tablehandling.lua

--[[
   Save Table to File/Stringtable
   Load Table from File/Stringtable
   v 0.94

   Lua 5.1 compatible

   Userdata and indices of these are not saved
   Functions are saved via string.dump, so make sure it has no upvalues
   References are saved
   ----------------------------------------------------
   table.save( table [, filename] )

   Saves a table so it can be called via the table.load function again
   table must a object of type 'table'
   filename is optional, and may be a string representing a filename or true/1

   table.save( table )
      on success: returns a string representing the table (stringtable)
      (uses a string as buffer, ideal for smaller tables)
   table.save( table, true or 1 )
      on success: returns a string representing the table (stringtable)
      (uses io.tmpfile() as buffer, ideal for bigger tables)
   table.save( table, "filename" )
      on success: returns 1
      (saves the table to file "filename")
   on failure: returns as second argument an error msg
   ----------------------------------------------------
   table.load( filename or stringtable )

   Loads a table that has been saved via the table.save function

   on success: returns a previously saved table
   on failure: returns as second argument an error msg
   ----------------------------------------------------

   chillcode, http://lua-users.org/wiki/SaveTableToFile
   Licensed under the same terms as Lua itself.
]]--

   -- declare local variables
   --// exportstring( string )
   --// returns a "Lua" portable version of the string
   local function exportstring( s )
      s = string.format( "%q",s )
      -- to replace
      s = string.gsub( s,"\\\n","\\n" )
      s = string.gsub( s,"\r","\\r" )
      s = string.gsub( s,string.char(26),"\"..string.char(26)..\"" )
      return s
   end
--// The Save Function
function table.save(  tbl,filename )
   local charS,charE = "   ","\n"
   local file,err
   -- create a pseudo file that writes to a string and return the string
   if not filename then
      file =  { write = function( self,newstr ) self.str = self.str..newstr end, str = "" }
      charS,charE = "",""
   -- write table to tmpfile
   elseif filename == true or filename == 1 then
      charS,charE,file = "","",io.tmpfile()
   -- write table to file
   -- use io.open here rather than io.output, since in windows when clicking on a file opened with io.output will create an error
   else
      file,err = io.open( filename, "w" )
      if err then return _,err end
   end
   -- initiate variables for save procedure
   local tables,lookup = { tbl },{ [tbl] = 1 }
   file:write( "return {"..charE )
   for idx,t in ipairs( tables ) do
      if filename and filename ~= true and filename ~= 1 then
         file:write( "-- Table: {"..idx.."}"..charE )
      end
      file:write( "{"..charE )
      local thandled = {}
      for i,v in ipairs( t ) do
         thandled[i] = true
         -- escape functions and userdata
         if type( v ) ~= "userdata" then
            -- only handle value
            if type( v ) == "table" then
               if not lookup[v] then
                  table.insert( tables, v )
                  lookup[v] = #tables
               end
               file:write( charS.."{"..lookup[v].."},"..charE )
            elseif type( v ) == "function" then
               file:write( charS.."loadstring("..exportstring(string.dump( v )).."),"..charE )
            else
               local value =  ( type( v ) == "string" and exportstring( v ) ) or tostring( v )
               file:write(  charS..value..","..charE )
            end
         end
      end
      for i,v in pairs( t ) do
         -- escape functions and userdata
         if (not thandled[i]) and type( v ) ~= "userdata" then
            -- handle index
            if type( i ) == "table" then
               if not lookup[i] then
                  table.insert( tables,i )
                  lookup[i] = #tables
               end
               file:write( charS.."[{"..lookup[i].."}]=" )
            else
               local index = ( type( i ) == "string" and "["..exportstring( i ).."]" ) or string.format( "[%d]",i )
               file:write( charS..index.."=" )
            end
            -- handle value
            if type( v ) == "table" then
               if not lookup[v] then
                  table.insert( tables,v )
                  lookup[v] = #tables
               end
               file:write( "{"..lookup[v].."},"..charE )
            elseif type( v ) == "function" then
               file:write( "loadstring("..exportstring(string.dump( v )).."),"..charE )
            else
               local value =  ( type( v ) == "string" and exportstring( v ) ) or tostring( v )
               file:write( value..","..charE )
            end
         end
      end
      file:write( "},"..charE )
   end
   file:write( "}" )
   -- Return Values
   -- return stringtable from string
   if not filename then
      -- set marker for stringtable
      return file.str.."--|"
   -- return stringttable from file
   elseif filename == true or filename == 1 then
      file:seek ( "set" )
      -- no need to close file, it gets closed and removed automatically
      -- set marker for stringtable
      return file:read( "*a" ).."--|"
   -- close file and return 1
   else
      file:close()
      return 1
   end
end

--// The Load Function
function table.load( sfile )
   -- catch marker for stringtable
   if string.sub( sfile,-3,-1 ) == "--|" then
      tables,err = loadstring( sfile )
   else
      tables,err = loadfile( sfile )
   end
   if err then return _,err
   end
   tables = tables()
   for idx = 1,#tables do
      local tolinkv,tolinki = {},{}
      for i,v in pairs( tables[idx] ) do
         if type( v ) == "table" and tables[v[1]] then
            table.insert( tolinkv,{ i,tables[v[1]] } )
         end
         if type( i ) == "table" and tables[i[1]] then
            table.insert( tolinki,{ i,tables[i[1]] } )
         end
      end
      -- link values, first due to possible changes of indices
      for _,v in ipairs( tolinkv ) do
         tables[idx][v[1]] = v[2]
      end
      -- link indices
      for _,v in ipairs( tolinki ) do
         tables[idx][v[2]],tables[idx][v[1]] =  tables[idx][v[1]],nil
      end
   end
   return tables[1]
end