mirror of https://github.com/gohugoio/hugo
126 lines
2.5 KiB
Go
126 lines
2.5 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 page
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import "sort"
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// Used in page binary search, the most common in front.
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var pageLessFunctions = []func(p1, p2 Page) bool{
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DefaultPageSort,
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lessPageDate,
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lessPagePubDate,
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lessPageTitle,
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lessPageLinkTitle,
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}
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func searchPage(p Page, pages Pages) int {
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if len(pages) < 1000 {
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// For smaller data sets, doing a linear search is faster.
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return searchPageLinear(p, pages, 0)
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}
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less := isPagesProbablySorted(pages, pageLessFunctions...)
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if less == nil {
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return searchPageLinear(p, pages, 0)
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}
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i := searchPageBinary(p, pages, less)
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if i != -1 {
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return i
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}
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return searchPageLinear(p, pages, 0)
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}
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func searchPageLinear(p Page, pages Pages, start int) int {
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for i := start; i < len(pages); i++ {
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c := pages[i]
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if c.Eq(p) {
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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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func searchPageBinary(p Page, pages Pages, less func(p1, p2 Page) bool) int {
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n := len(pages)
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f := func(i int) bool {
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c := pages[i]
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isLess := less(c, p)
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return !isLess || c.Eq(p)
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}
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i := sort.Search(n, f)
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if i == n {
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return -1
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}
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return searchPageLinear(p, pages, i)
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}
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// isPagesProbablySorted tests if the pages slice is probably sorted.
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func isPagesProbablySorted(pages Pages, lessFuncs ...func(p1, p2 Page) bool) func(p1, p2 Page) bool {
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n := len(pages)
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step := 1
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if n > 500 {
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step = 50
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}
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is := func(less func(p1, p2 Page) bool) bool {
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samples := 0
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for i := n - 1; i > 0; i = i - step {
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if less(pages[i], pages[i-1]) {
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return false
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}
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samples++
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if samples >= 15 {
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return true
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}
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}
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return samples > 0
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}
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isReverse := func(less func(p1, p2 Page) bool) bool {
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samples := 0
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for i := 0; i < n-1; i = i + step {
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if less(pages[i], pages[i+1]) {
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return false
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}
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samples++
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if samples > 15 {
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return true
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}
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}
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return samples > 0
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}
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for _, less := range lessFuncs {
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if is(less) {
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return less
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}
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if isReverse(less) {
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return func(p1, p2 Page) bool {
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return less(p2, p1)
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}
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}
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}
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return nil
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}
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