8287496: Alternative virtual thread implementation that maps to OS thread

Reviewed-by: rehn, mchung

src/java.base/share/classes/java/lang/BaseVirtualThread.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.lang;
+
+/**
+ * Base class for virtual thread implementations.
+ */
+sealed abstract class BaseVirtualThread extends Thread
+        permits VirtualThread, ThreadBuilders.BoundVirtualThread {
+
+    /**
+     * Initializes a virtual Thread.
+     *
+     * @param name thread name, can be null
+     * @param characteristics thread characteristics
+     * @param bound true when bound to an OS thread
+     */
+    BaseVirtualThread(String name, int characteristics, boolean bound) {
+        super(name, characteristics, bound);
+    }
+
+    /**
+     * Parks the current virtual thread until the parking permit is available or
+     * the thread is interrupted.
+     *
+     * The behavior of this method when the current thread is not this thread
+     * is not defined.
+     */
+    abstract void park();
+
+    /**
+     * Parks current virtual thread up to the given waiting time until the parking
+     * permit is available or the thread is interrupted.
+     *
+     * The behavior of this method when the current thread is not this thread
+     * is not defined.
+     */
+    abstract void parkNanos(long nanos);
+
+    /**
+     * Makes available the parking permit to the given this virtual thread.
+     */
+    abstract void unpark();
+}
+