مشكلة عند تنفيذ البرنامج يتخاطب مع ملف dll

كود :

Data Returned by DLL
The host application should allocate a destination data buffer for use by the DLL. When the scanner sends
data to the DLL, the destination buffer is filled with the scanner's data.
Once the destination buffer is filled by the DLL (if a buffer was set), the application is sent a WM_xxx message
with the number of bytes of data that were stored indicated in the WPARAM.
If the buffer was not large enough to hold all the data, the last two bits of WPARAM are set to zero. If no buffer
was given to the DLL for the data to be stored in, the last two bits of WPARAM are 01. If the data was stored
correctly, the last two bits of WPARAM are 11.
The following #defines are provided for this purpose:
• BUFFERSIZE_MASK – 0x0003
• BUFFERSIZE_GOOD – 0x0003
• BUFFERSIZE_ERROR – 0x0000
• NOBUFFER_ERROR – 0x0001
After the message is sent, the DLL marks the buffer as NULL indicating no user buffer is available for storage.
The host application should reset the buffer after a WM_xxx message occurs.
A second call to set the data buffer causes the new buffer to be used for incoming data. For example, after a
WM_DECODE message is sent to the application, the application should handle the message and process the
data in the destination buffer, then call SNAPI_SetDecodeBuffer again.

PHP كود :

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type TObjectList = class(TList)
  end;

type
  TScanner = class
  public
    Device: THandle;
    Connected: Boolean;
    ImageData: array of Byte;
    Pending: Boolean;

    procedure Connect;
    procedure Disconnect;
    procedure RequestSnapshot;
    procedure SetImageBuffer(Size: Integer);
  end;


const
  SNAPI_DLL = 'snapi.dll';

function SNAPI_Init(wnd: HWND; var DeviceHandles: THandle; var NumDevices: Integer): Integer; stdcall; external SNAPI_DLL;
function SNAPI_Connect(DeviceHandle: THandle): Integer; stdcall; external SNAPI_DLL;
function SNAPI_Disconnect(DeviceHandle: THandle): Integer; stdcall; external SNAPI_DLL;
function SNAPI_SetImageBuffer(DeviceHandle: THandle; Data: Pointer; MaxLength: Longint): Integer; stdcall; external SNAPI_DLL;
function SNAPI_SnapShot(DeviceHandle: THandle): Integer; stdcall; external SNAPI_DLL;

const
  MAX_SCANNER = 10; // you will have to look this up

  BUFFERSIZE_ERROR = $0000;
  NOBUFFER_ERROR = $0001;
  BUFFERSIZE_GOOD = $0003;
  BUFFERSIZE_MASK = $0003;

  WM_IMAGE = WM_APP+2;
  WM_ERROR = WM_APP+4;
  WM_TIMEOUT = WM_APP+5;
  WM_XFERSTATUS = WM_APP+7;
  WM_DEVICENOTIFICATION = WM_APP + 12;

  IMAGE_DATA_TIMEOUT = $B1;

type
  ESNAPIError = class(Exception)
  public
    Status: Integer;
    constructor CreateErr(AStatus: Integer);
  end;


type
  TMyform = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    ScannerWnd: HWND;
    Scanners: TObjectList;
    function  FindScanner(Device: THandle): TScanner;
    procedure ConnectScanner(Index:integer);
    procedure DisconnectScanner(Index:integer);
    procedure RequestSnapshot(Index:integer);
    procedure ScannerWndProc(var Message: TMessage);
  end;



var
  Myform: TMyform;
  scanner : TScanner;
implementation

{$R *.dfm}

constructor ESNAPIError.CreateErr(AStatus: Integer);
begin
  inherited CreateFmt('SNAPI Error %d', [AStatus]);
  Status := AStatus;
end;

procedure CheckSNAPIStatus(AStatus: Integer);
begin
  if AStatus <> 0 then
    raise ESNAPIError.CreateErr(AStatus);
end;

procedure TScanner.Connect;
begin
  if not Connected then
  begin
    CheckSNAPIStatus(SNAPI_Connect(Device));
    Connected := True;
  end;
end;

procedure TScanner.Disconnect;
begin
  if Connected then
  begin
    SNAPI_Disconnect(Device);
    Connected := False;
  end;
end;

procedure TScanner.RequestSnapshot;
begin
  Connect;

  if Pending then
    raise Exception.Create('Scanner is busy, try again later');

