xs_storage.script

--[[
    Very much based on Lua Table Persistence by 'Black'.

    @license MIT
        "I hope this code is useful for someone, use it as you wish, it
         is licensed under the MIT license."
    @see http://the-color-black.net/blog/article/LuaTablePersistence
    @see https://github.com/hipe/lua-table-persistence

    This 'module'* is specificity written without any dependencies on any other xs* library.

    Also, this is written to be fast (as it can be with a pure Lua implementation), lightweight and
    easy to use.
    Meant to be used with Lua 5.x or LuaJIT 1.1.x.
    LuaJIT 2.x would allow for a few lines less, while also being faster. But its C API has changed
    since 1.1.x and is therefore incompatible.

    * The word module is in quotes, because STALKER doesn't support modules, that is the
    _G.module()/require() function(s).
]]

---[ PRIVATE ]------------------------------------------------------------------

--[[
    For anyone wondering this is a LuaJIT 1.x thing (LuaJIT 2.0 does NOT need this).
    It's here to avoid global lookups, that is lookup into the _G table. Because these are
    slower than than lookups in the current/local table (or scope).
]]
local tostring, pairs, type, select, loadfile
    = tostring, pairs, type, select, loadfile
local sprintf, push, pop, osdate, fopen, ftype
    = string.format, table.insert, table.remove, os.date, io.open, io.type
local time_global
    = time_global

local writers = {
    ['nil']     = function (file, item) file:write('nil') end,
    ['number']  = function (file, item) file:write(tostring(item)) end,
    ['string']  = function (file, item) file:write(sprintf('%q', item)) end,
    ['boolean'] = function (file, item) file:write(item and 'true' or 'false') end,
    ['table']   = function (file, item, level, refNameMap)
        local refIndex = refNameMap[item]
        if refIndex then
            file:write('objects[', refIndex, ']')
        else
            file:write('{\n')
            local nextLevel = level + 1
            for k, v in pairs(item) do
                indent(file, nextLevel)
                file:write('[')
                write(file, k, nextLevel, refNameMap)
                file:write('] = ')
                write(file, v, nextLevel, refNameMap)
                file:write(';\n')
            end
            indent(file, level)
            file:write('}')
        end
    end,
    ['function'] = function (file, item) file:write('nil --[[function ', tostring(item), ']]') end,
    ['thread']   = function (file, item) file:write('nil --[[thread ',   tostring(item), ']]') end,
    ['userdata'] = function (file, item) file:write('nil --[[userdata ', tostring(item), ']]') end,
}

-- TODO: Maybe convert the currently recursive function to iterative+stack one?
-- Keep in mind that Lua can (since 5.0) optimize tail-recursive calls by its self.
-- See if LuaJIT supports this special case.
-- Because countRefs is called twice, and technicality only the last countRefs call is tail-recursive.
local function countRefs(refCountMap, item)
    if refCountMap[item] then
        refCountMap[item] = refCountMap[item] + 1
    else
        refCountMap[item] = 1
        for k, v in pairs(item) do
            countRefs(refCountMap, k)
            countRefs(refCountMap, v)
        end
    end
end

local function write(file, item, level, refNameMap)
    writers[type(item)](file, item, level, refNameMap)
end

local function indent(file, level)
    for i = 1, level do
        file:write('    ')
    end
end


---[ PUBLIC ]------------------------------------------------------------------

function save(path, ...)
    local file, e
    if ftype(path) == 'file' then
        file = path
    else
        file, e = fopen(path, 'w+')
        if not file then
            error(e, 2)
        end
    end

    file:write('-- OS Date/Time: ', osdate('%Y-%m-%d %H:%M %Z'), '\n')
    file:write('-- Game Time: ', time_global(), '\n')

    local n = select('#', ...)
    local refCountMap = {}
    for i = 1, n do
        countRefs(refCountMap, select(i, ...))
    end

    local refIndex   = 0
    local refNameMap = {}
    file:write('-- Persistent Data\n')

    file:write('local objects = { ')
    for obj, count in pairs(refCountMap) do
        if count > 1 then
            refIndex = refIndex + 1
            refNameMap[obj] = refIndex
            file:write('{}; ')
        end
    end

    file:write('}\n -- objects\n')
    for obj, idx in pairs(refNameMap) do
        for k, v in pairs(obj) do
            file:write('objects[', idx, '][')
            write(file, k, 0, refNameMap)
            file:write('] = ')
            write(file, v, 0, refNameMap)
            file:write(';\n')
        end
    end

    for i = 1, n do
        file:write('local obj', i ,' = ')
        write(file, select(i, ...), 0, refNameMap)
        file:write('\n')
    end

    if n > 0 then
        file:write('return obj1')
        for i = 2, n do
            file:write(', obj', i)
        end
        file:write('\n')
    else
        file:write('return\n')
    end

    file:close()
end

function load(path)
    local f, e = loadfile(path)
    if f then
        return f()
    else
        return nil, e
    end
end