swift-mirror/stdlib/public/SDK/Foundation/NSDictionary.swift

//===----------------------------------------------------------------------===//
//
// 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
import _SwiftFoundationOverlayShims

//===----------------------------------------------------------------------===//
// Dictionaries
//===----------------------------------------------------------------------===//

extension NSDictionary : ExpressibleByDictionaryLiteral {
  public required convenience init(
    dictionaryLiteral elements: (Any, Any)...
  ) {
    // FIXME: Unfortunate that the `NSCopying` check has to be done at runtime.
    self.init(
      objects: elements.map { $0.1 as AnyObject },
      forKeys: elements.map { $0.0 as AnyObject as! NSCopying },
      count: elements.count)
  }
}

extension Dictionary {
  /// Private initializer used for bridging.
  ///
  /// The provided `NSDictionary` will be copied to ensure that the copy can
  /// not be mutated by other code.
  public init(_cocoaDictionary: _NSDictionary) {
    _sanityCheck(
      _isBridgedVerbatimToObjectiveC(Key.self) &&
      _isBridgedVerbatimToObjectiveC(Value.self),
      "Dictionary can be backed by NSDictionary storage only when both key and value are bridged verbatim to Objective-C")
    // FIXME: We would like to call CFDictionaryCreateCopy() to avoid doing an
    // objc_msgSend() for instances of CoreFoundation types.  We can't do that
    // today because CFDictionaryCreateCopy() copies dictionary contents
    // unconditionally, resulting in O(n) copies even for immutable dictionaries.
    //
    // <rdar://problem/20690755> CFDictionaryCreateCopy() does not call copyWithZone:
    //
    // The bug is fixed in: OS X 10.11.0, iOS 9.0, all versions of tvOS
    // and watchOS.
    self = Dictionary(
      _immutableCocoaDictionary:
        unsafeBitCast(_cocoaDictionary.copy(with: nil) as AnyObject,
                      to: _NSDictionary.self))
  }
}

// Dictionary<Key, Value> is conditionally bridged to NSDictionary
extension Dictionary : _ObjectiveCBridgeable {
  @_semantics("convertToObjectiveC")
  public func _bridgeToObjectiveC() -> NSDictionary {
    return unsafeBitCast(_bridgeToObjectiveCImpl() as AnyObject,
                         to: NSDictionary.self)
  }

  public static func _forceBridgeFromObjectiveC(
    _ d: NSDictionary,
    result: inout Dictionary?
  ) {
    if let native = [Key : Value]._bridgeFromObjectiveCAdoptingNativeStorageOf(
        d as AnyObject) {
      result = native
      return
    }

    if _isBridgedVerbatimToObjectiveC(Key.self) &&
       _isBridgedVerbatimToObjectiveC(Value.self) {
      result = [Key : Value](
        _cocoaDictionary: unsafeBitCast(d as AnyObject, to: _NSDictionary.self))
      return
    }

    if Key.self == String.self {
      // String and NSString have different concepts of equality, so
      // string-keyed NSDictionaries may generate key collisions when bridged
      // over to Swift. See rdar://problem/35995647
      var dict = Dictionary(minimumCapacity: d.count)
      d.enumerateKeysAndObjects({ (anyKey: Any, anyValue: Any, _) in
        let key = Swift._forceBridgeFromObjectiveC(
          anyKey as AnyObject, Key.self)
        let value = Swift._forceBridgeFromObjectiveC(
          anyValue as AnyObject, Value.self)
        // FIXME: Log a warning if `dict` already had a value for `key`
        dict[key] = value
      })
      result = dict
      return
    }

    // `Dictionary<Key, Value>` where either `Key` or `Value` is a value type
    // may not be backed by an NSDictionary.
    var builder = _DictionaryBuilder<Key, Value>(count: d.count)
    d.enumerateKeysAndObjects({ (anyKey: Any, anyValue: Any, _) in
      let anyObjectKey = anyKey as AnyObject
      let anyObjectValue = anyValue as AnyObject
      builder.add(
          key: Swift._forceBridgeFromObjectiveC(anyObjectKey, Key.self),
          value: Swift._forceBridgeFromObjectiveC(anyObjectValue, Value.self))
    })
    result = builder.take()
  }

  public static func _conditionallyBridgeFromObjectiveC(
    _ x: NSDictionary,
    result: inout Dictionary?
  ) -> Bool {
    let anyDict = x as [NSObject : AnyObject]
    if _isBridgedVerbatimToObjectiveC(Key.self) &&
       _isBridgedVerbatimToObjectiveC(Value.self) {
      result = Swift._dictionaryDownCastConditional(anyDict)
      return result != nil
    }

