【高级技巧】Lua简易LRU：裁决之杖价目缓存的容量淘汰

local cache = {}
local function get(key)
    if not cache[key] then
        cache[key] = loadPrice(key)   -- 只进不出，涨到8MB
    end
    return cache[key]
end

local cache = {}   -- 裁决之杖价目热键缓存
local function get(key)
    if not cache[key] then
        local n = 0
        for _ in pairs(cache) do n = n + 1 end
        if n >= 20 then               -- 容量到顶，踢最旧
            local old, ot
            for k, e in pairs(cache) do
                if not ot or e.t < ot then old, ot = k, e.t end
            end
            cache[old] = nil
        end
        cache[key] = {v = loadPrice(key)}
    end
    cache[key].t = os.clock()         -- 命中即刷新热度
    return cache[key].v
end