[OSRS-PROJ] delphi API Conversion for proj.dll

Mike Schmidt mike at sepia.com
Thu Jul 11 10:40:44 EDT 2002

I use proj from both VC++ and VB. I don't know Delphi very well, but I have 
a few suggestions:

1. pj_errno is a variable, not a function. Calling it as a function will 
cause you to crash with an access violation.

2. There is no need to know the contents of PJ*, you should use it simply 
as an opaque pointer. Then there is no problem calling PJ_free.

3. I can't really comment on the stack overflow in the situation you show. 
All I can say is that I have not seen this problem myself.

BTW, You don't need definitions of UV and LP for anything.

At 04:23 PM 11/07/2002 +0800, bornkilled wrote:
>hi, I want to make a delphi API Conversion for  proj.dll( I have compile 
>it by VC6)
>I wrote pas  in this way
>unit proj_dll;
>   windows;
>   ProjDll='proj.dll';
>   projPJ=Pointer;
>   XY=record
>     X:Double;
>     Y:Double;
>   end;
>   UV=XY;
>   LP=XY;
>   function pj_init(argc:DWord;argv:PLPSTR):projPJ;stdcall;
>   function pj_init_plus(definition:PChar):projPJ;stdcall;
>   procedure pj_free(var P:projPJ);stdcall;
>   procedure pj_deallocate_grids();stdcall;
>   function pj_errno():DWORD;stdcall;
>   function pj_fwd(aLP:LP;P:projPJ):XY;stdcall;
>   function pj_inv(aXY:LP;P:projPJ):LP;stdcall;
>   function pj_is_latlong(P:projPJ):DWORD;stdcall;
>   function pj_init;external ProjDll Name 'pj_init';
>   function pj_init_plus;external ProjDll Name 'pj_init_plus';
>   procedure pj_free;external ProjDll Name 'pj_free';
>   procedure pj_deallocate_grids();external ProjDll Name 
> 'pj_deallocate_grids';
>   function pj_errno;external ProjDll Name 'pj_errno';
>   function pj_fwd;external ProjDll Name 'pj_fwd';
>   function pj_inv;external ProjDll Name 'pj_inv';
>   function pj_is_latlong ;external ProjDll Name 'pj_is_latlong';
>But I meet some trouble :
>1:pj_errno make an exception "Access Violation" in any case;
>2:I can not find the excatly definition of PJ*,so i can not use 
>pj_free(),that will cause a memory leak .
>3:pj_fwd will raise stack overflow in the case of the code below:
>procedure TForm2.Button1Click(Sender: TObject);
>   P:projPJ;
>   errorno:Integer;
>   temp:XY;
>   temp1:XY;
>   nu:Cardinal;
>   i:Integer;
>   P:=pj_init_plus(PChar(' +proj=utm +zone=11 +ellps=WGS84));
>   i:=pj_errno;
>   temp.X:=0;temp.Y:=0;
>   nu:=GetTickCount;
>   for i:=0 to 50000 do
>     temp1:=pj_inv(temp,P);
>   ShowMessage(IntToStr(GetTickCount-nu));
>if i<40000 there is no problem
><mailto:Bornkilled at 21cn.com>Bornkilled at 21cn.com

Mike Schmidt                        Systèmes Scientifiques SEPIA
President                              SEPIA Scientific Systems
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