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Merged
merged 1 commit into from
Oct 2, 2025
Merged

Merge release/6.2 into main #1531

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24 changes: 20 additions & 4 deletions Sources/FoundationEssentials/Data/Data.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -2255,11 +2255,19 @@ public struct Data : Equatable, Hashable, RandomAccessCollection, MutableCollect
start: UnsafeMutableRawPointer(Builtin.addressOfBorrow(self)),
count: _representation.count
)
case .large(let slice):
case .large(var slice):
// Clear _representation during the unique check to avoid double counting the reference, and assign the mutated slice back to _representation afterwards
_representation = .empty
slice.ensureUniqueReference()
_representation = .large(slice)
buffer = unsafe UnsafeMutableRawBufferPointer(
start: slice.storage.mutableBytes?.advanced(by: slice.startIndex), count: slice.count
)
case .slice(let slice):
case .slice(var slice):
// Clear _representation during the unique check to avoid double counting the reference, and assign the mutated slice back to _representation afterwards
_representation = .empty
slice.ensureUniqueReference()
_representation = .slice(slice)
buffer = unsafe UnsafeMutableRawBufferPointer(
start: slice.storage.mutableBytes?.advanced(by: slice.startIndex), count: slice.count
)
Expand Down Expand Up @@ -2288,11 +2296,19 @@ public struct Data : Equatable, Hashable, RandomAccessCollection, MutableCollect
start: UnsafeMutableRawPointer(Builtin.addressOfBorrow(self)),
count: _representation.count
)
case .large(let slice):
case .large(var slice):
// Clear _representation during the unique check to avoid double counting the reference, and assign the mutated slice back to _representation afterwards
_representation = .empty
slice.ensureUniqueReference()
_representation = .large(slice)
buffer = unsafe UnsafeMutableRawBufferPointer(
start: slice.storage.mutableBytes?.advanced(by: slice.startIndex), count: slice.count
)
case .slice(let slice):
case .slice(var slice):
// Clear _representation during the unique check to avoid double counting the reference, and assign the mutated slice back to _representation afterwards
_representation = .empty
slice.ensureUniqueReference()
_representation = .slice(slice)
buffer = unsafe UnsafeMutableRawBufferPointer(
start: slice.storage.mutableBytes?.advanced(by: slice.startIndex), count: slice.count
)
Expand Down
129 changes: 101 additions & 28 deletions Tests/FoundationEssentialsTests/DataTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1439,6 +1439,50 @@ private final class DataTests {
#expect(data.count == 0)
}
}

@Test func validateMutation_cow_mutableBytes() {
var data = Data(count: 32)
holdReference(data) {
var bytes = data.mutableBytes
bytes.storeBytes(of: 1, toByteOffset: 0, as: UInt8.self)

#expect(data[0] == 1)
#expect(heldData?[0] == 0)
}

var data2 = Data(count: 32)
// Escape the pointer to compare after a mutation without dereferencing the pointer
let originalPointer = data2.withUnsafeBytes { $0.baseAddress }

var bytes = data2.mutableBytes
bytes.storeBytes(of: 1, toByteOffset: 0, as: UInt8.self)
#expect(data2[0] == 1)
data2.withUnsafeBytes {
#expect($0.baseAddress == originalPointer)
}
}

@Test func validateMutation_cow_mutableSpan() {
var data = Data(count: 32)
holdReference(data) {
var bytes = data.mutableSpan
bytes[0] = 1

#expect(data[0] == 1)
#expect(heldData?[0] == 0)
}

var data2 = Data(count: 32)
// Escape the pointer to compare after a mutation without dereferencing the pointer
let originalPointer = data2.withUnsafeBytes { $0.baseAddress }

var bytes = data2.mutableSpan
bytes[0] = 1
#expect(data2[0] == 1)
data2.withUnsafeBytes {
#expect($0.baseAddress == originalPointer)
}
}

