137 lines
2.7 KiB
Go
137 lines
2.7 KiB
Go
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/*
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* Copyright 2014 Google Inc. 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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*
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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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*/
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// Package natsort provides an implementation of the natural sorting algorithm.
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// See http://blog.codinghorror.com/sorting-for-humans-natural-sort-order/.
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package natsort
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import (
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"errors"
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"sort"
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)
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// Strings sorts a slice of strings with Less.
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func Strings(s []string) {
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sort.Sort(stringSlice(s))
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}
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// Less reports whether s is less than t.
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func Less(s, t string) bool {
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return LessRunes([]rune(s), []rune(t))
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}
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// LessRunes reports whether s is less than t.
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func LessRunes(s, t []rune) bool {
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nprefix := commonPrefix(s, t)
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if len(s) == nprefix && len(t) == nprefix {
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// equal
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return false
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}
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sEnd := leadDigits(s[nprefix:]) + nprefix
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tEnd := leadDigits(t[nprefix:]) + nprefix
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if sEnd > nprefix || tEnd > nprefix {
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start := trailDigits(s[:nprefix])
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if sEnd-start > 0 && tEnd-start > 0 {
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// TODO(light): log errors?
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sn := atoi(s[start:sEnd])
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tn := atoi(t[start:tEnd])
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if sn != tn {
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return sn < tn
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}
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}
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}
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switch {
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case len(s) == nprefix:
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return true
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case len(t) == nprefix:
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return false
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default:
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return s[nprefix] < t[nprefix]
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}
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}
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func isDigit(r rune) bool {
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return '0' <= r && r <= '9'
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}
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func atoi(r []rune) uint64 {
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if len(r) < 1 {
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panic(errors.New("atoi got an empty slice"))
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}
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const cutoff = uint64((1<<64-1)/10 + 1)
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const maxVal = 1<<64 - 1
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var n uint64
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for _, d := range r {
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v := uint64(d - '0')
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if n >= cutoff {
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return 1<<64 - 1
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}
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n *= 10
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n1 := n + v
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if n1 < n || n1 > maxVal {
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// n+v overflows
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return 1<<64 - 1
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}
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n = n1
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}
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return n
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}
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func commonPrefix(s, t []rune) int {
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for i := range s {
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if i >= len(t) {
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return len(t)
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}
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if s[i] != t[i] {
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return i
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}
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}
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return len(s)
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}
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func trailDigits(r []rune) int {
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for i := len(r) - 1; i >= 0; i-- {
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if !isDigit(r[i]) {
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return i + 1
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}
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}
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return 0
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}
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func leadDigits(r []rune) int {
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for i := range r {
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if !isDigit(r[i]) {
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return i
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}
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}
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return len(r)
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}
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type stringSlice []string
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func (ss stringSlice) Len() int {
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return len(ss)
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}
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func (ss stringSlice) Less(i, j int) bool {
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return Less(ss[i], ss[j])
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}
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func (ss stringSlice) Swap(i, j int) {
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ss[i], ss[j] = ss[j], ss[i]
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}
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