repeatedZeroes = "" +
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"0000000000000000000000000000000000000000000000000000000000000000"
|
|
repeatedEquals = "" +
|
|
"================================================================" +
|
|
"================================================================"
|
|
repeatedTabs = "" +
|
|
"\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t" +
|
|
"\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"
|
|
)
|
|
|
|
// Repeat returns a new string consisting of count copies of the string s.
|
|
//
|
|
// It panics if count is negative or if the result of (len(s) * count)
|
|
// overflows.
|
|
func Repeat(s string, count int) string {
|
|
switch count {
|
|
case 0:
|
|
return ""
|
|
case 1:
|
|
return s
|
|
}
|
|
|
|
// Since we cannot return an error on overflow,
|
|
// we should panic if the repeat will generate an overflow.
|
|
// See golang.org/issue/16237.
|
|
if count < 0 {
|
|
panic("strings: negative Repeat count")
|
|
}
|
|
if len(s) > maxInt/count {
|
|
panic("strings: Repeat output length overflow")
|
|
}
|
|
n := len(s) * count
|
|
|
|
if len(s) == 0 {
|
|
return ""
|
|
}
|
|
|
|
// Optimize for commonly repeated strings of relatively short length.
|
|
switch s[0] {
|
|
case ' ', '-', '0', '=', '\t':
|
|
switch {
|
|
case n <= len(repeatedSpaces) && HasPrefix(repeatedSpaces, s):
|
|
return repeatedSpaces[:n]
|
|
case n <= len(repeatedDashes) && HasPrefix(repeatedDashes, s):
|
|
return repeatedDashes[:n]
|
|
case n <= len(repeatedZeroes) && HasPrefix(repeatedZeroes, s):
|
|
return repeatedZeroes[:n]
|
|
case n <= len(repeatedEquals) && HasPrefix(repeatedEquals, s):
|
|
return repeatedEquals[:n]
|
|
case n <= len(repeatedTabs) && HasPrefix(repeatedTabs, s):
|
|
return repeatedTabs[:n]
|
|
}
|
|
}
|
|
|
|
// Past a certain chunk size it is counterproductive to use
|
|
// larger chunks as the source of the write, as when the source
|
|
// is too large we are basically just thrashing the CPU D-cache.
|
|
// So if the result length is larger than an empirically-found
|
|
// limit (8KB), we stop growing the source string once the limit
|
|
// is reached and keep reusing the same source string - that
|
|
// should therefore be always resident in the L1 cache - until we
|
|
// have completed the construction of the result.
|
|
// This yields significant speedups (up to +100%) in cases where
|
|
// the result length is large (roughly, over L2 cache size).
|
|
const chunkLimit = 8 * 1024
|
|
chunkMax := n
|
|
if n > chunkLimit {
|
|
chunkMax = chunkLimit / len(s) * len(s)
|
|
if chunkMax == 0 {
|
|
chunkMax = len(s)
|
|
}
|
|
}
|
|
|
|
var b Builder
|
|
b.Grow(n)
|
|
b.WriteString(s)
|
|
for b.Len() < n {
|
|
chunk := n - b.Len()
|
|
if chunk > b.Len() {
|
|
chunk = b.Len()
|
|
}
|
|
if chunk > chunkMax {
|
|
chunk = chunkMax
|
|
}
|
|
b.WriteString(b.String()[:chunk])
|
|
}
|
|
return b.String()
|
|
}
|
|
|
|
// ToUpper returns s with all Unicode letters mapped to their upper case.
|
|
func ToUpper(s string) string {
|
|
isASCII, hasLower := true, false
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if c >= utf8.RuneSelf {
|
|
isASCII = false
|
|
break
|
|
}
|
|
hasLower = hasLower || ('a' <= c && c <= 'z')
|
|
}
|
|
|
|
if isASCII { // optimize for ASCII-only strings.
