chromium/third_party/dawn/src/dawn/common/TypedInteger.h

// Copyright 2020 The Dawn & Tint Authors
//
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#ifndef SRC_DAWN_COMMON_TYPEDINTEGER_H_
#define SRC_DAWN_COMMON_TYPEDINTEGER_H_

#include <limits>
#include <type_traits>
#include <utility>

#include "dawn/common/Assert.h"
#include "dawn/common/UnderlyingType.h"

namespace dawn {

// TypedInteger is helper class that provides additional type safety in Debug.
//  - Integers of different (Tag, BaseIntegerType) may not be used interoperably
//  - Allows casts only to the underlying type.
//  - Integers of the same (Tag, BaseIntegerType) may be compared or assigned.
// This class helps ensure that the many types of indices in Dawn aren't mixed up and used
// interchangably.
// In Release builds, when DAWN_ENABLE_ASSERTS is not defined, TypedInteger is a passthrough
// typedef of the underlying type.
//
// Example:
//     using UintA = dawn::TypedInteger<struct TypeA, uint32_t>;
//     using UintB = dawn::TypedInteger<struct TypeB, uint32_t>;
//
//  in Release:
//     using UintA = uint32_t;
//     using UintB = uint32_t;
//
//  in Debug:
//     using UintA = detail::TypedIntegerImpl<struct TypeA, uint32_t>;
//     using UintB = detail::TypedIntegerImpl<struct TypeB, uint32_t>;
//
//     Assignment, construction, comparison, and arithmetic with TypedIntegerImpl are allowed
//     only for typed integers of exactly the same type. Further, they must be
//     created / cast explicitly; there is no implicit conversion.
//
//     UintA a(2);
//     uint32_t aValue = static_cast<uint32_t>(a);
//
namespace detail {
template <typename Tag, typename T>
class TypedIntegerImpl;
}  // namespace detail

TypedInteger;
#else
using TypedInteger = T;
#endif

namespace detail {
template <typename Tag, typename T>
class alignas(T) TypedIntegerImpl {};

}  // namespace detail
}  // namespace dawn

namespace std {

numeric_limits<dawn::detail::TypedIntegerImpl<Tag, T>>;

}  // namespace std

namespace dawn::ityp {

// These helpers below are provided since the default arithmetic operators for small integer
// types like uint8_t and uint16_t return integers, not their same type. To avoid lots of
// casting or conditional code between Release/Debug. Callsites should use ityp::Add(a, b) and
// ityp::Sub(a, b) instead.

template <typename Tag, typename T>
constexpr ::dawn::detail::TypedIntegerImpl<Tag, T> Add(
    ::dawn::detail::TypedIntegerImpl<Tag, T> lhs,
    ::dawn::detail::TypedIntegerImpl<Tag, T> rhs) {}

template <typename Tag, typename T>
constexpr ::dawn::detail::TypedIntegerImpl<Tag, T> Sub(
    ::dawn::detail::TypedIntegerImpl<Tag, T> lhs,
    ::dawn::detail::TypedIntegerImpl<Tag, T> rhs) {}

template <typename Tag, typename T>
constexpr ::dawn::detail::TypedIntegerImpl<Tag, T> PlusOne(
    ::dawn::detail::TypedIntegerImpl<Tag, T> value) {}

template <typename T>
constexpr std::enable_if_t<std::is_integral<T>::value, T> Add(T lhs, T rhs) {}

template <typename T>
constexpr std::enable_if_t<std::is_integral<T>::value, T> Sub(T lhs, T rhs) {}

template <typename T>
constexpr std::enable_if_t<std::is_integral<T>::value, T> PlusOne(T value) {}

}  // namespace dawn::ityp

#endif  // SRC_DAWN_COMMON_TYPEDINTEGER_H_