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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_VALUE_H_
#define INCLUDE_PERFETTO_TRACING_TRACED_VALUE_H_
#include "perfetto/base/compiler.h"
#include "perfetto/base/export.h"
#include "perfetto/base/template_util.h"
#include "perfetto/protozero/message.h"
#include "perfetto/protozero/proto_utils.h"
#include "perfetto/tracing/internal/checked_scope.h"
#include "perfetto/tracing/string_helpers.h"
#include "perfetto/tracing/traced_value_forward.h"
#include <memory>
#include <string>
#include <string_view>
#include <type_traits>
#include <utility>
namespace perfetto {
namespace protos {
namespace pbzero {
class DebugAnnotation;
}
} // namespace protos
class DebugAnnotation;
class EventContext;
// These classes provide a JSON-inspired way to write structed data into traces.
//
// Each TracedValue can be consumed exactly once to write a value into a trace
// using one of the Write* methods.
//
// Write* methods fall into two categories:
// - Primitive types (int, string, bool, double, etc): they just write the
// provided value, consuming the TracedValue in the process.
// - Complex types (arrays and dicts): they consume the TracedValue and
// return a corresponding scoped object (TracedArray or TracedDictionary).
// This scope then can be used to write multiple items into the container:
// TracedArray::AppendItem and TracedDictionary::AddItem return a new
// TracedValue which then can be used to write an element of the
// dictionary or array.
//
// To define how a custom class should be written into the trace, users should
// define one of the two following functions:
// - Foo::WriteIntoTrace(TracedValue) const
// (preferred for code which depends on perfetto directly)
// - perfetto::TraceFormatTraits<T>::WriteIntoTrace(
// TracedValue, const T&);
// (should be used if T is defined in a library which doesn't know anything
// about tracing).
//
//
// After defining a conversion method, the object can be used directly as a
// TRACE_EVENT argument:
//
// Foo foo;
// TRACE_EVENT("cat", "Event", "arg", foo);
//
// Examples:
//
// TRACE_EVENT("cat", "event", "params", [&](perfetto::TracedValue context)
// {
// auto dict = std::move(context).WriteDictionary();
// dict->Add("param1", param1);
// dict->Add("param2", param2);
// ...
// dict->Add("paramN", paramN);
//
// {
// auto inner_array = dict->AddArray("inner");
// inner_array->Append(value1);
// inner_array->Append(value2);
// }
// });
//
// template <typename T>
// TraceFormatTraits<std::optional<T>>::WriteIntoTrace(
// TracedValue context, const std::optional<T>& value) {
// if (!value) {
// std::move(context).WritePointer(nullptr);
// return;
// }
// perfetto::WriteIntoTrace(std::move(context), *value);
// }
//
// template <typename T>
// TraceFormatTraits<std::vector<T>>::WriteIntoTrace(
// TracedValue context, const std::array<T>& value) {
// auto array = std::move(context).WriteArray();
// for (const auto& item: value) {
// array_scope.Append(item);
// }
// }
//
// class Foo {
// void WriteIntoTrace(TracedValue context) const {
// auto dict = std::move(context).WriteDictionary();
// dict->Set("key", 42);
// dict->Set("foo", "bar");
// dict->Set("member", member_);
// }
// }
namespace internal {
// TODO(altimin): Currently EventContext can be null due the need to support
// TracedValue-based serialisation with the Chrome's TraceLog. After this is
// gone, the second parameter should be changed to EventContext&.
PERFETTO_EXPORT_COMPONENT TracedValue
CreateTracedValueFromProto(protos::pbzero::DebugAnnotation*,
EventContext* = nullptr);
} // namespace internal
class PERFETTO_EXPORT_COMPONENT TracedValue {
public:
TracedValue(const TracedValue&) = delete;
TracedValue& operator=(const TracedValue&) = delete;
TracedValue& operator=(TracedValue&&) = delete;
TracedValue(TracedValue&&);
~TracedValue();
// TracedValue represents a context into which a single value can be written
// (either by writing it directly for primitive types, or by creating a
// TracedArray or TracedDictionary for the complex types). This is enforced
// by allowing Write* methods to be called only on rvalue references.
void WriteInt64(int64_t value) &&;
void WriteUInt64(uint64_t value) &&;
void WriteDouble(double value) &&;
void WriteBoolean(bool value) &&;
void WriteString(const char*) &&;
void WriteString(const char*, size_t len) &&;
void WriteString(const std::string&) &&;
void WriteString(std::string_view) &&;
void WritePointer(const void* value) &&;
template <typename MessageType>
TracedProto<MessageType> WriteProto() &&;
// Rules for writing nested dictionaries and arrays:
// - Only one scope (TracedArray, TracedDictionary or TracedValue) can be
// active at the same time. It's only allowed to call methods on the active
// scope.
