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03dd527414
Previously the implementation of NSFastEnumerationIterator would cause many allocations and was overly complex; leading to poor performance in certain cases like DirectoryEnumerator etc. This version instead acts more similarly to how the objc for-in syntax works. Resolves: rdar://problem/30905263 and partially addresses some of the concerns backing: rdar://problem/30195113
93 lines
4.4 KiB
Swift
93 lines
4.4 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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@_exported import Foundation // Clang module
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//===----------------------------------------------------------------------===//
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// Fast enumeration
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//===----------------------------------------------------------------------===//
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public struct NSFastEnumerationIterator : IteratorProtocol {
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var enumerable: NSFastEnumeration
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var objects: (Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?, Unmanaged<AnyObject>?) = (nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
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var state = NSFastEnumerationState(state: 0, itemsPtr: nil, mutationsPtr: _fastEnumerationStorageMutationsPtr, extra: (0, 0, 0, 0, 0))
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var index = 0
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var count = 0
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var useObjectsBuffer = false
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public init(_ enumerable: NSFastEnumeration) {
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self.enumerable = enumerable
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}
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public mutating func next() -> Any? {
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if index + 1 > count {
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index = 0
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// ensure NO ivars of self are actually captured
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let enumeratedObject = enumerable
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var localState = state
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var localObjects = objects
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(count, useObjectsBuffer) = withUnsafeMutablePointer(to: &localObjects) {
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let buffer = AutoreleasingUnsafeMutablePointer<AnyObject?>($0)
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return withUnsafeMutablePointer(to: &localState) { (statePtr: UnsafeMutablePointer<NSFastEnumerationState>) -> (Int, Bool) in
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let result = enumeratedObject.countByEnumerating(with: statePtr, objects: buffer, count: 16)
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if statePtr.pointee.itemsPtr == buffer {
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// Most cocoa classes will emit their own inner pointer buffers instead of traversing this path. Notable exceptions include NSDictionary and NSSet
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return (result, true)
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} else {
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// this is the common case for things like NSArray
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return (result, false)
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}
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}
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}
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state = localState // restore the state value
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objects = localObjects // copy the object pointers back to the self storage
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if count == 0 { return nil }
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}
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defer { index += 1 }
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if !useObjectsBuffer {
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return state.itemsPtr![index]
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} else {
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switch index {
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case 0: return objects.0!.takeUnretainedValue()
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case 1: return objects.1!.takeUnretainedValue()
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case 2: return objects.2!.takeUnretainedValue()
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case 3: return objects.3!.takeUnretainedValue()
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case 4: return objects.4!.takeUnretainedValue()
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case 5: return objects.5!.takeUnretainedValue()
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case 6: return objects.6!.takeUnretainedValue()
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case 7: return objects.7!.takeUnretainedValue()
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case 8: return objects.8!.takeUnretainedValue()
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case 9: return objects.9!.takeUnretainedValue()
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case 10: return objects.10!.takeUnretainedValue()
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case 11: return objects.11!.takeUnretainedValue()
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case 12: return objects.12!.takeUnretainedValue()
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case 13: return objects.13!.takeUnretainedValue()
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case 14: return objects.14!.takeUnretainedValue()
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case 15: return objects.15!.takeUnretainedValue()
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default: fatalError("Access beyond storage buffer")
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}
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}
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}
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}
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extension NSEnumerator : Sequence {
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/// Return an *iterator* over the *enumerator*.
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///
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/// - Complexity: O(1).
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public func makeIterator() -> NSFastEnumerationIterator {
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return NSFastEnumerationIterator(self)
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}
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}
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