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