Delphi 的内存操作函数(6): 跨进程的内存分配

Delphi 为我们提供了三个方便的函数:

GlobalAllocPtr   {简化自 API 的 GlobalAlloc}

GlobalReAllocPtr {简化自 API 的 GlobalReAlloc}

GlobalFreePtr    {简化自 API 的 GlobalFree}

读写本程序以外的数据时可以使用它们, 很方便, 譬如:

p := GlobalAllocPtr(0, Len);      {分配}

p := GlobalReAllocPtr(p, Len, 0); {重分配}

GlobalFreePtr(p);                 {释放}

注意 GlobalAllocPtr 的第一个参数和 GlobalReAllocPtr 的最后一个参数, 上面给的都是 0;
这两个参数的意义是一样的, 规范一点应该写成 GMEM_FIXED (表示分配固定内存), 常用的参数还有:

GMEM_MOVEABLE {分配可移动内存}

GMEM_ZEROINIT {同时清空内存}

GHND          {分配可移动内存同时清空}

GPTR          {分配固定内存同时清空}

参数还有很多, 和相应的 API 函数的参数是一致的.

下面的例子并没有使用进程以外的对象, 可以把 Memo1.Handle 换做外部的其他文本容器(譬如记事本)试一试:

---

代码文件:

---

unit Unit1;



interface



uses

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

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Memo1: TMemo;

    Button1: TButton;

    Button2: TButton;

    procedure FormCreate(Sender: TObject);

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.Button1Click(Sender: TObject);

var

  p: Pointer;

  Len: Integer;

begin

  Len := 6+1;                    {假如想要读出 6 个字符, 要留出结束的空字符}

  p := GlobalAllocPtr(0, Len*2); {分配内存 Len*2 是针对双字节字符}

  SendMessage(Memo1.Handle, WM_GETTEXT, Len, Cardinal(p));

  ShowMessage(PChar(p)); {CodeGe}

  GlobalFreePtr(p);

end;



procedure TForm1.Button2Click(Sender: TObject);

var

  p: Pointer;

  Len: Integer;

begin

  Len := 6+1;                    {假如想要读出 6 个字符, 要流出结束的空字符}

  p := GlobalAllocPtr(0, Len*2); {分配内存 Len*2 是针对双字节字符}

  SendMessage(Memo1.Handle, WM_GETTEXT, Len, Cardinal(p));

  ShowMessage(PChar(p)); {CodeGe}



  {在上一例的基础上继续, 先获取实际长度}

  Len := SendMessage(Memo1.Handle, WM_GETTEXTLENGTH, 0, 0);

  Len := (Len + 1) * 2;

  p := GlobalReAllocPtr(p, Len, GHND); {重新分配内存}

  SendMessage(Memo1.Handle, WM_GETTEXT, Len, Cardinal(p));

  ShowMessage(PChar(p)); {CodeGear Delphi 2009}



  GlobalFreePtr(p);

end;



procedure TForm1.FormCreate(Sender: TObject);

begin

  Memo1.Align := alLeft;

  Memo1.ScrollBars := ssVertical;

  Memo1.Text := 'CodeGear Delphi 2009';

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 151

  ClientWidth = 295

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  OnCreate = FormCreate

  PixelsPerInch = 96

  TextHeight = 13

  object Memo1: TMemo

    Left = 8

    Top = 8

    Width = 169

    Height = 89

    Lines.Strings = (

      'Memo1')

    TabOrder = 0

  end

  object Button1: TButton

    Left = 192

    Top = 32

    Width = 75

    Height = 25

    Caption = 'Button1'

    TabOrder = 1

    OnClick = Button1Click

  end

  object Button2: TButton

    Left = 192

    Top = 72

    Width = 75

    Height = 25

    Caption = 'Button2'

    TabOrder = 2

    OnClick = Button2Click

  end

end