@Test func sliceHash() {
let base1 = Data([0, 0xFF, 0xFF, 0])
Expand Down Expand Up @@ -2385,17 +2429,16 @@ extension DataTests {
// These tests require allocating an extremely large amount of data and are serialized to prevent the test runner from using all available memory at once
@Suite("Large Data Tests", .serialized)
struct LargeDataTests {
@Test
func largeSliceDataSpan() throws {
#if _pointerBitWidth(_64)
let count = Int(Int32.max)
let largeCount = Int(Int32.max)
#elseif _pointerBitWidth(_32)
let count = Int(Int16.max)
let largeCount = Int(Int16.max)
#else
#error("This test needs updating")
#endif

let source = Data(repeating: 0, count: count).dropFirst()
@Test
func largeSliceDataSpan() throws {
let source = Data(repeating: 0, count: largeCount).dropFirst()
#expect(source.startIndex != 0)
let span = source.span
let isEmpty = span.isEmpty
Expand All @@ -2404,20 +2447,11 @@ struct LargeDataTests {

@Test
func largeSliceDataMutableSpan() throws {
#if _pointerBitWidth(_64)
var count = Int(Int32.max)
#elseif _pointerBitWidth(_32)
var count = Int(Int16.max)
#else
#error("This test needs updating")
#endif

#if !canImport(Darwin) || FOUNDATION_FRAMEWORK
var source = Data(repeating: 0, count: count).dropFirst()
var source = Data(repeating: 0, count: largeCount).dropFirst()
#expect(source.startIndex != 0)
count = source.count
var span = source.mutableSpan
#expect(span.count == count)
#expect(span.count == largeCount - 1)
let i = try #require(span.indices.dropFirst().randomElement())
span[i] = .max
#expect(source[i] == 0)
Expand All @@ -2427,23 +2461,62 @@ struct LargeDataTests {

@Test
func largeSliceDataMutableRawSpan() throws {
#if _pointerBitWidth(_64)
var count = Int(Int32.max)
#elseif _pointerBitWidth(_32)
var count = Int(Int16.max)
#else
#error("This test needs updating")
#endif

var source = Data(repeating: 0, count: count).dropFirst()
var source = Data(repeating: 0, count: largeCount).dropFirst()
#expect(source.startIndex != 0)
count = source.count
var span = source.mutableBytes
let byteCount = span.byteCount
#expect(byteCount == count)
#expect(byteCount == largeCount - 1)
let i = try #require(span.byteOffsets.dropFirst().randomElement())
span.storeBytes(of: -1, toByteOffset: i, as: Int8.self)
#expect(source[i] == 0)
#expect(source[i+1] == .max)
}

@Test func validateMutation_cow_largeMutableBytes() {
// Avoid copying a large data on platforms with constrained memory limits
#if !canImport(Darwin) || os(macOS)
var data = Data(count: largeCount)
let heldData = data
var bytes = data.mutableBytes
bytes.storeBytes(of: 1, toByteOffset: 0, as: UInt8.self)

#expect(data[0] == 1)
#expect(heldData[0] == 0)
#endif

var data2 = Data(count: largeCount)
// Escape the pointer to compare after a mutation without dereferencing the pointer
let originalPointer = data2.withUnsafeBytes { $0.baseAddress }

var bytes2 = data2.mutableBytes
bytes2.storeBytes(of: 1, toByteOffset: 0, as: UInt8.self)
#expect(data2[0] == 1)
data2.withUnsafeBytes {
#expect($0.baseAddress == originalPointer)
}
}

@Test func validateMutation_cow_largeMutableSpan() {
// Avoid copying a large data on platforms with constrained memory limits
#if !canImport(Darwin) || os(macOS)
var data = Data(count: largeCount)
let heldData = data
var bytes = data.mutableSpan
bytes[0] = 1

#expect(data[0] == 1)
#expect(heldData[0] == 0)
#endif

var data2 = Data(count: largeCount)
// Escape the pointer to compare after a mutation without dereferencing the pointer
let originalPointer = data2.withUnsafeBytes { $0.baseAddress }

var bytes2 = data2.mutableSpan
bytes2[0] = 1
#expect(data2[0] == 1)
data2.withUnsafeBytes {
#expect($0.baseAddress == originalPointer)
}
}
}