I need to Read data from .exe file for example this is OEP (virtual address) 00000023 I've converted it to physical and now I need to check if data on this address = $55 then WriteFile(H, buf, SizeOf(buf), written, nil);

How to do that? Sorry for my bad English language

I need to Read data from .exe file for example this is OEP (virtual address) 00000023 I've converted it to physical and now I need to check if data on this address = $55 then WriteFile(H, buf, SizeOf(buf), written, nil);

How to do that? Sorry for my bad English language

Use ReadFile Api, has the same params as WriteFile.

You can read file into memory all at once, or use SetFilePointer api to choose where to read from ..

Also you can use FileStream / MemoryStream Delphi classes, but they are lame and you get much smaller code using apis ..

Check if this works for you. Of course, you can modify it to add checks and everything you need...

type
  BufferByte = array of Byte;procedure ReadBufferFromFile(PathToMyFile : AnsiString; Offset : Integer; var buf : BufferByte);
var
  MyFile : TFileStream;  begin
  try
    MyFile := TFileStream.Create(PathToMyFile,fmOpenRead);
    MyFile.Seek(Offset,SoFromBeginning);
    MyFile.Read(buf[0],Length(buf));
  finally
    MyFile.Free;
  end;
end;procedure WriteBufferToFile(PathToMyFile : AnsiString; Offset : Integer; var buf : BufferByte);
var
  MyFile : TFileStream;  begin
  try
    MyFile := TFileStream.Create(PathToMyFile,fmOpenWrite);
    MyFile.Seek(Offset,SoFromBeginning);
    MyFile.Write(buf[0],Length(buf));
  finally
    MyFile.Free;
  end;
end;procedure CheckOEPAndFix;
var
  Offset : Integer;
  PathToMyFile : AnsiString;
  bufRead, bufWrite : BufferByte;begin
  Offset := $1523; // Example of address of your OEP, it must be offset of a file, not Virtual Address
  PathToMyFile := 'C:\Program Files\MyExe.exe'
  SetLength(bufRead,1);
  ReadBufferFromFile(PathToMyFile,Offset,bufRead);
  if bufRead[0] = $55 then
  begin
    ........ // Treatment of your buffer to be written
    ........
    WriteBufferToFile(PathToMyFile,Offset,bufWrite);
  end;
end;

thanks it works !!

but,

 PathToMyFile := 'C:\Program Files\MyExe.exe' <-- here must be ";" this
PathToMyFile := 'C:\Program Files\MyExe.exe';

Nice! Now you can try to find how to improve your techniques, by modifying that code for your needings.

About the missing ';', hehe, when you code this happens for sure!

Luckily there are good coompilers warning you about things like that...

Best regards

Nacho_dj