    result = Swift._dictionaryBridgeFromObjectiveCConditional(anyDict)
    return result != nil
  }

  public static func _unconditionallyBridgeFromObjectiveC(
    _ d: NSDictionary?
  ) -> Dictionary {
    // `nil` has historically been used as a stand-in for an empty
    // dictionary; map it to an empty dictionary.
    if _slowPath(d == nil) { return Dictionary() }

    var result: Dictionary? = nil
    _forceBridgeFromObjectiveC(d!, result: &result)
    return result!
  }
}

extension NSDictionary : _HasCustomAnyHashableRepresentation {
  // Must be @nonobjc to avoid infinite recursion during bridging
  @nonobjc
  public func _toCustomAnyHashable() -> AnyHashable? {
    return AnyHashable(self as! Dictionary<AnyHashable, AnyHashable>)
  }
}

extension NSDictionary : Sequence {
  // FIXME: A class because we can't pass a struct with class fields through an
  // [objc] interface without prematurely destroying the references.
  final public class Iterator : IteratorProtocol {
    var _fastIterator: NSFastEnumerationIterator
    var _dictionary: NSDictionary {
      return _fastIterator.enumerable as! NSDictionary
    }

    public func next() -> (key: Any, value: Any)? {
      if let key = _fastIterator.next() {
        // Deliberately avoid the subscript operator in case the dictionary
        // contains non-copyable keys. This is rare since NSMutableDictionary
        // requires them, but we don't want to paint ourselves into a corner.
        return (key: key, value: _dictionary.object(forKey: key)!)
      }
      return nil
    }

    internal init(_ _dict: NSDictionary) {
      _fastIterator = NSFastEnumerationIterator(_dict)
    }
  }

  // Bridging subscript.
  @objc
  public subscript(key: Any) -> Any? {
    @objc(_swift_objectForKeyedSubscript:)
    get {
      // Deliberately avoid the subscript operator in case the dictionary
      // contains non-copyable keys. This is rare since NSMutableDictionary
      // requires them, but we don't want to paint ourselves into a corner.
      return self.object(forKey: key)
    }
  }

  /// Return an *iterator* over the elements of this *sequence*.
  ///
  /// - Complexity: O(1).
  public func makeIterator() -> Iterator {
    return Iterator(self)
  }
}

extension NSMutableDictionary {
  // Bridging subscript.
  override public subscript(key: Any) -> Any? {
    get {
      return self.object(forKey: key)
    }
    @objc(_swift_setObject:forKeyedSubscript:)
    set {
      // FIXME: Unfortunate that the `NSCopying` check has to be done at
      // runtime.
      let copyingKey = key as AnyObject as! NSCopying
      if let newValue = newValue {
        self.setObject(newValue, forKey: copyingKey)
      } else {
        self.removeObject(forKey: copyingKey)
      }
    }
  }
}

extension NSDictionary {
  /// Initializes a newly allocated dictionary and adds to it objects from
  /// another given dictionary.
  ///
  /// - Returns: An initialized dictionary--which might be different
  ///   than the original receiver--containing the keys and values
  ///   found in `otherDictionary`.
  @objc(_swiftInitWithDictionary_NSDictionary:)
  public convenience init(dictionary otherDictionary: NSDictionary) {
    // FIXME(performance)(compiler limitation): we actually want to do just
    // `self = otherDictionary.copy()`, but Swift does not have factory
    // initializers right now.
    let numElems = otherDictionary.count
    let stride = MemoryLayout<AnyObject>.stride
    let alignment = MemoryLayout<AnyObject>.alignment
    let singleSize = stride * numElems
    let totalSize = singleSize * 2
    _sanityCheck(stride == MemoryLayout<NSCopying>.stride)
    _sanityCheck(alignment == MemoryLayout<NSCopying>.alignment)

    // Allocate a buffer containing both the keys and values.
    let buffer = UnsafeMutableRawPointer.allocate(
      byteCount: totalSize, alignment: alignment)
    defer {
      buffer.deallocate()
      _fixLifetime(otherDictionary)
    }

    let valueBuffer = buffer.bindMemory(to: AnyObject.self, capacity: numElems)
    let buffer2 = buffer + singleSize

    __NSDictionaryGetObjects(otherDictionary, buffer, buffer2, numElems)

    let keyBufferCopying = buffer2.assumingMemoryBound(to: NSCopying.self)
    self.init(objects: valueBuffer, forKeys: keyBufferCopying, count: numElems)
  }
}

extension NSDictionary : CustomReflectable {
  public var customMirror: Mirror {
    return Mirror(reflecting: self as [NSObject : AnyObject])
  }
}

extension Dictionary: CVarArg {}