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| The serialize.lua file distributed with MUSHclient is handy for turning tables into strings, but can get a bit wordy for simple tables.
For example, with the mobs table shown in the original post in this thread, calling serialize.save produces fairly wordy output, like this:
print ((serialize.save ("mobs")))
--> Output
mobs = {}
mobs.kobold = {}
mobs.kobold.treasure = {}
mobs.kobold.treasure[1] = "sword"
mobs.kobold.treasure[2] = "gold"
mobs.kobold.treasure[3] = "helmet"
mobs.kobold.name = "killer"
mobs.kobold.gold = 5
mobs.kobold.location = "city square"
mobs.kobold.hp = 22
mobs.worm = {}
mobs.worm.attacks = {}
mobs.worm.attacks[1] = "bite"
mobs.worm.attacks[2] = "poison"
mobs.worm.treasure = {}
mobs.worm.treasure[1] = "food"
mobs.worm.treasure[2] = "knife"
mobs.worm.name = "gordon"
mobs.worm.gold = 15
mobs.worm.location = "underground"
mobs.worm.hp = 4
For tables that do not have cycles (that is they do not refer to themselves), or that do not refer to other tables, a simpler serialization is all that is required.
print ("mobs = " .. serialize.save_simple (mobs))
--> Output
mobs = {
kobold = {
treasure = {
[1] = "sword",
[2] = "gold",
[3] = "helmet",
},
name = "killer",
gold = 5,
location = "city square",
hp = 22,
},
worm = {
attacks = {
[1] = "bite",
[2] = "poison",
},
treasure = {
[1] = "food",
[2] = "knife",
},
name = "gordon",
gold = 15,
location = "underground",
hp = 4,
},
}
The function serialize.save_simple is simply passed a variable (not the name of a variable), and thus it doesn't know the top-level variable name. Hence I added "mobs = " to the print statement.
I think this looks neater for simple tables, and you can always use the standard serialization for more complex ones.
Below is the new serialize.lua file contents:
-- serialize.lua
module (..., package.seeall)
-- ----------------------------------------------------------
-- serializer
-- See "Programming In Lua" chapter 12.1.2.
-- Also see forum thread:
-- http://www.gammon.com.au/forum/?id=4960
-- ----------------------------------------------------------
--[[
Example of use:
require "serialize"
SetVariable ("mobs", serialize.save ("mobs")) --> serialize mobs table
loadstring (GetVariable ("mobs")) () --> restore mobs table
If you need to serialize two tables where subsequent ones refer to earlier ones
you can supply your own "saved tables" variable, like this:
require "serialize"
result, t = serialize.save ("mobs")
result = result .. "\n" .. serialize.save ("quests", nil, t)
In this example the serializing of "quests" also knows about the "mobs" table
and will use references to it where necessary.
You can also supply the actual variable if the variable to be serialized does
not exist in the global namespace (for instance, if the variable is a local
variable to a function). eg.
require "serialize"
do
local myvar = { 1, 2, 8, 9 }
print (serialize.save ("myvar", myvar))
end
In this example, without supplying the location of "myvar" the serialize would fail
because it would not be found in the _G namespace.
----- Added on 19 July 2007:
You can now do a "simple save" which is intended for tables without cycles. That is,
tables, that do not refer to other tables. This is appropriate for "simple" data, like
a straight table of keys/values, including subtables.
For a simple save, all you need to do is supply the value, like this:
print (serialize.save_simple ({ foo = 22, bar = "hi", t = { s = 9, k = 22 } }))
This produces:
{
t = {
s = 9,
k = 22,
},
bar = "hi",
foo = 22,
}
--]]
local save_item -- forward declaration, function appears near the end
local save_item_simple
function save (what, v, saved)
saved = saved or {} -- initial table of tables we have already done
v = v or _G [what] -- default to "what" in global namespace
assert (type (what) == "string",
"1st argument to serialize.save should be the *name* of a variable")
assert (v, "Variable '" .. what .. "' does not exist")
assert (type (saved) == "table" or saved == nil,
"3rd argument to serialize.save should be a table or nil")
local out = {} -- output to this table
save_item (what, v, out, 0, saved) -- do serialization
return table.concat (out, "\n"), saved -- turn into a string (also return our table)
end -- serialize.save
function save_simple (v)
local out = {} -- output to this table
save_item_simple (v, out, 2) -- do serialization
return table.concat (out) -- turn into a string
end -- serialize.save_simple
--- below are local functions for this module -------------
local function basicSerialize (o)
if type(o) == "number" or type(o) == "boolean" then
return tostring(o)
else -- assume it is a string
return string.format("%q", o)
end
end -- basicSerialize
--
-- Lua keywords might look OK to not be quoted as keys but must be.
