Saving and loading system in game?

Blitz3D Forums/Blitz3D Programming/Saving and loading system in game?

Cubed Inc.

(Posted 2013) [#1]

For my game, I'm trying to implement as simple "save point" system where you'd save in-game via statues (fairly commom trope) and it would save the level's number, player's position and other things like points and health. Another thing is, I'm trying to make a system where once you press start on the title screen, the game will automatically load that saved data from last time, but if the game can't find the save, it would start as if you'd never played it before (everything is default).

I'm only looking for help with the saving and loading. I've got the entire system of the statues and the title screen set and clear, but saving and loading the data is where I need help in.

Could someone please help me out? I hope my explaination of my problem wasn't too badly put:/

Yue	(Posted 2013) [#2]

I try to help.

You must create a file on the hard disk that holds the positions of the player and everything about the game, however the game Begin, that file will be read and if there continue.

That file can be created with a button "Save Game" or that it automatically each time interval.

Cubed Inc.

(Posted 2013) [#3]

Hi Yue
I'm very thankful for your willingness to help me, but I think you misunderstood my question. I want to know how to use the blitz functions of saving and loading. I'm still very grateful for your efforts to aid me:)

RemiD

(Posted 2013) [#4]

TaGames>>
This is a record+replay example but it shows how to write datas to a file, and then how to read datas from a file.
http://blitzbasic.com/codearcs/codearcs.php?code=2944

There are several others examples in the code archives,
http://www.google.fr/#q=write+read+file+site:blitzbasic.com

Charrua

(Posted 2013) [#5]

hi

see: http://blitzbasic.com/codearcs/codearcs.php?code=2863

Juan

Axel Wheeler

(Posted 2013) [#6]

One more point:

If you want a greater level of detail in your saves, consider BlitzXML:

http://www.blitzbasic.com/Community/posts.php?topic=46647

I notice the actual file wasn't at the link in the thread anymore, but if you want it I think I have it.

Cubed Inc.

(Posted 2013) [#7]

Okay, tell me if I'm doing this right or not ( just a brief genearalizition; not made to actually "run" )


savefile=WriteFile("savedgame.dat")

;Title screen stuff in here;
If gamestart=true 

saveopen=OpenFile("savedgame.dat")
saveread=ReadFile ("savedgame.dat")
EndIf

If gamestart=true And savefile=false
startgamenew=true
loadgame=false
else
startgamenew=false
loadgame=true
endif

I'm VERY sure I'm not understanding this...

Kryzon

(Posted 2013) [#8]

I don't think you need all those variables. Try something simpler:

Function TitleScreen()
	;Render whatever title\menu graphics you want.
	DrawTitleScreen()

	;If any of the keys assigned to "Start" are pressed, start the game.
	If (KeyHit(...) + KeyHit(...) + ...) Then
		If FileType("savedgame.dat") = 0 Then
			Return BEGIN_NEW_GAME ;No save-game file was found, so start the game from scratch.
		Else
			Return LOAD_GAME ;The file was found, so rebuild whatever level the player was in, down to the last details.
		EndIf
	EndIf
	
	Return TITLE_SCREEN
End Function

In your app's main loop...

Select currentState
	Case TITLE_SCREEN
		currentState = TitleScreen()
	Case BEGIN_NEW_GAME
		currentState = BeginNewGame()
	
	Case BUILD_LEVEL_1
		currentState = BuildLevel1()
	Case PLAY_LEVEL_1
		currentState = PlayLevel1()
	
	Case BUILD_LEVEL_2
		currentState = BuildLevel2()
	Case PLAY_LEVEL_2
		currentState = PlayLevel2()
	
	Case LOAD_GAME
		currentState = LoadGame()
End Select

Inside LoadGame() you'd load the file (ReadFile() is fine) and rebuild the state the game was in as it will be described in the file: all actors, props, objects etc. with current healths, frames of animation, positions.
When the loading function is done, at the end of it you set the currentState to whatever level the player was in, so that Select block runs the appropriate level function.
Thing is, the load function will have already built the level you're going to restore and repositioned everything as it was, so there's no need for the load function to change state to BUILD_LEVEL_#, but rather to PLAY_LEVEL_# so you continue straight into gameplay.

Consider the BUILD_LEVEL_# functions as code that sets up the levels: loads the environment mesh, creates objects, positions the player, shows level intro cutscenes etc. - These won't be needed if you're loading a game that has a level being played; that's why the saved-game loading function already heads to one of those PLAY_LEVEL_# functions that only let the game run.

mv333

(Posted 2013) [#9]

I notice the actual file wasn't at the link in the thread anymore

http://web.archive.org/web/20100126022607/http://www.alsbonsai.com/john/BlitzXML_v1.71.zip

Axel Wheeler

(Posted 2013) [#10]

To the rescue! Thanks.

