Merge pull request #3056 from xwu/sr-13837

Synchronize `Decimal` overlay and corelibs-foundation implementations

Author: xwu

Darwin/Foundation-swiftoverlay-Tests/TestDecimal.swift

@@ -386,6 +386,13 @@ class TestDecimal : XCTestCase {
         XCTAssertTrue(NSDecimalIsNotANumber(&result), "NaN e4")
         XCTAssertNotEqual(.noError, NSDecimalMultiplyByPowerOf10(&result, &NaN, 5, .plain))
         XCTAssertTrue(NSDecimalIsNotANumber(&result), "NaN e5")
+
+        XCTAssertFalse(Double(truncating: NSDecimalNumber(decimal: Decimal(0))).isNaN)
+        XCTAssertTrue(Decimal(Double.leastNonzeroMagnitude).isNaN)
+        XCTAssertTrue(Decimal(Double.leastNormalMagnitude).isNaN)
+        XCTAssertTrue(Decimal(Double.greatestFiniteMagnitude).isNaN)
+        XCTAssertTrue(Decimal(Double("1e-129")!).isNaN)
+        XCTAssertTrue(Decimal(Double("0.1e-128")!).isNaN)
     }
 
     func test_NegativeAndZeroMultiplication() {
@@ -597,4 +604,95 @@ class TestDecimal : XCTestCase {
     func test_unconditionallyBridgeFromObjectiveC() {
         XCTAssertEqual(Decimal(), Decimal._unconditionallyBridgeFromObjectiveC(nil))
     }
+
+    func test_parseDouble() throws {
+        XCTAssertEqual(Decimal(Double(0.0)), Decimal(Int.zero))
+        XCTAssertEqual(Decimal(Double(-0.0)), Decimal(Int.zero))
+
+        // These values can only be represented as Decimal.nan
+        XCTAssertEqual(Decimal(Double.nan), Decimal.nan)
+        XCTAssertEqual(Decimal(Double.signalingNaN), Decimal.nan)
+
+        // These values are out out range for Decimal
+        XCTAssertEqual(Decimal(-Double.leastNonzeroMagnitude), Decimal.nan)
+        XCTAssertEqual(Decimal(Double.leastNonzeroMagnitude), Decimal.nan)
+        XCTAssertEqual(Decimal(-Double.leastNormalMagnitude), Decimal.nan)
+        XCTAssertEqual(Decimal(Double.leastNormalMagnitude), Decimal.nan)
+        XCTAssertEqual(Decimal(-Double.greatestFiniteMagnitude), Decimal.nan)
+        XCTAssertEqual(Decimal(Double.greatestFiniteMagnitude), Decimal.nan)
+
+        // SR-13837
+        let testDoubles: [(Double, String)] = [
+            (1.8446744073709550E18, "1844674407370954752"),
+            (1.8446744073709551E18, "1844674407370954752"),
+            (1.8446744073709552E18, "1844674407370955264"),
+            (1.8446744073709553E18, "1844674407370955264"),
+            (1.8446744073709554E18, "1844674407370955520"),
+            (1.8446744073709555E18, "1844674407370955520"),
+
+            (1.8446744073709550E19, "18446744073709547520"),
+            (1.8446744073709551E19, "18446744073709552640"),
+            (1.8446744073709552E19, "18446744073709552640"),
+            (1.8446744073709553E19, "18446744073709552640"),
+            (1.8446744073709554E19, "18446744073709555200"),
+            (1.8446744073709555E19, "18446744073709555200"),
+
+            (1.8446744073709550E20, "184467440737095526400"),
+            (1.8446744073709551E20, "184467440737095526400"),
+            (1.8446744073709552E20, "184467440737095526400"),
+            (1.8446744073709553E20, "184467440737095526400"),
+            (1.8446744073709554E20, "184467440737095552000"),
+            (1.8446744073709555E20, "184467440737095552000"),
+        ]
+
+        for (d, s) in testDoubles {
+            XCTAssertEqual(Decimal(d), Decimal(string: s))
+            XCTAssertEqual(Decimal(d).description, try XCTUnwrap(Decimal(string: s)).description)
+        }
+    }
+
+    func test_initExactly() {
+        // This really requires some tests using a BinaryInteger of bitwidth > 128 to test failures.
+        let d1 = Decimal(exactly: UInt64.max)
+        XCTAssertNotNil(d1)
+        XCTAssertEqual(d1?.description, UInt64.max.description)
+        XCTAssertEqual(d1?._length, 4)
+
+        let d2 = Decimal(exactly: Int64.min)
+        XCTAssertNotNil(d2)
+        XCTAssertEqual(d2?.description, Int64.min.description)
+        XCTAssertEqual(d2?._length, 4)
+
+        let d3 = Decimal(exactly: Int64.max)
+        XCTAssertNotNil(d3)
+        XCTAssertEqual(d3?.description, Int64.max.description)
+        XCTAssertEqual(d3?._length, 4)
+
+        let d4 = Decimal(exactly: Int32.min)
+        XCTAssertNotNil(d4)
+        XCTAssertEqual(d4?.description, Int32.min.description)
+        XCTAssertEqual(d4?._length, 2)
+
+        let d5 = Decimal(exactly: Int32.max)
+        XCTAssertNotNil(d5)
+        XCTAssertEqual(d5?.description, Int32.max.description)
+        XCTAssertEqual(d5?._length, 2)
+
+        let d6 = Decimal(exactly: 0)
+        XCTAssertNotNil(d6)
+        XCTAssertEqual(d6, Decimal.zero)
+        XCTAssertEqual(d6?.description, "0")
+        XCTAssertEqual(d6?._length, 0)
+
+        let d7 = Decimal(exactly: 1)
+        XCTAssertNotNil(d7)
+        XCTAssertEqual(d7?.description, "1")
+        XCTAssertEqual(d7?._length, 1)
+
+        let d8 = Decimal(exactly: -1)
+        XCTAssertNotNil(d8)
+        XCTAssertEqual(d8?.description, "-1")
+        XCTAssertEqual(d8?._length, 1)
+    }
+
 }

