chromium/third_party/perfetto/include/perfetto/trace_processor/trace_blob_view.h

/*
 * Copyright (C) 2018 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.
 */

#ifndef INCLUDE_PERFETTO_TRACE_PROCESSOR_TRACE_BLOB_VIEW_H_
#define INCLUDE_PERFETTO_TRACE_PROCESSOR_TRACE_BLOB_VIEW_H_

#include <stddef.h>
#include <stdint.h>

#include <limits>
#include <memory>

#include "perfetto/base/logging.h"
#include "perfetto/trace_processor/ref_counted.h"
#include "perfetto/trace_processor/trace_blob.h"

namespace perfetto {
namespace trace_processor {

// A read-only view of a TraceBlob.
// This class is an equivalent of std::string_view for trace binary data, with
// a twist: it supports turning a TraceBlob into a refcounted reference. In this
// case the TraceBlobView acts directly as a shared_ptr, without requiring extra
// layers of indirection.
// The underlying TraceBlob will be freed once all the TraceBlobViews that refer
// to the same buffer have passed through the pipeline and been parsed.
// The overall idea is that a TraceBlob is passed around until it's written.
// When writing is done it transforms into a shared refcounted object which is
// held onto by one or more read-only TraceBlobView instances.
//
// In summary:
//  - TraceBlob: writable, move-only, single-instance.
//  - TraceBlobView: readable, copyable, multiple-instances can hold onto
//                   (different sub-slices of) the same refcounted TraceBlob.
class alignas(8) TraceBlobView { … };

}  // namespace trace_processor
}  // namespace perfetto

#endif  // INCLUDE_PERFETTO_TRACE_PROCESSOR_TRACE_BLOB_VIEW_H_