1 /* 2 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_JFR_METADATA_JFRSERIALIZER_HPP 26 #define SHARE_VM_JFR_METADATA_JFRSERIALIZER_HPP 27 28 #include "memory/allocation.hpp" 29 #include "jfr/recorder/checkpoint/jfrCheckpointWriter.hpp" 30 #include "jfrfiles/jfrTypes.hpp" 31 32 /* 33 * A "type" in Jfr is a binary relation defined by enumerating a set of <key, value> ordered pairs: 34 * 35 * { <1, myvalue>, <2, mysecondvalue>, ... } 36 * 37 * The key should be a type relative unique id. A value is an instance of the type. 38 * 39 * By defining and registering a type, keys can be written to event fields and the 40 * framework will maintain the mapping to the corresponding value (if you register as below). 41 * 42 * Inherit JfrSerializer, create a CHeapObj instance and then use JfrSerializer::register_serializer(...) to register. 43 * Once registered, the ownership of the serializer instance is transferred to Jfr. 44 * 45 * How to register: 46 * 47 * bool register_serializer(JfrTypeId id, bool require_safepoint, bool permit_cache, JfrSerializer* serializer) 48 * 49 * The type identifiers are machine generated into an enum located in jfrfiles/jfrTypes.hpp (included). 50 * 51 * enum JfrTypeId { 52 * ... 53 * TYPE_THREADGROUP, 54 * TYPE_CLASSLOADER, 55 * TYPE_METHOD, 56 * TYPE_SYMBOL, 57 * TYPE_THREADSTATE, 58 * TYPE_INFLATECAUSE, 59 * ... 60 * 61 * id this is the id of the type your are defining (see the enum above). 62 * require_safepoint indicate if your type need to be evaluated and serialized under a safepoint. 63 * permit_cache indicate if your type constants are stable to be cached. 64 * (implies the callback is invoked only once and the contents will be cached. Set this to true for static information). 65 * serializer the serializer instance. 66 * 67 * See below for guidance about how to implement serialize(). 68 * 69 */ 70 class JfrSerializer : public CHeapObj<mtTracing> { 71 public: 72 virtual ~JfrSerializer() {} 73 static bool register_serializer(JfrTypeId id, bool require_safepoint, bool permit_cache, JfrSerializer* serializer); 74 virtual void serialize(JfrCheckpointWriter& writer) = 0; 75 }; 76 77 /* 78 * Defining serialize(JfrCheckpointWriter& writer): 79 * 80 * Invoke writer.write_count(N) for the number of ordered pairs (cardinality) to be defined. 81 * 82 * You then write each individual ordered pair, <key, value> ... 83 * 84 * Here is a simple example, describing a type defining string constants: 85 * 86 * void MyType::serialize(JfrCheckpointWriter& writer) { 87 * const int nof_causes = ObjectSynchronizer::inflate_cause_nof; 88 * writer.write_count(nof_causes); // write number of ordered pairs (mappings) to follow 89 * for (int i = 0; i < nof_causes; i++) { 90 * writer.write_key(i); // write key 91 * writer.write(ObjectSynchronizer::inflate_cause_name((ObjectSynchronizer::InflateCause)i)); // write value 92 * } 93 * } 94 * 95 * Note that values can be complex, and can also referer to other types. 96 * 97 * Please see jfr/recorder/checkpoint/types/jfrType.cpp for reference. 98 */ 99 100 #endif // SHARE_VM_JFR_METADATA_JFRSERIALIZER_HPP