From 618acc6ea2e46cbc95647df9800514e55d2f4401 Mon Sep 17 00:00:00 2001
From: Ladislav Thon <lthon@redhat.com>
Date: Wed, 18 Oct 2023 17:58:22 +0200
Subject: [PATCH] improve error message when verifying magic bytes of the input

---
 core/src/main/java/org/jboss/jandex/Indexer.java | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/jboss/jandex/Indexer.java b/core/src/main/java/org/jboss/jandex/Indexer.java
index 47e66a03..29df11eb 100644
--- a/core/src/main/java/org/jboss/jandex/Indexer.java
+++ b/core/src/main/java/org/jboss/jandex/Indexer.java
@@ -2085,9 +2085,15 @@ private boolean isJDK11OrNewer(DataInputStream stream) throws IOException {
     }
 
     private void verifyMagic(DataInputStream stream) throws IOException {
-        final int magic = stream.readInt();
+        final int magic;
+        try {
+            magic = stream.readInt();
+        } catch (EOFException e) {
+            throw new EOFException("Input is not a valid class file; must begin with a 4-byte integer 0xCAFEBABE");
+        }
         if (magic != 0xCA_FE_BA_BE) {
-            throw new IOException("Invalid Magic");
+            throw new IOException("Input is not a valid class file; must begin with a 4-byte integer 0xCAFEBABE, "
+                    + "but seen 0x" + Integer.toHexString(magic).toUpperCase());
         }
     }