Guy Fawkes

(Posted 2013) [#11]

I'm wondering how to store my save data and read it in banks, so there IS no save file.

virtlands

(Posted 2013) [#12]

Thundros wrote "I'm wondering how to store my save data and read it..."

I assume that you want to use save-files sometimes, but not all the time.
In case you'd want to send the save-file into a bank then you can do something like this:

;;------------------------------------------------------------------------
;Creates and reads a bank from filename$
;size=file size, pos=file position
;Returns a bank
Function FiBankFromFile(filename$, size = 0, pos = 0)
Local bank, file
If size = 0 Then size = FileSize(filename$)
bank = CreateBank(size)
file = ReadFile(filename$)
If file
SeekFile(file, pos)
ReadBytes(bank, file, 0, size)
CloseFile(file)
EndIf
Return bank
End Function

;Appends a bank to filename$
;size=file size, pos=file position
;Returns True if succeeds or False if fails
Function FiBankToFile(bank, filename$, size = 0, pos = 0)
Local file
If bank = 0 Then Return 0 ;No bank
If size = 0 Then size = FileSize(filename$)
file = OpenFile(filename$) ;Existing file
If file = 0 Then file = WriteFile(filename$) ;New file
If file
SeekFile(file, pos)
WriteBytes(bank, file, 0, size)
CloseFile(file)
file = 1
EndIf
Return file
End Function
;;------------------------------------------------------------------------

The above functions were taken from the FreeImage.BB package:
( Has excellent image functions, along with some functions that don't involve images as well. )

FreeImage link: http://freeimage.sourceforge.net/

Sorry, the black background hurts my eyes so sometimes I'll just show stuff without using [codebox].

Ginger Tea

(Posted 2013) [#13]

Sorry, the black background hurts my eyes so sometimes I'll just show stuff without using [codebox].

Try a different theme, I am using default or something, whites and greys, boring to look at but easy on the eyes regarding text.

Although I do agree that at some point a bank would need to be saved to a file, unless of course you are making more of a checkpoint, in that regard no need to save it if it is a temp and RAM would suffice.

Guy Fawkes

(Posted 2013) [#14]

No, actually, I want to save the memory to a memory bank, and somehow have it there next time I open the app so I can load it from memory.

Yasha

(Posted 2013) [#15]

That's what a save file is for.

Yes I see post #11 where you also specify "no save file". What you are asking for is impossible and defies the entire concept of a filesystem. Memory doesn't work that way. It is reset every time the program runs. This is why your earlier attempt to save entity handles didn't work: the entities stop existing between program runs, and so does everything else that isn't a file.

Note that you can save the entire contents of a bank in one operation with WriteBytes, and load the entire contents of a file to a bank using CreateBank(FileSize(...)) + ReadBytes. But there's no magic solution that can keep memory valid between program runs without you doing at least that much.

Ginger Tea

(Posted 2013) [#16]

just for clarification, do you mean saving a memory bank to the hard drive and then retrieving said file upon start up or just assuming that nothing like a pc restart will happen between you exiting the game and then later reentering, cos I'm pretty sure most programs have a house clearance freeing up ram on exit.

basically for the first option you just need it to auto load a specific file upon start up, basically a save game file ...

2nd option, fools errand.

Guy Fawkes

(Posted 2013) [#17]

Ok, relax guys. I was just curious.

Who was John Galt?

(Posted 2013) [#18]

@TaGames...

First off, and this is only personal opinion, but I would forget XML and INI files for this as I think it complicates the task. The easiest way, is something like this... consider this pseudocode as my B3D is years rusty and it's from memory.

type tAlien
   field x,y
end type

function writeAlien(alien.tAlien)
    writeInt(alien\x)
    writeInt(alien\y)
end function

function readAlien.tAlien()
     alien.tAlien=new tAlien
     alien\x=readInt()
     alien\y=readInt()
end function

So if you have a type tAlien, this should write its fields to disc, and recreate it by reading the fields back into a new tAlien. Got a whole bunch of aliens? Write the number of aliens to disc, then call writeAlien for each one. To Recreate them, first read a number from file (this tells you how many aliens to create), then call readAlien that many times. The key here is to ensure you read everything back in the same order you wrote it. Do this by keeping your read and write function next to each other so you can compare orders.

function readgame()
      readaliens()
      readplayers()
end function

function writegame()
       writealiens()
       writeplayers()
end function

Using this method, you can rebuild all your types. Stuff that isn't based on types can use a similar method.

Obviously I've missed a few bits out like opening and closing files, but I'm sure you get the idea.

The advantage of INI files and XML is human readability, but it's all just bloat for a game load/save feature.