// - When a scope creates a nested scope, the new scope becomes active.
// - When a scope is destroyed, its parent scope becomes active again.
//
// Typically users will have to create a scope only at the beginning of a
// conversion function and this scope should be destroyed at the end of it.
// TracedArray::Append and TracedDictionary::Add create, write and complete
// inner scopes automatically.
// Scope which allows multiple values to be appended.
TracedArray WriteArray() && PERFETTO_WARN_UNUSED_RESULT;
// Scope which allows multiple key-value pairs to be added.
TracedDictionary WriteDictionary() && PERFETTO_WARN_UNUSED_RESULT;
private:
friend class TracedArray;
friend class TracedDictionary;
friend TracedValue internal::CreateTracedValueFromProto(
protos::pbzero::DebugAnnotation*,
EventContext*);
static TracedValue CreateFromProto(protos::pbzero::DebugAnnotation* proto,
EventContext* event_context = nullptr);
inline TracedValue(protos::pbzero::DebugAnnotation* annotation,
EventContext* event_context,
internal::CheckedScope* parent_scope)
: annotation_(annotation),
event_context_(event_context),
checked_scope_(parent_scope) {}
protozero::Message* WriteProtoInternal(const char* name);
// Temporary support for perfetto::DebugAnnotation C++ class before it's going
// to be replaced by TracedValue.
// TODO(altimin): Convert v8 to use TracedValue directly and delete it.
friend class DebugAnnotation;
protos::pbzero::DebugAnnotation* const annotation_ = nullptr;
EventContext* const event_context_ = nullptr;
internal::CheckedScope checked_scope_;
};
template <typename MessageType>
TracedProto<MessageType> TracedValue::WriteProto() && {
return TracedProto<MessageType>(
static_cast<MessageType*>(WriteProtoInternal(MessageType::GetName())),
event_context_);
}
class PERFETTO_EXPORT_COMPONENT TracedArray {
public:
// implicit
TracedArray(TracedValue);
TracedArray(const TracedArray&) = delete;
TracedArray& operator=(const TracedArray&) = delete;
TracedArray& operator=(TracedArray&&) = delete;
TracedArray(TracedArray&&) = default;
~TracedArray() = default;
TracedValue AppendItem();
template <typename T>
void Append(T&& value) {
WriteIntoTracedValue(AppendItem(), std::forward<T>(value));
}
TracedDictionary AppendDictionary() PERFETTO_WARN_UNUSED_RESULT;
TracedArray AppendArray();
private:
friend class TracedValue;
inline TracedArray(protos::pbzero::DebugAnnotation* annotation,
EventContext* event_context,
internal::CheckedScope* parent_scope)
: annotation_(annotation),
event_context_(event_context),
checked_scope_(parent_scope) {}
protos::pbzero::DebugAnnotation* annotation_;
EventContext* const event_context_;
internal::CheckedScope checked_scope_;
};
class PERFETTO_EXPORT_COMPONENT TracedDictionary {
public:
// implicit
TracedDictionary(TracedValue);
TracedDictionary(const TracedDictionary&) = delete;
TracedDictionary& operator=(const TracedDictionary&) = delete;
TracedDictionary& operator=(TracedDictionary&&) = delete;
TracedDictionary(TracedDictionary&&) = default;
~TracedDictionary() = default;
// There are two paths for writing dictionary keys: fast path for writing
// compile-time const, whose pointer is remains valid during the entire
// runtime of the program and the slow path for dynamic strings, which need to
// be copied.
// In the most common case, a string literal can be passed to `Add`/`AddItem`.
// In other cases, either StaticString or DynamicString declarations are
// needed.
TracedValue AddItem(StaticString key);
TracedValue AddItem(DynamicString key);
template <typename T>
void Add(StaticString key, T&& value) {
WriteIntoTracedValue(AddItem(key), std::forward<T>(value));
}
template <typename T>
void Add(DynamicString key, T&& value) {
WriteIntoTracedValue(AddItem(key), std::forward<T>(value));
}
TracedDictionary AddDictionary(StaticString key);
TracedDictionary AddDictionary(DynamicString key);
TracedArray AddArray(StaticString key);
TracedArray AddArray(DynamicString key);
private:
friend class TracedValue;
template <typename T>
friend class TracedProto;
// Create a |TracedDictionary| which will populate the given field of the
// given |message|.
