[swift-evolution] [Proposal] Introduces endianness specific type
Max Moiseev
moiseev at apple.com
Fri Jul 7 12:48:46 CDT 2017
Hi Susan,
Was there any motivation for this proposal that I missed? If not then, can you please provide it in a few sentences? Otherwise it’s not clear to me what problem it is supposed to fix.
Thanks,
Max
> On Jul 6, 2017, at 8:21 PM, Susan Cheng via swift-evolution <swift-evolution at swift.org> wrote:
>
> IMO, it has unclear representation when FixedWidthInteger working with endianness specific type.
>
> so I want to introduce the endianness specific wrapper:
>
> public struct BEInteger<Base : FixedWidthInteger> : FixedWidthInteger {
>
> public var bigEndian: BEInteger { get }
>
> public var littleEndian: LEInteger<Base> { get }
> }
>
> public struct LEInteger<Base : FixedWidthInteger> : FixedWidthInteger {
>
> public var bigEndian: BEInteger<Base> { get }
>
> public var littleEndian: LEInteger { get }
> }
>
> also, we should change the FixedWidthInteger as follow:
>
> public protocol FixedWidthInteger : BinaryInteger {
>
> /// deprecated, we should use value.bigEndian instead
> init(bigEndian value: Self)
>
> /// deprecated, we should use value.littleEndian instead
> init(littleEndian value: Self)
>
> associatedtype EndianRepresentingValue : FixedWidthInteger
>
> var bigEndian: BEInteger<EndianRepresentingValue> { get }
>
> var littleEndian: LEInteger<EndianRepresentingValue> { get }
> }
>
> =============================
>
> this is my working alternative implementation:
>
>
> @_versioned
> protocol EndianInteger : FixedWidthInteger {
>
> associatedtype BitPattern : FixedWidthInteger
>
> associatedtype RepresentingValue : FixedWidthInteger
>
> var bitPattern: BitPattern { get }
>
> init(bitPattern: BitPattern)
>
> var representingValue : RepresentingValue { get set }
>
> init(representingValue: RepresentingValue)
> }
>
> extension EndianInteger {
>
> @_transparent
> public init(integerLiteral value: RepresentingValue.IntegerLiteralType) {
> self.init(representingValue: RepresentingValue(integerLiteral: value))
> }
>
> @_transparent
> public init?<T>(exactly source: T) where T : BinaryInteger {
> guard let value = RepresentingValue(exactly: source) else { return nil }
> self.init(representingValue: value)
> }
>
> @_transparent
> public init?<T>(exactly source: T) where T : FloatingPoint {
> guard let value = RepresentingValue(exactly: source) else { return nil }
> self.init(representingValue: value)
> }
>
> @_transparent
> public init(_ value: RepresentingValue) {
> self.init(representingValue: value)
> }
>
> @_transparent
> public init<T>(_ source: T) where T : FloatingPoint {
> self.init(representingValue: RepresentingValue(source))
> }
>
> @_transparent
> public init<T>(_ source: T) where T : BinaryInteger {
> self.init(representingValue: RepresentingValue(source))
> }
>
> @_transparent
> public init<T>(extendingOrTruncating source: T) where T : BinaryInteger {
> self.init(representingValue: RepresentingValue(extendingOrTruncating: source))
> }
>
> @_transparent
> public init<T>(clamping source: T) where T : BinaryInteger {
> self.init(representingValue: RepresentingValue(clamping: source))
> }
>
> @_transparent
> public init(_truncatingBits bits: UInt) {
> self.init(representingValue: RepresentingValue(_truncatingBits: bits))
> }
> }
>
> extension EndianInteger {
>
> @_transparent
> public static var isSigned: Bool {
> return RepresentingValue.isSigned
> }
>
> @_transparent
> public static var bitWidth: Int {
> return RepresentingValue.bitWidth
> }
>
> @_transparent
> public static var max: Self {
> return Self(representingValue: RepresentingValue.max)
> }
>
> @_transparent
> public static var min: Self {
> return Self(representingValue: RepresentingValue.min)
> }
> }
>
> extension EndianInteger {
>
> @_transparent
> public var hashValue: Int {
> return representingValue.hashValue
> }
>
> @_transparent
> public var description: String {
> return representingValue.description
> }
>
> @_transparent
> public var bitWidth: Int {
> return representingValue.bitWidth
> }
>
> @_transparent
> public var magnitude: RepresentingValue.Magnitude {
