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78 lines
1.8 KiB
Go
78 lines
1.8 KiB
Go
package core
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import "container/list"
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// element wraps a map key and value
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type element struct {
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key string
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value *file
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}
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// lruCacheMap is a fixed-size LRU hash map
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type lruCacheMap struct {
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hashMap map[string]*list.Element
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list *list.List
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size int
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}
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// newLRUCacheMap returns a new LRUCacheMap of specified size
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func newLRUCacheMap(size int) *lruCacheMap {
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return &lruCacheMap{
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// size+1 to account for moment during put after adding new value but before old value is purged
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make(map[string]*list.Element, size+1),
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&list.List{},
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size,
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}
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}
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// Get returns file from LRUCacheMap for key
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func (lru *lruCacheMap) Get(key string) (*file, bool) {
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lElem, ok := lru.hashMap[key]
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if !ok {
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return nil, ok
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}
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// Move element to front of the list
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lru.list.MoveToFront(lElem)
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// Get Element and return *File value from it
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element, _ := lElem.Value.(*element)
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return element.value, ok
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}
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// Put file in LRUCacheMap at key
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func (lru *lruCacheMap) Put(key string, value *file) {
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lElem := lru.list.PushFront(&element{key, value})
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lru.hashMap[key] = lElem
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if lru.list.Len() > lru.size {
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// Get element at back of list and Element from it
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lElem = lru.list.Back()
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element, _ := lElem.Value.(*element)
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// Delete entry in hashMap with key from Element, and from list
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delete(lru.hashMap, element.key)
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lru.list.Remove(lElem)
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}
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}
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// Remove file in LRUCacheMap with key
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func (lru *lruCacheMap) Remove(key string) {
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lElem, ok := lru.hashMap[key]
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if !ok {
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return
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}
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// Delete entry in hashMap and list
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delete(lru.hashMap, key)
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lru.list.Remove(lElem)
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}
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// Iterate performs an iteration over all key:value pairs in LRUCacheMap with supplied function
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func (lru *lruCacheMap) Iterate(iterator func(key string, value *file)) {
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for key := range lru.hashMap {
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element := lru.hashMap[key].Value.(*element)
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iterator(element.key, element.value)
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}
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}
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