求字符相加的动态库如何写？

[jiangnan1218]

求字符相加的动态库如何写？各位高手麻烦解答下，急啊！！！

[feiba7288]

http://embarcadero.newsgroups.archived.at/public.delphi.nativeapi/201103/1103314922.html DLL：

library Project1;

{ Important note about DLL memory management: ShareMem must be the
  first unit in your library's USES clause AND your project's (select
  Project-View Source) USES clause if your DLL exports any procedures or
  functions that pass strings as parameters or function results. This
  applies to all strings passed to and from your DLL--even those that
  are nested in records and classes. ShareMem is the interface unit to
  the BORLNDMM.DLL shared memory manager, which must be deployed along
  with your DLL. To avoid using BORLNDMM.DLL, pass string information
  using PChar or ShortString parameters. }

uses
  Forms,
  SysUtils,
  Unit1 in 'Unit1.pas' {fmMain};

{$R *.res}

function JoinString(stringOne, stringTwo : PChar ) : PChar; export; stdcall;
var
  Buffer: PChar;
begin
  GetMem(Buffer,Length(stringOne) + Length(stringTwo) + 1);
  StrCopy(Buffer, PChar(stringOne));
  SysUtils.StrCat(Buffer, stringTwo);
  Result := Buffer;
  FreeMem(Buffer);
end;

exports
  JoinString;

begin
end.

调用：

unit Unit2;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
    Memo1: TMemo;
    Button2: TButton;
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function JoinString(stringOne, stringTwo : PChar ) : PChar; export; stdcall; external 'Project1.dll';

procedure TForm1.Button2Click(Sender: TObject);
begin
  Memo1.Lines.Add(JoinString(PChar(Edit1.Text), PChar(Edit2.Text)));
end;

end.

[武稀松]

其实可以直接用WideString这个是微软的格式,也不受Delphi的内存管理器管理. 他是OLE的BSTR是用SysAllocStrLen这类API分配的.