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lru_cache.lua

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---@generic T

---@class LruCache<T>

---@field private capacity integer

---@field private entries table<any, { value: T, used: integer }>

---@field private size integer

---@field private clock integer

local LruCache = {}

LruCache.__index = LruCache

---@param capacity integer

---@return LruCache<T>

function LruCache.new(capacity)

assert(capacity > 0, 'cache capacity must be positive')

return setmetatable({

capacity = capacity,

entries = {},

size = 0,

clock = 0,

}, LruCache)

end

---@param key any

---@return T

function LruCache:get(key)

local entry = self.entries[key]

if not entry then

return nil

end

self.clock = self.clock + 1

entry.used = self.clock

return entry.value

end

---@param key any

---@param value T

function LruCache:set(key, value)

local entry = self.entries[key]

if not entry and self.size >= self.capacity then

local oldest_key

local oldest_use = math.huge

for cached_key, cached_entry in pairs(self.entries) do

if cached_entry.used < oldest_use then

oldest_key = cached_key

oldest_use = cached_entry.used

end

end

self.entries[oldest_key] = nil

self.size = self.size - 1

end

if not entry then

self.size = self.size + 1

end

self.clock = self.clock + 1

self.entries[key] = { value = value, used = self.clock }

end

return LruCache