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Creating a Dynamic Link Library

For the beginning start Delphi and select File | New ... DLL. This will create a new DLL template in the editor window. Select the default text and replace it with the next piece of code.

 library TestLibrary;
 
 uses SysUtils, Classes, Dialogs;
 
 procedure DllMessage; export;
 begin
   ShowMessage('Hello world from a Delphi DLL') ;
 end;
 
 exports DllMessage;
 
 begin
 end. 

At the end of the source code we find an exports statement. This lists the routines that are actually exported from the DLL in a way that they can be called by another application. What this means is that we can have, let's say, 5 procedures in a DLL and only 2 of them (listed in the exports section) can be called from an external program (the remaining 3 are "sub procedures" in a DLL).

In order to use this simple DLL, we have to compile it by pressing Ctrl+F9. This should create a DLL called SimpleMessageDLL.DLL in your projects folder.

Finally, let's see how to call the DllMessage procedure from a (statically loaded) DLL.

To import a procedure contained in a DLL, we use the keyword external in the procedure declaration. For example, given the DllMessage procedure shown earlier, the declaration in the calling application would look like :

 procedure DllMessage; external 'SimpleMessageDLL.dll' 

 DllMessage; 

 unit Unit1;
 
 interface
 
 uses
    Windows, Messages, SysUtils, Variants, Classes,
    Graphics, Controls, Forms, Dialogs, StdCtrls;
 
 type
    TForm1 = class(TForm)
      Button1: TButton;
      procedure Button1Click(Sender: TObject) ;
    private
      { Private declarations }
    public
      { Public declarations }
    end;
 
 var
    Form1: TForm1;
 
   procedure DllMessage; external 'SimpleMessageDLL.dll'
 
 implementation
 
 {$R *.dfm}
 
 procedure TForm1.Button1Click(Sender: TObject) ;
 begin
    DllMessage;
 end;
 
 end. 

function ReadUnicode(fName: String): WideString;
var
  F: File;
  FileSize, ReadSize: Cardinal;
  SearchRec: TSearchRec;
  Buffer: WideString;

begin
  FileSize:=0;
  if FindFirst(fName, faAnyFile, SearchRec)=0 then begin
    FileSize:=SearchRec.Size;
    FindClose(SearchRec);
  end;

  AssignFile(F, fName);
  SetLength(Buffer, FileSize);
  Reset(F, 1);
  BlockRead(F, PAnsiChar(Buffer)^, FileSize, ReadSize);

  Result:=Buffer;
  CloseFile(F);
end;

사용예

procedure TForm1.Button1Click(Sender: TObject);

const 파일경로 = 'C:\유니코드파일.dat';

var sList: TStringList;

begin

  sList:=TStringList.Create;

  try

    sList.Text:=ReadUnicode(파일경로);

    Memo1.Text:=sList.Text;

  finally

    FreeAndNil(sList);

  end;

end

프로그램을 띄우거나 파일을 실행할경우 ShellAPI 함수인 ShellExecute() 를 사용합니다.
이 함수는 윈도우즈 탐색기에서 파일을 선택하고 더블클릭하는 기능과 동일한 동작을 합니다.
다음은 ShellExecute() 의 몇가지 사용예입니다.

(1) 파일과 연관(association)된 프로그램으로 파일을 엽니다
    ShellExecute(Handle, 'open', PChar('test.txt'), nil, nil, SW_SHOW);

(2) notepad.exe 에 파라미터로 config.sys 파일을 주어 메모장을 실행합니다
    ShellExecute(Handle, 'open', 'notepad', 'c:\config.sys', nil, SW_SHOW);

(3) PC에 설치된 기본 웝브라우저로 지정한 사이트를 엽니다.
    ShellExecute(Handle, 'open', 'www.howto.pe.kr', nil, nil, SW_SHOW);

(4) 특정 폴더를 시작 폴더로 하는 윈도우즈 탐색기를 엽니다
    ShellExecute(Handle, 'explore', PChar('c:\windows)', nil, nil, SW_SHOW);

(5) readme.doc 파일을 연결된 프로그램으로 인쇄하고 화면을 닫습니다
    ShellExecute(Handle, 'print', 'readme.doc', nil, nil, SW_SHOW);
   
(6) rMyDelphiFile.pas 파일을 wordpad 프로그램으로 인쇄하고 화면을 닫습니다
    ShellExecute(Handle, 'print', 'wordpad.wxe', 'MyDelphiFile.pas', nil, SW_SHOW);

(7) readme.doc 파일을 프린터를 선택하여 연결된 프로그램으로 인쇄하고 화면을 닫습니다
    var
      Device : array[0..255] of char;
      Driver : array[0..255] of char;
      Port   : array[0..255] of char;
      S: String;
      hDeviceMode: THandle;
    begin
      Printer.PrinterIndex := -1;  // 프린터 인덱스를 지정합니다. 여기서는 기본 프린터(-1) 선택
      Printer.GetPrinter(Device, Driver, Port, hDeviceMode);
      S := Format('"%s" "%s" "%s"',[Device, Driver, Port]);
      ShellExecute(Handle, 'printto', 'readme.doc', Pchar(S), nil, SW_HIDE);

(8) 기본 메일 프로그램을 실행합니다.
    ShellExecute(Handle, nil, 'mailto:cozy@howto.pe.kr', nil, nil, SW_SHOW);

