chromium/third_party/webrtc/logging/rtc_event_log/events/rtc_event_field_encoding.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_FIELD_ENCODING_H_
#define LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_FIELD_ENCODING_H_

#include <cstddef>
#include <cstdint>
#include <string>
#include <type_traits>
#include <vector>

#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "api/array_view.h"
#include "api/rtc_event_log/rtc_event.h"
#include "logging/rtc_event_log/events/fixed_length_encoding_parameters_v3.h"
#include "logging/rtc_event_log/events/rtc_event_field_extraction.h"
#include "rtc_base/checks.h"

namespace webrtc {

// To maintain backwards compatibility with past (or future) logs,
// the constants in this enum must not be changed.
// New field types with numerical IDs 5-7 can be added, but old
// parsers will fail to parse events containing the new fields.
enum class FieldType : uint8_t { … };

// EventParameters map an event name to a numerical ID.
struct EventParameters { … };

// FieldParameters define the encoding for a field.
struct FieldParameters { … };

// The EventEncoder is used to encode a batch of events.
class EventEncoder { … };

std::string EncodeSingleValue(uint64_t value, FieldType field_type);
std::string EncodeDeltasV3(FixedLengthEncodingParametersV3 params,
                           uint64_t base,
                           rtc::ArrayView<const uint64_t> values);

// Given a batch of RtcEvents and a member pointer, extract that
// member from each event in the batch. Signed integer members are
// encoded as unsigned, and the bitsize increased so the result can
// represented as a std::vector<uint64_t>.
// This is intended to be used in conjuction with
// EventEncoder::EncodeField to encode a batch of events as follows:
// auto values = ExtractRtcEventMember(batch, RtcEventFoo::timestamp_ms);
// encoder.EncodeField(timestamp_params, values)
template <typename T,
          typename E,
          std::enable_if_t<std::is_integral<T>::value, bool> = true>
std::vector<uint64_t> ExtractRtcEventMember(
    rtc::ArrayView<const RtcEvent*> batch,
    const T E::*member) { … }

// Extract an optional field from a batch of RtcEvents.
// The function returns a vector of positions in addition to the vector of
// values. The vector `positions` has the same length as the batch where
// `positions[i] == true` iff the batch[i]->member has a value.
// The values vector only contains the values that exists, so it
// may be shorter than the batch.
template <typename T,
          typename E,
          std::enable_if_t<std::is_integral<T>::value, bool> = true>
ValuesWithPositions ExtractRtcEventMember(rtc::ArrayView<const RtcEvent*> batch,
                                          const absl::optional<T> E::*member) { … }

// Extract an enum field from a batch of RtcEvents.
// Requires specializing RtcEventLogEnum<T> for the enum type T.
template <typename T,
          typename E,
          std::enable_if_t<std::is_enum<T>::value, bool> = true>
std::vector<uint64_t> ExtractRtcEventMember(
    rtc::ArrayView<const RtcEvent*> batch,
    const T E::*member) { … }

// Extract a string field from a batch of RtcEvents.
template <typename E>
std::vector<absl::string_view> ExtractRtcEventMember(
    rtc::ArrayView<const RtcEvent*> batch,
    const std::string E::*member) { … }

}  // namespace webrtc
#endif  // LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_FIELD_ENCODING_H_