scattered_stream_writer.h | Explore in Territory

/*
 * Copyright (C) 2017 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_PROTOZERO_SCATTERED_STREAM_WRITER_H_
#define INCLUDE_PERFETTO_PROTOZERO_SCATTERED_STREAM_WRITER_H_

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

#include <algorithm>

#include "perfetto/base/compiler.h"
#include "perfetto/base/export.h"
#include "perfetto/base/logging.h"
#include "perfetto/protozero/contiguous_memory_range.h"

namespace protozero {

// This class deals with the following problem: append-only proto messages want
// to write a stream of bytes, without caring about the implementation of the
// underlying buffer (which concretely will be either the trace ring buffer
// or a heap-allocated buffer). The main deal is: proto messages don't know in
// advance what their size will be.
// Due to the tracing buffer being split into fixed-size chunks, on some
// occasions, these writes need to be spread over two (or more) non-contiguous
// chunks of memory. Similarly, when the buffer is backed by the heap, we want
// to avoid realloc() calls, as they might cause a full copy of the contents
// of the buffer.
// The purpose of this class is to abstract away the non-contiguous write logic.
// This class knows how to deal with writes as long as they fall in the same
// ContiguousMemoryRange and defers the chunk-chaining logic to the Delegate.
class PERFETTO_EXPORT_COMPONENT ScatteredStreamWriter { … };

}  // namespace protozero

#endif  // INCLUDE_PERFETTO_PROTOZERO_SCATTERED_STREAM_WRITER_H_
chromium/third_party/perfetto/include/perfetto/protozero/scattered_stream_writer.h