(9) DOS 명령어를 실행하고 화면을 닫습니다
    ShellExecute(Handle, 'open', PChar('command.com'), PChar('/c copy file1.txt file2.txt'), nil, SW_SHOW);

(10) DOS 명령어를 실행하고 화면을 닫지 않습니다
     ShellExecute(Handle, 'open', PChar('command.com'), PChar('/k dir'), nil, SW_SHOW);

(11) ShellExecute()의 리턴값은 실행된 프로그램의 핸들이거나 에러코드입니다
     리턴값이 32 이하이면 에러가 발생한것으로 각각은 아래와 같은 의미가 있습니다

  var
    code: Integer;
  begin
    code := ShellExecute(...);
    if code <= 32 then ShowMessage(ShowShellExecuteError(code));
  end;
    
  // ShellExecute()의 리턴코드에 대한 에러 메시지
  function ShowShellExecuteError(i: integer): String;
  begin
    case i of 0: result := 'The operating system is out of memory or resources.';
      ERROR_FILE_NOT_FOUND: result := 'The specified file was not found.';
      ERROR_PATH_NOT_FOUND: result := 'The specified path was not found.';
      ERROR_BAD_FORMAT: result := 'The .EXE file is invalid (non-Win32 .EXE or error in .EXE image).';
      SE_ERR_ACCESSDENIED: result := 'The operating system denied access to the specified file.';
      SE_ERR_ASSOCINCOMPLETE: result := 'The filename association is incomplete or invalid.';
      SE_ERR_DDEBUSY: result := 'The DDE transaction could not be completed because other DDE transactions were being processed.';
      SE_ERR_DDEFAIL: result := 'The DDE transaction failed.';
      SE_ERR_DDETIMEOUT: result := 'The DDE transaction could not be completed because the request timed out.';
      SE_ERR_DLLNOTFOUND: result := 'The specified dynamic-link library was not found.';
      //SE_ERR_FNF          : result:='The specified file was not found.';
      SE_ERR_NOASSOC           : result:='Unbekannter Extender.';
      SE_ERR_OOM: result := 'There was not enough memory to complete the operation.';
      //SE_ERR_PNF          : result:='The specified path was not found.';
      SE_ERR_SHARE: result := 'A sharing violation occurred.';
    end;
  end;

(12) ShellExecuteEX()를 이용하여 notepad.exe 를 실행한 후 종료될때까지 기다립니다
  var
    SEInfo: TShellExecuteInfo;
    ExitCode: DWORD;
    ExecuteFile, ParamString, StartInString: string;
  begin
    ExecuteFile   := 'notepad.exe';   // 실행할 프로그램
    ParamString   := 'c:\winzip.log'; // 프로그램의 명령행 파라미터
    StartInString := 'c:\';           // 시작 위치
    FillChar(SEInfo, SizeOf(SEInfo), 0);
    SEInfo.cbSize := SizeOf(TShellExecuteInfo);

    with SEInfo do
    begin
      fMask        := SEE_MASK_NOCLOSEPROCESS;
      Wnd          := Application.Handle;
      lpFile       := PChar(ExecuteFile);
      lpParameters := PChar(ParamString);
      lpDirectory  := PChar(StartInString);
      nShow        := SW_SHOWNORMAL;
    end;
    if ShellExecuteEX(@SEInfo) then
    begin
      repeat
        Application.ProcessMessages;
        GetExitCodeProcess(SEInfo.hProcess, ExitCode);
      until (ExitCode <> STILL_ACTIVE) or Application.Terminated;
      ShowMessage('프로그램이 종료되었습니다');
    end
    else ShowMessage('프로그램을 실행할 수 없습니다');

출처 : http://www.howto.pe.kr 작성자 : 김영대님!

간단한 예제 입니다.

[uses : ShellApi 추가!]

function DeleteDirectory(Const DirPath: String): Boolean;
var
  SHFileOpStruct: TSHFileOpStruct;
  DirBuf: array [0..255] of char;
  Directory: string;

begin
  try
    Directory := ExcludeTrailingPathDelimiter(DirPath);
    Fillchar(SHFileOpStruct, sizeof(SHFileOpStruct), 0);
    FillChar(DirBuf, sizeof(DirBuf), 0);
    StrPCopy(DirBuf, Directory);

    with SHFileOpStruct do
    begin
      Wnd := 0;
      pFrom := @DirBuf;
      wFunc := FO_DELETE;
      //fFlags := fFlags or FOF_ALLOWUNDO; // 휴지통에 담기
      fFlags := fFlags or FOF_NOCONFIRMATION;
      fFlags := fFlags or FOF_SILENT;
    end;
    Result := (SHFileOperation(SHFileOpStruct) = 0);
  except
    Result := False;
  end;
end;

function ResponseCodeCheck(URL: String): Boolean;
var
  IdHTTP1: TIdHTTP;

begin
  Result := False;
  IdHTTP1 := TIdHTTP.Create;
  try
    IdHTTP1.Get(URL);

    case IdHTTP1.ResponseCode of
      200:
      begin
        Result := True;
        OutputDebugString('OK');
      end;

     403:OutputDebugString('Forbidden');
     404:OutputDebugString('Not Found');
     500:OutputDebugString('Server Error');

      else begin

        OutputDebugString('The Others ');

      end;
    end;
 finally
    FreeAndNil(IdHTTP1);
  end;