> return representingValue.magnitude
> }
>
> @_transparent
> public var trailingZeroBitCount: Int {
> return representingValue.trailingZeroBitCount
> }
>
> @_transparent
> public var nonzeroBitCount: Int {
> return representingValue.nonzeroBitCount
> }
>
> @_transparent
> public var leadingZeroBitCount: Int {
> return representingValue.leadingZeroBitCount
> }
>
> @_transparent
> public var byteSwapped: Self {
> return Self(representingValue: representingValue.byteSwapped)
> }
> }
>
> extension EndianInteger {
>
> @_transparent
> public func _word(at n: Int) -> UInt {
> return representingValue._word(at: n)
> }
>
> @_transparent
> public func distance(to other: Self) -> RepresentingValue.Stride {
> return self.representingValue.distance(to: other.representingValue)
> }
>
> @_transparent
> public func advanced(by n: RepresentingValue.Stride) -> Self {
> return Self(representingValue: self.representingValue.advanced(by: n))
> }
>
> @_transparent
> public func addingReportingOverflow(_ rhs: Self) -> (partialValue: Self, overflow: ArithmeticOverflow) {
> let (partialValue, overflow) = representingValue.addingReportingOverflow(rhs.representingValue)
> return (Self(representingValue: partialValue), overflow)
> }
>
> @_transparent
> public func subtractingReportingOverflow(_ rhs: Self) -> (partialValue: Self, overflow: ArithmeticOverflow) {
> let (partialValue, overflow) = representingValue.subtractingReportingOverflow(rhs.representingValue)
> return (Self(representingValue: partialValue), overflow)
> }
>
> @_transparent
> public func multipliedReportingOverflow(by rhs: Self) -> (partialValue: Self, overflow: ArithmeticOverflow) {
> let (partialValue, overflow) = representingValue.multipliedReportingOverflow(by: rhs.representingValue)
> return (Self(representingValue: partialValue), overflow)
> }
>
> @_transparent
> public func dividedReportingOverflow(by rhs: Self) -> (partialValue: Self, overflow: ArithmeticOverflow) {
> let (partialValue, overflow) = representingValue.dividedReportingOverflow(by: rhs.representingValue)
> return (Self(representingValue: partialValue), overflow)
> }
>
> @_transparent
> public func remainderReportingOverflow(dividingBy rhs: Self) -> (partialValue: Self, overflow: ArithmeticOverflow) {
> let (partialValue, overflow) = representingValue.remainderReportingOverflow(dividingBy: rhs.representingValue)
> return (Self(representingValue: partialValue), overflow)
> }
>
> @_transparent
> public func multipliedFullWidth(by other: Self) -> (high: Self, low: RepresentingValue.Magnitude) {
> let (high, low) = representingValue.multipliedFullWidth(by: other.representingValue)
> return (Self(representingValue: high), low)
> }
>
> @_transparent
> public func dividingFullWidth(_ dividend: (high: Self, low: RepresentingValue.Magnitude)) -> (quotient: Self, remainder: Self) {
> let (quotient, remainder) = representingValue.dividingFullWidth((dividend.high.representingValue, dividend.low))
> return (Self(representingValue: quotient), Self(representingValue: remainder))
> }
> }
>
> extension EndianInteger {
>
> @_transparent
> public static prefix func +(x: Self) -> Self {
> return x
> }
>
> @_transparent
> public static func +(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue + rhs.representingValue)
> }
>
> @_transparent
> public static func +=(lhs: inout Self, rhs: Self) {
> lhs.representingValue += rhs.representingValue
> }
>
> @_transparent
> public static func -(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue - rhs.representingValue)
> }
>
> @_transparent
> public static func -=(lhs: inout Self, rhs: Self) {
> lhs.representingValue -= rhs.representingValue
> }
>
> @_transparent
> public static func *(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue * rhs.representingValue)
> }
>
> @_transparent
> public static func *=(lhs: inout Self, rhs: Self) {
> lhs.representingValue *= rhs.representingValue
> }
>
> @_transparent
> public static func /(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue / rhs.representingValue)
> }
>
> @_transparent
> public static func /=(lhs: inout Self, rhs: Self) {
