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// Package lrucache implements LRU (Least Recently Used) cache |
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package lrucache |
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import ( |
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"github.com/arazmj/gerdu/dlinklist" |
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"github.com/arazmj/gerdu/metrics" |
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"github.com/inhies/go-bytesize" |
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"sync" |
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) |
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//LRUCache data structure |
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type LRUCache struct { |
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sync.RWMutex |
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cache map[string]*dlinklist.Node |
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linklist *dlinklist.DLinkedList |
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capacity bytesize.ByteSize |
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size bytesize.ByteSize |
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} |
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// NewCache LRUCache constructor |
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func NewCache(capacity bytesize.ByteSize) *LRUCache { |
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return &LRUCache{ |
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cache: map[string]*dlinklist.Node{}, |
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linklist: dlinklist.NewLinkedList(), |
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capacity: capacity, |
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size: 0, |
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} |
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} |
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// Get returns the value for the key |
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func (c *LRUCache) Get(key string) (value string, ok bool) { |
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defer c.Unlock() |
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c.Lock() |
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if value, ok := c.cache[key]; ok { |
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metrics.Hits.Inc() |
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node := value |
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c.linklist.RemoveNode(node) |
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c.linklist.AddNode(node) |
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return node.Value, true |
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} |
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metrics.Miss.Inc() |
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return "", false |
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} |
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// Put updates or insert a new entry, evicts the old entry |
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// if cache size is larger than capacity |
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func (c *LRUCache) Put(key string, value string) (created bool) { |
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defer c.Unlock() |
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c.Lock() |
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if v, ok := c.cache[key]; ok { |
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node := v |
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c.linklist.RemoveNode(node) |
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c.linklist.AddNode(node) |
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node.Value = value |
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created = false |
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} else { |
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node := &dlinklist.Node{Key: key, Value: value} |
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c.linklist.AddNode(node) |
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c.cache[key] = node |
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metrics.Adds.Inc() |
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c.size += bytesize.ByteSize(len(value)) |
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for c.size > c.capacity { |
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metrics.Deletes.Inc() |
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tail := c.linklist.PopTail() |
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c.size -= bytesize.ByteSize(len(tail.Value)) |
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delete(c.cache, tail.Key) |
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} |
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created = true |
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} |
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return created |
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} |
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// HasKey indicates the key exists or not |
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func (c *LRUCache) HasKey(key string) bool { |
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defer c.RUnlock() |
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c.RLock() |
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_, ok := c.cache[key] |
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return ok |
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} |
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//Delete the key from the cache |
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func (c *LRUCache) Delete(key string) (ok bool) { |
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if node, ok := c.cache[key]; ok { |
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metrics.Deletes.Inc() |
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c.linklist.RemoveNode(node) |
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delete(c.cache, key) |
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} else { |
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return false |
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} |
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return true |
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} |
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arazmj /
gerdu
