delphi 大文件的读写 使用 MapviewOffile

unit filemap;interfaceuses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
const
fileName = 'myTest.txt';
type
TForm1 = class(TForm)
btnUpper: TButton;
btnLower: TButton;
txtContent: TMemo;
Label1: TLabel;
btnClose: TButton;
procedure FormCreate(Sender: TObject);
procedure btnUpperClick(Sender: TObject);
procedure btnLowerClick(Sender: TObject);
procedure btnCloseClick(Sender: TObject);
private
{ Private declarations }
public
UCase:Boolean;
procedure ChangeFileCase;
end;var
Form1: TForm1;implementation{$R *.dfm}// 全文中的txtContent.Lines.LoadFromFile(fileName)其目的只是为了显示文件修改结果procedure TForm1.FormCreate(Sender: TObject);
begin
txtContent.Clear();
txtContent.Lines.LoadFromFile(fileName);
//缺省将其转变为大写
UCase := True;
end;procedure TForm1.btnUpperClick(Sender: TObject);
begin
UCase := true;
ChangeFileCase;
end;procedure TForm1.btnLowerClick(Sender: TObject);
begin
UCase := false;
ChangeFileCase;
end;procedure Tform1.ChangeFileCase;//这个是本示例文件的核心运算部分
var
FFileHandle : THandle;
FMapHandle : THandle;
FFileSize : Integer;
FData : PByte;
PData : PChar;
begin
//-------------------1 判断文件是否存在----------------------//
if not FileExists(fileName) then
raise Exception.Create('文件不存在!')
else
//-------------------2 使用FileOpen获取一个文件HANDLE--------//
FFileHandle := FileOPen(fileName,fmOPenReadWrite);
//如果创建文件失败，就抛出一个异常
if FFileHandle = INVALID_HANDLE_VALUE then
raise Exception.Create('打开或创建文件失败！');
//-------------------3 使用CreateFileMapping创建一个刚才用FileOpen创建的HANDLE的文件映射对象---//
try
FFileSize := GetFileSize(FFileHandle,nil);
FMapHandle := CreateFileMapping(FFileHandle,nil,PAGE_READWRITE,,FFileSize,nil); if FMapHandle = then
raise Exception.Create('创建内存映射文件失败！');
finally
CloseHandle(FFileHandle);
end;
//-------------------4 使用MapViewOfFile创建一个CreateFileMapping建立的HANDLE的映射文件的视图到进程的地址空间------//
try
FData := MapViewOfFile(FMapHandle,FILE_MAP_ALL_ACCESS,,,FFileSize);
if FData = nil then
raise Exception.Create('映射文件失败!');
finally
CloseHandle(FMapHandle);
end;
//-------------------5 对MapViewOfFile返回的指针做相应的运算操作------//
try
PData := PChar(FData);
inc(PData,FFileSize);
PData^ := #; if UCase then
StrUpper(PChar(FData))
else
StrLower(PChar(FData));
finally
//-------------------6 取消文件视图的映射------//
UnmapViewOfFile(FData);
end;
txtContent.Lines.Clear();
txtContent.Lines.LoadFromFile(fileName);
end;procedure TForm1.btnCloseClick(Sender: TObject);
begin
Form1.Close();
end;end.{
//-------------------------------------------------------//
在做指针具体运算时，可以采用这样直接获取该指针处的某一类型的值
procedure TForm1.Button1Click(Sender: TObject);
var i: Integer;
p: Pointer;
begin
i := 12345678;
p := @i;
showmessage(inttostr(integer(p))); //俺的电脑上1242664,这是一个地址
showmessage(inttostr(Pinteger(p)^)); //12345678
showmessage(inttostr(PWord(p)^)); //24910
end;Pinteger(p)^表示指针P处取得一个Integer值
PWord(p)^表示指针P处取得一个Word值在windows.pas和system.pas中还定义了很多指针类型如下
PInteger = ^Integer; {$NODEFINE PInteger} { defined in sysmac.h }
PCardinal = ^Cardinal;
PWord = ^Word;
PSmallInt = ^SmallInt; {$NODEFINE PSmallInt} { defined in sysmac.h }
{$POINTERMATH ON}
PByte = ^Byte; {$NODEFINE PByte} { defined in sysmac.h }
{$POINTERMATH OFF}
PShortInt = ^ShortInt; {$NODEFINE PShortInt} { defined in sysmac.h }
PInt64 = ^Int64; {$NODEFINE PInt64} { defined in sysmac.h }
PUInt64 = ^UInt64;
PLongWord = ^LongWord; {$NODEFINE PLongWord} { defined in sysmac.h }
PSingle = ^Single; {$NODEFINE PSingle} { defined in sysmac.h }
PDouble = ^Double; {$NODEFINE PDouble} { defined in sysmac.h }
PDate = ^Doub