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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TRACE_EVENT_TRACE_BUFFER_H_
#define BASE_TRACE_EVENT_TRACE_BUFFER_H_
#include <stddef.h>
#include <stdint.h>
#include "base/base_export.h"
#include "base/check.h"
#include "base/trace_event/trace_event.h"
#include "base/trace_event/trace_event_impl.h"
namespace base {
namespace trace_event {
// TraceBufferChunk is the basic unit of TraceBuffer.
class BASE_EXPORT TraceBufferChunk {
public:
explicit TraceBufferChunk(uint32_t seq);
~TraceBufferChunk();
void Reset(uint32_t new_seq);
TraceEvent* AddTraceEvent(size_t* event_index);
bool IsFull() const { return next_free_ == kTraceBufferChunkSize; }
uint32_t seq() const { return seq_; }
size_t capacity() const { return kTraceBufferChunkSize; }
size_t size() const { return next_free_; }
TraceEvent* GetEventAt(size_t index) {
DCHECK(index < size());
return &chunk_[index];
}
const TraceEvent* GetEventAt(size_t index) const {
DCHECK(index < size());
return &chunk_[index];
}
void EstimateTraceMemoryOverhead(TraceEventMemoryOverhead* overhead);
// These values must be kept consistent with the numbers of bits of
// chunk_index and event_index fields in TraceEventHandle
// (in trace_event_impl.h).
static const size_t kMaxChunkIndex = (1u << 26) - 1;
static const size_t kTraceBufferChunkSize = 64;
private:
size_t next_free_;
std::unique_ptr<TraceEventMemoryOverhead> cached_overhead_estimate_;
TraceEvent chunk_[kTraceBufferChunkSize];
uint32_t seq_;
};
// TraceBuffer holds the events as they are collected.
class BASE_EXPORT TraceBuffer {
public:
virtual ~TraceBuffer() = default;
virtual std::unique_ptr<TraceBufferChunk> GetChunk(size_t* index) = 0;
virtual void ReturnChunk(size_t index,
std::unique_ptr<TraceBufferChunk> chunk) = 0;
virtual bool IsFull() const = 0;
virtual size_t Size() const = 0;
virtual size_t Capacity() const = 0;
virtual TraceEvent* GetEventByHandle(TraceEventHandle handle) = 0;
// For iteration. Each TraceBuffer can only be iterated once.
virtual const TraceBufferChunk* NextChunk() = 0;
// Computes an estimate of the size of the buffer, including all the retained
// objects.
virtual void EstimateTraceMemoryOverhead(
TraceEventMemoryOverhead* overhead) = 0;
static TraceBuffer* CreateTraceBufferRingBuffer(size_t max_chunks);
static TraceBuffer* CreateTraceBufferVectorOfSize(size_t max_chunks);
};
// TraceResultBuffer collects and converts trace fragments returned by TraceLog
// to JSON output.
class BASE_EXPORT TraceResultBuffer {
public:
using OutputCallback = base::RepeatingCallback<void(const std::string&)>;
// If you don't need to stream JSON chunks out efficiently, and just want to
// get a complete JSON string after calling Finish, use this struct to collect
// JSON trace output.
struct BASE_EXPORT SimpleOutput {
OutputCallback GetCallback();
void Append(const std::string& json_string);
// Do what you want with the json_output_ string after calling
// TraceResultBuffer::Finish.
std::string json_output;
};
TraceResultBuffer();
~TraceResultBuffer();
// Set callback. The callback will be called during Start with the initial
// JSON output and during AddFragment and Finish with following JSON output
// chunks. The callback target must live past the last calls to
// TraceResultBuffer::Start/AddFragment/Finish.
void SetOutputCallback(OutputCallback json_chunk_callback);
// Start JSON output. This resets all internal state, so you can reuse
// the TraceResultBuffer by calling Start.
void Start();
// Call AddFragment 0 or more times to add trace fragments from TraceLog.
void AddFragment(const std::string& trace_fragment);
// When all fragments have been added, call Finish to complete the JSON
// formatted output.
void Finish();
private:
OutputCallback output_callback_;
bool append_comma_;
};
} // namespace trace_event
} // namespace base
#endif // BASE_TRACE_EVENT_TRACE_BUFFER_H_
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