[wpiutil] Add Struct and Protobuf clone and immutable checks (#6686)

wpiutil/src/main/java/edu/wpi/first/util/protobuf/Protobuf.java

@@ -97,6 +97,39 @@ public interface Protobuf<T, MessageType extends ProtoMessage<?>> {
     throw new UnsupportedOperationException("object does not support unpackInto");
   }
 
+  /**
+   * Returns whether or not objects are immutable. Immutable objects must also be comparable using
+   * the equals() method. Default implementation returns false.
+   *
+   * @return True if object is immutable
+   */
+  default boolean isImmutable() {
+    return false;
+  }
+
+  /**
+   * Returns whether or not objects are cloneable using the clone() method. Clonable objects must
+   * also be comparable using the equals() method. Default implementation returns false.
+   *
+   * @return True if object is clonable
+   */
+  default boolean isCloneable() {
+    return false;
+  }
+
+  /**
+   * Creates a (deep) clone of the object. May also return the object directly if the object is
+   * immutable. Default implementation throws CloneNotSupportedException. Typically this should be
+   * implemented by implementing clone() on the object itself, and calling it from here.
+   *
+   * @param obj object to clone
+   * @return Clone of object (if immutable, may be same object)
+   * @throws CloneNotSupportedException if clone not supported
+   */
+  default T clone(T obj) throws CloneNotSupportedException {
+    throw new CloneNotSupportedException();
+  }
+
   /**
    * Loops over all protobuf descriptors including nested/referenced descriptors.
    *

wpiutil/src/main/java/edu/wpi/first/util/struct/Struct.java

@@ -113,4 +113,37 @@ public interface Struct<T> {
   default void unpackInto(T out, ByteBuffer bb) {
     throw new UnsupportedOperationException("object does not support unpackInto");
   }
+
+  /**
+   * Returns whether or not objects are immutable. Immutable objects must also be comparable using
+   * the equals() method. Default implementation returns false.
+   *
+   * @return True if object is immutable
+   */
+  default boolean isImmutable() {
+    return false;
+  }
+
+  /**
+   * Returns whether or not objects are cloneable using the clone() method. Clonable objects must
+   * also be comparable using the equals() method. Default implementation returns false.
+   *
+   * @return True if object is clonable
+   */
+  default boolean isCloneable() {
+    return false;
+  }
+
+  /**
+   * Creates a (deep) clone of the object. May also return the object directly if the object is
+   * immutable. Default implementation throws CloneNotSupportedException. Typically this should be
+   * implemented by implementing clone() on the object itself, and calling it from here.
+   *
+   * @param obj object to clone
+   * @return Clone of object (if immutable, may be same object)
+   * @throws CloneNotSupportedException if clone not supported
+   */
+  default T clone(T obj) throws CloneNotSupportedException {
+    throw new CloneNotSupportedException();
+  }
 }