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POAsynchronous ReadFile in Delphi XE2
 

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  1. POAsynchronous ReadFile in Delphi XE2
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    <p>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 <code>ReadFile</code> function, as shown below:</p> <pre><code>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 &lt;&gt; 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; </code></pre> <p>The bad thing is that, depending on the size of the file, I noticed that the <code>ReadFile</code> 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 <code>ReadFile</code> in asynchronous mode. If there isn't, I'll jump to threading, even if I'll have a lot to modify in my code.</p> <p>Thank you in advance.</p>
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    1. USKen White
    1. USBogdan Botezatu
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    1. COJust out of curiosity, is there a reason you're reinventing the wheel here? Delphi versions prior to 2007 have a demo that dumps the PE information (don't have the demo name here, but will post it later), and the [JEDI Code Library](http://delphi-jedi.org) has an entire unit (`JclPEImage`) containing ready-to-use functions that do all this stuff for you. (There's even a PEViewer demo that displays everything in a way very similar to `DependencyWalker`.) All of the code performs just fine on even very large executables (5 MB+) without any UI issues or lags.
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      1. USKen White
    2. COHey there, @KenWhite, I don't have any preferences on the implementation. Indeed, I excluded JEDI, because of the fact that one unit links to another and so on and this - IMHO - makes the whole project mere difficult to maintain than if I had a single function in place. I'll take a look at the old Delphi demos, I think I still have the disc with Delphi 7 around.
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      1. USBogdan Botezatu
    3. COWhen I get to my home system, I'll find the demo name from D7 and post it in a comment here. `JCL` is better than `JVCL` about using unit after unit, because it's strictly code. It does add some other stuff, but in this case you're adding a single unit name to your uses clause to include `JclPEImage`, and calling simple functions from your code. It's not bad (although I agree the JVCL is annoyingly co-dependent on other units it contains).
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