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// Copyright 2020 The Tint Authors.
//
// 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 SRC_TINT_UTILS_CASTABLE_H_
#define SRC_TINT_UTILS_CASTABLE_H_
#include <stdint.h>
#include <functional>
#include <tuple>
#include <type_traits>
#include <utility>
#include "src/tint/utils/crc32.h"
#include "src/tint/utils/traits.h"
#if defined(__clang__)
/// Temporarily disable certain warnings when using Castable API
#define TINT_CASTABLE_PUSH_DISABLE_WARNINGS() \
_Pragma("clang diagnostic push") /**/ \
_Pragma("clang diagnostic ignored \"-Wundefined-var-template\"") /**/ \
static_assert(true, "require extra semicolon")
/// Restore disabled warnings
#define TINT_CASTABLE_POP_DISABLE_WARNINGS() \
_Pragma("clang diagnostic pop") /**/ \
static_assert(true, "require extra semicolon")
#else
#define TINT_CASTABLE_PUSH_DISABLE_WARNINGS() static_assert(true, "require extra semicolon")
#define TINT_CASTABLE_POP_DISABLE_WARNINGS() static_assert(true, "require extra semicolon")
#endif
TINT_CASTABLE_PUSH_DISABLE_WARNINGS();
// Forward declarations
namespace tint::utils {
class CastableBase;
/// Ignore is used as a special type used for skipping over types for trait
/// helper functions.
class Ignore {};
} // namespace tint::utils
namespace tint::utils::detail {
template <typename T>
struct TypeInfoOf;
} // namespace tint::utils::detail
namespace tint::utils {
/// True if all template types that are not Ignore derive from CastableBase
template <typename... TYPES>
static constexpr bool IsCastable =
((utils::traits::IsTypeOrDerived<TYPES, CastableBase> || std::is_same_v<TYPES, Ignore>)&&...) &&
!(std::is_same_v<TYPES, Ignore> && ...);
/// Helper macro to instantiate the TypeInfo<T> template for `CLASS`.
#define TINT_INSTANTIATE_TYPEINFO(CLASS) \
TINT_CASTABLE_PUSH_DISABLE_WARNINGS(); \
template <> \
const tint::utils::TypeInfo tint::utils::detail::TypeInfoOf<CLASS>::info{ \
&tint::utils::detail::TypeInfoOf<CLASS::TrueBase>::info, \
#CLASS, \
tint::utils::TypeInfo::HashCodeOf<CLASS>(), \
tint::utils::TypeInfo::FullHashCodeOf<CLASS>(), \
}; \
TINT_CASTABLE_POP_DISABLE_WARNINGS(); \
static_assert(std::is_same_v<CLASS, CLASS::Base::Class>, \
#CLASS " does not derive from Castable<" #CLASS "[, BASE]>")
/// Bit flags that can be passed to the template parameter `FLAGS` of Is() and As().
enum CastFlags {
/// Disables the static_assert() inside Is(), that compile-time-verifies that the cast is
/// possible. This flag may be useful for highly-generic template
/// code that needs to compile for template permutations that generate
/// impossible casts.
kDontErrorOnImpossibleCast = 1,
};
/// The type of a hash code
using HashCode = uint64_t;
/// Maybe checks to see if an object with the full hashcode @p object_full_hashcode could
/// potentially be of, or derive from the type with the hashcode @p query_hashcode.
/// @param type_hashcode the hashcode of the type
/// @param object_full_hashcode the full hashcode of the object being queried
/// @returns true if the object with the given full hashcode could be one of the template types.
inline bool Maybe(HashCode type_hashcode, HashCode object_full_hashcode) {
return (object_full_hashcode & type_hashcode) == type_hashcode;
}
/// MaybeAnyOf checks to see if an object with the full hashcode @p object_full_hashcode could
/// potentially be of, or derive from the types with the combined hashcode @p combined_hashcode.
