modlib/luon.lua

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-- Lua module to serialize values as Lua code
local assert, error, rawget, pairs, pcall, type, setfenv, setmetatable, select, loadstring, loadfile
= assert, error, rawget, pairs, pcall, type, setfenv, setmetatable, select, loadstring, loadfile
local table_concat, string_format, math_huge
= table.concat, string.format, math.huge
local count_objects = modlib.table.count_objects
local is_identifier = modlib.text.is_identifier
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local function quote(string)
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return string_format("%q", string)
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end
local _ENV = {}
setfenv(1, _ENV)
local metatable = {__index = _ENV}
_ENV.metatable = metatable
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function new(self)
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return setmetatable(self, metatable)
end
function aux_write(_self, _object)
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-- returns reader, arguments
return
end
aux_read = {}
function write(self, value, write)
-- TODO evaluate custom aux. writers *before* writing for circular structs
local reference, refnum = "1", 1
-- [object] = reference
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local references = {}
-- Circular tables that must be filled using `table[key] = value` statements
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local to_fill = {}
-- TODO (?) sort objects by count, give frequently referenced objects shorter references
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for object, count in pairs(count_objects(value)) do
local type_ = type(object)
-- Object must appear more than once. If it is a string, the reference has to be shorter than the string.
if count >= 2 and (type_ ~= "string" or #reference + 5 < #object) then
if refnum == 1 then
write"local _={};" -- initialize reference table
end
write"_["
write(reference)
write"]="
if type_ == "table" then
write"{}"
elseif type_ == "string" then
write(quote(object))
end
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write";"
references[object] = reference
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if type_ == "table" then
to_fill[object] = reference
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end
refnum = refnum + 1
reference = string_format("%d", refnum)
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end
end
-- Used to decide whether we should do "key=..."
local function use_short_key(key)
return not references[key] and type(key) == "string" and is_identifier(key)
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end
local function dump(value)
-- Primitive types
if value == nil then
return write"nil"
end if value == true then
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return write"true"
end if value == false then
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return write"false"
end
local type_ = type(value)
if type_ == "number" then
-- Explicit handling of special values for forwards compatibility
if value ~= value then -- nan
return write"0/0"
end if value == math_huge then
return write"1/0"
end if value == -math_huge then
return write"-1/0"
end
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return write(string_format("%.17g", value))
end
-- Reference types: table and string
local ref = references[value]
if ref then
-- Referenced
write"_["
write(ref)
return write"]"
end if type_ == "string" then
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return write(quote(value))
end if type_ == "table" then
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write"{"
-- First write list keys:
-- Don't use the table length #value here as it may horribly fail
-- for tables which use large integers as keys in the hash part;
-- stop at the first "hole" (nil value) instead
local len = 0
local first = true -- whether this is the first entry, which may not have a leading comma
while true do
local v = rawget(value, len + 1) -- use rawget to avoid metatables like the vector metatable
if v == nil then break end
if first then first = false else write(",") end
dump(v)
len = len + 1
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end
-- Now write map keys ([key] = value)
for k, v in pairs(value) do
-- We have written all non-float keys in [1, len] already
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if type(k) ~= "number" or k % 1 ~= 0 or k < 1 or k > len then
if first then first = false else write(",") end
if use_short_key(k) then
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write(k)
else
write"["
dump(k)
write"]"
end
write"="
dump(v)
end
end
return write"}"
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end
-- TODO move aux_write to start, to allow dealing with metatables etc.?
return (function(func, ...)
-- functions are the only way to deal with varargs
if not func then
return error("unsupported type: " .. type_)
end
write(func)
write"("
local n = select("#", ...)
for i = 1, n - 1 do
dump(select(i, ...))
write","
end
if n > 0 then
dump(select(n, ...))
end
write")"
end)(self:aux_write(value))
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end
-- Write the statements to fill circular tables
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for table, ref in pairs(to_fill) do
for k, v in pairs(table) do
write"_["
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write(ref)
write"]"
if use_short_key(k) then
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write"."
write(k)
else
write"["
dump(k)
write"]"
end
write"="
dump(v)
write";"
end
end
write"return "
dump(value)
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end
function write_file(self, value, file)
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return self:write(value, function(text)
file:write(text)
end)
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end
function write_string(self, value)
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local rope = {}
self:write(value, function(text)
rope[#rope + 1] = text
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end)
return table_concat(rope)
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end
function read(self, ...)
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local read = assert(...)
-- math.huge was serialized to inf, 0/0 was serialized to -nan by `%.17g`
setfenv(read, setmetatable({inf = math_huge, nan = 0/0}, {__index = self.aux_read}))
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local success, value_or_err = pcall(read)
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if success then
return value_or_err
end
return nil, value_or_err
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end
function read_file(self, path)
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return self:read(loadfile(path))
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end
function read_string(self, string)
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return self:read(loadstring(string))
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end
return _ENV