OpenEuphoria

Re: calling C function array pointer

• Posted by Jason Gade <jaygade at yahoo.c?m> Jul 16, 2007
• 556 views

rlistas wrote:
> 
> Hi,
> 
> How do I call a C function in a dll that asks an argument
> like *buffer ( a pointer to an array) ?
> 
> (from Pcomm.ew)
> 	--(int port, char *buf, int len)
> global function sio_read(integer port, integer lpRBuf, integer len)
> 		return c_func(sio_read_,{port,lpRBuf,len})
> end function
> 
> 
> I try :
> 
> sequence buffer
> buffer={'0','0'}
> 
> sio_read(1,buffer[1],2)
> >error -8
> 
> and sio_read(1,buffer,2)  
> >incorrect type for lpRBuf.
> 
> 
> Thanks
> 
> Rubens
> 
> 

I'm not the expert on this, but in order to use a C pointer you will have to use
allocate() and peek()/poke()

lpRBuf will have to be declared as an atom.

(untested)

global function sio_read(integer port, atom lpRBuf, integer len)
		return c_func(sio_read_,{port,lpRBuf,len})
end function

atom buffer
buffer=allocate(2)
if buffer = 0 then
    puts("Unable to allocate buffer!\n")
    abort(1)
end if

sequence bytes_read
bytes_read = sio_read(1,buffer,2)
free(buffer) -- make sure to free memory when you are done with it.

-- then use peek(buffer) and peek(buffer+1) to read back your data.

References:
http://www.rapideuphoria.com/lib_a_b.htm#allocate
http://www.rapideuphoria.com/lib_e_g.htm#free
http://www.rapideuphoria.com/lib_p_r.htm#peek
http://www.rapideuphoria.com/lib_p_r.htm#poke

--
"Any programming problem can be solved by adding a level of indirection."
--anonymous
"Any performance problem can be solved by removing a level of indirection."
--M. Haertel
"Premature optimization is the root of all evil in programming."
--C.A.R. Hoare
j.