|
|
if !hasLower {
|
|
return s
|
|
}
|
|
var (
|
|
b Builder
|
|
pos int
|
|
)
|
|
b.Grow(len(s))
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if 'a' <= c && c <= 'z' {
|
|
c -= 'a' - 'A'
|
|
if pos < i {
|
|
b.WriteString(s[pos:i])
|
|
}
|
|
b.WriteByte(c)
|
|
pos = i + 1
|
|
}
|
|
}
|
|
if pos < len(s) {
|
|
b.WriteString(s[pos:])
|
|
}
|
|
return b.String()
|
|
}
|
|
return Map(unicode.ToUpper, s)
|
|
}
|
|
|
|
// ToLower returns s with all Unicode letters mapped to their lower case.
|
|
func ToLower(s string) string {
|
|
isASCII, hasUpper := true, false
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if c >= utf8.RuneSelf {
|
|
isASCII = false
|
|
break
|
|
}
|
|
hasUpper = hasUpper || ('A' <= c && c <= 'Z')
|
|
}
|
|
|
|
if isASCII { // optimize for ASCII-only strings.
|
|
if !hasUpper {
|
|
return s
|
|
}
|
|
var (
|
|
b Builder
|
|
pos int
|
|
)
|
|
b.Grow(len(s))
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if 'A' <= c && c <= 'Z' {
|
|
c += 'a' - 'A'
|
|
if pos < i {
|
|
b.WriteString(s[pos:i])
|
|
}
|
|
b.WriteByte(c)
|
|
pos = i + 1
|
|
}
|
|
}
|
|
if pos < len(s) {
|
|
b.WriteString(s[pos:])
|
|
}
|
|
return b.String()
|
|
}
|
|
return Map(unicode.ToLower, s)
|
|
}
|
|
|
|
// ToTitle returns a copy of the string s with all Unicode letters mapped to
|
|
// their Unicode title case.
|
|
func ToTitle(s string) string { return Map(unicode.ToTitle, s) }
|
|
|
|
// ToUpperSpecial returns a copy of the string s with all Unicode letters mapped to their
|
|
// upper case using the case mapping specified by c.
|
|
func ToUpperSpecial(c unicode.SpecialCase, s string) string {
|
|
return Map(c.ToUpper, s)
|
|
}
|
|
|
|
// ToLowerSpecial returns a copy of the string s with all Unicode letters mapped to their
|
|
// lower case using the case mapping specified by c.
|
|
func ToLowerSpecial(c unicode.SpecialCase, s string) string {
|
|
return Map(c.ToLower, s)
|
|
}
|
|
|
|
// ToTitleSpecial returns a copy of the string s with all Unicode letters mapped to their
|
|
// Unicode title case, giving priority to the special casing rules.
|
|
func ToTitleSpecial(c unicode.SpecialCase, s string) string {
|
|
return Map(c.ToTitle, s)
|
|
}
|
|
|
|
// ToValidUTF8 returns a copy of the string s with each run of invalid UTF-8 byte sequences
|
|
// replaced by the replacement string, which may be empty.
|
|
func ToValidUTF8(s, replacement string) string {
|
|
var b Builder
|
|
|
|
for i, c := range s {
|
|
if c != utf8.RuneError {
|
|
continue
|
|
}
|
|
|
|
_, wid := utf8.DecodeRuneInString(s[i:])
|
|
if wid == 1 {
|
|
b.Grow(len(s) + len(replacement))
|
|
b.WriteString(s[:i])
|
|
s = s[i:]
|
|
break
|
|
}
|
|
}
|
|
|
|
// Fast path for unchanged input
|
|
if b.Cap() == 0 { // didn't call b.Grow above
|
|
return s
|
|
}
|
|
|
|
invalid := false // previous byte was from an invalid UTF-8 sequence
|
|
for i := 0; i < len(s); {
|
|
c := s[i]
|
|
if c < utf8.RuneSelf {
|
|
i++
|
|
invalid = false
|
|
b.WriteByte(c)
|
|
continue
|
|
}
|
|
_, wid := utf8.DecodeRuneInString(s[i:])
|
|
if wid == 1 {
|
|
i++
|
|
if !invalid {
|
|
invalid = true
|
|
b.WriteString(replacement)
|
|
}
|
|
continue
|
|
}
|
|
invalid = false
|
|
b.WriteString(s[i : i+wid])
|
|
i += wid
|
|
}
|
|
|
|
return b.String()
|
|
}
|
|
|
|
// isSeparator reports whether the rune could mark a word boundary.
