【网络通信】大版本更新包：分片下载与断点续传的校验

local done = {}
local function nextChunk(total)
    for i = 1, total do
        if done[i] ~= true then
            return i
        end
    end
    return nil
end
SL:RegisterLuaNetMsg(7201, function(data)
    local idx = tonumber(data.idx) or 0
    if data.ok == 1 then
        done[idx] = true
        saveProgress(done)
        SL:ShowSystemTips("已下载" .. idx .. "/" .. data.total)
    end
end)

local retry = {}
local function chunkFail(idx, total)
    retry[idx] = (retry[idx] or 0) + 1
    if retry[idx] >= 3 then
        retry[idx] = 0
        switchMirror()
    end
    SL:SendNetMsg(7202, { idx = idx })
end