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6.6

c/c++ dll callback calling from delphi

Asked by richard_exchange in Pascal Programming Language, C++ Programming Language, Delphi Programming

Tags: DLL Delphi Callback

Hello experts,

i have a C/C++ dll which exports a function where i have to give a pointer to an callback procedure...
I am using Delphi2009.

This is the only function of the library which does not work...

The program stops at the first line ("begin" in the .dpr-File) of the code, and after
resume (f9) the following exception is shown:

"access violation at 0x00407766: write of address 0x00040124...."

Other functions of the library are working fine. Only this callback doesn't work...
If i remove this line from the main code the program starts without error.

There must be something wrong in var convertion or parameter definition.
I have tried several versions to declare the procedure, but every time the same error...

Can anybody help, please?

Get your answer NOW

         
           
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             // stream.h definitions...
 
#define _HANDLE	int
 
//////////////////////////////////////////////
// Codec
//////////////////////////////////////////////
enum AUDIOCODEC
{
	AUDIO_CODEC_UNKNOWN,
	AUDIO_CODEC_G711_64K,
	AUDIO_CODEC_G726_40K,
};
 
enum VIDEOCODEC
{
	VIDEO_CODEC_UNKNOWN,
	VIDEO_CODEC_JPEG,
	VIDEO_CODEC_MPEG4,
};
 
////////////////////////////////////////////////////////////////////////////////
// S_ERROR
////////////////////////////////////////////////////////////////////////////////
enum S_ERROR
{
	S_OK					  	  = 0,
	S_ERR_PARAM	 			  = 400,			// Parameter error
	S_ERR_ALLOC					= 401,			// Failed to allocate memory
	S_ERR_VERSION				= 402			  // Failed to get the version information
};
 
//////////////////////////////////////////////
// Video/Audio codec
//////////////////////////////////////////////
struct VIDEOCODECINFO
{
	VIDEOCODEC		Codec;
	int				Width;
	int				Height;
};
struct AUDIOCODECINFO
{
	AUDIOCODEC		Codec;
	unsigned short  Channels;
  unsigned long	SamplesPerSec;
  unsigned short  BitsPerSample;
};
 
//////////////////////////////////////////////
// UserData
//////////////////////////////////////////////
struct USERDATA
{
	char			CamTim	[32];
	unsigned short	FrmRate;
	char			TimStamp[11];
};
 
//////////////////////////////////////////////
// Get Video/Audio data
//////////////////////////////////////////////
struct VIDEOINFO
{
	char			*pBuf;
	unsigned int	BufLen;
	VIDEOCODECINFO	VideoCodecInfo;
	USERDATA		UserData;
	bool			KeyFrame;
};
struct AUDIOINFO
{
	char			*pBuf;
	unsigned int	BufLen;
	AUDIOCODECINFO	AudioCodecInfo;
};
 
//////////////////////////////////////////////
// Call back
//////////////////////////////////////////////
typedef void (__stdcall *VCALLBACK )( VIDEOINFO *pVideoInfo, unsigned long Param );
typedef void (__stdcall *ACALLBACK )( AUDIOINFO *pAudioInfo, unsigned long Param );
typedef void (__stdcall *AVCALLBACK)( VIDEOINFO *pVideoInfo, AUDIOINFO *pAudioInfo, unsigned long Param );
 
enum CALLBACKTYPE
{
	CALLBACK_RAW_VIDEO,
	CALLBACK_RAW_AUDIO,
	CALLBACK_RAW_BOTH,
	CALLBACK_DEC_VIDEO,
	CALLBACK_DEC_AUDIO,
	CALLBACK_DEC_BOTH,
};
 
 
// The callback registering procedure...
 
S_ERROR __stdcall SetCallback( _HANDLE sHandle, CALLBACKTYPE callbackType, void* pCallbackFunction, unsigned long param );
 
================================================================================
//my library wrapper unit
 
unit StreamLib;
{$Z4,A4}
interface
 
uses Windows;
 
type
  _HANDLE = Integer;
 
//////////////////////////////////////////////
// Codec
//////////////////////////////////////////////
  _AUDIOCODEC = (
    AUDIO_CODEC_UNKNOWN,
    AUDIO_CODEC_G711_64K,
    AUDIO_CODEC_G726_40K
  );
  P_VIDEOCODEC = ^_VIDEOCODEC;
  _VIDEOCODEC = (
	  VIDEO_CODEC_UNKNOWN,
	  VIDEO_CODEC_JPEG,
	  VIDEO_CODEC_MPEG4
  );
 
//////////////////////////////////////////////
// S_ERROR
//////////////////////////////////////////////
  S_ERROR = (
    S_OK							    = 0,
    S_ERR_PARAM						= 400,			// Parameter error
    S_ERR_ALLOC						= 401,			// Failed to allocate memory
    S_ERR_VERSION					= 402			// Failed to get the version information
  );
 
//////////////////////////////////////////////
// Video/Audio codec
//////////////////////////////////////////////
  P_VIDEOCODECINFO = ^_VIDEOCODECINFO;
  _VIDEOCODECINFO = record
    Codec  : _VIDEOCODEC;
    Width  : Integer;
    Height : Integer;
  end;
  P_AUDIOCODECINFO = ^_AUDIOCODECINFO;
  _AUDIOCODECINFO = record
    Codec : _AUDIOCODEC;
    Channels : Word;
    SamplesPerSec : Cardinal;
    BitsPerSample : Word;
  end;
 