|
|
// TODO: update when package unicode captures more of the properties.
|
|
func isSeparator(r rune) bool {
|
|
// ASCII alphanumerics and underscore are not separators
|
|
if r <= 0x7F {
|
|
switch {
|
|
case '0' <= r && r <= '9':
|
|
return false
|
|
case 'a' <= r && r <= 'z':
|
|
return false
|
|
case 'A' <= r && r <= 'Z':
|
|
return false
|
|
case r == '_':
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
// Letters and digits are not separators
|
|
if unicode.IsLetter(r) || unicode.IsDigit(r) {
|
|
return false
|
|
}
|
|
// Otherwise, all we can do for now is treat spaces as separators.
|
|
return unicode.IsSpace(r)
|
|
}
|
|
|
|
// Title returns a copy of the string s with all Unicode letters that begin words
|
|
// mapped to their Unicode title case.
|
|
//
|
|
// Deprecated: The rule Title uses for word boundaries does not handle Unicode
|
|
// punctuation properly. Use golang.org/x/text/cases instead.
|
|
func Title(s string) string {
|
|
// Use a closure here to remember state.
|
|
// Hackish but effective. Depends on Map scanning in order and calling
|
|
// the closure once per rune.
|
|
prev := ' '
|
|
return Map(
|
|
func(r rune) rune {
|
|
if isSeparator(prev) {
|
|
prev = r
|
|
return unicode.ToTitle(r)
|
|
}
|
|
prev = r
|
|
return r
|
|
},
|
|
s)
|
|
}
|
|
|
|
// TrimLeftFunc returns a slice of the string s with all leading
|
|
// Unicode code points c satisfying f(c) removed.
|
|
func TrimLeftFunc(s string, f func(rune) bool) string {
|
|
i := indexFunc(s, f, false)
|
|
if i == -1 {
|
|
return ""
|
|
}
|
|
return s[i:]
|
|
}
|
|
|
|
// TrimRightFunc returns a slice of the string s with all trailing
|
|
// Unicode code points c satisfying f(c) removed.
|
|
func TrimRightFunc(s string, f func(rune) bool) string {
|
|
i := lastIndexFunc(s, f, false)
|
|
if i >= 0 && s[i] >= utf8.RuneSelf {
|
|
_, wid := utf8.DecodeRuneInString(s[i:])
|
|
i += wid
|
|
} else {
|
|
i++
|
|
}
|
|
return s[0:i]
|
|
}
|
|
|
|
// TrimFunc returns a slice of the string s with all leading
|
|
// and trailing Unicode code points c satisfying f(c) removed.
|
|
func TrimFunc(s string, f func(rune) bool) string {
|
|
return TrimRightFunc(TrimLeftFunc(s, f), f)
|
|
}
|
|
|
|
// IndexFunc returns the index into s of the first Unicode
|
|
// code point satisfying f(c), or -1 if none do.
|
|
func IndexFunc(s string, f func(rune) bool) int {
|
|
return indexFunc(s, f, true)
|
|
}
|
|
|
|
// LastIndexFunc returns the index into s of the last
|
|
// Unicode code point satisfying f(c), or -1 if none do.
|
|
func LastIndexFunc(s string, f func(rune) bool) int {
|
|
return lastIndexFunc(s, f, true)
|
|
}
|
|
|
|
// indexFunc is the same as IndexFunc except that if
|
|
// truth==false, the sense of the predicate function is
|
|
// inverted.
|
|
func indexFunc(s string, f func(rune) bool, truth bool) int {
|
|
for i, r := range s {
|
|
if f(r) == truth {
|
|
return i
|
|
}
|
|
}
|
|
return -1
|
|
}
|
|
|
|
// lastIndexFunc is the same as LastIndexFunc except that if
|
|
// truth==false, the sense of the predicate function is
|
|
// inverted.
