84 lines
1.9 KiB
Go
84 lines
1.9 KiB
Go
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package ifname
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// See https://girai.dev/blog/lru-cache-implementation-in-go/
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import (
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"container/list"
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)
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type LRUValType = TTLValType
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type hashType map[keyType]*list.Element
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type LRUCache struct {
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cap uint // capacity
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l *list.List // doubly linked list
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m hashType // hash table for checking if list node exists
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}
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// Pair is the value of a list node.
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type Pair struct {
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key keyType
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value LRUValType
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}
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// initializes a new LRUCache.
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func NewLRUCache(capacity uint) LRUCache {
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return LRUCache{
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cap: capacity,
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l: new(list.List),
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m: make(hashType, capacity),
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}
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}
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// Get a list node from the hash map.
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func (c *LRUCache) Get(key keyType) (LRUValType, bool) {
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// check if list node exists
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if node, ok := c.m[key]; ok {
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val := node.Value.(*list.Element).Value.(Pair).value
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// move node to front
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c.l.MoveToFront(node)
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return val, true
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}
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return LRUValType{}, false
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}
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// Put key and value in the LRUCache
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func (c *LRUCache) Put(key keyType, value LRUValType) {
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// check if list node exists
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if node, ok := c.m[key]; ok {
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// move the node to front
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c.l.MoveToFront(node)
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// update the value of a list node
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node.Value.(*list.Element).Value = Pair{key: key, value: value}
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} else {
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// delete the last list node if the list is full
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if uint(c.l.Len()) == c.cap {
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// get the key that we want to delete
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idx := c.l.Back().Value.(*list.Element).Value.(Pair).key
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// delete the node pointer in the hash map by key
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delete(c.m, idx)
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// remove the last list node
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c.l.Remove(c.l.Back())
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}
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// initialize a list node
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node := &list.Element{
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Value: Pair{
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key: key,
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value: value,
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},
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}
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// push the new list node into the list
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ptr := c.l.PushFront(node)
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// save the node pointer in the hash map
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c.m[key] = ptr
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}
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}
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func (c *LRUCache) Delete(key keyType) {
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if node, ok := c.m[key]; ok {
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c.l.Remove(node)
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delete(c.m, key)
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}
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}
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