[Fwd: ncdigest V1 #574]

Date: Thu, 8 Feb 2001 10:19:58 +0100
From: =?iso-8859-1?Q?Jos=E9_Mar=EDa_Gonz=E1lez_Ondina?=
<address@hidden>
Subject: Re: problem using netcdf and Borland Delphi

> I am trying to read some cdf data files using Borland Delphi v 5.0 on a
> Windows NT machine.  I downloaded netcdf.dll from the unidata ftp site
>
(ftp://ftp.unidata.ucar.edu/pub/netcdf/contrib/win32/netcdf-3.5-beta5.win32b
> in.ZIP) and put the following definitions in my Delphi code:
>
> function nc_inq_libvers : pchar; external 'netcdf.DLL';
> function nc_strerror (ncerr : integer) : pchar; external 'netcdf.DLL';
> function nc_open (path : pchar; omode : integer; var ncidp : integer) :
> integer; external 'netcdf.DLL';
> function nc_close (ncidp : integer) : integer; external 'netcdf.DLL';
>
> When I call nc_inq_libvers I get what appears (?) to be a reasonable
answer:
>
> 3.5-beta5 of Oct 17 2000 10:28:35 $
>
> but when I call nc_strerror with any integer (I tried a lot of them), I
> always get back

  I think the problem can be in the calling convention and perhaps with
the
type of the parameter.

  I have been mixing Delphi with DLLs made in Visual C++, and here is an
examples of external function declaration, perhaps it may help you.

  Delphi Declaration:

function SetValue(Variable: PChar; VariableLength: Cardinal;
                  Value: PChar; ValueLength: Cardinal;
                  var Index, ValueType: Cardinal): Integer; cdecl;
                  external 'Intermed.dll';


  DLL C++ declaration:

#define DllExport extern "C" __declspec( dllexport )

enum TValueType {vtNone=0, vtReal, vtInteger, vtString, vtRealVector};

DllExport int   SetValue(char *Variable, unsigned int VariableLength,
                         char *Value, unsigned int ValueLength, int
*Index,
                         TValueType *ValueType);

  As you can see, C++'s ints have been replaced by Delphi's Cardinal,
and
the calling convention have been set to "cdecl".

  The only way I know to determine which calling convention you have to
use
and which are the types that match C++ (or other languages) types is
test
and error (and sometimes a little of inspection of the CPU window).

  By the way, I am very interested in use NetCDF from Delphi in the
future,
but now I don´t have the time to do the porting. I'll like very much if
you
keep me informed of your progress.

  Of course, if I can help you just write me.

José María González Ondina.

address@hidden

------------------------------

Date: Thu, 08 Feb 2001 14:06:17 +0100
From: Catrin Pieri <address@hidden>
Subject: Delphi and NetCDF

Dear Sandy,

You should use cdecl; as calling convention. See Delphi help for
details.

e.g. i use :

function nc_open(const path : Pchar; mode : integer; var ncidp :
integer):integer; cdecl; external 'netcdf.dll';

which works fine with Version 3.4 of NetCDF but the version should not
be
relevant.

Best regards Catrin
- --
____________________________________________________________________________
Catrin Pieri
HYDROMOD Wissenschaftliche Beratung GbR  --  HYDROMOD Scientific
Consulting
Büroadresse / Office address:         Bahnhofstr. 52,   D-22880 Wedel
Postanschrift / Postal Address:       Postfach 1229,   D-22871 Wedel
Tel.: 04103 / 9 12 23-0               Fax: 04103 / 9 12 23-23
mailto:address@hidden              http://www.hydromod.de
____________________________________________________________________________

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