Array to MemoryBlock

General
1

Which is the best way to create a MemoryBlock that holds all the values of an array of doubles (two dimensions).
I must be able to send this array to a Declare for an external DLL, and I don’t know how.

If this conversion is automatic (I wish it was, but I think it’s not), how are values stored in the MemoryBlock, by columns or by rows?

Thanks for any help.

2

It’s going to depend on what the external DLL is expecting. What do the docs say?

3

Assuming this is a C based DLL means you’ll have to write all the values from your Xojo array in row major order

Create the memory block to hold all the values - width * height * sizeof double (which is 8 bytes)
Then iterate over the values row by row & plop them in the mb

   dim offset as integer 
   for row as integer = 0 to ubound(myArrayOfDoubles,1)
         for col as integer = 0 to ubound(myArrayOfDoubles,2)
                   memBlock.doublevalue(offset) = myArrayOfDoubles(row,col)
                   offset = offset + 8
          next
   next

EDIT : DUH there’s a bug … remember to increment the offset each time :stuck_out_tongue:

4

Thanks Norman.
That’s what I supposed, but I needed someone with more knowledge than me to confirm.

5

note my edit :slight_smile:

6

[quote=134400:@Norman Palardy]note my edit :)[/quote]ok

7

C arrays are fairly simple
You can calculate the position of any element (say in a 2 D array - I’d have to poke around to be sure about more dimensions)

position = ((row * column count) * size of element) + (col * sizeof element)

So in this case your element size is 8 (thats the size of a double)
If it we an int32 thats 4 bytes and away you go