mirror of
https://github.com/autc04/Retro68.git
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726 lines
18 KiB
Go
726 lines
18 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 strings.
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package strings
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import (
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"unicode"
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"unicode/utf8"
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)
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// explode splits s into an array of UTF-8 sequences, one per Unicode character (still strings) up to a maximum of n (n < 0 means no limit).
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// Invalid UTF-8 sequences become correct encodings of U+FFF8.
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func explode(s string, n int) []string {
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if n == 0 {
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return nil
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}
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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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var size int
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var ch rune
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i, cur := 0, 0
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for ; i+1 < n; i++ {
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ch, size = utf8.DecodeRuneInString(s[cur:])
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if ch == utf8.RuneError {
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a[i] = string(utf8.RuneError)
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} else {
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a[i] = s[cur : cur+size]
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}
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cur += size
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}
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// add the rest, if there is any
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if cur < len(s) {
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a[i] = s[cur:]
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}
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return a
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}
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// primeRK is the prime base used in Rabin-Karp algorithm.
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const primeRK = 16777619
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// hashstr returns the hash and the appropriate multiplicative
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// factor for use in Rabin-Karp algorithm.
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func hashstr(sep string) (uint32, uint32) {
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hash := uint32(0)
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for i := 0; i < len(sep); i++ {
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hash = hash*primeRK + uint32(sep[i])
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}
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var pow, sq uint32 = 1, primeRK
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for i := len(sep); i > 0; i >>= 1 {
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if i&1 != 0 {
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pow *= sq
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}
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sq *= sq
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}
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return hash, pow
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}
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// Count counts the number of non-overlapping instances of sep in s.
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func Count(s, sep string) int {
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n := 0
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// special cases
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switch {
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case len(sep) == 0:
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return utf8.RuneCountInString(s) + 1
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case len(sep) == 1:
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// special case worth making fast
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c := sep[0]
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for i := 0; i < len(s); i++ {
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if s[i] == c {
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n++
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}
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}
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return n
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case len(sep) > len(s):
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return 0
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case len(sep) == len(s):
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if sep == s {
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return 1
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}
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return 0
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}
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hashsep, pow := hashstr(sep)
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h := uint32(0)
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for i := 0; i < len(sep); i++ {
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h = h*primeRK + uint32(s[i])
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}
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lastmatch := 0
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if h == hashsep && s[:len(sep)] == sep {
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n++
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lastmatch = len(sep)
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}
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for i := len(sep); i < len(s); {
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h *= primeRK
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h += uint32(s[i])
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h -= pow * uint32(s[i-len(sep)])
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i++
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if h == hashsep && lastmatch <= i-len(sep) && s[i-len(sep):i] == sep {
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n++
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lastmatch = i
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}
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}
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return n
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}
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// Contains returns true if 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 returns true if 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 returns true if 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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// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
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func Index(s, sep string) int {
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n := len(sep)
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switch {
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case n == 0:
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return 0
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case n == 1:
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return IndexByte(s, sep[0])
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case n == len(s):
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if sep == 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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// Hash sep.
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hashsep, pow := hashstr(sep)
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var h uint32
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for i := 0; i < n; i++ {
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h = h*primeRK + uint32(s[i])
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}
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if h == hashsep && s[:n] == sep {
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return 0
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}
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for i := n; i < len(s); {
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h *= primeRK
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h += uint32(s[i])
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h -= pow * uint32(s[i-n])
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i++
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if h == hashsep && s[i-n:i] == sep {
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return i - n
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}
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}
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return -1
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}
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// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
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func LastIndex(s, sep string) int {
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n := len(sep)
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if n == 0 {
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return len(s)
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}
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c := sep[0]
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if n == 1 {
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// special case worth making fast
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for i := len(s) - 1; i >= 0; i-- {
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if s[i] == c {
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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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// n > 1
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for i := len(s) - n; i >= 0; i-- {
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if s[i] == c && s[i:i+n] == sep {
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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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// 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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func IndexRune(s string, r rune) int {
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switch {
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case r < 0x80:
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b := byte(r)
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for i := 0; i < len(s); i++ {
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if s[i] == b {
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return i
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}
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}
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default:
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for i, c := range s {
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if c == r {
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return i
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}
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}
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}
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return -1
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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 len(chars) > 0 {
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for i, c := range s {
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for _, m := range chars {
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if c == m {
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return i
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}
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}
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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 len(chars) > 0 {
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for i := len(s); i > 0; {
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rune, size := utf8.DecodeLastRuneInString(s[0:i])
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i -= size
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for _, m := range chars {
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if rune == m {
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return i
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}
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}
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}
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}
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return -1
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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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c := sep[0]
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start := 0
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a := make([]string, n)
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na := 0
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for i := 0; i+len(sep) <= len(s) && na+1 < n; i++ {
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if s[i] == c && (len(sep) == 1 || s[i:i+len(sep)] == sep) {
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a[na] = s[start : i+sepSave]
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na++
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start = i + len(sep)
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i += len(sep) - 1
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}
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}
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a[na] = s[start:]
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return a[0 : na+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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// If sep is empty, SplitN splits after each UTF-8 sequence.