Darwin/Foundation-swiftoverlay/Decimal.swift

@@ -26,6 +26,7 @@ public func pow(_ x: Decimal, _ y: Int) -> Decimal {
 }
 
 extension Decimal : Hashable, Comparable {
+    // (Used by `doubleValue`.)
     private subscript(index: UInt32) -> UInt16 {
         get {
             switch index {
@@ -42,6 +43,7 @@ extension Decimal : Hashable, Comparable {
         }
     }
 
+    // (Used by `NSDecimalNumber` and `hash(into:)`.)
     internal var doubleValue: Double {
         if _length == 0 {
             return _isNegative == 1 ? Double.nan : 0
@@ -124,7 +126,7 @@ extension Decimal : Codable {
 
         var mantissaContainer = try container.nestedUnkeyedContainer(forKey: .mantissa)
         var mantissa: (CUnsignedShort, CUnsignedShort, CUnsignedShort, CUnsignedShort,
-                       CUnsignedShort, CUnsignedShort, CUnsignedShort, CUnsignedShort) = (0,0,0,0,0,0,0,0)
+            CUnsignedShort, CUnsignedShort, CUnsignedShort, CUnsignedShort) = (0,0,0,0,0,0,0,0)
         mantissa.0 = try mantissaContainer.decode(CUnsignedShort.self)
         mantissa.1 = try mantissaContainer.decode(CUnsignedShort.self)
         mantissa.2 = try mantissaContainer.decode(CUnsignedShort.self)
@@ -134,12 +136,12 @@ extension Decimal : Codable {
         mantissa.6 = try mantissaContainer.decode(CUnsignedShort.self)
         mantissa.7 = try mantissaContainer.decode(CUnsignedShort.self)
 
-        self = Decimal(_exponent: exponent,
-                       _length: length,
-                       _isNegative: CUnsignedInt(isNegative ? 1 : 0),
-                       _isCompact: CUnsignedInt(isCompact ? 1 : 0),
-                       _reserved: 0,
-                       _mantissa: mantissa)
+        self.init(_exponent: exponent,
+                  _length: length,
+                  _isNegative: CUnsignedInt(isNegative ? 1 : 0),
+                  _isCompact: CUnsignedInt(isCompact ? 1 : 0),
+                  _reserved: 0,
+                  _mantissa: mantissa)
     }
 
     public func encode(to encoder: Encoder) throws {
@@ -182,9 +184,50 @@ extension Decimal : SignedNumeric {
             _reserved: 0, _mantissa: self._mantissa)
     }
 
