--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/jfr/metadata/jfrSerializer.hpp	Tue May 15 20:24:34 2018 +0200
@@ -0,0 +1,100 @@
+/*
+ * 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_JFRSERIALIZER_HPP
+#define SHARE_VM_JFR_METADATA_JFRSERIALIZER_HPP
+
+#include "memory/allocation.hpp"
+#include "jfr/recorder/checkpoint/jfrCheckpointWriter.hpp"
+#include "jfrfiles/jfrTypes.hpp"
+
+/*
+ * A "type" in Jfr is a binary relation defined by enumerating a set of <key, value> ordered pairs:
+ *
+ * { <1, myvalue>, <2, mysecondvalue>, ... }
+ *
+ * The key should be a type relative unique id. A value is an instance of the type.
+ *
+ * By defining and registering a type, keys can be written to event fields and the
+ * framework will maintain the mapping to the corresponding value (if you register as below).
+ *
+ * Inherit JfrSerializer, create a CHeapObj instance and then use JfrSerializer::register_serializer(...) to register.
+ * Once registered, the ownership of the serializer instance is transferred to Jfr.
+ *
+ * How to register:
+ *
+ * bool register_serializer(JfrTypeId id, bool require_safepoint, bool permit_cache, JfrSerializer* serializer)
+ *
+ * The type identifiers are machine generated into an enum located in jfrfiles/jfrTypes.hpp (included).
+ *
+ *  enum JfrTypeId {
+ *    ...
+ *    TYPE_THREADGROUP,
+ *    TYPE_CLASSLOADER,
+ *    TYPE_METHOD,
+ *    TYPE_SYMBOL,
+ *    TYPE_THREADSTATE,
+ *    TYPE_INFLATECAUSE,
+ *    ...
+ *
+ * id                 this is the id of the type your are defining (see the enum above).
+ * require_safepoint  indicate if your type need to be evaluated and serialized under a safepoint.
+ * permit_cache       indicate if your type 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.
+ *
+ * See below for guidance about how to implement serialize().
+ *
+ */
+class JfrSerializer : public CHeapObj<mtTracing> {
+ public:
+  virtual ~JfrSerializer() {}
+  static bool register_serializer(JfrTypeId id, bool require_safepoint, bool permit_cache, JfrSerializer* serializer);
+  virtual void serialize(JfrCheckpointWriter& writer) = 0;
+};
+
+/*
+ * Defining serialize(JfrCheckpointWriter& writer):
+ *
+ *  Invoke writer.write_count(N) for the number of ordered pairs (cardinality) to be defined.
+ *
+ *  You then write each individual ordered pair, <key, value> ...
+ *
+ *  Here is a simple example, describing a type defining string constants:
+ *
+ *  void MyType::serialize(JfrCheckpointWriter& writer) {
+ *    const int nof_causes = ObjectSynchronizer::inflate_cause_nof;
+ *    writer.write_count(nof_causes);                           // write number of ordered pairs (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
+ *    }
+ *  }
+ *
+ * Note that values can be complex, and can also referer to other types.
+ *
+ * Please see jfr/recorder/checkpoint/types/jfrType.cpp for reference.
+ */
+
+#endif // SHARE_VM_JFR_METADATA_JFRSERIALIZER_HPP