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// The count determines the number of substrings to return:
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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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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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// If sep is empty, SplitAfterN splits after each UTF-8 sequence.
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// The count determines the number of substrings to return:
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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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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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// If sep is empty, Split splits after each UTF-8 sequence.
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// It is equivalent to SplitN with a count of -1.
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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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// If sep is empty, SplitAfter splits after each UTF-8 sequence.
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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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// 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 an array of substrings of s or an
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// empty list if s contains only white space.
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func Fields(s string) []string {
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return FieldsFunc(s, unicode.IsSpace)
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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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func FieldsFunc(s string, f func(rune) bool) []string {
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// First count the fields.
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n := 0
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inField := false
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for _, rune := range s {
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wasInField := inField
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inField = !f(rune)
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if inField && !wasInField {
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n++
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}
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}
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// Now create them.
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a := make([]string, n)
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na := 0
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fieldStart := -1 // Set to -1 when looking for start of field.
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for i, rune := range s {
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if f(rune) {
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if fieldStart >= 0 {
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a[na] = s[fieldStart:i]
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na++
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fieldStart = -1
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}
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} else if fieldStart == -1 {
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fieldStart = i
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}
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}
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if fieldStart >= 0 { // 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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// Join concatenates the elements of a to create a single string. The separator string
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// sep is placed between elements in the resulting string.
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func Join(a []string, sep string) string {
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if len(a) == 0 {
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return ""
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}
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if len(a) == 1 {
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return a[0]
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}
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n := len(sep) * (len(a) - 1)
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for i := 0; i < len(a); i++ {
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n += len(a[i])
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}
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b := make([]byte, n)
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bp := copy(b, a[0])
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for _, s := range a[1:] {
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bp += copy(b[bp:], sep)
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bp += copy(b[bp:], s)
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}
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return string(b)
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}
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// HasPrefix tests whether the string s begins with prefix.
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func HasPrefix(s, prefix string) bool {
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return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
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}
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// HasSuffix tests whether the string s ends with suffix.
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func HasSuffix(s, suffix string) bool {
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return len(s) >= len(suffix) && s[len(s)-len(suffix):] == 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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maxbytes := len(s) // length of b
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nbytes := 0 // number of bytes encoded in b
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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 []byte
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for i, c := range s {
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r := mapping(c)
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if b == nil {
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if r == c {
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continue
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}
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b = make([]byte, maxbytes)
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nbytes = copy(b, s[:i])
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}
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if r >= 0 {
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wid := 1
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if r >= utf8.RuneSelf {
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wid = utf8.RuneLen(r)
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}
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if nbytes+wid > maxbytes {
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// Grow the buffer.
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maxbytes = maxbytes*2 + utf8.UTFMax
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nb := make([]byte, maxbytes)
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copy(nb, b[0:nbytes])
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b = nb
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}
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nbytes += utf8.EncodeRune(b[nbytes:maxbytes], r)
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}
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}
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if b == nil {
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return s
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}
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return string(b[0:nbytes])
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}
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// Repeat returns a new string consisting of count copies of the string s.
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func Repeat(s string, count int) string {
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b := make([]byte, len(s)*count)
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bp := 0
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for i := 0; i < count; i++ {
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bp += copy(b[bp:], s)
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}
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return string(b)
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}
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// ToUpper returns a copy of the string s with all Unicode letters mapped to their upper case.
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func ToUpper(s string) string { return Map(unicode.ToUpper, s) }
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// ToLower returns a copy of the string s with all Unicode letters mapped to their lower case.
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func ToLower(s string) string { return Map(unicode.ToLower, s) }
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// ToTitle returns a copy of the string s with all Unicode letters mapped to their title case.
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func ToTitle(s string) string { return Map(unicode.ToTitle, s) }
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// ToUpperSpecial returns a copy of the string s with all Unicode letters mapped to their
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// upper case, giving priority to the special casing rules.
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func ToUpperSpecial(_case unicode.SpecialCase, s string) string {
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return Map(func(r rune) rune { return _case.ToUpper(r) }, s)
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}
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// ToLowerSpecial returns a copy of the string s with all Unicode letters mapped to their
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// lower case, giving priority to the special casing rules.
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func ToLowerSpecial(_case unicode.SpecialCase, s string) string {
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return Map(func(r rune) rune { return _case.ToLower(r) }, s)
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}
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// ToTitleSpecial returns a copy of the string s with all Unicode letters mapped to their
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// title case, giving priority to the special casing rules.
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func ToTitleSpecial(_case unicode.SpecialCase, s string) string {
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return Map(func(r rune) rune { return _case.ToTitle(r) }, s)
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}
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// isSeparator reports whether the rune could mark a word boundary.
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// TODO: update when package unicode captures more of the properties.