-    // FIXME(integers): implement properly
     public init?<T : BinaryInteger>(exactly source: T) {
-        fatalError()
+        let zero = 0 as T
+
+        if source == zero {
+            self = Decimal.zero
+            return
+        }
+
+        let negative: UInt32 = (T.isSigned && source < zero) ? 1 : 0
+        var mantissa = source.magnitude
+        var exponent: Int32 = 0
+
+        let maxExponent = Int8.max
+        while mantissa.isMultiple(of: 10) && (exponent < maxExponent) {
+            exponent += 1
+            mantissa /= 10
+        }
+
+        // If the mantissa still requires more than 128 bits of storage then it is too large.
+        if mantissa.bitWidth > 128 && (mantissa >> 128 != zero) { return nil }
+
+        let mantissaParts: (UInt16, UInt16, UInt16, UInt16, UInt16, UInt16, UInt16, UInt16)
+        let loWord = UInt64(truncatingIfNeeded: mantissa)
+        var length = ((loWord.bitWidth - loWord.leadingZeroBitCount) + (UInt16.bitWidth - 1)) / UInt16.bitWidth
+        mantissaParts.0 = UInt16(truncatingIfNeeded: loWord >> 0)
+        mantissaParts.1 = UInt16(truncatingIfNeeded: loWord >> 16)
+        mantissaParts.2 = UInt16(truncatingIfNeeded: loWord >> 32)
+        mantissaParts.3 = UInt16(truncatingIfNeeded: loWord >> 48)
+
+        let hiWord = mantissa.bitWidth > 64 ? UInt64(truncatingIfNeeded: mantissa >> 64) : 0
+        if hiWord != 0 {
+            length = 4 + ((hiWord.bitWidth - hiWord.leadingZeroBitCount) + (UInt16.bitWidth - 1)) / UInt16.bitWidth
+            mantissaParts.4 = UInt16(truncatingIfNeeded: hiWord >> 0)
+            mantissaParts.5 = UInt16(truncatingIfNeeded: hiWord >> 16)
+            mantissaParts.6 = UInt16(truncatingIfNeeded: hiWord >> 32)
+            mantissaParts.7 = UInt16(truncatingIfNeeded: hiWord >> 48)
+        } else {
+            mantissaParts.4 = 0
+            mantissaParts.5 = 0
+            mantissaParts.6 = 0
+            mantissaParts.7 = 0
+        }
+
+        self = Decimal(_exponent: exponent, _length: UInt32(length), _isNegative: negative, _isCompact: 1, _reserved: 0, _mantissa: mantissaParts)
     }
 
     public static func +=(lhs: inout Decimal, rhs: Decimal) {
@@ -332,11 +375,11 @@ extension Decimal {
         _mantissa: (0x6623, 0x7d57, 0x16e7, 0xad0d, 0xaf52, 0x4641, 0xdfa7, 0xec58)
     )
 
-    @available(*, unavailable, message: "Decimal does not yet fully adopt FloatingPoint.")
-    public static var infinity: Decimal { fatalError("Decimal does not yet fully adopt FloatingPoint") }
+    @available(*, unavailable, message: "Decimal does not fully adopt FloatingPoint.")
+    public static var infinity: Decimal { fatalError("Decimal does not fully adopt FloatingPoint") }
 
-    @available(*, unavailable, message: "Decimal does not yet fully adopt FloatingPoint.")
-    public static var signalingNaN: Decimal { fatalError("Decimal does not yet fully adopt FloatingPoint") }
+    @available(*, unavailable, message: "Decimal does not fully adopt FloatingPoint.")
+    public static var signalingNaN: Decimal { fatalError("Decimal does not fully adopt FloatingPoint") }
 
     public static var quietNaN: Decimal {
         return Decimal(
@@ -411,7 +454,7 @@ extension Decimal {
     }
 
     public init(_ value: Double) {
-        precondition(!value.isInfinite, "Decimal does not yet fully adopt FloatingPoint")
+        precondition(!value.isInfinite, "Decimal does not fully adopt FloatingPoint")
         if value.isNaN {
             self = Decimal.nan
         } else if value == 0.0 {
@@ -420,16 +463,36 @@ extension Decimal {
             self = Decimal()
             let negative = value < 0
             var val = negative ? -1 * value : value
-            var exponent = 0
+            var exponent: Int8 = 0
+
+            // Try to get val as close to UInt64.max whilst adjusting the exponent
+            // to reduce the number of digits after the decimal point.
             while val < Double(UInt64.max - 1) {
+                guard exponent > Int8.min else {
+                    self = Decimal.nan
+                    return
+                }
                 val *= 10.0
                 exponent -= 1
             }
-            while Double(UInt64.max - 1) < val {
+            while Double(UInt64.max) <= val {
+                guard exponent < Int8.max else {
+                    self = Decimal.nan
+                    return
+                }
                 val /= 10.0
                 exponent += 1
             }
-            var mantissa = UInt64(val)
+
+            var mantissa: UInt64
+            let maxMantissa = Double(UInt64.max).nextDown
+            if val > maxMantissa {
+                // UInt64(Double(UInt64.max)) gives an overflow error; this is the largest
+                // mantissa that can be set.
+                mantissa = UInt64(maxMantissa)
+            } else {
+                mantissa = UInt64(val)
+            }
 
             var i: UInt32 = 0
             // This is a bit ugly but it is the closest approximation of the C
@@ -601,8 +664,8 @@ extension Decimal {
         return true
     }
 
-    @available(*, unavailable, message: "Decimal does not yet fully adopt FloatingPoint.")
-    public mutating func formTruncatingRemainder(dividingBy other: Decimal) { fatalError("Decimal does not yet fully adopt FloatingPoint") }
+    @available(*, unavailable, message: "Decimal does not fully adopt FloatingPoint.")
+    public mutating func formTruncatingRemainder(dividingBy other: Decimal) { fatalError("Decimal does not fully adopt FloatingPoint") }
 }
 
 extension Decimal : _ObjectiveCBridgeable {