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Allow specifying StorageType for BitField

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This is useful for BitFields that are bools.
This commit is contained in:
Pokechu22
2021-02-17 20:23:06 -08:00
parent 6653bd7199
commit cf95deaf6d
2 changed files with 27 additions and 13 deletions
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27
Source/Core/Common/BitField.h
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@ -110,7 +110,13 @@
* symptoms.
*/
#pragma pack(1)
template <std::size_t position, std::size_t bits, typename T>
template <std::size_t position, std::size_t bits, typename T,
// StorageType is T for non-enum types and the underlying type of T if
// T is an enumeration. Note that T is wrapped within an enable_if in the
// former case to workaround compile errors which arise when using
// std::underlying_type<T>::type directly.
typename StorageType = typename std::conditional_t<
std::is_enum<T>::value, std::underlying_type<T>, std::enable_if<true, T>>::type>
struct BitField
{
private:
@ -149,20 +155,13 @@ public:
constexpr std::size_t NumBits() const { return bits; }
private:
// StorageType is T for non-enum types and the underlying type of T if
// T is an enumeration. Note that T is wrapped within an enable_if in the
// former case to workaround compile errors which arise when using
// std::underlying_type<T>::type directly.
using StorageType = typename std::conditional_t<std::is_enum<T>::value, std::underlying_type<T>,
std::enable_if<true, T>>::type;
// Unsigned version of StorageType
using StorageTypeU = std::make_unsigned_t<StorageType>;
constexpr T Value(std::true_type) const
{
using shift_amount = std::integral_constant<size_t, 8 * sizeof(T) - bits>;
return static_cast<T>((storage << (shift_amount() - position)) >> shift_amount());
const size_t shift_amount = 8 * sizeof(StorageType) - bits;
return static_cast<T>((storage << (shift_amount - position)) >> shift_amount);
}
constexpr T Value(std::false_type) const
@ -172,15 +171,17 @@ private:
static constexpr StorageType GetMask()
{
return (std::numeric_limits<StorageTypeU>::max() >> (8 * sizeof(T) - bits)) << position;
return (std::numeric_limits<StorageTypeU>::max() >> (8 * sizeof(StorageType) - bits))
<< position;
}
StorageType storage;
static_assert(bits + position <= 8 * sizeof(T), "Bitfield out of range");
static_assert(bits + position <= 8 * sizeof(StorageType), "Bitfield out of range");
static_assert(sizeof(T) <= sizeof(StorageType), "T must fit in StorageType");
// And, you know, just in case people specify something stupid like bits=position=0x80000000
static_assert(position < 8 * sizeof(T), "Invalid position");
static_assert(position < 8 * sizeof(StorageType), "Invalid position");
static_assert(bits <= 8 * sizeof(T), "Invalid number of bits");
static_assert(bits > 0, "Invalid number of bits");
};