Array Pointer

BlitzMax Forums/BlitzMax Beginners Area/Array Pointer

mothmanbr

(Posted 2007) [#1]

Hi,

I converted an int array to a byte pointer, but I cannot figure out how I can create an int array from the byte pointer or how to access the members directly.

Global Array:Int[] = [100,200]
Global Pointer:Byte Ptr = Varptr Array

This is how I am getting the array address. How can I convert it back to an int array, or even better, access the values from the pointer correctly?

Dreamora

(Posted 2007) [#2]

You can not create an int array from a byte ptr again. BM is typesafe and won't let you get an object from a typeless pointer again.
You must access it on memory level, this means int(pointer[i*4]) where i is the index.

GW	(Posted 2007) [#3]

this means int(pointer[i*4]) where i is the index.

Does that even work? Are not the first 16 or so bytes used for type info?

Gabriel

(Posted 2007) [#4]

Are not the first 16 or so bytes used for type info?

In types (objects) they are, but ints are not objects in BlitzMax.

GW	(Posted 2007) [#5]

In types (objects) they are, but ints are not objects in BlitzMax.

really? Pass a bmax array to a C function and see what it gets you.

Brucey

(Posted 2007) [#6]

I converted an int array to a byte pointer

I'm not sure why on earth you'd ever want to do that... but you'll need some c/c++ glue to get it back from a pointer to the array...

something like this untested example :

' max code

Extern
  Function convertIntArrayPointerBackToArray:Int[](pointer:Byte Ptr)
End Extern

// some c++ glue

#include "blitz.h"

extern "C" {

   BBArray * convertIntArrayPointerBackToArray(BBArray * array) {
      return array;
   }

}

Azathoth

(Posted 2007) [#7]

You must access it on memory level, this means int(pointer[i*4]) where i is the index.

You could use Int Ptr(pointer)[i]

really? Pass a bmax array to a C function and see what it gets you.

Use Varptr Array[0] instead to treat it like a C array.