|
|
func lastIndexFunc(s string, f func(rune) bool, truth bool) int {
|
|
for i := len(s); i > 0; {
|
|
r, size := utf8.DecodeLastRuneInString(s[0:i])
|
|
i -= size
|
|
if f(r) == truth {
|
|
return i
|
|
}
|
|
}
|
|
return -1
|
|
}
|
|
|
|
// asciiSet is a 32-byte value, where each bit represents the presence of a
|
|
// given ASCII character in the set. The 128-bits of the lower 16 bytes,
|
|
// starting with the least-significant bit of the lowest word to the
|
|
// most-significant bit of the highest word, map to the full range of all
|
|
// 128 ASCII characters. The 128-bits of the upper 16 bytes will be zeroed,
|
|
// ensuring that any non-ASCII character will be reported as not in the set.
|
|
// This allocates a total of 32 bytes even though the upper half
|
|
// is unused to avoid bounds checks in asciiSet.contains.
|
|
type asciiSet [8]uint32
|
|
|
|
// makeASCIISet creates a set of ASCII characters and reports whether all
|
|
// characters in chars are ASCII.
|
|
func makeASCIISet(chars string) (as asciiSet, ok bool) {
|
|
for i := 0; i < len(chars); i++ {
|
|
c := chars[i]
|
|
if c >= utf8.RuneSelf {
|
|
return as, false
|
|
}
|
|
as[c/32] |= 1 << (c % 32)
|
|
}
|
|
return as, true
|
|
}
|
|
|
|
// contains reports whether c is inside the set.
|
|
func (as *asciiSet) contains(c byte) bool {
|
|
return (as[c/32] & (1 << (c % 32))) != 0
|
|
}
|
|
|
|
// Trim returns a slice of the string s with all leading and
|
|
// trailing Unicode code points contained in cutset removed.
|
|
func Trim(s, cutset string) string {
|
|
if s == "" || cutset == "" {
|
|
return s
|
|
}
|
|
if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
|
|
return trimLeftByte(trimRightByte(s, cutset[0]), cutset[0])
|
|
}
|
|
if as, ok := makeASCIISet(cutset); ok {
|
|
return trimLeftASCII(trimRightASCII(s, &as), &as)
|
|
}
|
|
return trimLeftUnicode(trimRightUnicode(s, cutset), cutset)
|
|
}
|
|
|
|
// TrimLeft returns a slice of the string s with all leading
|
|
// Unicode code points contained in cutset removed.
|
|
//
|
|
// To remove a prefix, use [TrimPrefix] instead.
|
|
func TrimLeft(s, cutset string) string {
|
|
if s == "" || cutset == "" {
|
|
return s
|
|
}
|
|
if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
|
|
return trimLeftByte(s, cutset[0])
|
|
}
|
|
if as, ok := makeASCIISet(cutset); ok {
|
|
return trimLeftASCII(s, &as)
|
|
}
|
|
return trimLeftUnicode(s, cutset)
|
|
}
|
|
|
|
func trimLeftByte(s string, c byte) string {
|
|
for len(s) > 0 && s[0] == c {
|
|
s = s[1:]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimLeftASCII(s string, as *asciiSet) string {
|
|
for len(s) > 0 {
|
|
if !as.contains(s[0]) {
|
|
break
|
|
}
|
|
s = s[1:]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimLeftUnicode(s, cutset string) string {
|
|
for len(s) > 0 {
|
|
r, n := rune(s[0]), 1
|
|
if r >= utf8.RuneSelf {
|
|
r, n = utf8.DecodeRuneInString(s)
|
|
}
|
|
if !ContainsRune(cutset, r) {
|
|
break
|
|
}
|
|
s = s[n:]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// TrimRight returns a slice of the string s, with all trailing
|
|
// Unicode code points contained in cutset removed.
|
|
//
|
|
// To remove a suffix, use [TrimSuffix] instead.
