chromium/third_party/webrtc/logging/rtc_event_log/events/rtc_event_definition.h

/*
 *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_DEFINITION_H_
#define LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_DEFINITION_H_

#include <cstdint>
#include <string>
#include <vector>

#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "api/rtc_event_log/rtc_event.h"
#include "logging/rtc_event_log/events/rtc_event_field_encoding.h"
#include "logging/rtc_event_log/events/rtc_event_field_encoding_parser.h"
#include "logging/rtc_event_log/events/rtc_event_log_parse_status.h"

namespace webrtc {

template <typename EventType, typename LoggedType, typename T>
struct RtcEventFieldDefinition { … };

// Base case
template <typename EventType, typename LoggedType, typename... Ts>
class RtcEventDefinitionImpl { … };

// Recursive case
RtcEventDefinitionImpl<EventType, LoggedType, T, Ts...>;

// The RtcEventDefinition sets up a mapping between the fields
// in an RtcEvent and the corresponding fields in the parsed struct.
// For example, an RtcFoo class containing two fields; `uint32_t bar`
// and `bool baz` (a log timestamp is always implicitly added)
// might have a definition
// RtcEventDefinition<RtcFoo, LoggedFoo, uint32_t, bool>(
//   {"foo", RtcFoo::Type},
//   {&RtcFoo::bar_, &LoggedFoo::bar, {"bar", 1, FieldType::kVarInt, 32}},
//   {&RtcFoo::baz_, &LoggedFoo::baz, {"baz", 2, FieldType::kFixed8, 1}},
// );
// In addition to defining string names to aid debugging,
// this specifies that
// * RtcFoo::Type uniquely identifies an RtcFoo in the encoded stream
// * The `bar` field has ID 1, is encoded as a VarInt
//   (when not delta compressed), and wraps around after 32 bits.
// * The `baz` field has ID 2, is encoded as an 8-bit field
//   (when not delta compressed), and wraps around after 1 bit.
// Note that the numerical field and event IDs can't be changed since
// that would break compatibility with old logs.
// In most cases (including all cases where wrap around isn't
// expected), the wrap around should be equal to the bitwidth of
// the field.
template <typename EventType, typename LoggedType, typename... Ts>
class RtcEventDefinition { … };

}  // namespace webrtc

#endif  // LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_DEFINITION_H_