-- So, we make a list of them.
--
local lua_reserved_words = {}
for _, v in ipairs ({
"and", "break", "do", "else", "elseif", "end", "false",
"for", "function", "if", "in", "local", "nil", "not", "or",
"repeat", "return", "then", "true", "until", "while"
}) do lua_reserved_words [v] = true end
-- ----------------------------------------------------------
-- save one variable (calls itself recursively)
--
-- Modified on 23 October 2005 to better handle keys (like table keys)
-- ----------------------------------------------------------
function save_item (name, value, out, indent, saved) -- important! no "local" keyword
local iname = string.rep (" ", indent) .. name -- indented name
-- numbers, strings, and booleans can be simply serialized
if type (value) == "number" or
type (value) == "string" or
type (value) == "boolean" then
table.insert (out, iname .. " = " .. basicSerialize(value))
-- tables need to be constructed, unless we have already done it
elseif type (value) == "table" then
if saved[value] then -- value already saved?
table.insert (out, iname .. " = " .. saved[value]) -- use its previous name
else
-- remember we have created this table so we don't do it twice
saved [value] = name -- save name for next time
-- make the table constructor, and recurse to save its contents
assert (string.find (name, '^[_%a][_%a%d%.%[%]" ]*$')
and not lua_reserved_words [name],
"Invalid name '" .. name .. "' for table")
table.insert (out, iname .. " = {}") -- create a new table
for k, v in pairs (value) do -- save its fields
local fieldname
-- if key is a Lua variable name which is not a reserved word
-- we can express it as tablename.keyname
if type (k) == "string"
and string.find (k, "^[_%a][_%a%d]*$")
and not lua_reserved_words [k] then
fieldname = string.format("%s.%s", name, k)
-- if key is a table itself, and we know its name then we can use that
-- eg. tablename [ tablekeyname ]
elseif type (k) == "table" and saved[k] then
fieldname = string.format("%s[%s]", name, saved [k])
-- if key is an unknown table, we have to raise an error as we cannot
-- deduce its name
elseif type (k) == "table" then
error ("Key table entry " .. tostring (k) ..
" in table " .. name .. " is not known")
-- if key is a number or a boolean it can simply go in brackets,
-- like this: tablename [5] or tablename [true]
elseif type (k) == "number" or type (k) == "boolean" then
fieldname = string.format("%s[%s]", name, tostring (k))
-- now key should be a string, otherwise an error
elseif type (k) ~= "string" then
error ("Cannot serialize table keys of type '" .. type (k) ..
"' in table " .. name)
-- if key is a non-variable name (eg. "++") then we have to put it
-- in brackets and quote it, like this: tablename ["keyname"]
else
fieldname = string.format("%s[%s]", name,
basicSerialize(k))
end
-- now we have finally worked out a suitable name for the key,
-- recurse to save the value associated with it
save_item(fieldname, v, out, indent + 2, saved)
end
end
-- cannot serialize things like functions, threads
else
error ("Cannot serialize '" .. name .. "' (" .. type (value) .. ")")
end -- if type of variable
end -- save_item
-- saves tables *without* cycles (produces smaller output)
function save_item_simple (value, out, indent)
-- numbers, strings, and booleans can be simply serialized
if type (value) == "number" or
type (value) == "string" or
type (value) == "boolean" then
table.insert (out, basicSerialize(value))
elseif type (value) == "table" then
table.insert (out, "{\n")
for k, v in pairs (value) do -- save its fields
table.insert (out, string.rep (" ", indent))
if not string.find (k, '^[_%a][_%a%d]*$')
or lua_reserved_words [k] then
table.insert (out, "[" .. basicSerialize (k) .. "] = ")
else
table.insert (out, k .. " = ")
end -- if
save_item_simple (v, out, indent + 2)
table.insert (out, ",\n")
end -- for each table item
table.insert (out, string.rep (" ", indent) .. "}")
-- cannot serialize things like functions, threads
else
error ("Cannot serialize " .. type (value))
end -- if type of variable
end -- save_item_simple
|
- Nick Gammon
www.gammon.com.au, www.mushclient.com | | Top |
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