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