From 41d1e22522bd8892d709849801ae36ea0b078352 Mon Sep 17 00:00:00 2001
From: Hermes Agent <hermes@nousresearch.com>
Date: Thu, 28 May 2026 15:46:36 +0200
Subject: [PATCH] Fix platform detection: LE (DOS/4GW extender) is DOS, not
 Windows
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Many classic DOS games (Blood, DOOM, Duke Nukem 3D, Quake) use
DOS/4GW or DOS/32A — 32-bit DOS extenders with Linear Executable
(LE) format. My code was detecting LE as 'windows', causing these
games to be incorrectly flagged as unplayable.

Only PE (Portable Executable / Win32) and NE (New Executable /
Windows 3.x) are actually Windows.
---
 src/main/java/com/dostalgia/UploadResource.java | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/main/java/com/dostalgia/UploadResource.java b/src/main/java/com/dostalgia/UploadResource.java
index 58feb76..71ae61d 100644
--- a/src/main/java/com/dostalgia/UploadResource.java
+++ b/src/main/java/com/dostalgia/UploadResource.java
@@ -447,10 +447,13 @@ public class UploadResource {
     /**
      * Detect whether an executable targets DOS or Windows by reading its PE/NE header.
      * <ul>
-     *   <li>Pure MZ (no NE/PE/LE) → "dos"</li>
-     *   <li>NE (Windows 3.x), PE (Win32), LE (VxD) → "windows"</li>
+     *   <li>Pure MZ, LE (DOS/4GW extender), LX (OS/2) → "dos"</li>
+     *   <li>NE (Windows 3.x), PE (Win32) → "windows"</li>
      *   <li>Cannot read → null</li>
      * </ul>
+     * Note: LE (Linear Executable) is used by DOS/4GW, DOS/32A, PMODE/W
+     * — all 32-bit DOS extenders for games like DOOM, Blood, Duke Nukem 3D.
+     * Only PE (Portable Executable) and NE (New Executable) are Windows.
      */
     static String detectPlatform(Path exePath) {
         String name = exePath.getFileName().toString().toLowerCase();
@@ -487,12 +490,10 @@ public class UploadResource {
 
             // PE  = Portable Executable (Win32)
             // NE  = New Executable (Windows 3.x)
-            // LE  = Linear Executable (VxD, OS/2)
+            // LE  = Linear Executable (DOS/4GW, DOS/32A — 32-bit DOS extenders)
             // LX  = Extended Linear Executable (OS/2 2.x)
             if ((sig1 == 0x50 && sig2 == 0x45)   // PE
-             || (sig1 == 0x4E && sig2 == 0x45)   // NE
-             || (sig1 == 0x4C && sig2 == 0x45)   // LE
-             || (sig1 == 0x4C && sig2 == 0x58))  // LX
+             || (sig1 == 0x4E && sig2 == 0x45))  // NE
                 return "windows";
 
             return "dos"; // Plain MZ without known Windows signature