modlib/persistence/lua_log_file.lua

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-- Localize globals
local assert, error, io, loadfile, math, minetest, modlib, pairs, setfenv, setmetatable, type
= assert, error, io, loadfile, math, minetest, modlib, pairs, setfenv, setmetatable, type
-- Set environment
local _ENV = {}
setfenv(1, _ENV)
-- Default value
reference_strings = true
-- Note: keys may not be marked as weak references: garbage collected log files wouldn't close the file:
-- The `__gc` metamethod doesn't work for tables in Lua 5.1; a hack using `newproxy` would be needed
-- See https://stackoverflow.com/questions/27426704/lua-5-1-workaround-for-gc-metamethod-for-tables)
-- Therefore, :close() must be called on log files to remove them from the `files` table
local files = {}
local metatable = {__index = _ENV}
_ENV.metatable = metatable
function new(file_path, root, reference_strings)
local self = setmetatable({
file_path = assert(file_path),
root = root,
reference_strings = reference_strings
}, metatable)
if minetest then
files[self] = true
end
return self
end
local function set_references(self, table)
-- Weak table keys to allow the collection of dead reference tables
-- TODO garbage collect strings in the references table
self.references = setmetatable(table, {__mode = "k"})
end
function load(self)
-- Bytecode is blocked by the engine
local read = assert(loadfile(self.file_path))
-- math.huge is serialized to inf
local env = {inf = math.huge}
setfenv(read, env)
read()
env.R = env.R or {{}}
local reference_count = #env.R
for ref in pairs(env.R) do
if ref > reference_count then
-- Ensure reference count always has the value of the largest reference
-- in case of "holes" (nil values) in the reference list
reference_count = ref
end
end
self.reference_count = reference_count
self.root = env.R[1]
set_references(self, {})
end
function open(self)
self.file = io.open(self.file_path, "a+")
end
function init(self)
if modlib.file.exists(self.file_path) then
self:load()
self:_rewrite()
self:open()
return
end
self:open()
self.root = {}
self:_write()
end
function log(self, statement)
self.file:write(statement)
self.file:write"\n"
end
function flush(self)
self.file:flush()
end
function close(self)
self.file:close()
self.file = nil
files[self] = nil
end
if minetest then
minetest.register_on_shutdown(function()
for self in pairs(files) do
self.file:close()
end
end)
end
local function _dump(self, value, is_key)
if value == nil then
return "nil"
end
if value == true then
return "true"
end
if value == false then
return "false"
end
if value ~= value then
-- nan
return "0/0"
end
local _type = type(value)
if _type == "number" then
return ("%.17g"):format(value)
end
local reference = self.references[value]
if reference then
return "R[" .. reference .."]"
end
reference = self.reference_count + 1
local key = "R[" .. reference .."]"
local function create_reference()
self.reference_count = reference
self.references[value] = reference
end
if _type == "string" then
local reference_strings = self.reference_strings
if is_key and ((not reference_strings) or value:len() <= key:len()) and value:match"^[%a_][%a%d_]*$" then
-- Short key
return value, true
end
local formatted = ("%q"):format(value)
if (not reference_strings) or formatted:len() <= key:len() then
-- Short string
return formatted
end
-- Use reference
create_reference()
self:log(key .. "=" .. formatted)
elseif _type == "table" then
-- Tables always need a reference before they are traversed to prevent infinite recursion
create_reference()
-- TODO traverse tables to determine whether this is actually needed
self:log(key .. "={}")
for k, v in pairs(value) do
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local dumped, short = _dump(self, k, true)
self:log(key .. (short and ("." .. dumped) or ("[" .. dumped .. "]")) .. "=" .. _dump(self, v))
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end
else
error("unsupported type: " .. _type)
end
return key
end
function set(self, table, key, value)
if not self.references[table] then
error"orphan table"
end
if table[key] == value then
-- No change
return
end
table[key] = value
table = _dump(self, table)
local key, short_key = _dump(self, key, true)
self:log(table .. (short_key and ("." .. key) or ("[" .. key .. "]")) .. "=" .. _dump(self, value))
end
function set_root(self, key, value)
return self:set(self.root, key, value)
end
function _write(self)
set_references(self, {})
self.reference_count = 0
self:log"R={}"
_dump(self, self.root)
end
function _rewrite(self)
self.file = io.open(self.file_path, "w+")
self:_write()
self.file:close()
end
function rewrite(self)
if self.file then
self.file:close()
end
self:_rewrite()
self:open()
end
-- Export environment
return _ENV