--- /dev/null	2017-11-09 09:38:01.297999907 +0100
+++ new/src/hotspot/share/jfr/metadata/jfrConstantSerializer.hpp	2018-04-09 14:49:15.949228411 +0200
@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2016, 2018, 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.
+ *
+ */
+
+#ifndef SHARE_VM_JFR_METADATA_JFRCONSTANTSERIALIZER_HPP
+#define SHARE_VM_JFR_METADATA_JFRCONSTANTSERIALIZER_HPP
+
+#include "memory/allocation.hpp"
+#include "jfr/recorder/checkpoint/jfrCheckpointWriter.hpp"
+#include "tracefiles/traceTypes.hpp"
+
+/*
+ * A JfrConstant (type) is a relation defined by enumerating a set of <key, value> ordered pairs:
+ *
+ * { <1, "my_first_constant">, <2, "my_second_constant">, ... }
+ *
+ * Write the key into event fields and the framework will maintain the mapping (if you register as below).
+ *
+ * In order to support mapping of constants, we use an interface called JfrConstantSerializer.
+ * Inherit JfrConstantSerializer, create a CHeapObj instance and use JfrConstantSerializer::register_serializer(...) to register.
+ * Once registered, the ownership of the serializer instance is transferred to Jfr.
+ *
+ * How to register:
+ *
+ * bool register_serializer(JfrConstantTypeId id, bool require_safepoint, bool permit_cache, JfrConstantSerializer* serializer)
+ *
+ * The constant types are machine generated into an enum located in tracefiles/traceTypes.hpp (included).
+ *
+ *  enum JfrConstantTypeId {
+ *    ...
+ *    CONSTANT_TYPE_THREADGROUP,
+ *    CONSTANT_TYPE_CLASSLOADER,
+ *    CONSTANT_TYPE_METHOD,
+ *    CONSTANT_TYPE_SYMBOL,
+ *    CONSTANT_TYPE_THREADSTATE,
+ *    CONSTANT_TYPE_INFLATECAUSE,
+ *    ...
+ *
+ * id                 this is the id of the constant type your are defining (see the enum above).
+ * require_safepoint  indicate if your constants need to be evaluated and written under a safepoint.
+ * permit_cache       indicate if your constants are stable to be cached.
+ *                    (implies the callback is invoked only once and the contents will be cached. Set this to true for static information).
+ * serializer         the serializer instance you define.
+ *
+ * See below for guidance about how to implement write_constants().
+ *
+ */
+class JfrConstantSerializer : public CHeapObj<mtTracing> {
+ public:
+  virtual void write_constants(JfrCheckpointWriter& writer) = 0;
+  virtual ~JfrConstantSerializer() {}
+  static bool register_serializer(JfrConstantTypeId id, bool require_safepoint, bool permit_cache, JfrConstantSerializer* serializer);
+};
+
+/*
+ *  Invoke writer.write_number_of_constants(num) to define the total number of constant mappings.
+ *
+ *  You then write the individual constants as ordered pairs, <key, value> ...
+ *
+ *  Here is an example:
+ *
+ *  void MyConstant::write_constants(JfrCheckpointWriter& writer) {
+ *    const int nof_causes = ObjectSynchronizer::inflate_cause_nof;
+ *    writer.write_number_of_constants(nof_causes);             // write number of constant (mappings) to follow
+ *    for (int i = 0; i < nof_causes; i++) {
+ *      writer.write_key(i);                                    // write key
+ *      writer.write(ObjectSynchronizer::inflate_cause_name((ObjectSynchronizer::InflateCause)i)); // write value
+ *    }
+ *  }
+ *
+ * Please see jfr/recorder/checkpoint/constant/jfrConstant.cpp for reference.
+ */
+
+#endif // SHARE_VM_JFR_METADATA_JFRCONSTANTSERIALIZER_HPP