blob: 2d475c132303d56b941ceacb8719dc020617e928 [file] [log] [blame]
/*
* Copyright (C) 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// This example demonstrates a custom tracing data source.
#include <perfetto.h>
#include <fstream>
#include <thread>
// The definition of our custom data source. Instances of this class will be
// automatically created and destroyed by Perfetto.
class CustomDataSource : public perfetto::DataSource<CustomDataSource> {
public:
void OnSetup(const SetupArgs&) override {
// Use this callback to apply any custom configuration to your data source
// based on the TraceConfig in SetupArgs.
}
// Optional callbacks for tracking the lifecycle of the data source.
void OnStart(const StartArgs&) override {}
void OnStop(const StopArgs&) override {}
};
PERFETTO_DECLARE_DATA_SOURCE_STATIC_MEMBERS(CustomDataSource);
PERFETTO_DEFINE_DATA_SOURCE_STATIC_MEMBERS(CustomDataSource);
void InitializePerfetto() {
perfetto::TracingInitArgs args;
// The backends determine where trace events are recorded. For this example we
// are going to use the in-process tracing service, which only includes in-app
// events.
args.backends = perfetto::kInProcessBackend;
perfetto::Tracing::Initialize(args);
// Register our custom data source. Only the name is required, but other
// properties can be advertised too.
perfetto::DataSourceDescriptor dsd;
dsd.set_name("com.example.custom_data_source");
CustomDataSource::Register(dsd);
}
std::unique_ptr<perfetto::TracingSession> StartTracing() {
// The trace config defines which types of data sources are enabled for
// recording. In this example we enable the custom data source we registered
// above.
perfetto::TraceConfig cfg;
cfg.add_buffers()->set_size_kb(1024);
auto* ds_cfg = cfg.add_data_sources()->mutable_config();
ds_cfg->set_name("com.example.custom_data_source");
auto tracing_session = perfetto::Tracing::NewTrace();
tracing_session->Setup(cfg);
tracing_session->StartBlocking();
return tracing_session;
}
void StopTracing(std::unique_ptr<perfetto::TracingSession> tracing_session) {
// Flush to make sure the last written event ends up in the trace.
CustomDataSource::Trace(
[](CustomDataSource::TraceContext ctx) { ctx.Flush(); });
// Stop tracing and read the trace data.
tracing_session->StopBlocking();
std::vector<char> trace_data(tracing_session->ReadTraceBlocking());
// Write the result into a file.
// Note: To save memory with longer traces, you can tell Perfetto to write
// directly into a file by passing a file descriptor into Setup() above.
std::ofstream output;
output.open("example_custom_data_source.pftrace",
std::ios::out | std::ios::binary);
output.write(&trace_data[0], trace_data.size());
output.close();
}
int main(int, const char**) {
InitializePerfetto();
auto tracing_session = StartTracing();
// Write an event using our custom data source.
CustomDataSource::Trace([](CustomDataSource::TraceContext ctx) {
auto packet = ctx.NewTracePacket();
packet->set_timestamp(42);
packet->set_for_testing()->set_str("Hello world!");
});
StopTracing(std::move(tracing_session));
return 0;
}