PEid plug-in-Principle Analysis of Generic OEP Finder

This small plug-in of PEid has been used for a long time, and has always felt that the function is good and the accuracy is quite high. I tried to avoid it during shell writing, but it has never been successful, so after taking some time to look at its implementation principles, I suddenly realized it.
Below are the first-level output functions of this plug-in:

10001870; Exported entry 1. DoMyJob
10001870
10001870; * ************ s u B r o u t I N E **************** *************************
10001870
10001870
10001870 public DoMyJob
10001870 DoMyJob proc near
10001870
10001870 hWnd = dword ptr 4
10001870 arg_4 = dword ptr 8
10001870 arg_8 = dword ptr 0Ch
10001870
10001870 mov eax, [esp + arg_8]
10001874 push ebx
10001875 push esi
10001876 cmp eax, 50456944 h
1000187B push edi
1000187C jz short loc_10001889
1000187E cmp eax, 5852445Ah
10001883 jnz loc_10001A81
10001889
10001889 loc_10001889 :;...
10001889 mov ebx, [esp + 0Ch + arg_4]
1000188D or ecx, 0 FFFFFFFFh
10001890 mov edi, ebx
10001892 xor eax, eax
10001894 repne scasb
10001896 not ecx
10001898 dec ecx
10001899 cmp ecx, 1
1000189C jnb short loc_100018BE
1000189E mov eax, [esp + 0Ch + hWnd]
100018A2 push 40000 h; uType
100018A7 push offset szError; lpCaption
100018AC push offset szNoFileSpecifie; lpText
100018B1 push eax; hWnd
100018B2 call ds: MessageBoxA
100018B8 pop edi
100018B9 pop esi
100018BA xor eax, eax
100018BC pop ebx
100018BD retn
100018BE ;----------------------------------------------------------------------------
100018BE
100018BE loc_100018BE :;...
100018BE push 0; hTemplateFile
100018C0 push 80 h; dwFlagsAndAttributes
100018C5 push 3