Implement runtime support for non-exhaustive enums in Java

src/main/java/io/kaitai/struct/IKaitaiEnum.java

@@ -0,0 +1,56 @@
+/**
+ * Copyright 2015-2024 Kaitai Project: MIT license
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package io.kaitai.struct;
+
+/**
+ * Interface, implemented by every enum class generated by Kaitai Struct compiler.
+ *
+ * @since 0.11
+ */
+public interface IKaitaiEnum {
+    /**
+     * Base class for all unknown variants of Kaitai-generated enums.
+     *
+     * If you want to determine is the variant that you have is known or not,
+     * you can use {@code <variant> instanceof IKaitaiEnum.Unknown}.
+     *
+     * The descendants of this class have value semantic, like enums: their
+     * {@code equals} method compares inner long values of the same class (so
+     * {@code Unknown} values of different Kaitai enums are not equal) and
+     * {@code hashCode} method returns {@code Long.hashCode(this.id())}.
+     */
+    public abstract class Unknown implements IKaitaiEnum {
+        protected final long id;
+        protected Unknown(long id) { this.id = id; }
+
+        @Override
+        public int hashCode() { return Long.hashCode(id); }
+
+        @Override
+        public long id() { return id; }
+    }
+
+    /** Returns the underlying number which represents this enum variant. */
+    public long id();
+}