OpenEuphoria

RE: QWORD (int64) question

• Posted by Elliott Sales de Andrade <quantum_analyst at hotmail.com> Oct 17, 2002
• 450 views

Thanks, it looks great. I'd like to know a few other things first though. 
First off, to get the first param for that function, I'm using 
GetProcAddress(). I'm using the value returned from open_dll(). I'm not sure 
if that is right, so I'd like to know. Second, I have a few functions that 
need to pass floats. So, how would I do this exactly? Just atom_to_float32() 
and then bytes_to_int() ?  TIA


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>From: Matthew Lewis <matthewwalkerlewis at YAHOO.COM>
> > From: Robert Craig [mailto:rds at RapidEuphoria.com]
> > Elliott Sales de Andrade writes:
> > > I think I asked this before, but I would like to know how
> > > to get return values that are QWORD's. Someone said
> > > that QWORD's are pointers, but they are not. When
> > > passing QWORD's they use two INT's in VB, so it is definitely
> > > not 32 bits. I am guessing that I would have to use ASM to do this.
>
>
> > More likely, they use two 32-bit registers. You'd have to
> > maybe disassemble some compiled C code to get the answer,
> > and then use some machine code similar to Matt Lewis' DLL code.
>
>I found this on http://gcc.gnu.org/ml/gcc-bugs/2000-02/msg00104.html
>
>/*
>  * All the functions listed here are C callable, and may also be called
>  * from assembly using the C calling mechanism.  All INT64 functions
>  * return their results in edx:eax, where edx is the upper longword.
>  * Functions returning a long place the result in eax, and the contents
>  * of edx are destroyed.  All other registers are preserved.
>  */
>
>Based on that, I think this code (untested) should work.  The only real
>change from the standard code (in fptr.e) is that I added the mov edx to 
>get
>the second dword.  A similar fix could be added to the cdecl calls.  You 
>can
>use this to call a function that returns a qword, and it will return a
>sequence of two 32-bit unsigned integers.  When I get a chance, I'll work
>this into the main lib.
>
>include machine.e
>constant
>q_fptr_asm = {
>     #60,                    --    0: pusha
>     #BB,#00,#00,#00,#00,    --    1: mov ebx, paramcount (2)
>     #B9,#00,#00,#00,#00,    --    6: mov ecx, params (7)
>                             --    B: start:
>     #8B,#01,                --    B: mov eax, [ecx]
>     #50,                    --    D: push eax
>     #83,#C1,#04,            --    E: add ecx, 4
>     #4B,                    --   11: dec ebx
>     #75,#F7,                --   12: jnz start
>     #FF,#15,#00,#00,#00,#00,--   14: call dword ptr [comfunc] (22)
>     #A5,#00,#00,#00,#00,    --   1A: mov [retpointer], eax (27)
>     #A3,#00,#00,#00,#00,    --   1A: mov [retpointer], edx (31)
>     #61,                    --   20: popa
>     #C3},                   --   21: ret
>
>q_fptr_paramcount = 2,
>q_fptr_params = 7,
>q_fptr_funcptr = 22+0,
>q_fptr_retptr = 27+0,
>q_retval = allocate(8),
>
>q_fptr_asm_addr = allocate( length( q_fptr_asm ) + 20 * 5 )
>
>constant
>q_fptr_func = q_fptr_asm_addr + 33,
>q_fptr_retval = q_fptr_asm_addr + 37,
>q_fptr_param_ptr = q_fptr_asm_addr + 41
>
>poke( fptr_asm_q_addr, fptr_q_asm )
>poke4( q_fptr_asm_addr + q_fptr_funcptr, fptr_q_func )
>poke4( q_fptr_asm_addr + q_fptr_params, q_fptr_param_ptr )
>poke4( q_fptr_asm_addr + q_fptr_retptr, q_fptr_retval )
>poke4( q_fptr_asm_addr + q_fptr_retptr + 5, q_fptr_retval + 4 )
>
>global function call_fptr_qword( atom fptr, sequence params )
>     sequence ret
>     -- store the pointer to the function
>     poke4( q_fptr_func, fptr )
>
>     -- reverse the params for stdcall calling convention
>     params = reverse(params)
>
>     -- store the params
>     poke4( q_fptr_param_ptr, params )
>
>     -- tell the asm how many params to push
>     poke4( q_fptr_asm_addr + q_fptr_paramcount, length(params) )
>     -- run the asm
>     call( q_fptr_asm_addr )
>
>     -- get the value returned from the function
>     ret = peek4u( {q_fptr_retval,2} )
>     return ret
>end function
>
>Matt Lewis