/// @param combined_hashcode the bitwise OR'd hashcodes of the types
/// @param object_full_hashcode the full hashcode of the object being queried
/// @returns true if the object with the given full hashcode could be one of the template types.
inline bool MaybeAnyOf(HashCode combined_hashcode, HashCode object_full_hashcode) {
// Compare the object's hashcode to the bitwise-or of all the tested type's hashcodes. If
// there's no intersection of bits in the two masks, then we can guarantee that the type is not
// in `TO`.
HashCode mask = object_full_hashcode & combined_hashcode;
// HashCodeOf() ensures that two bits are always set for every hash, so we can quickly
// eliminate the bitmask where only one bit is set.
HashCode two_bits = mask & (mask - 1);
return two_bits != 0;
}
/// TypeInfo holds type information for a Castable type.
struct TypeInfo {
/// The base class of this type
const TypeInfo* base;
/// The type name
const char* name;
/// The type hash code
const HashCode hashcode;
/// The type hash code bitwise-or'd with all ancestor's hashcodes.
const HashCode full_hashcode;
/// @returns true if `type` derives from the class `TO`
/// @param object the object type to test from, which must be, or derive from type `FROM`.
/// @see CastFlags
template <typename TO, typename FROM, int FLAGS = 0>
static inline bool Is(const tint::utils::TypeInfo* object) {
constexpr const bool downcast = std::is_base_of<FROM, TO>::value;
constexpr const bool upcast = std::is_base_of<TO, FROM>::value;
constexpr const bool nocast = std::is_same<FROM, TO>::value;
constexpr const bool assert_is_castable = (FLAGS & kDontErrorOnImpossibleCast) == 0;
static_assert(upcast || downcast || nocast || !assert_is_castable, "impossible cast");
return upcast || nocast || object->Is<TO>();
}
/// @returns true if this type derives from the class `T`
template <typename T>
inline bool Is() const {
auto* type = &Of<std::remove_cv_t<T>>();
if constexpr (std::is_final_v<T>) {
// T is final, so nothing can derive from T.
// We do not need to check ancestors, only whether this type is equal to the type T.
return type == this;
} else {
return Is(type);
}
}
/// @param type the test type info
/// @returns true if the class with this TypeInfo is of, or derives from the
/// class with the given TypeInfo.
inline bool Is(const tint::utils::TypeInfo* type) const {
if (!Maybe(type->hashcode, full_hashcode)) {
return false;
}
// Walk the base types, starting with this TypeInfo, to see if any of the pointers match
// `type`.
for (auto* ti = this; ti != nullptr; ti = ti->base) {
if (ti == type) {
return true;
}
}
return false;
}
/// @returns the static TypeInfo for the type T
template <typename T>
static const TypeInfo& Of() {
return detail::TypeInfoOf<std::remove_cv_t<T>>::info;
}
/// @returns a compile-time hashcode for the type `T`.
/// @note the returned hashcode will have exactly 2 bits set, as the hashes are expected to be
/// used in bloom-filters which will quickly saturate when multiple hashcodes are bitwise-or'd
/// together.
template <typename T>
static constexpr HashCode HashCodeOf() {
static_assert(IsCastable<T>, "T is not Castable");
static_assert(std::is_same_v<T, std::remove_cv_t<T>>,
"Strip const / volatile decorations before calling HashCodeOf");
/// Use the compiler's "pretty" function name, which includes the template
/// type, to obtain a unique hash value.
#ifdef _MSC_VER
constexpr uint32_t crc = utils::CRC32(__FUNCSIG__);
#else
constexpr uint32_t crc = utils::CRC32(__PRETTY_FUNCTION__);
#endif
constexpr uint32_t bit_a = (crc & 63);
constexpr uint32_t bit_b = ((crc >> 6) & 63);
constexpr uint32_t bit_c = (bit_a == bit_b) ? ((bit_a + 1) & 63) : bit_b;
return (static_cast<HashCode>(1) << bit_a) | (static_cast<HashCode>(1) << bit_c);
}
/// @returns the hashcode of the given type, bitwise-or'd with the hashcodes of all base
/// classes.
template <typename T>
static constexpr HashCode FullHashCodeOf() {
if constexpr (std::is_same_v<T, CastableBase>) {
return HashCodeOf<CastableBase>();
} else {
return HashCodeOf<T>() | FullHashCodeOf<typename T::TrueBase>();
}
}
/// @returns the bitwise-or'd hashcodes of all the types of the tuple `TUPLE`.