template <typename MessageType, typename FieldMetadata>
inline TracedDictionary(MessageType* message,
FieldMetadata,
EventContext* event_context,
internal::CheckedScope* parent_scope)
: message_(message),
field_id_(FieldMetadata::kFieldId),
event_context_(event_context),
checked_scope_(parent_scope) {
static_assert(std::is_base_of<protozero::Message, MessageType>::value,
"Message should be a subclass of protozero::Message");
static_assert(std::is_base_of<protozero::proto_utils::FieldMetadataBase,
FieldMetadata>::value,
"FieldMetadata should be a subclass of FieldMetadataBase");
static_assert(
std::is_same<typename FieldMetadata::message_type, MessageType>::value,
"Field does not belong to this message");
static_assert(
std::is_same<typename FieldMetadata::cpp_field_type,
::perfetto::protos::pbzero::DebugAnnotation>::value,
"Field should be of DebugAnnotation type");
static_assert(
FieldMetadata::kRepetitionType ==
protozero::proto_utils::RepetitionType::kRepeatedNotPacked,
"Field should be non-packed repeated");
}
protozero::Message* const message_;
const uint32_t field_id_;
EventContext* event_context_;
internal::CheckedScope checked_scope_;
};
namespace internal {
// SFINAE helpers for finding a right overload to convert a given class to
// trace-friendly form, ordered from most to least preferred.
constexpr int kMaxWriteImplPriority = 4;
// If T has WriteIntoTracedValue member function, call it.
template <typename T>
decltype(std::declval<T>().WriteIntoTracedValue(std::declval<TracedValue>()),
void())
WriteImpl(base::priority_tag<4>, TracedValue context, T&& value) {
value.WriteIntoTracedValue(std::move(context));
}
// If T has WriteIntoTrace member function, call it.
template <typename T>
decltype(std::declval<T>().WriteIntoTrace(std::declval<TracedValue>()), void())
WriteImpl(base::priority_tag<4>, TracedValue context, T&& value) {
value.WriteIntoTrace(std::move(context));
}
// If perfetto::TraceFormatTraits<T>::WriteIntoTracedValue(TracedValue, const
// T&) is available, use it.
template <typename T>
decltype(TraceFormatTraits<base::remove_cvref_t<T>>::WriteIntoTracedValue(
std::declval<TracedValue>(),
std::declval<T>()),
void())
WriteImpl(base::priority_tag<3>, TracedValue context, T&& value) {
TraceFormatTraits<base::remove_cvref_t<T>>::WriteIntoTracedValue(
std::move(context), std::forward<T>(value));
}
// If perfetto::TraceFormatTraits<T>::WriteIntoTrace(TracedValue, const T&)
// is available, use it.
template <typename T>
decltype(TraceFormatTraits<base::remove_cvref_t<T>>::WriteIntoTrace(
std::declval<TracedValue>(),
std::declval<T>()),
void())
WriteImpl(base::priority_tag<3>, TracedValue context, T&& value) {
TraceFormatTraits<base::remove_cvref_t<T>>::WriteIntoTrace(
std::move(context), std::forward<T>(value));
}
// If T has operator(), which takes TracedValue, use it.
// Very useful for lambda resolutions.
template <typename T>
decltype(std::declval<T>()(std::declval<TracedValue>()), void())
WriteImpl(base::priority_tag<2>, TracedValue context, T&& value) {
std::forward<T>(value)(std::move(context));
}
// If T is a container and its elements have tracing support, use it.
//
// Note: a reference to T should be passed to std::begin, otherwise
// for non-reference types const T& will be passed to std::begin, losing
// support for non-const WriteIntoTracedValue methods.
template <typename T>
typename check_traced_value_support<
decltype(*std::begin(std::declval<T&>()))>::type
WriteImpl(base::priority_tag<1>, TracedValue context, T&& value) {
auto array = std::move(context).WriteArray();
for (auto&& item : value) {
array.Append(item);
}
}
// std::underlying_type can't be used with non-enum types, so we need this
// indirection.
template <typename T, bool = std::is_enum<T>::value>
struct safe_underlying_type {
using type = typename std::underlying_type<T>::type;
};
template <typename T>
struct safe_underlying_type<T, false> {
using type = T;
};
template <typename T>
struct is_incomplete_type {
static constexpr bool value = sizeof(T) != 0;
};
// sizeof is not available for const char[], but it's still not considered to be
// an incomplete type for our purposes as the size can be determined at runtime
// due to strings being null-terminated.
