OpenEuphoria

RE: Accessing EHLLAPI DLL files

• Posted by Matt Lewis <matthewwalkerlewis at yahoo.com> Sep 10, 2003
• 548 views

> From: pete_stoner at btconnect.com [mailto:pete_stoner at btconnect.com] 

> >The EHLLAPI entry point (hllapi) is always called with the following 
> >four
> parameters:
> >1.EHLLAPI Function Number (input)
> >2. Data Buffer (input/output)
> >3. Buffer Length (input/output)
> >4. Position (input); Return Code (output)
>  >   The prototype for the EHLLAPI is; (long hllapi(LPINT, 
> LPSTR, LPINT,
> LPINT)"
> > Each parameter is passed by reference not by value...... (etc etc)
> 
> My first problem is that I always get an error (-1) from my 
> define_c_function . The function I am calling is not listed 
> in the DLL I have to call, I am assuming that it must be in 
> another DLLs that the first one links to (?), also the book 
> says I have to call the function by number (I still don't 
> fully understand if I am defining it correctly) i.e. ehlapi = 
> open_dll("EHLAPI32.DLL") ConnectPS = define_c_func(ehlapi, 
> "1", {C_INT, C_POINTER, C_INT}, C_INT)
> 
> The ref book goes on to say..
> >All the parameters in the hllapi call are pointers and the 
> return code 
> >of
> the EHLLAPI function is returned in the value of the 4th 
> parameter, not as the value of the function.. Which would 
> suggest that I cannot get the return code with just the 
> normal ret = c_func(ConnectPS....

OK, let's start with the function prototype:

long hllapi(LPINT, LPSTR, LPINT,LPINT)

This tells us that it returns a long value (probably an error indicator for
hllapi itself, not the function you're calling).  The other parameters are
all pointers, do your define_c_func should look like:

xhllapi = define_c_func( elhapi, "hllapi", repeat(C_POINTER,4), C_INT )

Any function you want to call, you will need to call through the hllapi
function.  First, you need to allocate space in order to poke the values for
hllapi:

func_no = allocate(4)
buffer = allocate( 256 )
buffer_len = allocate(4)
position_return = allocate(4)

Then poke the values for the function (assuming that ConnectPS is function
#1):

poke4( func_no, 1 )
poke( buffer, your_input_data )
poke4( buffer_len, 256 )
poke4( position_return, whatever_this_means )

ret = c_func( xhllapi, {func_no,buffer,buffer_len,position_return} )

-- to see what the return value was:
? peek4s( position_return )


You should use whatever buffer size that makes sense.  Also, you should
check it after calling, because hllapi will probably tell you if it needs
more room to return whatever it was going to return in the buffer (if
anything--you'll have to read the documentation on each routine).  I'm not
sure what #4, Position means to hllapi, so I can't help you out there.

Matt Lewis