/// @see HashCodeOf
template <typename TUPLE>
static constexpr HashCode CombinedHashCodeOfTuple() {
constexpr auto kCount = std::tuple_size_v<TUPLE>;
if constexpr (kCount == 0) {
return 0;
} else if constexpr (kCount == 1) {
return HashCodeOf<std::remove_cv_t<std::tuple_element_t<0, TUPLE>>>();
} else {
constexpr auto kMid = kCount / 2;
return CombinedHashCodeOfTuple<utils::traits::SliceTuple<0, kMid, TUPLE>>() |
CombinedHashCodeOfTuple<utils::traits::SliceTuple<kMid, kCount - kMid, TUPLE>>();
}
}
/// @returns the bitwise-or'd hashcodes of all the template parameter types.
/// @see HashCodeOf
template <typename... TYPES>
static constexpr HashCode CombinedHashCodeOf() {
return CombinedHashCodeOfTuple<std::tuple<TYPES...>>();
}
/// @returns true if this TypeInfo is of, or derives from any of the types in `TUPLE`.
template <typename TUPLE>
inline bool IsAnyOfTuple() const {
constexpr auto kCount = std::tuple_size_v<TUPLE>;
if constexpr (kCount == 0) {
return false;
} else if constexpr (kCount == 1) {
return Is(&Of<std::tuple_element_t<0, TUPLE>>());
} else {
if (MaybeAnyOf(TypeInfo::CombinedHashCodeOfTuple<TUPLE>(), full_hashcode)) {
// Possibly one of the types in `TUPLE`.
// Split the search in two, and scan each block.
static constexpr auto kMid = kCount / 2;
return IsAnyOfTuple<utils::traits::SliceTuple<0, kMid, TUPLE>>() ||
IsAnyOfTuple<utils::traits::SliceTuple<kMid, kCount - kMid, TUPLE>>();
}
return false;
}
}
/// @returns true if this TypeInfo is of, or derives from any of the types in `TYPES`.
template <typename... TYPES>
inline bool IsAnyOf() const {
return IsAnyOfTuple<std::tuple<TYPES...>>();
}
};
namespace detail {
/// TypeInfoOf contains a single TypeInfo field for the type T.
/// TINT_INSTANTIATE_TYPEINFO() must be defined in a .cpp file for each type `T`.
template <typename T>
struct TypeInfoOf {
/// The unique TypeInfo for the type T.
static const TypeInfo info;
};
/// A placeholder structure used for template parameters that need a default type, but can always be
/// automatically inferred.
struct Infer;
} // namespace detail
/// @returns true if `obj` is a valid pointer, and is of, or derives from the class `TO`
/// @param obj the object to test from
/// @see CastFlags
template <typename TO, int FLAGS = 0, typename FROM = detail::Infer>
inline bool Is(FROM* obj) {
if (obj == nullptr) {
return false;
}
return TypeInfo::Is<TO, FROM, FLAGS>(&obj->TypeInfo());
}
/// @returns true if `obj` is a valid pointer, and is of, or derives from the type `TYPE`, and
/// pred(const TYPE*) returns true
/// @param obj the object to test from
/// @param pred predicate function with signature `bool(const TYPE*)` called iff object is of, or
/// derives from the class `TYPE`.
/// @see CastFlags
template <typename TYPE, int FLAGS = 0, typename OBJ = detail::Infer, typename Pred = detail::Infer>
inline bool Is(OBJ* obj, Pred&& pred) {
return Is<TYPE, FLAGS, OBJ>(obj) && pred(static_cast<std::add_const_t<TYPE>*>(obj));
}
/// @returns true if `obj` is a valid pointer, and is of, or derives from any of the types in
/// `TYPES`.
/// @param obj the object to query.
template <typename... TYPES, typename OBJ>
inline bool IsAnyOf(OBJ* obj) {
if (!obj) {
return false;
}
return obj->TypeInfo().template IsAnyOf<TYPES...>();
}
/// @returns obj dynamically cast to the type `TO` or `nullptr` if this object does not derive from
/// `TO`.