template <>
struct is_incomplete_type<const char[]> {
static constexpr bool value = true;
};
} // namespace internal
// Helper template to determine if a given type can be passed to
// perfetto::WriteIntoTracedValue. These templates will fail to resolve if the
// class does not have it support, so they are useful in SFINAE and in producing
// helpful compiler results.
template <typename T, class Result = void>
using check_traced_value_support_t =
decltype(internal::WriteImpl(
std::declval<
base::priority_tag<internal::kMaxWriteImplPriority>>(),
std::declval<TracedValue>(),
std::declval<T>()),
std::declval<Result>());
// check_traced_value_support<T, V>::type is defined (and equal to V) iff T
// supports being passed to WriteIntoTracedValue. See the comment in
// traced_value_forward.h for more details.
template <typename T, class Result>
struct check_traced_value_support<T,
Result,
check_traced_value_support_t<T, Result>> {
static_assert(
internal::is_incomplete_type<T>::value,
"perfetto::TracedValue should not be used with incomplete types");
static constexpr bool value = true;
using type = Result;
};
namespace internal {
// Helper class to check if a given type can be passed to
// perfetto::WriteIntoTracedValue. This template will always resolve (with
// |value| being set to either true or false depending on presence of the
// support, so this macro is useful in the situation when you want to e.g. OR
// the result with some other conditions.
//
// In this case, compiler will not give you the full deduction chain, so, for
// example, use check_traced_value_support for writing positive static_asserts
// and has_traced_value_support for writing negative.
template <typename T>
class has_traced_value_support {
using Yes = char[1];
using No = char[2];
template <typename V>
static Yes& check_support(check_traced_value_support_t<V, int>);
template <typename V>
static No& check_support(...);
public:
static constexpr bool value = sizeof(Yes) == sizeof(check_support<T>(0));
};
} // namespace internal
template <typename T>
void WriteIntoTracedValue(TracedValue context, T&& value) {
// TODO(altimin): Add a URL to documentation and a list of common failure
// patterns.
static_assert(
internal::has_traced_value_support<T>::value,
"The provided type (passed to TRACE_EVENT argument / TracedArray::Append "
"/ TracedDictionary::Add) does not support being written in a trace "
"format. Please see the comment in traced_value.h for more details.");
// Should be kept in sync with check_traced_value_support_t!
internal::WriteImpl(base::priority_tag<internal::kMaxWriteImplPriority>(),
std::move(context), std::forward<T>(value));
}
// Helpers to write a given value into TracedValue even if the given type
// doesn't support conversion (in which case the provided fallback should be
// used). Useful for automatically generating conversions for autogenerated
// code, but otherwise shouldn't be used as non-autogenerated code is expected
// to define WriteIntoTracedValue convertor.
// See WriteWithFallback test in traced_value_unittest.cc for a concrete
// example.
template <typename T>
typename std::enable_if<internal::has_traced_value_support<T>::value>::type
WriteIntoTracedValueWithFallback(TracedValue context,
T&& value,
const std::string&) {
WriteIntoTracedValue(std::move(context), std::forward<T>(value));
}
template <typename T>
typename std::enable_if<!internal::has_traced_value_support<T>::value>::type
WriteIntoTracedValueWithFallback(TracedValue context,
T&&,
const std::string& fallback) {
std::move(context).WriteString(fallback);
}
// TraceFormatTraits implementations for primitive types.
// Specialisation for signed integer types (note: it excludes enums, which have
// their own explicit specialisation).
template <typename T>
struct TraceFormatTraits<
T,
typename std::enable_if<std::is_integral<T>::value &&
!std::is_same<T, bool>::value &&
std::is_signed<T>::value>::type> {
inline static void WriteIntoTrace(TracedValue context, T value) {
std::move(context).WriteInt64(value);
}
};
// Specialisation for unsigned integer types (note: it excludes enums, which
// have their own explicit specialisation).
template <typename T>
struct TraceFormatTraits<
T,
typename std::enable_if<std::is_integral<T>::value &&
!std::is_same<T, bool>::value &&
std::is_unsigned<T>::value>::type> {
inline static void WriteIntoTrace(TracedValue context, T value) {
std::move(context).WriteUInt64(value);
}
};
// Specialisation for bools.
template <>
struct TraceFormatTraits<bool> {
inline static void WriteIntoTrace(TracedValue context, bool value) {
std::move(context).WriteBoolean(value);
}
};
// Specialisation for floating point values.
template <typename T>
struct TraceFormatTraits<
T,
typename std::enable_if<std::is_floating_point<T>::value>::type> {
inline static void WriteIntoTrace(TracedValue context, T value) {
std::move(context).WriteDouble(static_cast<double>(value));
}
};
// Specialisation for signed enums.
