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Fix the new Swift NSMutableArray subclass to match edge case behavior in two more cases #27504

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Merged
merged 1 commit into from
Oct 3, 2019
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Fix the new Swift NSMutableArray subclass to match edge case behavior in two more cases #27504

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10 changes: 8 additions & 2 deletions stdlib/public/core/SwiftNativeNSArray.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -254,7 +254,7 @@ extension __SwiftNativeNSArrayWithContiguousStorage: _NSArrayCore {

@objc(exchangeObjectAtIndex:withObjectAtIndex:)
dynamic internal func exchange(at index: Int, with index2: Int) {
swap(&contents[index], &contents[index2])
contents.swapAt(index, index2)
}

@objc(replaceObjectsInRange:withObjects:count:)
Expand All @@ -263,7 +263,13 @@ extension __SwiftNativeNSArrayWithContiguousStorage: _NSArrayCore {
count: Int) {
let range = range.location ..< range.location + range.length
let buf = UnsafeBufferPointer(start: objects, count: count)
contents.replaceSubrange(range, with: buf)
if range == contents.startIndex..<contents.endIndex {
contents = Array(buf)
} else {
// We make an Array here to make sure that something is holding onto the
// objects in `buf`, since replaceSubrange could release them
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Oof. Optimize later to check, I guess?

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If it looks relevant in practice, sure

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You're performing an extra copy this way, at least formally.

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(which is the point, of course)

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Right, but that just brings us down to NSMutableArray's speed, in theory. Anything better here would be a win on top of that which (probably) makes it nice to have rather than necessary.

contents.replaceSubrange(range, with: Array(buf))
}
}

@objc(insertObjects:count:atIndex:)
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