/// @param obj the object to cast from
/// @see CastFlags
template <typename TO, int FLAGS = 0, typename FROM = detail::Infer>
inline TO* As(FROM* obj) {
auto* as_castable = static_cast<CastableBase*>(obj);
return Is<TO, FLAGS>(obj) ? static_cast<TO*>(as_castable) : nullptr;
}
/// @returns obj dynamically cast to the type `TO` or `nullptr` if this object does not derive from
/// `TO`.
/// @param obj the object to cast from
/// @see CastFlags
template <typename TO, int FLAGS = 0, typename FROM = detail::Infer>
inline const TO* As(const FROM* obj) {
auto* as_castable = static_cast<const CastableBase*>(obj);
return Is<TO, FLAGS>(obj) ? static_cast<const TO*>(as_castable) : nullptr;
}
/// CastableBase is the base class for all Castable objects.
/// It is not encouraged to directly derive from CastableBase without using the Castable helper
/// template.
/// @see Castable
class CastableBase {
public:
/// Copy constructor
CastableBase(const CastableBase&);
/// Destructor
virtual ~CastableBase();
/// Copy assignment
/// @param other the CastableBase to copy
/// @returns the new CastableBase
CastableBase& operator=(const CastableBase& other) = default;
/// @returns the TypeInfo of the object
inline const tint::utils::TypeInfo& TypeInfo() const { return *type_info_; }
/// @returns true if this object is of, or derives from the class `TO`
template <typename TO>
inline bool Is() const {
return tint::utils::Is<TO>(this);
}
/// @returns true if this object is of, or derives from the class `TO` and pred(const TO*)
/// returns true
/// @param pred predicate function with signature `bool(const TO*)` called iff object is of, or
/// derives from the class `TO`.
template <typename TO, int FLAGS = 0, typename Pred = detail::Infer>
inline bool Is(Pred&& pred) const {
return tint::utils::Is<TO, FLAGS>(this, std::forward<Pred>(pred));
}
/// @returns true if this object is of, or derives from any of the `TO` classes.
template <typename... TO>
inline bool IsAnyOf() const {
return tint::utils::IsAnyOf<TO...>(this);
}
/// @returns this object dynamically cast to the type `TO` or `nullptr` if this object does not
/// derive from `TO`.
/// @see CastFlags
template <typename TO, int FLAGS = 0>
inline TO* As() {
return tint::utils::As<TO, FLAGS>(this);
}
/// @returns this object dynamically cast to the type `TO` or `nullptr` if this object does not
/// derive from `TO`.
/// @see CastFlags
template <typename TO, int FLAGS = 0>
inline const TO* As() const {
return tint::utils::As<const TO, FLAGS>(this);
}
protected:
CastableBase() = default;
/// The type information for the object
const tint::utils::TypeInfo* type_info_ = nullptr;
};
/// Castable is a helper to derive `CLASS` from `BASE`, automatically implementing the Is() and As()
/// methods, along with a #Base type alias.
///
/// Example usage:
///
/// ```
/// class Animal : public Castable<Animal> {};
///
/// class Sheep : public Castable<Sheep, Animal> {};
///
/// Sheep* cast_to_sheep(Animal* animal) {
/// // You can query whether a Castable is of the given type with Is<T>():
/// printf("animal is a sheep? %s", animal->Is<Sheep>() ? "yes" : "no");
///
/// // You can always just try the cast with As<T>().
