mirror of
https://github.com/gohugoio/hugo.git
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109 lines
2.3 KiB
Go
109 lines
2.3 KiB
Go
// Copyright 2015 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 hugolib
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import (
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"sync"
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)
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type pageCache struct {
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sync.RWMutex
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m map[string][][2]Pages
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}
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func newPageCache() *pageCache {
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return &pageCache{m: make(map[string][][2]Pages)}
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}
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// get gets a Pages slice from the cache matching the given key and Pages slice.
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// If none found in cache, a copy of the supplied slice is created.
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//
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// If an apply func is provided, that func is applied to the newly created copy.
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//
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// The cache and the execution of the apply func is protected by a RWMutex.
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func (c *pageCache) get(key string, p Pages, apply func(p Pages)) (Pages, bool) {
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c.RLock()
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if cached, ok := c.m[key]; ok {
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for _, ps := range cached {
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if probablyEqualPages(p, ps[0]) {
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c.RUnlock()
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return ps[1], true
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}
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}
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}
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c.RUnlock()
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c.Lock()
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defer c.Unlock()
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// double-check
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if cached, ok := c.m[key]; ok {
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for _, ps := range cached {
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if probablyEqualPages(p, ps[0]) {
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return ps[1], true
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}
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}
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}
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pagesCopy := append(Pages(nil), p...)
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if apply != nil {
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apply(pagesCopy)
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}
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if v, ok := c.m[key]; ok {
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c.m[key] = append(v, [2]Pages{p, pagesCopy})
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} else {
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c.m[key] = [][2]Pages{{p, pagesCopy}}
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}
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return pagesCopy, false
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}
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// "probably" as in: we do not compare every element for big slices, but that is
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// good enough for our use case.
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// TODO(bep) there is a similar method in pagination.go. DRY.
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func probablyEqualPages(p1, p2 Pages) bool {
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if p1 == nil && p2 == nil {
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return true
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}
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if p1 == nil || p2 == nil {
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return false
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}
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if p1.Len() != p2.Len() {
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return false
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}
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if p1.Len() == 0 {
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return true
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}
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step := 1
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if len(p1) >= 50 {
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step = len(p1) / 10
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}
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for i := 0; i < len(p1); i += step {
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if p1[i] != p2[i] {
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return false
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}
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}
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return true
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}
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