Re: object serialization

On 4/21/2011 6:28 PM, Szymon Gatner wrote:
> Hi,
>
> what would be the simple and elegant way to do serialization /
> persistance of a specific luabind::object?
>
> I only need to save numeric and string values and tables of them. I
> was thinking about recursive visitation like so:
>
> void visit(const luabind::object&  obj)
> {
>    using namespace luabind;
>
>    if (type(obj) == LUA_TTABLE)
>    {
>      cout<<  "{"<<  endl;
>
>      for (luabind::iterator it(obj); it != luabind::iterator(); ++it)
>      {
>        if (type(it.key()) == LUA_TSTRING)
>        {
>          if (type(*it) != LUA_TTABLE)
>          {
>            cout<<  it.key()<<  " = "<<  *it<<  endl;
>          }
>          else
>          {
>            visit(*it);
>          }
>        }
>      }
>
>      cout<<  "}"<<  endl;
>    }
> }
>
> cout is used here to print name/value pairs but in real case actual
> persistance code would be used.
>
> Am I going the right way?
>
> Cheers,
> Szymon
If the luabind::object is a Lua table, wouldn't the easiest way to 
serialize it be to convert it into a Lua script file? I've included a 
Lua script I wrote which takes an arbitary table (that contains only 
standard Lua types: numbers, tables, arrays, and strings) and writes a 
file that contains the table as a valid Lua script. All you need to do 
is print "return" to the file before calling "WriteTable", and you will 
get a Lua script. If you call "dofile" on this Lua script, it will 
return the table.

Luabind is *way* overkill for this.

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--This file exports a funciton, WriteTable, that writes a given table out to a given file handle.

require "_util";

local writeKey = {};

function writeKey.string(hFile, value, iRecursion)
	WriteFormatted(hFile, "[\"%s\"]", value);
end

function writeKey.number(hFile, value, iRecursion)
	WriteFormatted(hFile, "[%i]", value);
end

local writeValue = {};

function writeValue.string(hFile, value, iRecursion)
	WriteFormatted(hFile, "[==[%s]==]", value);
end

function writeValue.number(hFile, value, iRecursion)
	WriteFormatted(hFile, "%i", value);
end

function writeValue.boolean(hFile, value, iRecursion)
	if(value) then hFile:write("true"); else hFile:write("false"); end;
end

function writeValue.table(hFile, value, iRecursion)
	WriteTable(hFile, value, iRecursion)
end

local function WriteTabs(hFile, iRecursion)
	for iCount = 1, iRecursion, 1 do
		hFile:write("\t");
	end
end

function WriteTable(hFile, outTable, iRecursion)
	if(iRecursion == nil) then iRecursion = 1; end
	
	hFile:write("{\n");
	
	local bHasArray = false;
	local arraySize = 0;
	
	if(#outTable > 0) then bHasArray = true; arraySize = #outTable; end;
	
	for key, value in pairs(outTable) do
		if(writeKey[type(key)] == nil) then print("Malformed table key."); return; end
		if(writeValue[type(value)] == nil) then
			print( string.format("Bad value in table: key: '%s' value type '%s'.", key, type(value)));
			return;
		end
		
		--If the key is not an array index, process it.
		if((not bHasArray) or
				(type(key) ~= "number") or
				not((1 <= key) and (key <= arraySize))) then
			WriteTabs(hFile, iRecursion);
			writeKey[type(key)](hFile, key, iRecursion + 1);
			hFile:write(" = ");
			writeValue[type(value)](hFile, value, iRecursion + 1);
			
			hFile:write(",\n");
		end
	end
	
	if(bHasArray) then
		for i, value in ipairs(outTable) do
			WriteTabs(hFile, iRecursion);
			writeValue[type(value)](hFile, value, iRecursion + 1);
			hFile:write(",\n");
		end
	end

	WriteTabs(hFile, iRecursion - 1);
	hFile:write("}");
end