Writing Array to a File - GameCreators Forum

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D a r k

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Posted: 22nd Oct 2007 03:34

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I am trying to read a map file so I can load the tiles to my grid accordingly. But I seem to get into trouble when writing it. (The problem could be when I read the file but I dout it.)

Here is my code to write the map data (Stored in more than one array)

+ Code Snippet

Open To Write 1,"newMap.txt"

`Saving the Array's
For SaveNo=1 to 850
    Write Byte 1,ImgNo(SaveNo)
    Write Byte 1,xCoords(SaveNo)
    Write Byte 1,yCoords(SaveNo)
    Write Byte 1,tileNo(SaveNo)
Next SaveNo

The problem I am having is that it seems to write in only the first four data spots.

So when I read I get something like this:

40
133
10
12
Then 846 0's

And the data is always of the last tile placed. I want it to write each set of numbers, not just overwrite the first four over and over again. How can I do this. Or, is there a better way of going about this?

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Latch

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Posted: 22nd Oct 2007 18:05 Edited at: 22nd Oct 2007 18:06

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Hello,

Even though it's hard to tell from your post whether you are dealing with a 3d matrix or a custom 2d grid, the method of approach I'll demonstrate should still be applicable.

One thing that stuck out immediately when I looked at your code was that you were writing BYTES. This is fine as long as the values are between 0 and 255. If your x and y are in screen coordinates, then 255 (a byte) is generally not going to be a high enough number, the same goes for an image number (up to 65535) and your tile numbers which your loop suggests goes up to 850. Now if this was 3d, then x and y could be float values (ex 123.456) which also wouldn't work when writing only a BYTE to a file.

Again, without knowing the format or the types of your data, I can only make some assumptions. First thing, is to make sure you are writing the same data type to the file as your program uses. If your x and y are float values, write a FLOAT to the file. If your image number is larger than 255, then write that as a WORD to your file. Here's an example. I assume that x and y are the number of tiles across and up so I'll leave that data type as a byte (you could have a grid size of 255 x 255). I assume the max image number is 65535 and that the maximum number of tiles is 255 * 255 so they can both be written as WORDs.

The example only has ImgNo() stored as an array and the other values are just determined by the loop. This is just one way of doing it:

+ Code Snippet

rem assuming grid size in tiles is 25 x 34 = 850 tiles
rem y could be the lower or upper left hand corner and x goes from left to right
highx=25
highy=34
tile=0
dim ImgNo(850)

open to write 1,"newMap.txt"
for y=0 to highy-1
   for x=0 to highx-1
      inc tile
      write word 1,ImgNo(tile)
      write byte 1,x
      write byte 1,y
      write word 1,tile
   next x
next y
close file 1

When you read the data back, you have to read it with the same data types, but you can assign the values to whatever arrays or variables you want.

Enjoy your day.

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Libervurto

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Posted: 23rd Oct 2007 19:18

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Haven't read through Latch's answer so sorry if you've already said this.
Arrays are perfect for maps, because they themselves have coordinates you can use. You should only have one array to store your entire map, like this: map(x,y).
If you are only storing the image used for the tile then you don't need to specify a 3rd dimension, you can store your image data in the appropriate coordinates like this: map(1,5)=3, so now the tile at 1,5 will use image 3.
If you want to store more than one piece of data on each tile, you'll need a 3rd dimension.

Lets say that this is a strategy game and we want to store how much stone, wood and food each tile contains; We'd do this: DIM map(100,100,3). We will use map(x,y,0) to store the image for the tile, map(x,y,1) to store the amount of stone, map(x,y,2) to store the amount of wood and map(x,y,3) to store the amount of food.

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Bluestar4

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Posted: 1st Dec 2007 20:53

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I recomend after studying up on arrays in the manual that you use the save array command - its a very nice command that will allow you to save your arrays with only one line. Loading the arrays back are just as simple using the "load array" command. These commands also work with multi-dimension arrays as well. The only thing you have to remember when using arrays is that arrays in db are zero based like in c++ - the first element is 0 and the last you dont want to write to or it will corrupt any data.

Sutter Soft
http://www.geocities.com/suttersoft

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TDK

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Posted: 1st Dec 2007 21:51

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There are two down-sides to using Save Array (ignoring the fact that in the past it has occasionally failed to work for me).

The first is that you can only save a single array in a file. If you have multiple arrays and other data, you can't save them in a single file.

The second is that other than using Load Array, you can't easily check what you have written to a file. If Load Array doesn't work then there's no way of knowing whether the Save or the Load part is the problem.

I would suggest that at first, you use the same method you are using, but use WRITE STRING for every piece of data.

You can then open up the file with Windows Notepad and check to see if the data matches with what your loading routine expects to be there. At the moment, I tend to agree with what latch said.

So, your save routine would be:

+ Code Snippet

Open To Write 1,"newMap.txt"
`Saving the Array's
For SaveNo=1 to 850
    Write String 1,Str$(ImgNo(SaveNo))
    Write String 1,Str$(xCoords(SaveNo))
    Write String 1,Str$(yCoords(SaveNo))
    Write String 1,Str$(tileNo(SaveNo))
Next SaveNo
Close File 1

As an aside, I would be tempted to instead use:

+ Code Snippet

Open To Write 1,"newMap.txt"
`Saving the Array's
For SaveNo=1 to 850
  Write String 1,Str$(ImgNo(SaveNo))
Next SaveNo
For SaveNo=1 to 850
  Write String 1,Str$(xCoords(SaveNo))
Next SaveNo
For SaveNo=1 to 850
  Write String 1,Str$(yCoords(SaveNo))
Next SaveNo
For SaveNo=1 to 850
  Write String 1,Str$(tileNo(SaveNo))
Next SaveNo
Close File 1

but the end result is the same - it's just a matter of preference. The only advantage is that all the data of the same type is written together in blocks.