|
|
func TrimRight(s, cutset string) string {
|
|
if s == "" || cutset == "" {
|
|
return s
|
|
}
|
|
if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
|
|
return trimRightByte(s, cutset[0])
|
|
}
|
|
if as, ok := makeASCIISet(cutset); ok {
|
|
return trimRightASCII(s, &as)
|
|
}
|
|
return trimRightUnicode(s, cutset)
|
|
}
|
|
|
|
func trimRightByte(s string, c byte) string {
|
|
for len(s) > 0 && s[len(s)-1] == c {
|
|
s = s[:len(s)-1]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimRightASCII(s string, as *asciiSet) string {
|
|
for len(s) > 0 {
|
|
if !as.contains(s[len(s)-1]) {
|
|
break
|
|
}
|
|
s = s[:len(s)-1]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimRightUnicode(s, cutset string) string {
|
|
for len(s) > 0 {
|
|
r, n := rune(s[len(s)-1]), 1
|
|
if r >= utf8.RuneSelf {
|
|
r, n = utf8.DecodeLastRuneInString(s)
|
|
}
|
|
if !ContainsRune(cutset, r) {
|
|
break
|
|
}
|
|
s = s[:len(s)-n]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// TrimSpace returns a slice of the string s, with all leading
|
|
// and trailing white space removed, as defined by Unicode.
|
|
func TrimSpace(s string) string {
|
|
// Fast path for ASCII: look for the first ASCII non-space byte
|
|
start := 0
|
|
for ; start < len(s); start++ {
|
|
c := s[start]
|
|
if c >= utf8.RuneSelf {
|
|
// If we run into a non-ASCII byte, fall back to the
|
|
// slower unicode-aware method on the remaining bytes
|
|
return TrimFunc(s[start:], unicode.IsSpace)
|
|
}
|
|
if asciiSpace[c] == 0 {
|
|
break
|
|
}
|
|
}
|
|
|
|
// Now look for the first ASCII non-space byte from the end
|
|
stop := len(s)
|
|
for ; stop > start; stop-- {
|
|
c := s[stop-1]
|
|
if c >= utf8.RuneSelf {
|
|
// start has been already trimmed above, should trim end only
|
|
return TrimRightFunc(s[start:stop], unicode.IsSpace)
|
|
}
|
|
if asciiSpace[c] == 0 {
|
|
break
|
|
}
|
|
}
|
|
|
|
// At this point s[start:stop] starts and ends with an ASCII
|
|
// non-space bytes, so we're done. Non-ASCII cases have already
|
|
// been handled above.
|
|
return s[start:stop]
|
|
}
|
|
|
|
// TrimPrefix returns s without the provided leading prefix string.
|
|
// If s doesn't start with prefix, s is returned unchanged.
|
|
func TrimPrefix(s, prefix string) string {
|
|
return stringslite.TrimPrefix(s, prefix)
|
|
}
|
|
|
|
// TrimSuffix returns s without the provided trailing suffix string.
|
|
// If s doesn't end with suffix, s is returned unchanged.
|
|
func TrimSuffix(s, suffix string) string {
|
|
return stringslite.TrimSuffix(s, suffix)
|
|
}
|
|
|
|
// Replace returns a copy of the string s with the first n
|
|
// non-overlapping instances of old replaced by new.
|
|
// If old is empty, it matches at the beginning of the string
|
|
// and after each UTF-8 sequence, yielding up to k+1 replacements
|
|
// for a k-rune string.
|
|
// If n < 0, there is no limit on the number of replacements.
|
|
func Replace(s, old, new string, n int) string {
|
|
if old == new || n == 0 {
|
|
return s // avoid allocation
|
|
}
|
|
|
|
// Compute number of replacements.
|
|
if m := Count(s, old); m == 0 {
|
|
return s // avoid allocation
|
|
} else if n < 0 || m < n {
|
|
n = m
|
|
}
|
|
|
|
// Apply replacements to buffer.
|
|
var b Builder
|
|
b.Grow(len(s) + n*(len(new)-len(old)))
|
|
start := 0
|
|
for i := 0; i < n; i++ {
|
|
j := start
|
|
if len(old) == 0 {
|
|
if i > 0 {
|
|
_, wid := utf8.DecodeRuneInString(s[start:])
|
|
j += wid
|
|
}
|
|
} else {
|
|
j += Index(s[start:], old)
|
|
}
|
|
b.WriteString(s[start:j])
|
|
b.WriteString(new)
|
|
start = j + len(old)
|
|
}
|
|
b.WriteString(s[start:])
|
|
return b.String()
|
|
}
|
|
|
|
// ReplaceAll returns a copy of the string s with all
|
|
// non-overlapping instances of old replaced by new.
