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