@@ -1,11 +1,30 @@ -------------------------------------------------------------------------------- +-- Metalua +-- Summary: Table-to-source serializer +-------------------------------------------------------------------------------- +-- +-- Copyright (c) 2008-2009, Fabien Fleutot <metalua@gmail.com>. +-- +-- This software is released under the MIT Licence, see licence.txt +-- for details. +-- +-------------------------------------------------------------------------------- +-- -- Serialize an object into a source code string. This string, when passed as -- an argument to loadstring()(), returns an object structurally identical --- to the original one. The following are currently supported: +-- to the original one. +-- +-- The following are supported: +-- -- * strings, numbers, booleans, nil +-- -- * functions without upvalues --- * tables thereof. Tables can have shared part, but can't be recursive yet. --- Caveat: metatables and environments aren't saved. +-- +-- * tables thereof. There is no restriction on keys; recursive and shared +-- sub-tables are handled correctly. +-- +-- Caveat: metatables and environments aren't saved; this might or might not +-- be what you want. -------------------------------------------------------------------------------- local no_identity = { number=1, boolean=1, string=1, ['nil']=1 } @@ -16,28 +35,37 @@ function serialize (x) local seen_once = { } -- element->true set of elements seen exactly once in the table local multiple = { } -- element->varname set of elements seen more than once local nested = { } -- transient, set of elements currently being traversed - local nest_points = { } + local nest_points = { } local nest_patches = { } + -- Generate fresh indexes to store new sub-tables: local function gensym() gensym_max = gensym_max + 1 ; return gensym_max end ----------------------------------------------------------------------------- - -- nest_points are places where a table appears within itself, directly or not. - -- for instance, all of these chunks create nest points in table x: - -- "x = { }; x[x] = 1", "x = { }; x[1] = x", "x = { }; x[1] = { y = { x } }". - -- To handle those, two tables are created by mark_nest_point: - -- * nest_points [parent] associates all keys and values in table parent which - -- create a nest_point with boolean `true' - -- * nest_patches contain a list of { parent, key, value } tuples creating - -- a nest point. They're all dumped after all the other table operations - -- have been performed. + -- `nest_points' are places where a (recursive) table appears within + -- itself, directly or not. for instance, all of these chunks + -- create nest points in table `x': + -- + -- "x = { }; x[x] = 1" + -- "x = { }; x[1] = x" + -- "x = { }; x[1] = { y = { x } }". + -- + -- To handle those, two tables are created by `mark_nest_point()': + -- + -- * `nest_points [parent]' associates all keys and values in table + -- parent which create a nest_point with boolean `true' + -- + -- * `nest_patches' contains a list of `{ parent, key, value }' + -- tuples creating a nest point. They're all dumped after all the + -- other table operations have been performed. -- - -- mark_nest_point (p, k, v) fills tables nest_points and nest_patches with - -- informations required to remember that key/value (k,v) create a nest point - -- in table parent. It also marks `parent' as occuring multiple times, since - -- several references to it will be required in order to patch the nest + -- `mark_nest_point (p, k, v)' fills tables `nest_points' and + -- `nest_patches' with informations required to remember that + -- key/value `(k,v)' creates a nest point in parent table `p'. It + -- also marks `p' as occuring multiple times, since several + -- references to it will be required in order to patch the nest -- points. ----------------------------------------------------------------------------- local function mark_nest_point (parent, k, v) @@ -54,7 +82,7 @@ function serialize (x) end ----------------------------------------------------------------------------- - -- First pass, list the tables and functions which appear more than once in x + -- 1st pass, list the tables and functions which appear more than once in `x' ----------------------------------------------------------------------------- local function mark_multiple_occurences (x) if no_identity [type(x)] then return end @@ -81,11 +109,11 @@ function serialize (x) -- mutually recursive functions: local dump_val, dump_or_ref_val - -------------------------------------------------------------------- - -- if x occurs multiple times, dump the local var rather than the + ------------------------------------------------------------------------------ + -- if `x' occurs multiple times, dump the local var rather than the -- value. If it's the first time it's dumped, also dump the content -- in localdefs. - -------------------------------------------------------------------- + ------------------------------------------------------------------------------ function dump_or_ref_val (x) if nested[x] then return 'false' end -- placeholder for recursive reference if not multiple[x] then return dump_val (x) end @@ -99,9 +127,9 @@ function serialize (x) end ----------------------------------------------------------------------------- - -- Second pass, dump the object; subparts occuring multiple times are dumped - -- in local variables which can be referenced multiple times; - -- care is taken to dump locla vars in asensible order. + -- 2nd pass, dump the object; subparts occuring multiple times are dumped + -- in local variables, which can then be referenced multiple times; + -- care is taken to dump local vars in an order which repect dependencies. ----------------------------------------------------------------------------- function dump_val(x) local t = type(x) @@ -137,6 +165,7 @@ function serialize (x) end end + -- Patch the recursive table entries: local function dump_nest_patches() for _, entry in ipairs(nest_patches) do local p, k, v = unpack (entry) @@ -152,10 +181,13 @@ function serialize (x) dump_nest_patches() if next (localdefs) then + -- Dump local vars containing shared or recursive parts, + -- then the main table using them. return "local _={ }\n" .. table.concat (localdefs, "\n") .. "\nreturn " .. toplevel else + -- No shared part, straightforward dump: return "return " .. toplevel end end src/lib/serialize.lua 6fe04c64ce4bbf58c2130036042b2e3412766d17 Fabien Fleutot metalua@gmail.com http://github.com/fab13n/metalua/commit/2e27663f7bb88c9a7b3d5a5fa995e5df44b33d39 2e27663f7bb88c9a7b3d5a5fa995e5df44b33d39 2009-02-10T09:27:59-08:00 2009-02-10T09:27:59-08:00 comment cleanup on serialize dcb121563f78aa19f374d6cf12d5ef36995498bc Fabien Fleutot metalua@gmail.com