OpenEuphoria

RE: C structs & bad aftershave...

• Posted by Steve <bleak_outlook at hotmail.com> Feb 25, 2006
• 460 views

Hi Bernie,

Thanks for the response.  I just wanted to see if this example is up the 
right tree or not:

atom videoInfo

videoInfo = SDL_GetVideoInfo()

if and_bits(videoInfo, #8000) then
  -- hw available
else
  -- hw unavailable
end if

Does that look correct?  

Thanks for the help!

Steve












Bernie Ryan wrote:
> 
> 
> posted by: Bernie Ryan <xotron at bluefrog.com>
> 
> 
> Steve wrote:
> > 
> > 
> > Anyone have any idea about this?
> > 
> > Do you need more information?  Is it not possible?
> > 
> > Hello?  :)
> > 
> > Steve
> > 
> > 
> > Steve wrote:
> > > 
> > > 
> > > Ok no Old Spice... I just wanted some attention! :)
> > > 
> > > Background: Lest I get ahead of myself.
> > > I am using M Akita's SDL for Eu wrapper. SDL is compiled into a DLL.
> > > I want to access a member of a C structure. 
> > > 
> > > typedef struct{
> > >   Uint32 hw_available:1;
> > >   Uint32 wm_available:1;
> > >   Uint32 blit_hw:1;
> > >   Uint32 blit_hw_CC:1;
> > >   Uint32 blit_hw_A:1;
> > >   Uint32 blit_sw:1;
> > >   Uint32 blit_sw_CC:1;
> > >   Uint32 blit_sw_A:1;
> > >   Uint32 blit_fill;
> > >   Uint32 video_mem;
> > >   SDL_PixelFormat *vfmt;
> > > } SDL_VideoInfo;
> > > 
> > > I can access its value by doing this:
> > > 
> > > atom videoInfo
> > > 
> > > videoInfo = SDL_GetVideoInfo()
> > > 
> > > How do I, using Euphoria, best go about reading the above bit flags?
> > > I have tried this:
> > > 
> > > <EuCode)
> > > sequence mbits
> > > atom lflg
> > > 
> > > mbits = int_to_bits(videoInfo)
> > > 
> > > sprintf("flags: %d %d %d ...<snip>", {mbits[1], mbits[2], ...<snip>})
> > > 
> > <font color="#330033">> <EuCode></font>
> > <font color="#330033">> </font>
> > <font color="#330033">> Which gives me some really odd results.  When I 
> > </font><font color="#FF00FF">peek </font><font color="#330033">36 bytes 
> > into this </font>
> > <font color="#330033">> structure, </font><font color="#0000FF">and 
> > </font><font color="#330033">grab 4 bytes, I </font><font 
> > color="#0000FF">do </font><font color="#330033">get the correct amount 
> > of video memory </font>
> > <font color="#330033">> </font>
> > <font color="#330033">> </font><font color="#0000FF">for </font><font 
> > color="#330033">my graphics card.  There ends my success though.</font>
> > <font color="#330033">> </font>
> > <font color="#330033">> Could someone explain </font><font 
> > color="#0000FF">to </font><font color="#330033">me how </font><font 
> > color="#0000FF">to </font><font color="#330033">access the bit flags of 
> > that struct?</font>
> > <font color="#330033">> I seem </font><font color="#0000FF">to 
> > </font><font color="#330033">be doing this all wrong despite my best 
> > intentions. :)</font>
> > <font color="#330033">> </font>
> > <font color="#330033">> For more info, here is the SDL API page.</font>
> > <font color="#330033">> 
> > http://www.libsdl.org/cgi/docwiki.cgi/SDL_20API</font>
> > <font color="#330033">> </font>
> > <font color="#330033">> Thanks again. As always, you guys rule.</font>
> > <font color="#330033">> </font>
> > <font color="#330033"></font>
> > <font color="#330033"></font>
> 
> Steve:
> 
> The part of the structure Uint32 is a 32bit unsigned integer
> 
> In order to look at bitfield hw_available for example,  you have to AND
> the binary number 1000 0000 0000 0000  or #8000 hex with
> Uint32 portion of the structure 
> 
> Therefore:  and_bits(Uint32,#8000) would give you hw_available
>             
>                     -- binary 0010 0000 0000 0000
>             and_bits(Uint32,#2000) would give you blit_hw
>    etc.
>  
> Bernie
> 
> My files in archive:
> WMOTOR, XMOTOR, W32ENGIN, MIXEDLIB, EU_ENGIN, WIN32ERU, WIN32API 
> 
> Can be downloaded here:
>
> http://www.rapideuphoria.com/cgi-bin/asearch.exu?dos=on&win=on&lnx=on&gen=on&keywords=bernie+ryan
>