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[4.2] Decimal: Fix .doubleValue to use _length to only index valid mantissa elements. #1900

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Merged
merged 1 commit into from
Feb 13, 2019
Merged

[4.2] Decimal: Fix .doubleValue to use _length to only index valid mantissa elements. #1900

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25 changes: 13 additions & 12 deletions Foundation/Decimal.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -201,20 +201,19 @@ extension Decimal {

extension Decimal : Hashable, Comparable {
internal var doubleValue: Double {
if _length == 0 {
if _isNegative == 1 {
return Double.nan
} else {
return 0
}
}

var d = 0.0
if _length == 0 && _isNegative == 1 {
return Double.nan
for idx in stride(from: min(_length, 8), to: 0, by: -1) {
d = d * 65536 + Double(self[idx - 1])
}

d = d * 65536 + Double(_mantissa.7)
d = d * 65536 + Double(_mantissa.6)
d = d * 65536 + Double(_mantissa.5)
d = d * 65536 + Double(_mantissa.4)
d = d * 65536 + Double(_mantissa.3)
d = d * 65536 + Double(_mantissa.2)
d = d * 65536 + Double(_mantissa.1)
d = d * 65536 + Double(_mantissa.0)


if _exponent < 0 {
for _ in _exponent..<0 {
d /= 10.0
Expand All @@ -226,9 +225,11 @@ extension Decimal : Hashable, Comparable {
}
return _isNegative != 0 ? -d : d
}

public var hashValue: Int {
return Int(bitPattern: __CFHashDouble(doubleValue))
}

public static func ==(lhs: Decimal, rhs: Decimal) -> Bool {
if lhs.isNaN {
return rhs.isNaN
Expand Down
85 changes: 85 additions & 0 deletions TestFoundation/TestDecimal.swift
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Expand Up @@ -31,6 +31,7 @@ class TestDecimal: XCTestCase {
("test_SimpleMultiplication", test_SimpleMultiplication),
("test_SmallerNumbers", test_SmallerNumbers),
("test_ZeroPower", test_ZeroPower),
("test_doubleValue", test_doubleValue)
]
}

Expand Down Expand Up @@ -697,4 +698,88 @@ class TestDecimal: XCTestCase {
XCTAssertEqual(1, negativeSix.raising(toPower: 0))
}

func test_doubleValue() {
XCTAssertEqual(NSDecimalNumber(decimal:Decimal(0)).doubleValue, 0)
XCTAssertEqual(NSDecimalNumber(decimal:Decimal(1)).doubleValue, 1)
XCTAssertEqual(NSDecimalNumber(decimal:Decimal(-1)).doubleValue, -1)
XCTAssertTrue(NSDecimalNumber(decimal:Decimal.nan).doubleValue.isNaN)
XCTAssertEqual(NSDecimalNumber(decimal:Decimal(UInt64.max)).doubleValue, Double(1.8446744073709552e+19))
XCTAssertEqual(NSDecimalNumber(decimal:Decimal(string: "1234567890123456789012345678901234567890")!).doubleValue, Double(1.2345678901234568e+39))

var d = Decimal()
d._mantissa.0 = 1
d._mantissa.1 = 2
d._mantissa.2 = 3
d._mantissa.3 = 4
d._mantissa.4 = 5
d._mantissa.5 = 6
d._mantissa.6 = 7
d._mantissa.7 = 8

XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 0)
XCTAssertEqual(d, Decimal(0))

d._length = 1
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 1)
XCTAssertEqual(d, Decimal(1))

d._length = 2
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 131073)
XCTAssertEqual(d, Decimal(131073))

d._length = 3
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 12885032961)
XCTAssertEqual(d, Decimal(12885032961))

d._length = 4
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 1125912791875585)
XCTAssertEqual(d, Decimal(1125912791875585))

d._length = 5
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 9.223484628133963e+19)
XCTAssertEqual(d, Decimal(string: "92234846281339633665")!)

d._length = 6
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 7.253647152534056e+24)
XCTAssertEqual(d, Decimal(string: "7253647152534056387870721")!)

d._length = 7
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 5.546043912470029e+29)
XCTAssertEqual(d, Decimal(string: "554604391247002897211195523073")!)

d._length = 8
XCTAssertEqual(NSDecimalNumber(decimal: d).doubleValue, 4.153892947266987e+34)
XCTAssertEqual(d, Decimal(string: "41538929472669868031141181829283841")!)

// The result of the subtractions can leave values in the internal mantissa of a and b,
// although _length = 0 which is correct.
let x = Decimal(10.5)
let y = Decimal(9.0)
let z = Decimal(1.5)
let a = x - y - z
let b = x - z - y

XCTAssertEqual(x.description, "10.5")
XCTAssertEqual(y.description, "9")
XCTAssertEqual(z.description, "1.5")
XCTAssertEqual(a.description, "0")
XCTAssertEqual(b.description, "0")
XCTAssertEqual(NSDecimalNumber(decimal: x).doubleValue, 10.5)
XCTAssertEqual(NSDecimalNumber(decimal: y).doubleValue, 9.0)
XCTAssertEqual(NSDecimalNumber(decimal: z).doubleValue, 1.5)
XCTAssertEqual(NSDecimalNumber(decimal: a).doubleValue, 0.0)
XCTAssertEqual(NSDecimalNumber(decimal: b).doubleValue, 0.0)

let nf = NumberFormatter()
nf.locale = Locale(identifier: "en_US")
nf.numberStyle = .decimal
nf.minimumFractionDigits = 2
nf.maximumFractionDigits = 2

XCTAssertEqual(nf.string(from: NSDecimalNumber(decimal: x)), "10.50")
XCTAssertEqual(nf.string(from: NSDecimalNumber(decimal: y)), "9.00")
XCTAssertEqual(nf.string(from: NSDecimalNumber(decimal: z)), "1.50")
XCTAssertEqual(nf.string(from: NSDecimalNumber(decimal: a)), "0.00")
XCTAssertEqual(nf.string(from: NSDecimalNumber(decimal: b)), "0.00")
}
}