--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.internal.vm.compiler/share/classes/jdk.internal.vm.compiler.libgraal/src/jdk/internal/vm/compiler/libgraal/LibGraalScope.java	Thu Jun 27 03:33:44 2019 +0200
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2019, 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.
+ *
+ * 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 jdk.internal.vm.compiler.libgraal;
+
+import jdk.vm.ci.hotspot.HotSpotJVMCIRuntime;
+
+/**
+ * Scope for calling CEntryPoints in libgraal. {@linkplain #LibGraalScope(HotSpotJVMCIRuntime)
+ * Opening} a scope attaches the current thread to libgraal and {@linkplain #close() closing} it
+ * detaches the current thread.
+ */
+public final class LibGraalScope implements AutoCloseable {
+
+    static final ThreadLocal<LibGraalScope> currentScope = new ThreadLocal<>();
+
+    private final LibGraalScope parent;
+    private final boolean topLevel;
+    private final HotSpotJVMCIRuntime runtime;
+    private final long isolateThread;
+
+    /**
+     * Gets the isolate thread associated with the current thread. The current thread must be in an
+     * {@linkplain #LibGraalScope(HotSpotJVMCIRuntime) opened} scope.
+     *
+     * @returns a value that can be used for the IsolateThreadContext argument of a {@code native}
+     *          method {@link LibGraal#registerNativeMethods linked} to a CEntryPoint function in
+     *          libgraal
+     * @throws IllegalStateException if not the current thread is not attached to libgraal
+     */
+    public static long getIsolateThread() {
+        LibGraalScope scope = currentScope.get();
+        if (scope == null) {
+            throw new IllegalStateException("Cannot get isolate thread outside of a " + LibGraalScope.class.getSimpleName());
+        }
+        return scope.isolateThread;
+    }
+
+    /**
+     * Enters a scope for making calls into libgraal. If there is no existing libgraal scope for the
+     * current thread, the current thread is attached to libgraal. When the outer most scope is
+     * closed, the current thread is detached from libgraal.
+     *
+     * This must be used in a try-with-resources statement.
+     *
+     * This cannot be called from {@linkplain LibGraal#inLibGraal() within} libgraal.
+     *
+     * @throws IllegalStateException if libgraal is {@linkplain LibGraal#isAvailable() unavailable}
+     *             or {@link LibGraal#inLibGraal()} returns true
+     */
+    public LibGraalScope(HotSpotJVMCIRuntime runtime) {
+        if (LibGraal.inLibGraal() || !LibGraal.isAvailable()) {
+            throw new IllegalStateException();
+        }
+        this.runtime = runtime;
+        parent = currentScope.get();
+        boolean top = false;
+        if (parent == null) {
+            top = LibGraal.attachCurrentThread(runtime);
+            isolateThread = LibGraal.getCurrentIsolateThread(LibGraal.isolate);
+        } else {
+            isolateThread = parent.isolateThread;
+        }
+        topLevel = top;
+        currentScope.set(this);
+    }
+
+    @Override
+    public void close() {
+        if (topLevel) {
+            LibGraal.detachCurrentThread(runtime);
+        }
+        currentScope.set(parent);
+    }
+}