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[Foundation] Data: Hash the entire contents, not just an arbitrary subset #23876

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[Foundation] Data: Hash the entire contents, not just an arbitrary subset #23876

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10 changes: 4 additions & 6 deletions stdlib/public/Darwin/Foundation/Data.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1046,9 +1046,8 @@ public struct Data : ReferenceConvertible, Equatable, Hashable, RandomAccessColl
func hash(into hasher: inout Hasher) {
hasher.combine(count)

// At most, hash the first 80 bytes of this data.
let range = startIndex ..< Swift.min(startIndex + 80, endIndex)
storage.withUnsafeBytes(in: range) {
// To ensure strong hashing, all bytes must be fed into the hasher.
withUnsafeBytes {
hasher.combine(bytes: $0)
}
}
Expand Down Expand Up @@ -1250,9 +1249,8 @@ public struct Data : ReferenceConvertible, Equatable, Hashable, RandomAccessColl
func hash(into hasher: inout Hasher) {
hasher.combine(count)

// Hash at most the first 80 bytes of this data.
let range = startIndex ..< Swift.min(startIndex + 80, endIndex)
storage.withUnsafeBytes(in: range) {
// To ensure strong hashing, all bytes must be fed into the hasher.
withUnsafeBytes {
hasher.combine(bytes: $0)
}
}
Expand Down
71 changes: 60 additions & 11 deletions test/stdlib/TestData.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -974,6 +974,59 @@ class TestData : TestDataSuper {
expectTrue(d.classForKeyedArchiver == expected)
}

func test_Hashing() {
func bridgedData(_ bytes: [UInt8]) -> Data {
return bytes.withUnsafeBytes { buffer in
NSData(bytes: buffer.baseAddress, length: buffer.count) as Data
}
}

let simpleTests: [[Data]] = [
[
Data(),
bridgedData([]),
],
[
Data([1]),
bridgedData([1]),
],
[
Data([1, 2]),
bridgedData([1, 2]),
],
[
Data([1, 2, 3]),
Data([1, 2, 3]),
bridgedData([1, 2, 3]),
bridgedData([1, 2, 3]),
],
[
Data([2, 1, 3]),
bridgedData([2, 1, 3]),
],
]
checkHashableGroups(simpleTests)

// To ensure strong hashing, all bytes must be fed into the hasher.
let longTest: [Data] = [
Data([1]) + Data(UInt8.min ... UInt8.max),
Data([2]) + Data(UInt8.min ... UInt8.max),
Data(UInt8.min ... UInt8.max) + Data([1]),
Data(UInt8.min ... UInt8.max) + Data([2]),
Data(UInt8.min ..< 128) + Data([1]) + Data(128 ... UInt8.max),
Data(UInt8.min ..< 128) + Data([2]) + Data(128 ... UInt8.max),
]
checkHashable(longTest, equalityOracle: { $0 == $1 })

let concatenationTest: [[Data]] = [
[Data([1, 2, 3]), Data()],
[Data([1, 2]), Data([3])],
[Data([1]), Data([2, 3])],
[Data(), Data([1, 2, 3])],
]
checkHashable(concatenationTest, equalityOracle: { $0 == $1 })
}

func test_AnyHashableContainingData() {
let values: [Data] = [
Data(base64Encoded: "AAAA")!,
Expand Down Expand Up @@ -3708,13 +3761,14 @@ class TestData : TestDataSuper {
let base2 = Data(bytes: [0, 0xFF, 0xFF, 0])
let base3 = Data(bytes: [0xFF, 0xFF, 0xFF, 0])
let sliceEmulation = Data(bytes: [0xFF, 0xFF])
expectEqual(base1.hashValue, base2.hashValue)
let slice1 = base1[base1.startIndex.advanced(by: 1)..<base1.endIndex.advanced(by: -1)]
let slice2 = base2[base2.startIndex.advanced(by: 1)..<base2.endIndex.advanced(by: -1)]
let slice3 = base3[base3.startIndex.advanced(by: 1)..<base3.endIndex.advanced(by: -1)]
expectEqual(slice1.hashValue, sliceEmulation.hashValue)
expectEqual(slice1.hashValue, slice2.hashValue)
expectEqual(slice2.hashValue, slice3.hashValue)
checkHashableGroups([
[base1, base2],
[base3],
[sliceEmulation, slice1, slice2, slice3],
])
}

func test_slice_resize_growth() {
Expand All @@ -3725,16 +3779,10 @@ class TestData : TestDataSuper {

func test_hashEmptyData() {
let d1 = Data()
let h1 = d1.hashValue

let d2 = NSData() as Data
let h2 = d2.hashValue
expectEqual(h1, h2)

let data = Data(bytes: [0, 1, 2, 3, 4, 5, 6])
let d3 = data[4..<4]
let h3 = d3.hashValue
expectEqual(h1, h3)
checkHashableGroups([[d1, d2, d3]])
}

func test_validateMutation_slice_withUnsafeMutableBytes_lengthLessThanLowerBound() {
Expand Down Expand Up @@ -3847,6 +3895,7 @@ DataTests.test("test_basicMutableDataMutation") { TestData().test_basicMutableDa
DataTests.test("test_passing") { TestData().test_passing() }
DataTests.test("test_bufferSizeCalculation") { TestData().test_bufferSizeCalculation() }
DataTests.test("test_classForCoder") { TestData().test_classForCoder() }
DataTests.test("test_Hashing") { TestData().test_Hashing() }
DataTests.test("test_AnyHashableContainingData") { TestData().test_AnyHashableContainingData() }
DataTests.test("test_AnyHashableCreatedFromNSData") { TestData().test_AnyHashableCreatedFromNSData() }
DataTests.test("test_noCopyBehavior") { TestData().test_noCopyBehavior() }
Expand Down