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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 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
//
//===----------------------------------------------------------------------===//
import Foundation
/// A thread safe container that contains a value of type `T`.
///
/// - Note: Unchecked sendable conformance because value is guarded by a lock.
package class ThreadSafeBox<T: Sendable>: @unchecked Sendable {
/// Lock guarding `_value`.
private let lock = NSLock()
private var _value: T
package var value: T {
get {
return lock.withLock {
return _value
}
}
set {
lock.withLock {
_value = newValue
}
}
_modify {
lock.lock()
defer { lock.unlock() }
yield &_value
}
}
package init(initialValue: T) {
_value = initialValue
}
package func withLock<Result>(_ body: (inout T) throws -> Result) rethrows -> Result {
return try lock.withLock {
return try body(&_value)
}
}
/// If the value in the box is an optional, return it and reset it to `nil`
/// in an atomic operation.
package func takeValue<U>() -> T where U? == T {
lock.withLock {
guard let value = self._value else { return nil }
self._value = nil
return value
}
}
}
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