【高级技巧】超时回收：借用超时的对象池强制回收

local pool, lent = {}, {}
local CAP = 8
local TIMEOUT = 360
local function borrow(owner)
    for i = 1, CAP do
        if pool[i] then
            pool[i] = nil
            lent[i] = { owner = owner, at = os.time() }
            return i
        end
    end
    sweep()
    for i = 1, CAP do
        if pool[i] then
            pool[i] = nil
            lent[i] = { owner = owner, at = os.time() }
            return i
        end
    end
    return nil
end
local function giveBack(idx)
    if lent[idx] then
        lent[idx] = nil
        pool[idx] = true
    end
end
local function sweep()
    local now = os.time()
    for idx, rec in pairs(lent) do
        if now - rec.at > TIMEOUT then
            lent[idx] = nil
            pool[idx] = true
        end
    end
end

local function onSweepTick(actor)
    actor = getplayerbyname(actor)
    sweep()
    sendmsg(actor, 1, "对象池清扫完成，超时借用已强制回收。")
end