Make BitField and ResultCode constexpr-initializable
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@ -108,7 +108,7 @@
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* symptoms.
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*/
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#pragma pack(1)
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template <std::size_t position, std::size_t bits, typename T>
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template <std::size_t Position, std::size_t Bits, typename T>
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struct BitField {
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private:
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// We hide the copy assigment operator here, because the default copy
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@ -117,40 +117,6 @@ private:
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// We don't delete it because we want BitField to be trivially copyable.
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BitField& operator=(const BitField&) = default;
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public:
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// This constructor and assignment operator might be considered ambiguous:
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// Would they initialize the storage or just the bitfield?
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// Hence, delete them. Use the Assign method to set bitfield values!
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BitField(T val) = delete;
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BitField& operator=(T val) = delete;
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// Force default constructor to be created
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// so that we can use this within unions
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BitField() = default;
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FORCE_INLINE operator T() const {
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return Value();
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}
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FORCE_INLINE void Assign(const T& value) {
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storage = (storage & ~GetMask()) | (((StorageType)value << position) & GetMask());
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}
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FORCE_INLINE T Value() const {
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if (std::numeric_limits<T>::is_signed) {
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std::size_t shift = 8 * sizeof(T) - bits;
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return (T)((storage << (shift - position)) >> shift);
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} else {
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return (T)((storage & GetMask()) >> position);
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}
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}
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// TODO: we may want to change this to explicit operator bool() if it's bug-free in VS2015
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FORCE_INLINE bool ToBool() const {
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return Value() != 0;
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}
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private:
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// StorageType is T for non-enum types and the underlying type of T if
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// T is an enumeration. Note that T is wrapped within an enable_if in the
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// former case to workaround compile errors which arise when using
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@ -161,10 +127,63 @@ private:
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// Unsigned version of StorageType
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typedef typename std::make_unsigned<StorageType>::type StorageTypeU;
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FORCE_INLINE StorageType GetMask() const {
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return (((StorageTypeU)~0) >> (8 * sizeof(T) - bits)) << position;
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public:
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/// Constants to allow limited introspection of fields if needed
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static constexpr size_t position = Position;
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static constexpr size_t bits = Bits;
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static constexpr StorageType mask = (((StorageTypeU)~0) >> (8 * sizeof(T) - bits)) << position;
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/**
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* Formats a value by masking and shifting it according to the field parameters. A value
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* containing several bitfields can be assembled by formatting each of their values and ORing
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* the results together.
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*/
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static constexpr FORCE_INLINE StorageType FormatValue(const T& value) {
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return ((StorageType)value << position) & mask;
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}
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/**
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* Extracts a value from the passed storage. In most situations prefer use the member functions
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* (such as Value() or operator T), but this can be used to extract a value from a bitfield
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* union in a constexpr context.
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*/
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static constexpr FORCE_INLINE T ExtractValue(const StorageType& storage) {
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if (std::numeric_limits<T>::is_signed) {
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std::size_t shift = 8 * sizeof(T) - bits;
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return (T)((storage << (shift - position)) >> shift);
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} else {
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return (T)((storage & mask) >> position);
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}
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}
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// This constructor and assignment operator might be considered ambiguous:
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// Would they initialize the storage or just the bitfield?
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// Hence, delete them. Use the Assign method to set bitfield values!
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BitField(T val) = delete;
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BitField& operator=(T val) = delete;
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// Force default constructor to be created
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// so that we can use this within unions
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constexpr BitField() = default;
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FORCE_INLINE operator T() const {
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return Value();
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}
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FORCE_INLINE void Assign(const T& value) {
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storage = (storage & ~mask) | FormatValue(value);
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}
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FORCE_INLINE T Value() const {
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return ExtractValue(storage);
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}
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// TODO: we may want to change this to explicit operator bool() if it's bug-free in VS2015
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FORCE_INLINE bool ToBool() const {
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return Value() != 0;
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}
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private:
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StorageType storage;
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static_assert(bits + position <= 8 * sizeof(T), "Bitfield out of range");
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@ -228,45 +228,42 @@ union ResultCode {
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// error
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BitField<31, 1, u32> is_error;
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explicit ResultCode(u32 raw) : raw(raw) {}
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ResultCode(ErrorDescription description_, ErrorModule module_, ErrorSummary summary_,
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ErrorLevel level_)
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: raw(0) {
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description.Assign(description_);
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module.Assign(module_);
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summary.Assign(summary_);
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level.Assign(level_);
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}
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constexpr explicit ResultCode(u32 raw) : raw(raw) {}
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ResultCode& operator=(const ResultCode& o) {
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constexpr ResultCode(ErrorDescription description_, ErrorModule module_, ErrorSummary summary_,
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ErrorLevel level_)
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: raw(description.FormatValue(description_) | module.FormatValue(module_) |
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summary.FormatValue(summary_) | level.FormatValue(level_)) {}
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constexpr ResultCode& operator=(const ResultCode& o) {
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raw = o.raw;
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return *this;
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}
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bool IsSuccess() const {
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return is_error == 0;
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constexpr bool IsSuccess() const {
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return is_error.ExtractValue(raw) == 0;
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}
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bool IsError() const {
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return is_error == 1;
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constexpr bool IsError() const {
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return is_error.ExtractValue(raw) == 1;
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}
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};
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inline bool operator==(const ResultCode& a, const ResultCode& b) {
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constexpr bool operator==(const ResultCode& a, const ResultCode& b) {
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return a.raw == b.raw;
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}
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inline bool operator!=(const ResultCode& a, const ResultCode& b) {
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constexpr bool operator!=(const ResultCode& a, const ResultCode& b) {
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return a.raw != b.raw;
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}
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// Convenience functions for creating some common kinds of errors:
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/// The default success `ResultCode`.
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const ResultCode RESULT_SUCCESS(0);
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constexpr ResultCode RESULT_SUCCESS(0);
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/// Might be returned instead of a dummy success for unimplemented APIs.
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inline ResultCode UnimplementedFunction(ErrorModule module) {
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constexpr ResultCode UnimplementedFunction(ErrorModule module) {
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return ResultCode(ErrorDescription::NotImplemented, module, ErrorSummary::NotSupported,
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ErrorLevel::Permanent);
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}
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