[SOLVED] const char** in FPC?

[Key-Real]

got this:

Code: C  [Select][+][-]

1. typedef struct ACameraIdList {
2.     int numCameras;          ///< Number of camera device Ids
3.     const char** cameraIds;  ///< list of camera device Ids
4. } ACameraIdList;
5.  

pls help to translate this into pascal

[cdbc]

Hi
This:

Code: Pascal  [Select][+][-]

1. char**  == C
2. PPChar = Pascal

It points to an array of pchars, you could say, that 'char**' is the C equivalent to Pascal's 'TStringArray' ~ a dynamic array of strings
added a couple of minutes later...

Code: Pascal  [Select][+][-]

1. type
2.   TCameraIdList = record
3.     NumCameras: cint; // from c-types unit
4.     CameraIds: ppchar; // we have that in pascal too
5.   end;
6.  

Regards Benny

[Key-Real]

how to access it?

Code: Pascal  [Select][+][-]

1. writeln(camera^.cameraIds[0]^);
2.  

?

[cdbc]

Hi

Code: Pascal  [Select][+][-]

1. writeln(camera^.cameraIds[0]^);

will get you the pointer, you'll need to:

Code: Pascal  [Select][+][-]

1. writeln(camera^.cameraIds[0]^^);

Regards Benny

[Key-Real]

have now:

Code: Pascal  [Select][+][-]

1. ACameraIdList = record
2.         numCameras : longint;          ///< Number of camera device Ids
3.         cameraIds : PPChar;           ///< list of camera device Ids
4. end;
5.  

Code: Pascal  [Select][+][-]

1. ...  string(camera^.cameraIds[0]^^)  <--  Error: Illegal qualifier
2.  

[cdbc]

Hi
Could it be, that it's:

Code: Pascal  [Select][+][-]

1. camera^.cameraIds^[0]^

I must admit, I'm a bit rusty in that ol' C, been a looong while...
Regards Benny

[Key-Real]

Error: Illegal qualifier

[cdbc]

Hi
I guess trial 'n error is called for...
It's late night here, so I can write a small check-app in the morning, at the earliest...
Maybe google knows how to access it?!? I think there are some examples of use in the 'typinfo' rtl-unit, one could look in there...
Regards Benny

[440bx]

The cameraIds is a pointer to an array of pointers to null terminated character arrays (C strings.)

Here is an example in Pascal of how to declare that:

Code: Pascal  [Select][+][-]

1.  
2. var
3.   Names : array[0..1] of pchar = ('Name1', 'Name2');
4.  
5.   ACameraList : record
6.     CameraCount : integer;
7.     CameraList  : ^pchar;
8.   end = (CameraCount:5;CameraList:@Names[0]);
9.  
10.   { accessing the above }
11.  
12. begin
13.   { the way it would be done in C }
14.  
15.   p := ACameraList.CameraList^;
16.   p := (ACameraList.CameraList + 1)^;
17.  
18.   { the way it's normally done in Pascal }
19.  
20.   p := ACameraList.CameraList[0];
21.   p := ACameraList.CameraList[1];  { <- note the index is (cameraCount - 1) since there are two cameras) }
22. end.
23.  

[Key-Real]

yes, thx, this works now

[440bx]

yes, thx, this works now

You're welcome.