|
|
// If old is empty, it matches at the beginning of the string
|
|
// and after each UTF-8 sequence, yielding up to k+1 replacements
|
|
// for a k-rune string.
|
|
func ReplaceAll(s, old, new string) string {
|
|
return Replace(s, old, new, -1)
|
|
}
|
|
|
|
// EqualFold reports whether s and t, interpreted as UTF-8 strings,
|
|
// are equal under simple Unicode case-folding, which is a more general
|
|
// form of case-insensitivity.
|
|
func EqualFold(s, t string) bool {
|
|
// ASCII fast path
|
|
i := 0
|
|
for ; i < len(s) && i < len(t); i++ {
|
|
sr := s[i]
|
|
tr := t[i]
|
|
if sr|tr >= utf8.RuneSelf {
|
|
goto hasUnicode
|
|
}
|
|
|
|
// Easy case.
|
|
if tr == sr {
|
|
continue
|
|
}
|
|
|
|
// Make sr < tr to simplify what follows.
|
|
if tr < sr {
|
|
tr, sr = sr, tr
|
|
}
|
|
// ASCII only, sr/tr must be upper/lower case
|
|
if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' {
|
|
continue
|
|
}
|
|
return false
|
|
}
|
|
// Check if we've exhausted both strings.
|
|
return len(s) == len(t)
|
|
|
|
hasUnicode:
|
|
s = s[i:]
|
|
t = t[i:]
|
|
for _, sr := range s {
|
|
// If t is exhausted the strings are not equal.
|
|
if len(t) == 0 {
|
|
return false
|
|
}
|
|
|
|
// Extract first rune from second string.
|
|
var tr rune
|
|
if t[0] < utf8.RuneSelf {
|
|
tr, t = rune(t[0]), t[1:]
|
|
} else {
|
|
r, size := utf8.DecodeRuneInString(t)
|
|
tr, t = r, t[size:]
|
|
}
|
|
|
|
// If they match, keep going; if not, return false.
|
|
|
|
// Easy case.
|
|
if tr == sr {
|
|
continue
|
|
}
|
|
|
|
// Make sr < tr to simplify what follows.
|
|
if tr < sr {
|
|
tr, sr = sr, tr
|
|
}
|
|
// Fast check for ASCII.
|
|
if tr < utf8.RuneSelf {
|
|
// ASCII only, sr/tr must be upper/lower case
|
|
if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' {
|
|
continue
|
|
}
|
|
return false
|
|
}
|
|
|
|
// General case. SimpleFold(x) returns the next equivalent rune > x
|
|
// or wraps around to smaller values.
|
|
r := unicode.SimpleFold(sr)
|
|
for r != sr && r < tr {
|
|
r = unicode.SimpleFold(r)
|
|
}
|
|
if r == tr {
|
|
continue
|
|
}
|
|
return false
|
|
}
|
|
|
|
// First string is empty, so check if the second one is also empty.
|
|
return len(t) == 0
|
|
}
|
|
|
|
// 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 {
|
|
return stringslite.Index(s, substr)
|
|
}
|
|
|
|
// Cut slices s around the first instance of sep,
|
|
// returning the text before and after sep.
|
|
// The found result reports whether sep appears in s.
|
|
// If sep does not appear in s, cut returns s, "", false.
|
|
func Cut(s, sep string) (before, after string, found bool) {
|
|
return stringslite.Cut(s, sep)
|
|
}
|
|
|
|
// CutPrefix returns s without the provided leading prefix string
|
|
// and reports whether it found the prefix.
|
|
// If s doesn't start with prefix, CutPrefix returns s, false.
|
|
// If prefix is the empty string, CutPrefix returns s, true.
|
|
func CutPrefix(s, prefix string) (after string, found bool) {
|
|
return stringslite.CutPrefix(s, prefix)
|
|
}
|
|
|
|
// CutSuffix returns s without the provided ending suffix string
|
|
// and reports whether it found the suffix.
|
|
// If s doesn't end with suffix, CutSuffix returns s, false.
|
|
// If suffix is the empty string, CutSuffix returns s, true.
|
|
func CutSuffix(s, suffix string) (before string, found bool) {
|
|
return stringslite.CutSuffix(s, suffix)
|
|
}
|