tracing: split out ThreadLocalEventBuffer

base/trace_event/thread_local_event_buffer.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/trace_event/thread_local_event_buffer.h"
+
+#include "base/trace_event/trace_buffer.h"
+#include "base/trace_event/trace_event_impl.h"
+#include "base/trace_event/trace_log.h"
+
+namespace base {
+namespace trace_event {
+
+ThreadLocalEventBuffer::ThreadLocalEventBuffer(int generation)
+    : chunk_index_(0), generation_(generation) {}
+
+ThreadLocalEventBuffer::~ThreadLocalEventBuffer() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  // The instance must have been flushed before destruction. Otherwise the
+  // owned chunk will be lost forever.
+  DCHECK(!chunk_);
+}
+
+TraceEvent* ThreadLocalEventBuffer::AddTraceEvent(TraceEventHandle* handle) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  if (chunk_ && chunk_->IsFull())
+    Flush();  // |chunk_| will be empty and evaluate to false after this call.
+
+  if (!chunk_) {
+    chunk_ = TraceLog::GetInstance()->TakeChunk(&chunk_index_);
+    if (!chunk_)
+      return NULL;
+  }
+
+  size_t event_index;
+  TraceEvent* trace_event = chunk_->AddTraceEvent(&event_index);
+  DCHECK(trace_event);
+  if (handle)
+    chunk_->MakeHandle(chunk_index_, event_index, handle);
+  return trace_event;
+}
+
+TraceEvent* ThreadLocalEventBuffer::GetEventByHandle(TraceEventHandle handle) {
+  if (!chunk_ || handle.chunk_seq != chunk_->seq() ||
+      handle.chunk_index != chunk_index_) {
+    return nullptr;
+  }
+  return chunk_->GetEventAt(handle.event_index);
+}
+
+void ThreadLocalEventBuffer::Flush() {
+  if (!chunk_)
+    return;
+  TraceLog::GetInstance()->ReturnChunk(std::move(chunk_), generation_,
+                                       chunk_index_);
+}
+
+}  // namespace trace_event
+}  // namespace base