[Delphi] Get Offset By A/B

[0xFF]

This little function will return an offset inside a binary typed file by a given array of byte.

function RetOffset(const FileName: String; const bSrc: Array Of Byte): DWORD;  
var  
  hFile : DWORD;  
  CompareArray : Array Of Byte;  
  FileLength : DWORD;  
  Pos : DWORD;  
  BytesRead : DWORD;  
begin  
  Result := 0;  
  Pos := 0;  
  hFile := CreateFile(PChar(FileName), GENERIC_READ, 0, nil, OPEN_EXISTING, 0, 0);  
  If hFile = INVALID_HANDLE_VALUE Then Exit;  
  SetLength(CompareArray, Length(bSrc));  
  Try  
    FileLength := SetFilePointer(hfile, 0, nil, FILE_END) - Length(bSrc);  
    SetFilePointer(hFile, 0, nil, FILE_BEGIN);  
    While Pos <= FileLength Do  
      begin  
      If ReadFile(hFile, CompareArray[0], Length(CompareArray), BytesRead, nil) Then  
        begin  
        If CompareMem(PByteArray(@bSrc[0]), PByteArray(@CompareArray[0]), Length(bSrc)) Then  
          begin  
          Result := Pos;  
          Break;  
        end;  
        Inc(Pos, 1);  
        SetFilePointer(hFile, Pos, nil, FILE_BEGIN);  
      end  
      Else  
        begin  
        Break;  
      end;  
    end;  
  Finally  
    CompareArray := nil;  
    CloseHandle(hFile);  
  end;  
end;

Edited November 10, 2010 by rotem156

[Nacho_dj]

Nice code!

A couple of tips for Delphi coders:

The array of Byte type can also be used as TByteDynArray, you just need to add in uses the unit Types. There are a lot of predefined types there!

Pos is a Delphi function, if you use it as a variable you are redefining it and it won't be possible to use in your code as a function. Although doing in that way is not an error, though.

Best regards

Nacho_dj

[Departure]

Nacho,

So whats the differences between an "Array of Byte" and "TByteDynArray"? Just interested because I have always put it into a Array of Byte, Have never used "TbyteDynArray" type.

[Nacho_dj]

This is very useful when you want to code a function giving as result an array of Byte type. Well, Delphi compiler does not allow you define such a function, however if you define the type of the result of that function as TByteDynArray, it will be accepted by the compiler...

Cheers

Nacho_dj

[0xFF]

  On 11/10/2010 at 7:51 AM, Departure said:

Nacho,

So whats the differences between an "Array of Byte" and "TByteDynArray"? Just interested because I have always put it into a Array of Byte, Have never used "TbyteDynArray" type.

Nothing, it's just instead of writing array of byte you will make the code look more tidier by writing a predefined definition.

[Departure]

so really its just

type

TByteArray: Array of byte;

[0xFF]

  On 11/10/2010 at 5:06 PM, Departure said:

so really its just

type

TByteArray: Array of byte;

I would rename it TDynamicArray, and yes.

[Nacho_dj]

Well, there is also TCardinalDynArray = array of Cardinal, and much more...

I was defining my own types for array of anything, till I found that library, that I never heard before of. Now it is used in all my tools, since when dealing with files always use array of Byte.

Best regards

Nacho_dj

[0xFF]

Yeah, It's the first time I hear about this Unit too, looks very interesting one.