hugo

Fork of github.com/gohugoio/hugo with reverse pagination support

git clone git://git.shimmy1996.com/hugo.git

named_cache.go (2061B)

    1 // Copyright 2018 The Hugo Authors. All rights reserved.
    2 //
    3 // Licensed under the Apache License, Version 2.0 (the "License");
    4 // you may not use this file except in compliance with the License.
    5 // You may obtain a copy of the License at
    6 // http://www.apache.org/licenses/LICENSE-2.0
    7 //
    8 // Unless required by applicable law or agreed to in writing, software
    9 // distributed under the License is distributed on an "AS IS" BASIS,
   10 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   11 // See the License for the specific language governing permissions and
   12 // limitations under the License.
   13 
   14 // Package namedmemcache provides a memory cache with a named lock. This is suitable
   15 // for situations where creating the cached resource can be time consuming or otherwise
   16 // resource hungry, or in situations where a "once only per key" is a requirement.
   17 package namedmemcache
   18 
   19 import (
   20 	"sync"
   21 
   22 	"github.com/BurntSushi/locker"
   23 )
   24 
   25 // Cache holds the cached values.
   26 type Cache struct {
   27 	nlocker *locker.Locker
   28 	cache   map[string]cacheEntry
   29 	mu      sync.RWMutex
   30 }
   31 
   32 type cacheEntry struct {
   33 	value any
   34 	err   error
   35 }
   36 
   37 // New creates a new cache.
   38 func New() *Cache {
   39 	return &Cache{
   40 		nlocker: locker.NewLocker(),
   41 		cache:   make(map[string]cacheEntry),
   42 	}
   43 }
   44 
   45 // Clear clears the cache state.
   46 func (c *Cache) Clear() {
   47 	c.mu.Lock()
   48 	defer c.mu.Unlock()
   49 
   50 	c.cache = make(map[string]cacheEntry)
   51 	c.nlocker = locker.NewLocker()
   52 }
   53 
   54 // GetOrCreate tries to get the value with the given cache key, if not found
   55 // create will be called and cached.
   56 // This method is thread safe. It also guarantees that the create func for a given
   57 // key is invoked only once for this cache.
   58 func (c *Cache) GetOrCreate(key string, create func() (any, error)) (any, error) {
   59 	c.mu.RLock()
   60 	entry, found := c.cache[key]
   61 	c.mu.RUnlock()
   62 
   63 	if found {
   64 		return entry.value, entry.err
   65 	}
   66 
   67 	c.nlocker.Lock(key)
   68 	defer c.nlocker.Unlock(key)
   69 
   70 	// Create it.
   71 	value, err := create()
   72 
   73 	c.mu.Lock()
   74 	c.cache[key] = cacheEntry{value: value, err: err}
   75 	c.mu.Unlock()
   76 
   77 	return value, err
   78 }