//////////////////////////////////////////////
// UserData
//////////////////////////////////////////////
  _USERDATA = record
	  CamTim : array[0..31] of AnsiChar;
	  FrmRate : Word;
	  TimStamp : array[0..10] of AnsiChar;
  end;
//////////////////////////////////////////////
// Get Video/Audio data
//////////////////////////////////////////////
  P_VIDEOINFO = ^VIDEOINFO;
  VIDEOINFO = record
    pBuf : PAnsiChar;
    BufLen : Cardinal;
    VideoCodecInfo : _VIDEOCODECINFO;
    UserData : _USERDATA;
    KeyFrame : Boolean;
  end;
  P_AUDIOINFO = ^AUDIOINFO;
  AUDIOINFO = record
    pBuf : PAnsiChar;
    BufLen : Cardinal;
    AudioCodecInfo : _AUDIOCODECINFO;
  end;
 
//////////////////////////////////////////////
// Call back
//////////////////////////////////////////////
VCALLBACK = procedure(pVideoInfo : P_VIDEOINFO; param : Cardinal); stdcall;
ACALLBACK = procedure(pAudioInfo : P_AUDIOINFO; param : Cardinal); stdcall;
AVCALLBACK = procedure(pVideoInfo : P_VIDEOINFO; pAudioInfo : P_AUDIOINFO; param : Cardinal); stdcall;
 
type
  CALLBACKTYPE =(
    CALLBACK_RAW_VIDEO,
    CALLBACK_RAW_AUDIO,
    CALLBACK_RAW_BOTH,
    CALLBACK_DEC_VIDEO,
    CALLBACK_DEC_AUDIO,
    CALLBACK_DEC_BOTH
  );
 
// Here the definition of the callback registering procedure, which does not work...
function SetCallback( Handle : _HANDLE; callbackType : CALLBACKTYPE; pCallbackFunction : pointer; param : Cardinal ) : S_ERROR; stdcall;
 
implementation
 
const
  myDLL = 'stream.dll';
 
function SetCallback;  external myDLL;
 
end.
 
==============================================================================
// Example Testprogram
 
unit Main;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  StreamLib;
 
type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
    myHandle : Integer;
  public
    { Public-Deklarationen }
  end;
 
var
  Form1: TForm1;
 
 
// My Callback procedure to handle the frame...
procedure MyCallback(pVideoInfo : Pointer; pAudioInfo : Pointer; param : Cardinal); stdcall;
begin
  // ....
end;
 
procedure TForm1.Button1Click(Sender: TObject);
Var myErrorCode : S_ERROR;
begin
   // register the callback procedure...
   myErrorCode := SetCallback( myHandle, CALLBACK_RAW_BOTH, @MyCallback, 0 );
 
end;
 
end.
 
==================================================================================
 
Following are the debugging outputs:
 
Stack:
> :00407766 LoadResString + $E
  :00410abf GetExceptionObject + $57
  :00404181 @HandleAnyException + $35
  :7c91378b ntdll.RtlConvertUlongToLargeInteger + 0x46
  :7c91eafa ntdll.KiUserExceptionDispatcher + 0xe
  :7c91378b ntdll.RtlConvertUlongToLargeInteger + 0x46
  :00404224 @HandleAnyException + $D8
  :7c91378b ntdll.RtlConvertUlongToLargeInteger + 0x46
  :7c91eafa ntdll.KiUserExceptionDispatcher + 0xe
  :7e369dbb USER32.LoadCursorW + 0x52
  :7e369e4e USER32.LoadStringW + 0x18
  :004077a2 LoadResString + $4A
  :00410abf GetExceptionObject + $57
 
CPU:
  LoadResString:
  00407758 53               push ebx
  00407759 56               push esi
  0040775A 50               push eax
  0040775B B802000000       mov eax,$00000002
  00407760 81C404F0FFFF     add esp,$fffff004
> 00407766 50               push eax
  00407767 48               dec eax
 
Protokoll:
...
Modul laden: Camera.dll. Ohne Debug-Infos. Basisadresse: $004F0000. Prozess Test.exe (1984)
Modul laden: WS2_32.dll. Ohne Debug-Infos. Basisadresse: $71A10000. Prozess Test.exe (1984)
Modul laden: WS2HELP.dll. Ohne Debug-Infos. Basisadresse: $71A00000. Prozess Test.exe (1984)
Modul laden: UNKNOWN_MODULE_50. Ohne Debug-Infos. Basisadresse: $0A000000. Prozess Test.exe (1984)
Modul laden: PSAPI.DLL. Ohne Debug-Infos. Basisadresse: $76BB0000. Prozess Test.exe (1984)
Modul laden: NETAPI32.dll. Ohne Debug-Infos. Basisadresse: $597D0000. Prozess Test.exe (1984)
Modul entladen: UNKNOWN_MODULE_50. Prozess Test.exe (1984)
Modul entladen: NETAPI32.dll. Prozess Test.exe (1984)
Modul entladen: PSAPI.DLL. Prozess Test.exe (1984)
Modul laden: IMM32.dll. Ohne Debug-Infos. Basisadresse: $76330000. Prozess Test.exe (1984)
Modul laden: MSCTF.dll. Ohne Debug-Infos. Basisadresse: $746A0000. Prozess Test.exe (1984)

           
         

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c/c++ dll callback calling from delphi

Asked by richard_exchange in Pascal Programming Language, C++ Programming Language, Delphi Programming

Tags: DLL Delphi Callback

About this solution