Author: Jonas Bilinkevicius

How to determine the size of an executable from its exe header

Answer:

This code does not work with 16 bit executables. It assumes that the application is 
trying to find the size of itself, but could easily be modified to find the size of 
any 32bit exe loaded into a stream.

1   {$IFDEF VER100}
2   
3   {TImageDosHeader isn't defined in Delphi 3 so here's an an abbreviated structure 
4   definition}
5   type
6     PImageDosHeader = ^TImageDosHeader;
7     TImageDosHeader = packed record
8       e_ignore: packed array[0..29] of WORD;
9       _lfanew: Longint;
10    end;
11  
12  {$ENDIF}
13  
14  function GetExeSize: cardinal;
15  var
16    p: PChar;
17    i, NumSections: integer;
18  begin
19    result := 0;
20    {hInstance is actually a pointer to the exe's image base in memory}
21    p := pointer(hinstance);
22    inc(p, PImageDosHeader(p)._lfanew);
23    inc(p, sizeof(dword));
24    NumSections := PImageFileHeader(p).NumberOfSections;
25    inc(p, sizeof(TImageFileHeader) + sizeof(TImageOptionalHeader));
26    for i := 1 to NumSections do
27    begin
28      with PImageSectionHeader(p)^ do
29        if PointerToRawData + SizeOfRawData > result then
30          result := PointerToRawData + SizeOfRawData;
31      inc(p, sizeof(TImageSectionHeader));
32    end;
33  end;