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func isSeparator(r rune) bool {
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// ASCII alphanumerics and underscore are not separators
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if r <= 0x7F {
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switch {
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case '0' <= r && r <= '9':
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return false
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case 'a' <= r && r <= 'z':
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return false
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case 'A' <= r && r <= 'Z':
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return false
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case r == '_':
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return false
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}
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return true
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}
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// Letters and digits are not separators
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if unicode.IsLetter(r) || unicode.IsDigit(r) {
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return false
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}
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// Otherwise, all we can do for now is treat spaces as separators.
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return unicode.IsSpace(r)
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}
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// Title returns a copy of the string s with all Unicode letters that begin words
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// mapped to their title case.
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//
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// BUG: The rule Title uses for word boundaries does not handle Unicode punctuation properly.
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func Title(s string) string {
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// Use a closure here to remember state.
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// Hackish but effective. Depends on Map scanning in order and calling
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// the closure once per rune.
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prev := ' '
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return Map(
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func(r rune) rune {
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if isSeparator(prev) {
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prev = r
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return unicode.ToTitle(r)
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}
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prev = r
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return r
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},
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s)
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}
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// TrimLeftFunc returns a slice of the string s with all leading
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// Unicode code points c satisfying f(c) removed.
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func TrimLeftFunc(s string, f func(rune) bool) string {
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i := indexFunc(s, f, false)
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if i == -1 {
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return ""
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}
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return s[i:]
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}
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// TrimRightFunc returns a slice of the string s with all trailing
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// Unicode code points c satisfying f(c) removed.
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func TrimRightFunc(s string, f func(rune) bool) string {
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i := lastIndexFunc(s, f, false)
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if i >= 0 && s[i] >= utf8.RuneSelf {
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_, wid := utf8.DecodeRuneInString(s[i:])
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i += wid
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} else {
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i++
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}
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return s[0:i]
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}
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|
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// TrimFunc returns a slice of the string s with all leading
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// and trailing Unicode code points c satisfying f(c) removed.
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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 {
|
|
start := 0
|
|
for start < len(s) {
|
|
wid := 1
|
|
r := rune(s[start])
|
|
if r >= utf8.RuneSelf {
|
|
r, wid = utf8.DecodeRuneInString(s[start:])
|
|
}
|
|
if f(r) == truth {
|
|
return start
|
|
}
|
|
start += wid
|
|
}
|
|
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
|
|
}
|
|
|
|
func makeCutsetFunc(cutset string) func(rune) bool {
|
|
return func(r rune) bool { return IndexRune(cutset, r) >= 0 }
|
|
}
|
|
|
|
// Trim returns a slice of the string s with all leading and
|
|
// trailing Unicode code points contained in cutset removed.
|
|
func Trim(s string, cutset string) string {
|
|
if s == "" || cutset == "" {
|
|
return s
|
|
}
|
|
return TrimFunc(s, makeCutsetFunc(cutset))
|
|
}
|
|
|
|
// TrimLeft returns a slice of the string s with all leading
|
|
// Unicode code points contained in cutset removed.
|
|
func TrimLeft(s string, cutset string) string {
|
|
if s == "" || cutset == "" {
|
|
return s
|
|
}
|
|
return TrimLeftFunc(s, makeCutsetFunc(cutset))
|
|
}
|
|
|
|
// TrimRight returns a slice of the string s, with all trailing
|
|
// Unicode code points contained in cutset removed.
|
|
func TrimRight(s string, cutset string) string {
|
|
if s == "" || cutset == "" {
|
|
return s
|
|
}
|
|
return TrimRightFunc(s, makeCutsetFunc(cutset))
|
|
}
|
|
|
|
// 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 {
|
|
return TrimFunc(s, unicode.IsSpace)
|
|
}
|
|
|
|
// 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 {
|
|
if HasPrefix(s, prefix) {
|
|
return s[len(prefix):]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// 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 {
|
|
if HasSuffix(s, suffix) {
|
|
return s[:len(s)-len(suffix)]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// Replace returns a copy of the string s with the first n
|
|
// non-overlapping instances of old replaced by new.
|
|
// 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.
|
|
t := make([]byte, len(s)+n*(len(new)-len(old)))
|
|
w := 0
|
|
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)
|
|
}
|
|
w += copy(t[w:], s[start:j])
|
|
w += copy(t[w:], new)
|
|
start = j + len(old)
|
|
}
|
|
w += copy(t[w:], s[start:])
|
|
return string(t[0:w])
|
|
}
|
|
|
|
// EqualFold reports whether s and t, interpreted as UTF-8 strings,
|
|
// are equal under Unicode case-folding.
|
|
func EqualFold(s, t string) bool {
|
|
for s != "" && t != "" {
|
|
// Extract first rune from each string.
|
|
var sr, tr rune
|
|
if s[0] < utf8.RuneSelf {
|
|
sr, s = rune(s[0]), s[1:]
|
|
} else {
|
|
r, size := utf8.DecodeRuneInString(s)
|
|
sr, s = r, s[size:]
|
|
}
|
|
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 && 'A' <= sr && sr <= 'Z' {
|
|
// ASCII, and sr is upper case. tr must be lower case.
|
|
if 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
|
|
}
|
|
|
|
// One string is empty. Are both?
|
|
return s == t
|
|
}
|