> lhs.representingValue /= rhs.representingValue
> }
>
> @_transparent
> public static func %(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue % rhs.representingValue)
> }
>
> @_transparent
> public static func %=(lhs: inout Self, rhs: Self) {
> lhs.representingValue %= rhs.representingValue
> }
>
> @_transparent
> public static func &(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue & rhs.representingValue)
> }
>
> @_transparent
> public static func &=(lhs: inout Self, rhs: Self) {
> lhs.representingValue &= rhs.representingValue
> }
>
> @_transparent
> public static func |(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue | rhs.representingValue)
> }
>
> @_transparent
> public static func |=(lhs: inout Self, rhs: Self) {
> lhs.representingValue |= rhs.representingValue
> }
>
> @_transparent
> public static func ^(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue ^ rhs.representingValue)
> }
>
> @_transparent
> public static func ^=(lhs: inout Self, rhs: Self) {
> lhs.representingValue ^= rhs.representingValue
> }
>
> @_transparent
> prefix public static func ~(x: Self) -> Self {
> return Self(representingValue: ~x.representingValue)
> }
>
> @_transparent
> public static func &>>(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue &>> rhs.representingValue)
> }
>
> @_transparent
> public static func &<<(lhs: Self, rhs: Self) -> Self {
> return Self(representingValue: lhs.representingValue &<< rhs.representingValue)
> }
>
> @_transparent
> public static func ==(lhs: Self, rhs: Self) -> Bool {
> return lhs.bitPattern == rhs.bitPattern
> }
>
> @_transparent
> public static func !=(lhs: Self, rhs: Self) -> Bool {
> return lhs.bitPattern != rhs.bitPattern
> }
>
> @_transparent
> public static func >(lhs: Self, rhs: Self) -> Bool {
> return lhs.representingValue > rhs.representingValue
> }
>
> @_transparent
> public static func <(lhs: Self, rhs: Self) -> Bool {
> return lhs.representingValue < rhs.representingValue
> }
>
> @_transparent
> public static func >=(lhs: Self, rhs: Self) -> Bool {
> return lhs.representingValue >= rhs.representingValue
> }
>
> @_transparent
> public static func <=(lhs: Self, rhs: Self) -> Bool {
> return lhs.representingValue <= rhs.representingValue
> }
> }
>
> public struct BEInteger<Base : FixedWidthInteger> : FixedWidthInteger, EndianInteger {
>
> public var bitPattern: Base
>
> @_transparent
> public init(bitPattern: Base) {
> self.bitPattern = bitPattern
> }
>
> @_versioned
> @_transparent
> init(representingValue: Base) {
> self.bitPattern = representingValue.bigEndian
> }
>
> @_versioned
> @_transparent
> var representingValue: Base {
> get {
> return Base(bigEndian: bitPattern)
> }
> set {
> bitPattern = newValue.bigEndian
> }
> }
>
> @_transparent
> public init(bigEndian value: BEInteger) {
> self.bitPattern = value.bitPattern
> }
>
> @_transparent
> public init(littleEndian value: BEInteger) {
> self.bitPattern = value.bitPattern.byteSwapped
> }
>
> @_transparent
> public var bigEndian: BEInteger {
> return self
> }
>
> @_transparent
> public var littleEndian: BEInteger {
> return BEInteger(littleEndian: self)
> }
> }
>
> public struct LEInteger<Base : FixedWidthInteger> : FixedWidthInteger, EndianInteger {
>
> public var bitPattern: Base
>
> @_transparent
> public init(bitPattern: Base) {
> self.bitPattern = bitPattern
> }
>
> @_versioned
> @_transparent
> init(representingValue: Base) {
> self.bitPattern = representingValue.littleEndian
> }
>
> @_versioned
> @_transparent
> var representingValue: Base {
> get {
> return Base(littleEndian: bitPattern)
> }
> set {
> bitPattern = newValue.littleEndian
> }
> }
>
> @_transparent
> public init(bigEndian value: LEInteger) {
> self.bitPattern = value.bitPattern.byteSwapped
> }
>
> @_transparent
> public init(littleEndian value: LEInteger) {
> self.bitPattern = value.bitPattern
> }
>
> @_transparent
> public var bigEndian: LEInteger {
> return LEInteger(bigEndian: self)
> }
>
> @_transparent
> public var littleEndian: LEInteger {
> return self
> }
> }
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
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