Help with blockread/blockwrite

[Frank Heckenbach]

Prof A Olowofoyeku (The African Chief) wrote:

> On 7 Feb 2004 at 21:25, Peter Norton wrote:
> 
> > The Chief wrote:
> > > Please send an example of such code.
> > 
> > <code snippet>
> > bmpinfo = record (*BMP header*)
> [...]
> You will need to pack the record (bearing in mind CBF's warning about 
> portability, etc.). Using "packed" may not always be portable. The 
> following solution may or may not be portable (Frank can tell us):
> 
> type
> {$ifdef __GPC__}{$pack-struct, maximum-field-alignment 8} {$endif}
> bmpinfo = record (*BMP header*)
>     b1, b2 : char;
>     size : integer;
>     reserved : integer;
>     offset : integer;
>     headersize : integer;
>     width : integer;
>     height : integer;
>     planes : shortword;
>     bpp : shortword;
>     compression : integer;
>     comprsize : integer;
>     horresolution : integer;
>     verresolution : integer;
>     usedcolors : integer;
>     importantcol : integer;
>     end;
> {$ifdef __GPC__}{$no-pack-struct, maximum-field-alignment 0}{$endif}

To be portable, you cannot use types like `Integer' and `ShortWord'
which can have different sizes. You can define your own types to be
`Integer attribute (Size = 32)', `Cardinal attribute (Size = 16)'
etc. Also you have to do explicit endianness conversions (see
`ConvertFromLittleEndian' etc. in gpc.pas).

Frank

-- 
Frank Heckenbach, frank at g-n-u.de, http://fjf.gnu.de/, 7977168E
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