1 /* 2 * Copyright (C) 2018 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 SRC_TRACING_CORE_NULL_TRACE_WRITER_H_ 18 #define SRC_TRACING_CORE_NULL_TRACE_WRITER_H_ 19 20 #include <cstdint> 21 #include <functional> 22 #include <memory> 23 24 #include "perfetto/ext/tracing/core/basic_types.h" 25 #include "perfetto/ext/tracing/core/trace_writer.h" 26 #include "perfetto/protozero/root_message.h" 27 #include "perfetto/protozero/scattered_stream_null_delegate.h" 28 #include "perfetto/protozero/scattered_stream_writer.h" 29 30 namespace perfetto { 31 32 // A specialization of TraceWriter which no-ops all the writes routing them 33 // into a fixed region of memory 34 // See //include/perfetto/ext/tracing/core/trace_writer.h for docs. 35 class NullTraceWriter : public TraceWriter { 36 public: 37 NullTraceWriter(); 38 ~NullTraceWriter() override; 39 40 // TraceWriter implementation. See documentation in trace_writer.h. 41 // TracePacketHandle is defined in trace_writer.h 42 TracePacketHandle NewTracePacket() override; 43 void FinishTracePacket() override; 44 void Flush(std::function<void()> callback = {}) override; 45 WriterID writer_id() const override; 46 uint64_t written() const override; 47 uint64_t drop_count() const override; 48 49 private: 50 NullTraceWriter(const NullTraceWriter&) = delete; 51 NullTraceWriter& operator=(const NullTraceWriter&) = delete; 52 53 protozero::ScatteredStreamWriterNullDelegate delegate_; 54 protozero::ScatteredStreamWriter stream_; 55 56 // The packet returned via NewTracePacket(). It is owned by this class, 57 // TracePacketHandle has just a pointer to it. 58 std::unique_ptr<protozero::RootMessage<protos::pbzero::TracePacket>> 59 cur_packet_; 60 }; 61 62 } // namespace perfetto 63 64 #endif // SRC_TRACING_CORE_NULL_TRACE_WRITER_H_ 65