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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
// This file is for internal use of Foundation
/// A class type which acts as a handle (pointer-to-pointer) to a Foundation reference type which has only a mutable class (e.g., NSURLComponents).
///
/// Note: This assumes that the result of calling copy() is mutable. The documentation says that classes which do not have a mutable/immutable distinction should just adopt NSCopying instead of NSMutableCopying.
///
/// `Sendable` Note: A `_MutableHandle` can be considered safely `Sendable` if and only if the following conditions of the `_MutableBoxing`-conforming type are met:
/// - All calls within `mapWithoutMutation` calls are read-only, and are safe to execute concurrently across multiple actors
/// - The passed pointer to the `MutableType` does not escape any `mapWithoutMutation`/`_applyMutation` blocks
/// - Any and all mutations of the held mutable type are only performed in an `_applyMutation` block
/// If both of those conditions are met and verified, the Copy on Write protections will make the `_MutableHandle` safely `Sendable` (the `_MutableBoxing`-conforming type can be marked `Sendable` if these
/// conditions are met and the type is otherwise `Sendable`)
internal final class _MutableHandle<MutableType : NSObject> : @unchecked Sendable where MutableType : NSCopying {
@usableFromInline internal var _pointer : MutableType
init(reference : MutableType) {
_pointer = reference.copy() as! MutableType
}
init(adoptingReference reference: MutableType) {
_pointer = reference
}
/// Apply a closure to the reference type.
func map<ReturnType>(_ whatToDo : (MutableType) throws -> ReturnType) rethrows -> ReturnType {
return try whatToDo(_pointer)
}
func _copiedReference() -> MutableType {
return _pointer.copy() as! MutableType
}
func _uncopiedReference() -> MutableType {
return _pointer
}
}
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