复杂的结构化存取(二)

本例效果图:

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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;
    Button2: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

Uses Activex;

type
  TRec = record
    Name: string[8];
    Age: Word;
  end;

const FileName = 'C:\Temp\Test.dat';

procedure TForm1.FormCreate(Sender: TObject);
begin
  Button1.Caption := '写复合文件';
  Button2.Caption := '读复合文件';
  Position := poDesktopCenter;
end;

procedure TForm1.Button1Click(Sender: TObject);
const
  Mode = STGM_CREATE or STGM_READWRITE or STGM_SHARE_EXCLUSIVE;
var
  StgRoot, StgSub: IStorage;
  Stm: IStream;
  Rec1: TRec;
begin
  {建立根 IStorage: StgRoot}
  StgCreateDocfile(FileName, Mode, 0, StgRoot);

  {建立子 IStorage: StgSub}
  StgRoot.CreateStorage('StgSub', Mode, 0, 0, StgSub);

  {在子 IStorage: StgSub 中建立 IStream: Stm}
  StgSub.CreateStream('Stm', Mode, 0, 0, Stm);

  {写入数据}
  Rec1.Name := '张三';
  Rec1.Age := 99;
  Stm.Write(@Rec1, SizeOf(TRec), nil);
end;

procedure TForm1.Button2Click(Sender: TObject);
const
  Mode = STGM_READ or STGM_SHARE_EXCLUSIVE;
Var
  StgRoot, StgSub :IStorage;
  Stm: IStream;
  Rec1: TRec;
Begin
  {如果不是结构化存储文件则退出}
  if StgIsStorageFile(FileName) <> S_OK then Exit;

  {获取根 IStorage: StgRoot}
  StgOpenStorage(FileName, nil, Mode, nil, 0, StgRoot);

  {获取子 IStorage: StgSub; 注意: 第一个参数的名称必须和保存时一致}
  StgRoot.OpenStorage('StgSub', nil, Mode, nil, 0, StgSub);

  {获取 IStream: Stm; 注意: 第一个参数的名称必须和保存时一致}
  StgSub.OpenStream('Stm', nil, Mode, 0, Stm);

  {读出数据}
  Stm.Read(@Rec1, SizeOf(TRec), nil);
  ShowMessageFmt('%s, %d', [Rec1.Name, Rec1.Age]);
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 107
  ClientWidth = 251
  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 Button1: TButton
    Left = 32
    Top = 40
    Width = 88
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 134
    Top = 40
    Width = 88
    Height = 25
    Caption = 'Button2'
    TabOrder = 1
    OnClick = Button2Click
  end
end