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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package str provides string manipulation utilities.
package str
import (
"fmt"
"strings"
"unicode"
"unicode/utf8"
)
// StringList flattens its arguments into a single []string.
// Each argument in args must have type string or []string.
func StringList(args ...any) []string {
var x []string
for _, arg := range args {
switch arg := arg.(type) {
case []string:
x = append(x, arg...)
case string:
x = append(x, arg)
default:
panic("stringList: invalid argument of type " + fmt.Sprintf("%T", arg))
}
}
return x
}
// ToFold returns a string with the property that
//
// strings.EqualFold(s, t) iff ToFold(s) == ToFold(t)
//
// This lets us test a large set of strings for fold-equivalent
// duplicates without making a quadratic number of calls
// to EqualFold. Note that strings.ToUpper and strings.ToLower
// do not have the desired property in some corner cases.
func ToFold(s string) string {
// Fast path: all ASCII, no upper case.
// Most paths look like this already.
for i := 0; i < len(s); i++ {
c := s[i]
if c >= utf8.RuneSelf || 'A' <= c && c <= 'Z' {
goto Slow
}
}
return s
Slow:
var b strings.Builder
for _, r := range s {
// SimpleFold(x) cycles to the next equivalent rune > x
// or wraps around to smaller values. Iterate until it wraps,
// and we've found the minimum value.
for {
r0 := r
r = unicode.SimpleFold(r0)
if r <= r0 {
break
}
}
// Exception to allow fast path above: A-Z => a-z
if 'A' <= r && r <= 'Z' {
r += 'a' - 'A'
}
b.WriteRune(r)
}
return b.String()
}
// FoldDup reports a pair of strings from the list that are
// equal according to strings.EqualFold.
// It returns "", "" if there are no such strings.
func FoldDup(list []string) (string, string) {
clash := map[string]string{}
for _, s := range list {
fold := ToFold(s)
if t := clash[fold]; t != "" {
if s > t {
s, t = t, s
}
return s, t
}
clash[fold] = s
}
return "", ""
}
// Contains reports whether x contains s.
func Contains(x []string, s string) bool {
for _, t := range x {
if t == s {
return true
}
}
return false
}
// Uniq removes consecutive duplicate strings from ss.
func Uniq(ss *[]string) {
if len(*ss) <= 1 {
return
}
uniq := (*ss)[:1]
for _, s := range *ss {
if s != uniq[len(uniq)-1] {
uniq = append(uniq, s)
}
}
*ss = uniq
}
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