unit1.pas

在delphi中实现windows核心编程.原书光盘代码核心编程.原书光盘代码

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}
procedure Speed(count:word); stdcall;
const ExceptionUsed = $03;        { 中断号也可以用其它的中断号}
var
  IDT : array [0..5] of byte; { 保存中断描述符表}
  lpOldGate : dword;          {存放旧向量}
begin
   asm
     push ebx
     sidt IDT                  {读入中断描述符表}
     mov ebx, dword ptr [IDT+2]{IDT表基地址}
     add ebx, 8*ExceptionUsed  {计算中断在中断描述符表中的位置}
     cli                       {关中断}
     mov dx, word ptr [ebx+6]  {取6,7字节 另外4字节用于门属性和选择子 }
     shl edx, 16d              {左移16位}
     mov dx, word ptr [ebx]    {取1,2字节  }
     mov [lpOldGate], edx      {保存旧的中断门}
     mov eax, offset @@Ring0Code   {修改向量，指向Ring0级代码段}
     mov word ptr [ebx], ax        {低16位,保存到1,2字}
     shr eax, 16d
     mov word ptr [ebx+6], ax      {高16位，保存到6,7位}
     int ExceptionUsed             {发生中断}
     mov ebx, dword ptr [IDT+2]    {重新定位到中断描述符表中}
     add ebx, 8*ExceptionUsed
     mov edx, [lpOldGate]
     mov word ptr [ebx], dx
     shr edx, 16d
     mov word ptr [ebx+6], dx      {恢复被改了的向量}
     pop ebx
     jmp @@exit1
    @@Ring0Code:    {Ring0级代码段}
     {0011 0100}
      mov al,$34    {写入8253控制寄存器，设置写0号定时器}
      out $43,al
      mov ax,Count
      out $40,al    {写定时值低位}
      mov al,ah
      out $40,al    {写定时值高位}
      iretd         {中断返回}
   @@exit1:
   end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
   Speed($6000); //慢
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
   Speed($1742); 
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
   Speed($500); //快
end;

end.