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[stdlib] Span gardening #77688

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Merged
merged 4 commits into from
Nov 19, 2024
Merged

[stdlib] Span gardening #77688

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2b916a1
[gardening] improves some comments in Span and RawSpan
glessard Nov 18, 2024
9073576
[span] formulate `Span.withUnsafeBytes()` better
glessard Nov 18, 2024
9936393
[span] temporarily add a feature guard
glessard Nov 18, 2024
9084af1
[span] remove the `_elementsEqual()` functions
glessard Nov 18, 2024
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3 changes: 1 addition & 2 deletions stdlib/public/core/Span/RawSpan.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -426,7 +426,6 @@ extension RawSpan {
@available(SwiftStdlib 6.1, *)
extension RawSpan {

//FIXME: mark closure parameter as non-escaping
/// Calls the given closure with a pointer to the underlying bytes of
/// the viewed contiguous storage.
///
Expand Down Expand Up @@ -633,7 +632,7 @@ extension RawSpan {
}
}

//MARK: one-sided slicing operations
//MARK: prefixes and suffixes
@_disallowFeatureSuppression(NonescapableTypes)
@available(SwiftStdlib 6.1, *)
extension RawSpan {
Expand Down
91 changes: 7 additions & 84 deletions stdlib/public/core/Span/Span.swift
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Expand Up @@ -95,7 +95,8 @@ extension Span where Element: ~Copyable {
public init(
_unsafeElements buffer: borrowing UnsafeBufferPointer<Element>
) {
let baseAddress = buffer.baseAddress //FIXME: rdar://138665760
//FIXME: Workaround for https://github.com/swiftlang/swift/issues/77235
let baseAddress = buffer.baseAddress
_precondition(
((Int(bitPattern: baseAddress) &
(MemoryLayout<Element>.alignment &- 1)) == 0),
Expand Down Expand Up @@ -204,7 +205,8 @@ extension Span where Element: BitwiseCopyable {
public init(
_unsafeBytes buffer: borrowing UnsafeRawBufferPointer
) {
let baseAddress = buffer.baseAddress //FIXME: rdar://138665760
//FIXME: Workaround for https://github.com/swiftlang/swift/issues/77235
let baseAddress = buffer.baseAddress
_precondition(
((Int(bitPattern: baseAddress) &
(MemoryLayout<Element>.alignment &- 1)) == 0),
Expand Down Expand Up @@ -321,87 +323,6 @@ extension Span where Element: BitwiseCopyable {
}
}

@_disallowFeatureSuppression(NonescapableTypes)
@available(SwiftStdlib 6.1, *)
extension Span where Element: Equatable {

/// Returns a Boolean value indicating whether this and another span
/// contain equal elements in the same order.
///
/// - Parameters:
/// - other: A span to compare to this one.
/// - Returns: `true` if this sequence and `other` contain equivalent items,
/// using `areEquivalent` as the equivalence test; otherwise, `false.`
///
/// - Complexity: O(*m*), where *m* is the lesser of the length of the
/// sequence and the length of `other`.
@_disallowFeatureSuppression(NonescapableTypes)
@_alwaysEmitIntoClient
public func _elementsEqual(_ other: Self) -> Bool {
guard count == other.count else { return false }
if count == 0 { return true }

// This could be short-cut with a layout constraint
// where stride equals size, as long as there is
// at most 1 unused bit pattern, e.g.:
// if Element is BitwiseEquatable {
// return _swift_stdlib_memcmp(lhs.baseAddress, rhs.baseAddress, count) == 0
// }
if _pointer != other._pointer {
for o in 0..<count {
if self[unchecked: o] != other[unchecked: o] { return false }
}
}
return true
}

/// Returns a Boolean value indicating whether this span and a Collection
/// contain equal elements in the same order.
///
/// - Parameters:
/// - other: A Collection to compare to this span.
/// - Returns: `true` if this sequence and `other` contain equivalent items,
/// using `areEquivalent` as the equivalence test; otherwise, `false.`
///
/// - Complexity: O(*m*), where *m* is the lesser of the length of the
/// sequence and the length of `other`.
@_disallowFeatureSuppression(NonescapableTypes)
@_alwaysEmitIntoClient
public func _elementsEqual(_ other: some Collection<Element>) -> Bool {
let equal = other.withContiguousStorageIfAvailable {
_elementsEqual(Span(_unsafeElements: $0))
}
if let equal { return equal }

guard count == other.count else { return false }
if count == 0 { return true }

return _elementsEqual(AnySequence(other))
}

/// Returns a Boolean value indicating whether this span and a Sequence
/// contain equal elements in the same order.
///
/// - Parameters:
/// - other: A Sequence to compare to this span.
/// - Returns: `true` if this sequence and `other` contain equivalent items,
/// using `areEquivalent` as the equivalence test; otherwise, `false.`
///
/// - Complexity: O(*m*), where *m* is the lesser of the length of the
/// sequence and the length of `other`.
@_disallowFeatureSuppression(NonescapableTypes)
@_alwaysEmitIntoClient
public func _elementsEqual(_ other: some Sequence<Element>) -> Bool {
var offset = 0
for otherElement in other {
if offset >= count { return false }
if self[unchecked: offset] != otherElement { return false }
offset += 1
}
return offset == count
}
}

@_disallowFeatureSuppression(NonescapableTypes)
@available(SwiftStdlib 6.1, *)
extension Span where Element: ~Copyable {
Expand Down Expand Up @@ -701,7 +622,9 @@ extension Span where Element: BitwiseCopyable {
public func withUnsafeBytes<E: Error, Result: ~Copyable>(
_ body: (_ buffer: UnsafeRawBufferPointer) throws(E) -> Result
) throws(E) -> Result {
try RawSpan(_elements: self).withUnsafeBytes(body)
try body(
.init(start: _pointer, count: _count * MemoryLayout<Element>.stride)
)
}
}

Expand Down