Платформа ЦРНП "Мирокод" для разработки проектов
https://git.mirocod.ru
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87 lines
2.3 KiB
87 lines
2.3 KiB
// Copyright (c) 2016 Couchbase, Inc. |
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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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package registry |
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import ( |
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"fmt" |
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"sync" |
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) |
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var ErrAlreadyDefined = fmt.Errorf("item already defined") |
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type CacheBuild func(name string, config map[string]interface{}, cache *Cache) (interface{}, error) |
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type ConcurrentCache struct { |
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mutex sync.RWMutex |
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data map[string]interface{} |
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} |
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func NewConcurrentCache() *ConcurrentCache { |
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return &ConcurrentCache{ |
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data: make(map[string]interface{}), |
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} |
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} |
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func (c *ConcurrentCache) ItemNamed(name string, cache *Cache, build CacheBuild) (interface{}, error) { |
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c.mutex.RLock() |
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item, cached := c.data[name] |
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if cached { |
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c.mutex.RUnlock() |
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return item, nil |
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} |
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// give up read lock |
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c.mutex.RUnlock() |
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// try to build it |
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newItem, err := build(name, nil, cache) |
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if err != nil { |
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return nil, err |
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} |
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// acquire write lock |
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c.mutex.Lock() |
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defer c.mutex.Unlock() |
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// check again because it could have been created while trading locks |
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item, cached = c.data[name] |
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if cached { |
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return item, nil |
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} |
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c.data[name] = newItem |
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return newItem, nil |
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} |
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func (c *ConcurrentCache) DefineItem(name string, typ string, config map[string]interface{}, cache *Cache, build CacheBuild) (interface{}, error) { |
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c.mutex.RLock() |
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_, cached := c.data[name] |
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if cached { |
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c.mutex.RUnlock() |
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return nil, ErrAlreadyDefined |
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} |
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// give up read lock so others lookups can proceed |
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c.mutex.RUnlock() |
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// really not there, try to build it |
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newItem, err := build(typ, config, cache) |
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if err != nil { |
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return nil, err |
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} |
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// now we've built it, acquire lock |
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c.mutex.Lock() |
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defer c.mutex.Unlock() |
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// check again because it could have been created while trading locks |
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_, cached = c.data[name] |
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if cached { |
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return nil, ErrAlreadyDefined |
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} |
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c.data[name] = newItem |
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return newItem, nil |
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}
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