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/*
* Copyright (C) 2021 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_TRACING_TRACED_PROTO_H_
#define INCLUDE_PERFETTO_TRACING_TRACED_PROTO_H_
#include "perfetto/base/template_util.h"
#include "perfetto/protozero/field_writer.h"
#include "perfetto/protozero/proto_utils.h"
namespace perfetto {
class EventContext;
// A Wrapper around a protozero message to allow C++ classes to specify how it
// should be serialised into the trace:
//
// class Foo {
// public:
// void WriteIntoTrace(perfetto::TracedProto<pbzero::Foo> message) {
// message->set_int_field(int_field_);
// }
// };
//
// This class also exposes EventContext, e.g. to enable data interning.
//
// NOTE: the functionality below is not ready yet.
// TODO(altimin): Make the interop below possible.
// TracedProto also provides a seamless integration with writing untyped
// values via TracedValue / TracedDictionary / TracedArray:
//
// - TracedValue can be converted to a TracedProto, either by calling
// TracedValue::WriteProto<T>() or implicitly.
// - If a proto message has a repeating DebugAnnotation debug_annotations
// field, it can be filled using the TracedDictionary obtained from
// TracedProto::WriteDebugAnnotations.
template <typename MessageType>
class TracedProto {
public:
TracedProto(const TracedProto&) = delete;
TracedProto& operator=(const TracedProto&) = delete;
TracedProto& operator=(TracedProto&&) = delete;
TracedProto(TracedProto&&) = default;
~TracedProto() = default;
MessageType* operator->() const { return message_; }
MessageType* message() { return message_; }
EventContext& context() const { return context_; }
private:
friend class EventContext;
TracedProto(MessageType* message, EventContext& context)
: message_(message), context_(context) {}
MessageType* const message_;
EventContext& context_;
};
namespace internal {
// TypedProtoWriter takes the protozero message (TracedProto<MessageType>),
// field description (FieldMetadata) and value and writes the given value
// into the given field of the given protozero message.
//
// This is primarily used for inline writing of typed messages:
// TRACE_EVENT(..., pbzero::Message:kField, value);
//
// Ideally we would use a function here and not a struct, but passing template
// arguments directly to the function (e.g. foo<void>()) isn't supported until
// C++20, so we have to use a helper struct here.
template <typename FieldMetadata>
struct TypedProtoWriter {
private:
using ProtoSchemaType = protozero::proto_utils::ProtoSchemaType;
using RepetitionType = protozero::proto_utils::RepetitionType;
static_assert(FieldMetadata::kRepetitionType !=
RepetitionType::kRepeatedPacked,
"writing packed fields isn't supported yet");
public:
// Implementation note: typename Check=void is used to ensure that SFINAE
// kicks in and the methods which do not match FieldMetadata do not fail
// to compile. std::is_same<Check,void> prevents early evaluation of the
// first enable_if_t argument.
// Simple non-repeated field.
template <typename Proto, typename ValueType, typename Check = void>
static typename base::enable_if_t<
FieldMetadata::kProtoFieldType != ProtoSchemaType::kMessage &&
FieldMetadata::kRepetitionType == RepetitionType::kNotRepeated &&
std::is_same<Check, void>::value>
Write(TracedProto<Proto> context, ValueType&& value) {
protozero::internal::FieldWriter<FieldMetadata::kProtoFieldType>::Append(
*context.message(), FieldMetadata::kFieldId, value);
}
// Simple repeated non-packed field.
template <typename Proto, typename ValueType, typename Check = void>
static typename base::enable_if_t<
FieldMetadata::kProtoFieldType != ProtoSchemaType::kMessage &&
FieldMetadata::kRepetitionType == RepetitionType::kRepeatedNotPacked &&
std::is_same<Check, void>::value>
Write(TracedProto<Proto> context, ValueType&& value) {
for (auto&& item : value) {
protozero::internal::FieldWriter<FieldMetadata::kProtoFieldType>::Append(
*context.message(), FieldMetadata::kFieldId, item);
}
}
// Nested non-repeated field.
template <typename Proto, typename ValueType, typename Check = void>
static typename base::enable_if_t<
FieldMetadata::kProtoFieldType == ProtoSchemaType::kMessage &&
FieldMetadata::kRepetitionType == RepetitionType::kNotRepeated &&
std::is_same<Check, void>::value>
Write(TracedProto<Proto> context, ValueType&& value) {
// TODO(altimin): support TraceFormatTraits here.
value.WriteIntoTrace(
context.context().Wrap(context.message()
->template BeginNestedMessage<
typename FieldMetadata::cpp_field_type>(
FieldMetadata::kFieldId)));
}
// Nested repeated non-packed field.
template <typename Proto, typename ValueType, typename Check = void>
static typename base::enable_if_t<
FieldMetadata::kProtoFieldType == ProtoSchemaType::kMessage &&
FieldMetadata::kRepetitionType == RepetitionType::kRepeatedNotPacked &&
std::is_same<Check, void>::value>
Write(TracedProto<Proto> context, ValueType&& value) {
// TODO(altimin): support TraceFormatTraits here.
for (auto&& item : value) {
item.WriteIntoTrace(context.context().Wrap(
context.message()
->template BeginNestedMessage<
typename FieldMetadata::cpp_field_type>(
FieldMetadata::kFieldId)));
}
}
};
} // namespace internal
template <typename MessageType, typename FieldMetadataType, typename ValueType>
void WriteIntoTracedProto(
TracedProto<MessageType> message,
protozero::proto_utils::internal::FieldMetadataHelper<FieldMetadataType>,
ValueType&& value) {
static_assert(
std::is_base_of<protozero::proto_utils::FieldMetadataBase,
FieldMetadataType>::value,
"Field name should be a protozero::internal::FieldMetadata<...>");
static_assert(
std::is_base_of<MessageType,
typename FieldMetadataType::message_type>::value,
"Field's parent type should match the context.");
internal::TypedProtoWriter<FieldMetadataType>::Write(
std::move(message), std::forward<ValueType>(value));
}
} // namespace perfetto
#endif // INCLUDE_PERFETTO_TRACING_TRACED_PROTO_H_
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