From 040245fe79b2bf1483a17d9ffbafe813a9f6407f Mon Sep 17 00:00:00 2001
From: Martin Paljak <martin@martinpaljak.net>
Date: Tue, 5 Mar 2024 00:00:42 +0200
Subject: [PATCH] Add small helper to parse export file versions for #92

---
 .../pro/javacard/sdk/ExportFileHelper.java    | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 capfile/src/main/java/pro/javacard/sdk/ExportFileHelper.java

diff --git a/capfile/src/main/java/pro/javacard/sdk/ExportFileHelper.java b/capfile/src/main/java/pro/javacard/sdk/ExportFileHelper.java
new file mode 100644
index 0000000..2958964
--- /dev/null
+++ b/capfile/src/main/java/pro/javacard/sdk/ExportFileHelper.java
@@ -0,0 +1,36 @@
+package pro.javacard.sdk;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Optional;
+
+public final class ExportFileHelper {
+
+    public enum ExportFileVersion {
+        V21, V23
+    }
+
+    private ExportFileHelper() {
+    }
+
+    public static Optional<ExportFileVersion> getVersion(Path path) throws IOException {
+        try (DataInputStream dis = new DataInputStream(Files.newInputStream(path))) {
+            int magic = dis.readInt();
+
+            byte minor = dis.readByte();
+            byte major = dis.readByte();
+
+            if (magic != 0x00FACADE)
+                return Optional.empty();
+            if (major != 2)
+                throw new IOException("Invalid major version: " + major);
+            if (minor == 1)
+                return Optional.of(ExportFileVersion.V21);
+            if (minor == 3)
+                return Optional.of(ExportFileVersion.V23);
+            throw new IOException("Invalid minor version: " + minor);
+        }
+    }
+}