Asynchronous ReadFile in Delphi XE2 - multithreading

Question

I'm writing a small PE file analyzer and I have to read the contents of the PE file. I'm doing this via the ReadFile function, as shown below:
function TMainForm.GetPEData(var filename: string) : boolean;
var
hFile: DWORD;
IDH: TImageDosHeader;
INH: TImageNtHeaders;
ISH: TImageSectionHeader;
dwRead: DWORD;
szBuff: array[0..7] of Char;
i: WORD;
PE: TPEFile;
begin
Result := False;
PE := TPeFile.Create;
if PE.LoadFromFile (filename) then
Form2.edEntryPoint.Text := IntToHex(PE.RvaToFileOffset(PE.AddressOfEntryPoint), 8);
SplashScreen.sLabel1.Caption := 'PE File Loaded';
hFile := CreateFile(PChar(filename), GENERIC_READ,
FILE_SHARE_WRITE, nil,
OPEN_EXISTING, 0, 0);
if hFile <> INVALID_HANDLE_VALUE then
begin
SetFilePointer(hFile, 0, nil, FILE_BEGIN);
SplashScreen.sLabel1.Caption := 'Reading DOS File Headers...';
ReadFile(hFile, IDH, 64, dwRead, nil);
if IDH.e_magic = IMAGE_DOS_SIGNATURE then
begin
SetFilePointer(hFile, IDH._lfanew, nil, FILE_BEGIN);
SplashScreen.sLabel1.Caption := 'Reading NT File Headers...';
//Here is where the UI freezes while the file is read...
ReadFile(hFile, INH, 248, dwRead, nil);
if INH.Signature = IMAGE_NT_SIGNATURE then
begin
Form2.edImageBase.Text := IntToHex(INH.OptionalHeader.ImageBase, 8);
Form2.edSizeOfImage.Text := IntToHex(INH.OptionalHeader.SizeOfImage, 8);
Form2.edLinkerVersion.Text := IntToStr(INH.OptionalHeader.MajorLinkerVersion) + '.' +
IntToStr(INH.OptionalHeader.MinorLinkerVersion);
Form2.edFileAlignment.Text := IntToHex(INH.OptionalHeader.FileAlignment, 8);
Form2.edSectionAlignment.Text := IntToHex(INH.OptionalHeader.SectionAlignment, 8);
Form2.edSubSystem.Text := IntToHex(INH.OptionalHeader.Subsystem, 4);
Form2.edEPFilestamp.Text := IntToStr(INH.FileHeader.TimeDateStamp);
Form2.edFileType.Text := GetPEFileType(PE.ImageNtHeaders.Signature);
for i := 0 to INH.FileHeader.NumberOfSections - 1 do
begin
SetFilePointer(hFile, IDH._lfanew + 248 + i * 40, nil, FILE_BEGIN);
ReadFile(hFile, ISH, 40, dwRead, nil);
CopyMemory(#szBuff[0], #ISH.Name[0], 8);
with Form2.sListView1.Items.Add do
begin
Caption := ShortString(szBuff);
SubItems.Add(IntToHex(ISH.VirtualAddress, 8));
SubItems.Add(IntToHex(ISH.Misc.VirtualSize, 8));
SubItems.Add(IntToHex(ISH.PointerToRawData, 8));
SubItems.Add(IntToHex(ISH.SizeOfRawData, 8));
SubItems.Add(IntToHex(ISH.Characteristics, 8));
end;
end;
end;
end;
CloseHandle(hFile);
Result := True;
end;
end;
The bad thing is that, depending on the size of the file, I noticed that the ReadFile would often lag - and it happens synchronously. In the meantime, the UI freezes and looks horribly wrong to the user, who would be tempted to terminate it. I have considered threading, but I just want to see if there is any way I can use ReadFile in asynchronous mode. If there isn't, I'll jump to threading, even if I'll have a lot to modify in my code.
Thank you in advance.

Answer 1

In this cases I always read the whole file to the memory also I use the TFileStream class for easier manipulation.
It is simpler to have the whole file in memory and PE files are usually small.
type
TSections = array [0..0] of TImageSectionHeader;
PSections = ^TSections;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var
FS : TFileStream;
fisier : PImageDosHeader;
INH : PImageNtHeaders;
ISH : PSections;
i : Word;
begin
FS := TFileStream.Create('fisierul_tau.exe',fmOpenRead);
GetMem(fisier,FS.size); //Aloci memorie pentru fisier
FS.Read(fisier^,FS.Size); // Il citesti;
FS.Free;
INH := PImageNtHeaders(DWORD(fisier) + DWORD(fisier^._lfanew));
ISH := PSections(DWORD(INH) + SizeOf(TImageNtHeaders));
for i := 0 to INH^.FileHeader.NumberOfSections - 1 do
begin
ShowMessage(PAnsiChar(#ISH[i].Name[0]));
end;
end;

Answer 2

The ReadFile function reads data from a file, and starts at the
position that the file pointer indicates. You can use this function
for both synchronous and asynchronous operations.
It is possible to use ReadFile asynchronously but depending on your UI this may not be the best solution. Do you want your users to do anything while they're waiting for the PE file to load?
If you want your users to wait but have confidence that your program didn't freeze you could add a progress bar or just update your SplashScreen.
for i := 0 to INH.FileHeader.NumberOfSections - 1 do
begin
SplashScreen.sLabel1.Caption := 'Reading section ' + IntToStr(i) + ' of ' + IntToStr(INH.FileHeader.NumberOfSections);
SplashScreen.sLabel1.Update; // see Ken Whites comment
// Application.ProcessMessages;
...
end