Lua Persistence Guide — Serialization and Data Storage Techniques

function serialize(t)
    local parts = {}
    parts[#parts + 1] = "{"
    for k, v in pairs(t) do
        local key = type(k) == "string" and
            string.format("[%q]", k) or k
        local val
        if type(v) == "table" then
            val = serialize(v)
        elseif type(v) == "string" then
            val = string.format("%q", v)
        else
            val = tostring(v)
        end
        parts[#parts + 1] = string.format("%s = %s,", key, val)
    end
    parts[#parts + 1] = "}"
    return table.concat(parts, "\n")
end

local data = {name = "Lua", version = 5.4, tags = {"scripting", "embed"}}
print(serialize(data))

function saveTable(filename, t)
    local f = io.open(filename, "w")
    if not f then return false end
    f:write("return ")
    f:write(serialize(t))
    f:close()
    return true
end

function loadTable(filename)
    local f = io.open(filename, "r")
    if not f then return nil end
    local content = f:read("*all")
    f:close()
    local chunk, err = load("return " .. content)
    if not chunk then return nil, err end
    return chunk()
end

-- config.lua file:
-- return {
--     host = "localhost",
--     port = 8080,
--     debug = true
-- }

-- Loading config
local config = dofile("config.lua")
print(config.host)  --> localhost
print(config.port)  --> 8080

local function pack(...)
    local args = {...}
    local data = {}
    for _, v in ipairs(args) do
        if type(v) == "number" then
            data[#data + 1] = string.pack("I4", v)
        elseif type(v) == "string" then
            data[#data + 1] = string.pack("I4", #v) .. v
        end
    end
    return table.concat(data)
end

local function unpack(data)
    local pos = 1
    local results = {}
    while pos <= #data do
        local len = string.unpack("I4", data, pos)
        pos = pos + 4
        local str = string.unpack("c" .. len, data, pos)
        pos = pos + len
        results[#results + 1] = str
    end
    return table.unpack(results)
end