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[stdlib] fast path for UMBP.initialize<C>(from: C) when C is a Slice #38677

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Merged
merged 5 commits into from
Aug 3, 2021
Merged

[stdlib] fast path for UMBP.initialize<C>(from: C) when C is a Slice #38677

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23bed31
[test] test UnsafeMutableBufferPointer.initialize(from: Slice<_>)
glessard Jul 28, 2021
a9e0af4
[stdlib] make Sequence's _copyContents call into a non-protocol function
glessard Jul 28, 2021
2bc053f
[stdlib] implement _copyContents for Slice
glessard Jul 28, 2021
f6f36fa
[stdlib] simplify indexing
glessard Aug 2, 2021
3302750
[stdlib] avoid ABI impact
glessard Aug 2, 2021
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7 changes: 7 additions & 0 deletions stdlib/public/core/Sequence.swift
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Expand Up @@ -1140,6 +1140,13 @@ extension Sequence {
@inlinable
public __consuming func _copyContents(
initializing buffer: UnsafeMutableBufferPointer<Element>
) -> (Iterator,UnsafeMutableBufferPointer<Element>.Index) {
return _copySequenceContents(initializing: buffer)
}

@inlinable
internal __consuming func _copySequenceContents(
initializing buffer: UnsafeMutableBufferPointer<Element>
) -> (Iterator,UnsafeMutableBufferPointer<Element>.Index) {
var it = self.makeIterator()
guard var ptr = buffer.baseAddress else { return (it,buffer.startIndex) }
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17 changes: 17 additions & 0 deletions stdlib/public/core/Slice.swift
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Expand Up @@ -229,6 +229,23 @@ extension Slice: Collection {
}
}

extension Slice {
@inlinable
public __consuming func _copyContents(
initializing buffer: UnsafeMutableBufferPointer<Element>
) -> (Iterator, UnsafeMutableBufferPointer<Element>.Index) {
if let (_, copied) = self.withContiguousStorageIfAvailable({
$0._copyContents(initializing: buffer)
}) {
let distance = buffer.distance(from: buffer.startIndex, to: copied)
let i = index(startIndex, offsetBy: distance)
return (Iterator(_elements: self, _position: i), copied)
}

return _copySequenceContents(initializing: buffer)
}
}

extension Slice: BidirectionalCollection where Base: BidirectionalCollection {
@inlinable // generic-performance
public func index(before i: Index) -> Index {
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16 changes: 16 additions & 0 deletions validation-test/stdlib/UnsafeBufferPointer.swift.gyb
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Expand Up @@ -361,6 +361,22 @@ UnsafeMutableBufferPointerTestSuite.test("withContiguous(Mutable)StorageIfAvaila
expectEqual(result1, result2)
}

UnsafeMutableBufferPointerTestSuite.test("initialize(from: Slice)") {
let o = 91
let c = 1_000
let a = Slice(base: Array(0..<c), bounds: o..<c)

let buffer = UnsafeMutableBufferPointer<Int>.allocate(capacity: c-o)
defer { buffer.deallocate() }

var (iterator, copied) = buffer.initialize(from: a)
expectEqual(iterator.next(), nil)
expectEqual(copied, c-o)

let t = buffer.indices.randomElement()!
expectEqual(a[t+o], buffer[t])
}

UnsafeMutableBufferPointerTestSuite.test("Slice.withContiguousStorageIfAvailable") {
guard #available(macOS 10.16, iOS 14.0, watchOS 7.0, tvOS 14.0, *) else {
return
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