NSAutoreleasePool.swift

internal class NSAutoreleasePool {
    fileprivate static var _current = NSThreadSpecific<NSAutoreleasePool>()
    internal static var current: NSAutoreleasePool {
        return _current.get() {
            return NSAutoreleasePool()
        }
    }
    
    var depth: Int = 0
    var objects = [[AnyObject]]()
    
    fileprivate override init() { }
    
    fileprivate func push() {
        objects.append([AnyObject]())
        depth += 1
    }
    
    fileprivate func pop() {
        objects.removeLast()
        depth -= 1
    }
    
    func add(_ object: AnyObject) {
        objects[depth - 1].append(object)
    }
}

public func autoreleasepool(_ code: () -> ()) {
    NSAutoreleasePool.current.push()
    code()
    NSAutoreleasePool.current.pop()
}