Dll 使用 PChar 参数的小例子

当用delphi开发的dll中有参数或返回值是字符串时，需要调用sharemem单元，且需要borlnmm.dll一起发布程序。用Pchar代替string是一个解决方案，只不过对pchar的使用要复杂一些：

Dll 文件:

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library Lib;



uses

  SysUtils, Classes;



{$R *.res}



procedure Test(p: PChar);

const

  Title = 'Title ';

var

  str: string;

begin

  str := p;

  StrCopy(p, Title);

  StrCat(p, PChar(str));

end;



exports Test;



begin

end.

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调用的代码文件:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

  end;



var

 Form1: TForm1;



implementation



{$R *.dfm}



procedure Test(p: PChar); external 'Lib.dll';



var num: Integer;



procedure TForm1.Button1Click(Sender: TObject);

var

  p: PChar;

begin

  Inc(num);

  p := StrAlloc(255);

  StrCopy(p, PChar(IntToStr(num)));

  Test(p);

  Text := p;

  StrDispose(p);

end;



end.

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调用的窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 103

  ClientWidth = 173

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  PixelsPerInch = 96

  TextHeight = 13

  object Button1: TButton

    Left = 48

    Top = 40

    Width = 75

    Height = 25

    Caption = 'Button1'

    TabOrder = 0

    OnClick = Button1Click

  end

end