/// // If the object is not of the correct type, As<T>() will return nullptr:
/// return animal->As<Sheep>();
/// }
/// ```
template <typename CLASS, typename BASE = CastableBase>
class Castable : public BASE {
public:
/// A type alias to this Castable. Commonly used in derived type constructors to forward
/// constructor arguments to BASE.
using Base = Castable;
/// A type alias for `BASE`.
using TrueBase = BASE;
/// A type alias for `CLASS`.
using Class = CLASS;
/// Constructor
/// @param arguments the arguments to forward to the base class.
template <typename... ARGS>
inline explicit Castable(ARGS&&... arguments) : TrueBase(std::forward<ARGS>(arguments)...) {
this->type_info_ = &TypeInfo::Of<CLASS>();
}
/// @returns true if this object is of, or derives from the class `TO`
/// @see CastFlags
template <typename TO, int FLAGS = 0>
inline bool Is() const {
return tint::utils::Is<TO, FLAGS>(static_cast<const CLASS*>(this));
}
/// @returns true if this object is of, or derives from the class `TO` and
/// pred(const TO*) returns true
/// @param pred predicate function with signature `bool(const TO*)` called iff
/// object is of, or derives from the class `TO`.
template <int FLAGS = 0, typename Pred = detail::Infer>
inline bool Is(Pred&& pred) const {
using TO = typename std::remove_pointer<utils::traits::ParameterType<Pred, 0>>::type;
return tint::utils::Is<TO, FLAGS>(static_cast<const CLASS*>(this),
std::forward<Pred>(pred));
}
/// @returns true if this object is of, or derives from any of the `TO`
/// classes.
template <typename... TO>
inline bool IsAnyOf() const {
return tint::utils::IsAnyOf<TO...>(static_cast<const CLASS*>(this));
}
/// @returns this object dynamically cast to the type `TO` or `nullptr` if
/// this object does not derive from `TO`.
/// @see CastFlags
template <typename TO, int FLAGS = 0>
inline TO* As() {
return tint::utils::As<TO, FLAGS>(this);
}
/// @returns this object dynamically cast to the type `TO` or `nullptr` if
/// this object does not derive from `TO`.
/// @see CastFlags
template <typename TO, int FLAGS = 0>
inline const TO* As() const {
return tint::utils::As<const TO, FLAGS>(this);
}
};
namespace detail {
/// <code>typename CastableCommonBaseImpl<TYPES>::type</code> resolves to the common base class for
/// all of TYPES.
template <typename... TYPES>
struct CastableCommonBaseImpl {};
/// Alias to typename CastableCommonBaseImpl<TYPES>::type
template <typename... TYPES>
using CastableCommonBase = typename CastableCommonBaseImpl<TYPES...>::type;
/// CastableCommonBaseImpl template specialization for a single type
template <typename T>
struct CastableCommonBaseImpl<T> {
/// Common base class of a single type is itself
using type = T;
};
/// CastableCommonBaseImpl A <-> CastableBase specialization
template <typename A>
struct CastableCommonBaseImpl<A, CastableBase> {
/// Common base class for A and CastableBase is CastableBase
using type = CastableBase;
};
/// CastableCommonBaseImpl T <-> Ignore specialization
template <typename T>
struct CastableCommonBaseImpl<T, Ignore> {
/// Resolves to T as the other type is ignored
using type = T;
};
/// CastableCommonBaseImpl Ignore <-> T specialization
template <typename T>
struct CastableCommonBaseImpl<Ignore, T> {
/// Resolves to T as the other type is ignored
using type = T;
};
/// CastableCommonBaseImpl A <-> B specialization
template <typename A, typename B>
struct CastableCommonBaseImpl<A, B> {
/// The common base class for A, B and OTHERS
using type = std::conditional_t<utils::traits::IsTypeOrDerived<A, B>,
B, // A derives from B
CastableCommonBase<A, typename B::TrueBase>>;
};
/// CastableCommonBaseImpl 3+ types specialization
template <typename A, typename B, typename... OTHERS>
struct CastableCommonBaseImpl<A, B, OTHERS...> {
/// The common base class for A, B and OTHERS
using type = CastableCommonBase<CastableCommonBase<A, B>, OTHERS...>;
};
} // namespace detail
/// Resolves to the common most derived type that each of the types in `TYPES` derives from.
template <typename... TYPES>
using CastableCommonBase = detail::CastableCommonBase<TYPES...>;
} // namespace tint::utils
namespace tint {
using utils::As;
using utils::Is;
} // namespace tint
TINT_CASTABLE_POP_DISABLE_WARNINGS();
#endif // SRC_TINT_UTILS_CASTABLE_H_