template <typename T>
struct TraceFormatTraits<
T,
typename std::enable_if<
std::is_enum<T>::value &&
std::is_signed<
typename internal::safe_underlying_type<T>::type>::value>::type> {
inline static void WriteIntoTrace(TracedValue context, T value) {
std::move(context).WriteInt64(static_cast<int64_t>(value));
}
};
// Specialisation for unsigned enums.
template <typename T>
struct TraceFormatTraits<
T,
typename std::enable_if<
std::is_enum<T>::value &&
std::is_unsigned<
typename internal::safe_underlying_type<T>::type>::value>::type> {
inline static void WriteIntoTrace(TracedValue context, T value) {
std::move(context).WriteUInt64(static_cast<uint64_t>(value));
}
};
// Specialisations for C-style strings.
template <>
struct TraceFormatTraits<const char*> {
inline static void WriteIntoTrace(TracedValue context, const char* value) {
std::move(context).WriteString(value);
}
};
template <>
struct TraceFormatTraits<char[]> {
inline static void WriteIntoTrace(TracedValue context, const char value[]) {
std::move(context).WriteString(value);
}
};
template <size_t N>
struct TraceFormatTraits<char[N]> {
inline static void WriteIntoTrace(TracedValue context, const char value[N]) {
std::move(context).WriteString(value);
}
};
// Specialization for Perfetto strings.
template <>
struct TraceFormatTraits<perfetto::StaticString> {
inline static void WriteIntoTrace(TracedValue context,
perfetto::StaticString str) {
std::move(context).WriteString(str.value);
}
};
template <>
struct TraceFormatTraits<perfetto::DynamicString> {
inline static void WriteIntoTrace(TracedValue context,
perfetto::DynamicString str) {
std::move(context).WriteString(str.value, str.length);
}
};
// Specialisation for C++ strings.
template <>
struct TraceFormatTraits<std::string> {
inline static void WriteIntoTrace(TracedValue context,
const std::string& value) {
std::move(context).WriteString(value);
}
};
// Specialisation for C++ string_views.
template <>
struct TraceFormatTraits<std::string_view> {
inline static void WriteIntoTrace(TracedValue context,
std::string_view value) {
std::move(context).WriteString(value);
}
};
// Specialisation for (const) void*, which writes the pointer value.
template <>
struct TraceFormatTraits<void*> {
inline static void WriteIntoTrace(TracedValue context, void* value) {
std::move(context).WritePointer(value);
}
};
template <>
struct TraceFormatTraits<const void*> {
inline static void WriteIntoTrace(TracedValue context, const void* value) {
std::move(context).WritePointer(value);
}
};
// Specialisation for std::unique_ptr<>, which writes either nullptr or the
// object it points to.
template <typename T>
struct TraceFormatTraits<std::unique_ptr<T>, check_traced_value_support_t<T>> {
inline static void WriteIntoTrace(TracedValue context,
const std::unique_ptr<T>& value) {
::perfetto::WriteIntoTracedValue(std::move(context), value.get());
}
template <typename MessageType>
inline static void WriteIntoTrace(TracedProto<MessageType> message,
const std::unique_ptr<T>& value) {
::perfetto::WriteIntoTracedProto(std::move(message), value.get());
}
};
// Specialisation for raw pointer, which writes either nullptr or the object it
// points to.
template <typename T>
struct TraceFormatTraits<T*, check_traced_value_support_t<T>> {
inline static void WriteIntoTrace(TracedValue context, T* value) {
if (!value) {
std::move(context).WritePointer(nullptr);
return;
}
::perfetto::WriteIntoTracedValue(std::move(context), *value);
}
template <typename MessageType>
inline static void WriteIntoTrace(TracedProto<MessageType> message,
T* value) {
if (!value) {
// Start the message, but do not write anything. TraceProcessor will emit
// a NULL value.
return;
}
::perfetto::WriteIntoTracedProto(std::move(message), *value);
}
};
// Specialisation for nullptr.
template <>
struct TraceFormatTraits<std::nullptr_t> {
inline static void WriteIntoTrace(TracedValue context, std::nullptr_t) {
std::move(context).WritePointer(nullptr);
}
template <typename MessageType>
inline static void WriteIntoTrace(TracedProto<MessageType>, std::nullptr_t) {
// Start the message, but do not write anything. TraceProcessor will emit a
// NULL value.
}
};
} // namespace perfetto
#endif // INCLUDE_PERFETTO_TRACING_TRACED_VALUE_H_