1 /* 2 * Copyright (C) 2019 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef INCLUDE_PERFETTO_TRACING_EVENT_CONTEXT_H_ 18 #define INCLUDE_PERFETTO_TRACING_EVENT_CONTEXT_H_ 19 20 #include "perfetto/protozero/message_handle.h" 21 #include "perfetto/tracing/internal/track_event_internal.h" 22 #include "perfetto/tracing/traced_proto.h" 23 #include "protos/perfetto/trace/trace_packet.pbzero.h" 24 25 namespace perfetto { 26 namespace internal { 27 class TrackEventInternal; 28 } 29 30 // Allows adding custom arguments into track events. Example: 31 // 32 // TRACE_EVENT_BEGIN("category", "Title", 33 // [](perfetto::EventContext ctx) { 34 // auto* dbg = ctx.event()->add_debug_annotations(); 35 // dbg->set_name("name"); 36 // dbg->set_int_value(1234); 37 // }); 38 // 39 class PERFETTO_EXPORT EventContext { 40 public: 41 EventContext(EventContext&&) = default; 42 43 // For Chromium during the transition phase to the client library. 44 // TODO(eseckler): Remove once Chromium has switched to client lib entirely. 45 explicit EventContext( 46 protos::pbzero::TrackEvent* event, 47 internal::TrackEventIncrementalState* incremental_state = nullptr) event_(event)48 : event_(event), incremental_state_(incremental_state) {} 49 50 ~EventContext(); 51 52 // Get a TrackEvent message to write typed arguments to. 53 // 54 // event() is a template method to allow callers to specify a subclass of 55 // TrackEvent instead. Those subclasses correspond to TrackEvent message with 56 // application-specific extensions. More information in 57 // design-docs/extensions.md. 58 template <typename EventType = protos::pbzero::TrackEvent> event()59 EventType* event() const { 60 // As the method does downcasting, we check that a target subclass does 61 // not add new fields. 62 static_assert( 63 sizeof(EventType) == sizeof(protos::pbzero::TrackEvent), 64 "Event type must be binary-compatible with protos::pbzero::TrackEvent"); 65 return static_cast<EventType*>(event_); 66 } 67 68 // Convert a raw pointer to protozero message to TracedProto which captures 69 // the reference to this EventContext. 70 template <typename MessageType> Wrap(MessageType * message)71 TracedProto<MessageType> Wrap(MessageType* message) { 72 static_assert(std::is_base_of<protozero::Message, MessageType>::value, 73 "TracedProto can be used only with protozero messages"); 74 75 return TracedProto<MessageType>(message, *this); 76 } 77 78 private: 79 template <typename, size_t, typename, typename> 80 friend class TrackEventInternedDataIndex; 81 friend class internal::TrackEventInternal; 82 83 using TracePacketHandle = 84 ::protozero::MessageHandle<protos::pbzero::TracePacket>; 85 86 EventContext(TracePacketHandle, internal::TrackEventIncrementalState*); 87 EventContext(const EventContext&) = delete; 88 89 TracePacketHandle trace_packet_; 90 protos::pbzero::TrackEvent* event_; 91 internal::TrackEventIncrementalState* incremental_state_; 92 }; 93 94 } // namespace perfetto 95 96 #endif // INCLUDE_PERFETTO_TRACING_EVENT_CONTEXT_H_ 97