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Diffstat (limited to 'cache/namedmemcache/named_cache.go')
-rw-r--r-- | cache/namedmemcache/named_cache.go | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/cache/namedmemcache/named_cache.go b/cache/namedmemcache/named_cache.go new file mode 100644 index 000000000..18fbea391 --- /dev/null +++ b/cache/namedmemcache/named_cache.go @@ -0,0 +1,84 @@ +// Copyright 2018 The Hugo Authors. All rights reserved. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// Package namedmemcache provides a memory cache with a named lock. This is suitable +// for situations where creating the cached resource can be time consuming or otherwise +// resource hungry, or in situations where a "once only per key" is a requirement. +package namedmemcache + +import ( + "sync" + + "github.com/BurntSushi/locker" +) + +// Cache holds the cached values. +type Cache struct { + nlocker *locker.Locker + cache map[string]cacheEntry + mu sync.RWMutex +} + +type cacheEntry struct { + value interface{} + err error +} + +// New creates a new cache. +func New() *Cache { + return &Cache{ + nlocker: locker.NewLocker(), + cache: make(map[string]cacheEntry), + } +} + +// Clear clears the cache state. +func (c *Cache) Clear() { + c.mu.Lock() + defer c.mu.Unlock() + + c.cache = make(map[string]cacheEntry) + c.nlocker = locker.NewLocker() + +} + +// GetOrCreate tries to get the value with the given cache key, if not found +// create will be called and cached. +// This method is thread safe. It also guarantees that the create func for a given +// key is invoced only once for this cache. +func (c *Cache) GetOrCreate(key string, create func() (interface{}, error)) (interface{}, error) { + c.mu.RLock() + entry, found := c.cache[key] + c.mu.RUnlock() + + if found { + return entry.value, entry.err + } + + c.nlocker.Lock(key) + defer c.nlocker.Unlock(key) + + // Double check + if entry, found := c.cache[key]; found { + return entry.value, entry.err + } + + // Create it. + value, err := create() + + c.mu.Lock() + c.cache[key] = cacheEntry{value: value, err: err} + c.mu.Unlock() + + return value, err +} |