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// Copyright 2019 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package compare
import (
"strings"
"unicode"
"unicode/utf8"
)
// Strings returns an integer comparing two strings lexicographically.
func Strings(s, t string) int {
c := compareFold(s, t)
if c == 0 {
// "B" and "b" would be the same so we need a tiebreaker.
return strings.Compare(s, t)
}
return c
}
// This function is derived from strings.EqualFold in Go's stdlib.
// https://github.com/golang/go/blob/ad4a58e31501bce5de2aad90a620eaecdc1eecb8/src/strings/strings.go#L893
func compareFold(s, t string) int {
for s != "" && t != "" {
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 tr == sr {
continue
}
c := 1
if tr < sr {
tr, sr = sr, tr
c = -c
}
// ASCII only.
if tr < utf8.RuneSelf {
if sr >= 'A' && sr <= 'Z' {
if tr <= 'Z' {
// Same case.
return -c
}
diff := tr - (sr + 'a' - 'A')
if diff == 0 {
continue
}
if diff < 0 {
return c
}
if diff > 0 {
return -c
}
}
}
// Unicode.
r := unicode.SimpleFold(sr)
for r != sr && r < tr {
r = unicode.SimpleFold(r)
}
if r == tr {
continue
}
return -c
}
if s == "" && t == "" {
return 0
}
if s == "" {
return -1
}
return 1
}
// LessStrings returns whether s is less than t lexicographically.
func LessStrings(s, t string) bool {
return Strings(s, t) < 0
}
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