I'm translating some WinAPI structs so I can make use of the Raw Input API exposed by user32.dll. Most of them are straight forward but a few have unions. I've never attempted to translate structs to records before and I'm just need some confirmation.

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I'm translating some WinAPI structs so I can make use of the Raw Input API exposed by user32.dll. Most of them are straight forward but a few have unions. I've never attempted to translate structs to records before and I'm just need some confirmation.

I have the following two structs:

typedef struct tagRAWMOUSE {
  USHORT usFlags;
  union {
    ULONG  ulButtons;
    struct {
      USHORT usButtonFlags;
      USHORT usButtonData;
    };
  };
  ULONG  ulRawButtons;
  LONG   lLastX;
  LONG   lLastY;
  ULONG  ulExtraInformation;
} RAWMOUSE, *PRAWMOUSE, *LPRAWMOUSE;

typedef struct tagRAWINPUT {
  RAWINPUTHEADER header;
  union {
    RAWMOUSE    mouse;
    RAWKEYBOARD keyboard;
    RAWHID      hid;
  } data;
} RAWINPUT, *PRAWINPUT, *LPRAWINPUT;

And here are my attempts to translate:

type
  RAWMOUSE = record
    usFlags: USHORT;
    case Boolean of
    False: (ulButtons: ULONG);
    True: (usButtonFlags: USHORT;
           usButtonData: USHORT;
           ulRawButtons: ULONG;
           lLastX: LongInt;
           lLastY: LongInt;
           ulExtraInformation: ULONG);
  end;
  PRAWMOUSE = ^RAWMOUSE;
  LPRAWMOUSE = PRAWMOUSE;

type
  RAWINPUT = record
    header: RAWINPUTHEADER;
    case Integer of
    0: (mouse: RAWMOUSE);
    1: (keyboard: RAWKEYBOARD);
    2: (hid: RAWHID);
  end;
PRAWINPUT = ^RAWINPUT;
LPRAWINPUT = PRAWINPUT;

How close to the mark did I get?

Comments

  1. Achim KalwaOctober 29, 2014 at 12:29 PM

    The RAWMOUSE record has a wrong closing bracket. It must be placed after the ulButtonData:USHORT declaration.

    ReplyDelete
  2. Kenneth CochranOctober 29, 2014 at 12:33 PM

    That was intentional. See http://rvelthuis.de/articles/articles-convert.html on translating structs with unions in the middle. If I understood it correctly the offsets for ulRawButtons et al should be the same.

    ReplyDelete
  3. Arioch TheOctober 29, 2014 at 12:40 PM

    Go Delphi-Jedi and download from svn last release of jwa (Jedi windows api) project, chances are it is already there

    ReplyDelete
  4. Achim KalwaOctober 29, 2014 at 12:45 PM

    Oh, thanks for the info.

    ReplyDelete
  5. Achim KalwaOctober 29, 2014 at 12:59 PM

    Yes, it is in JwaWinUser.pas. And it is declared like this (comments stripped):

    type
      tagRAWMOUSE = record
        usFlags: USHORT;
        union: record
        case Integer of
          0: (
            ulButtons: ULONG);
          1: (
            usButtonFlags: USHORT;
            usButtonData: USHORT);
        end;
        ulRawButtons: ULONG;
        //
        lLastX: LONG;
        lLastY: LONG;
        ulExtraInformation: ULONG;
      end;
      
    So the trick was to translate the anonymous C++ union to a named sub-record "union". Which has a little drawback when accessing the variables inside.

    ReplyDelete
  6. Kenneth CochranOctober 29, 2014 at 1:14 PM

    Ah, I see. I had looked at jedi wapi already but was looking in the wrong place. I'll give it another look.

    ReplyDelete
  7. Phillip WoonOctober 30, 2014 at 8:43 PM

    In Pascal, that's called a variant record.

    ReplyDelete

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