OpenEuphoria

Re: sprites

• Posted by Michael Bolin <michaeltom at GEOCITIES.COM> Apr 01, 1997
• 1084 views

> David,
> This is what i made with the source code you sent.
> For some strange reason the program just crash, and i
> don't have any idea why. Perhaps Robert Craig can explain
> this. I send the code and the CW.ERR file produced by
> Causeway. I guess the problem is just of Causeway, because
> there's no ex.err file generated (well, causeway didn't let
> the asm routine to finish).
> Rob, are you sure i can PUSH and POP?

Your problem is that Euphoria is running in 32-bit protected mode,
not real mode, and machine code instructions are processed
differently in this mode.

For example, the code #50 for which your comment shows :  -- push ax
is actually executing the instruction: -- push eax!

The instruction to load the DX register is actually loading the EAX
register, which takes four bytes, so you will need some extra zeros.
Also, you want a TEST instruction, not an AND.
Lastly, there's no reason to waste precious DOS memory, when you can
use extended memory. Just use allocate() instead of allocate_low().

Like this:

include machine.e

sequence code
atom code_space

code = {
               #50,                                         -- push eax
               #52,                                         -- push edx
               #BA, #DA, #03, #00,#00,      -- mov edx,#3DA
               #EC,                                        -- loop: in al,edx
               #A8, #08,                                -- test al,#8
               #75, #FB,                                -- jnz loop
               #EC,                                        -- finish: in al,edx
               #A8, #08,                                -- test al,#8
               #74, #FB,                                -- jz finish
               #5A,                                        -- pop edx
               #58,                                         -- pop eax
               #C3}                                        -- ret

code_space = allocate(length(code))
poke(code_space,code)

puts(1,"\n Calling machine code routine for waiting retrace... \n ")

call(code_space)

free(code_space)

puts(1,"All done!\n")

Regards,
              Michael Bolin