shad-go/lrucache/lru.go

//go:build !solution

package lrucache

import (
	"container/list"
)

type cacheEntry struct {
	key   int
	value int
}

type lrucache struct {
	cap           int
	data          map[int]*list.Element
	recentEntries *list.List
}

func (c *lrucache) isFull() bool {
	return c.recentEntries.Len() == c.cap
}

func (c *lrucache) Get(key int) (int, bool) {
	e, ok := c.data[key]
	if !ok {
		return 0, false
	}
	entry := c.recentEntries.Remove(e).(cacheEntry)
	c.data[key] = c.recentEntries.PushBack(entry)
	return entry.value, true
}

func (c *lrucache) Set(key int, value int) {
	if c.cap == 0 {
		return
	}
	e, ok := c.data[key]
	if ok {
		c.recentEntries.Remove(e)
		c.data[key] = c.recentEntries.PushBack(cacheEntry{key, value})
		return
	}
	if c.isFull() {
		removed := c.recentEntries.Remove(c.recentEntries.Front()).(cacheEntry)
		delete(c.data, removed.key)
	}
	c.data[key] = c.recentEntries.PushBack(cacheEntry{key, value})
}

func (c *lrucache) Range(f func(key, value int) bool) {
	for e := c.recentEntries.Front(); e != nil; e = e.Next() {
		entry := e.Value.(cacheEntry)
		if !f(entry.key, entry.value) {
			return
		}
	}
}

func (c *lrucache) Clear() {
	clear(c.data)
	c.recentEntries.Init()
}

func New(cap int) Cache {
	return &lrucache{cap, make(map[int]*list.Element), list.New()}
}