  SetLength(ImageData, 0);
  CheckSNAPIStatus(SNAPI_SnapShot(Device));

  Pending := True;
end;

procedure TScanner.SetImageBuffer(Size: Integer);
begin
  SetLength(ImageData, Size);
  CheckSNAPIStatus(SNAPI_SetImageBuffer(Device, Pointer(ImageData), Length(ImageData)));
end;




procedure TMyform.FormCreate(Sender: TObject);
var
  Devices: array[0..MAX_SCANNER-1] of THandle;
  NumScanners, I: Integer;
  Scanner: TScanner;
begin
  Scanners := TObjectList.Create;
  ScannerWnd := AllocateHWnd(ScannerWndProc);

  CheckSNAPIStatus(SNAPI_Init(ScannerWnd, Devices[0], NumScanners));
  for I := 0 to NumScanners-1 do
  begin
    Scanner := TScanner.Create;
    Scanner.Device := Devices[I];
    Scanners.Add(Scanner);
    // add it to the UI somewhere...
  end;
end;

procedure TMyform.FormDestroy(Sender: TObject);
begin
  DeallocateHWnd(ScannerWnd);
  Scanners.Free;
end;

function TMyform.FindScanner(Device: THandle): TScanner;
var
  I: Integer;
begin
  for I := 0 to Scanners.Count-1 do
  begin
    Result := TScanner(Scanners[I]);
    if Scanner.Device = Device then
      Exit;
  end;
  Result := nil;
end;

procedure TMyform.Button1Click(Sender: TObject);
begin
RequestSnapshot(0);
end;

procedure TMyform.ConnectScanner(Index:integer);
begin
  TScanner(Scanners[Index]).Connect;
end;

procedure TMyform.DisconnectScanner(Index:integer);
begin
  TScanner(Scanners[Index]).Disconnect;
end;

procedure TMyform.RequestSnapshot(Index:integer);
begin
  TScanner(Scanners[Index]).RequestSnapshot;
end;

procedure TMyform.ScannerWndProc(var Message: TMessage);
var
  Scanner: TScanner;
begin
  case Message.Msg of

    WM_XFERSTATUS:
    begin
      Scanner := FindScanner(THandle(Message.LParam));
      if Scanner = nil then Exit;

      //BytesRecv := LODWORD(Message.WParam)
      //BytesTotal := HIDWORD(Message.WParam)

      if Scanner.ImageData = nil then
       Scanner.SetImageBuffer( Message.WParamHi);
    end;

    WM_IMAGE:
    begin
      Scanner := FindScanner(THandle(Message.LParam));
      if Scanner = nil then Exit;

      Scanner.Pending := False;

      if (LO(Message.WParam) and BUFFERSIZE_MASK) <> BUFFERSIZE_GOOD then
        raise Exception.Create('Image buffer error');

      // use Scanner.ImageData up to HIDWORD(Message.WParam) bytes as needed...

      SetLength(Scanner.ImageData, 0);
    end;


    WM_TIMEOUT:
    begin
      Scanner := FindScanner(THandle(Message.LParam));
      if Scanner = nil then Exit;

      Scanner.Pending := False;

      case HI(Message.WParam) of

        IMAGE_DATA_TIMEOUT:
        begin
          raise Exception.Create('Image timeout');
        end;

      end;
    end;

    WM_ERROR:
    begin
      Scanner := FindScanner(THandle(Message.LParam));
      if Scanner = nil then Exit;

      Scanner.Pending := False;

      CheckSNAPIStatus(Integer(LO(Message.WParam)));
    end;

  else
    Message.Result := DefWindowProc(ScannerWnd, Message.Msg, Message.WParam, Message.LParam);
end;
end;

end.