You can then add comments before each block stating what the block of data is:

Open To Write 1,"newMap.txt"
`Saving the Array's
Write String 1,"; ***************************************"
Write String 1,"; Section 1: 850 Image Numbers (Integers)"
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(ImgNo(SaveNo))
Next SaveNo
Write String 1,";"
Write String 1,"; ***************************************"
Write String 1,";    Section 2: 850 xCoords (Integers)   "
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(xCoords(SaveNo))
Next SaveNo
Write String 1,";"
Write String 1,"; ***************************************"
Write String 1,";    Section 3: 850 yCoords (Integers)   "
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(yCoords(SaveNo))
Next SaveNo
Write String 1,";"
Write String 1,"; ***************************************"
Write String 1,";    Section 4: 850 tileNo (Integers)    "
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(tileNo(SaveNo))
Next SaveNo
Close File 1

+ Code Snippet

Open To Write 1,"newMap.txt"
`Saving the Array's
Write String 1,"; ***************************************"
Write String 1,"; Section 1: 850 Image Numbers (Integers)"
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(ImgNo(SaveNo))
Next SaveNo
Write String 1,";"
Write String 1,"; ***************************************"
Write String 1,";    Section 2: 850 xCoords (Integers)   "
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(xCoords(SaveNo))
Next SaveNo
Write String 1,";"
Write String 1,"; ***************************************"
Write String 1,";    Section 3: 850 yCoords (Integers)   "
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(yCoords(SaveNo))
Next SaveNo
Write String 1,";"
Write String 1,"; ***************************************"
Write String 1,";    Section 4: 850 tileNo (Integers)    "
Write String 1,"; ***************************************"
For SaveNo=1 to 850
  Write String 1,Str$(tileNo(SaveNo))
Next SaveNo
Close File 1

OK, it's longer, but if it works or helps solve the problem...

To read the file back in you would use something like:

Open To Read 1,"newMap.txt"
`Saving the Array's
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: ImgNo(SaveNo)=VAL(T$)
Next SaveNo
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: xCoords(SaveNo)=VAL(T$)
Next SaveNo
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: yCoords(SaveNo)=VAL(T$)
Next SaveNo
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: tileNo(SaveNo)=VAL(T$)
Next SaveNo
Close File 1

+ Code Snippet

Open To Read 1,"newMap.txt"
`Saving the Array's
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: ImgNo(SaveNo)=VAL(T$)
Next SaveNo
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: xCoords(SaveNo)=VAL(T$)
Next SaveNo
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: yCoords(SaveNo)=VAL(T$)
Next SaveNo
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
Read String 1,T$: Rem Read and ignore comment
For SaveNo=1 to 850
  Read String 1,T$: tileNo(SaveNo)=VAL(T$)
Next SaveNo
Close File 1

Once it's all working, you can remove the comments.

To be honest, I load and save all my data files this way as it's no slower and much quicker to track down any problems which occur.

TDK_Man

* TDK's Game Programming Forums - Open To All - DB & Team Request Boards *

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Bluestar4

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Posted: 2nd Dec 2007 01:55

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@ tdk
I have never had load or save array commands fail except when I mistyped something.

now , as tdk pointed out, there are downsides , but there are equally good reasons to use this command - firstly as tdk pointed out , you can only save one array to a file. This array can be as big or little as you wish and at your discretion can also be a multi-dimentional array. since each file would only contain one array it makes good for debugging as there is no onscreen variable debugger in dbc - in short , it allows you to deal with one arrray per a file at a time. The second advantage is that its one line ,not 5,10 or 20. that said, I now point out that both ways to save imformation are equally good so long as you as the programmer are comfortable with it. There may be cases when you want to only save an array in which case this would be the ultimate command, however, there may be times when you want to store more than just the array , but all kinds of data and you want it all in one file. In this case, you wouldn't want to use the save array command. In any event , I hope that tdk & my responses to your questions have in some way helped you to be a better programmer.

Sutter Soft
http://www.geocities.com/suttersoft

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TrueDB

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Posted: 30th Dec 2007 03:56

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if you use save array, then save array again to another file you have 2 temp files, then write a little code to join them into a perminent filesave(multiarray) then delete temp arrays

Now write the reverse code to unjoin them and load 2 temp arrays, then delete temp arrays.

ok hope it helps

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Pixelator

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Posted: 31st Dec 2007 04:43

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one last problem to add to the LONG list of problems for save and load array - you can only save in .txt files!!!

Maryville Game Developers
Visit our website at http://www.freewebs.com/maryville-game-developers/index.htm

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Bluestar4

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Posted: 31st Dec 2007 09:02

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@pixelator
nope - save to .dat i.e....

save array "positions.dat",positions#(110)
save array "names.dat",names$(17)
save array "hitpoints.dat",health(17)

Sutter Soft
http://www.geocities.com/suttersoft

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