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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift open source project
//
// Copyright (c) 2020-2023 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
//
//===----------------------------------------------------------------------===//
import class Foundation.NSLock
/// Thread-safe value boxing structure
@dynamicMemberLookup
public final class ThreadSafeBox<Value> {
private var underlying: Value?
private let lock = NSLock()
public init() {}
public init(_ seed: Value) {
self.underlying = seed
}
public func mutate(body: (Value?) throws -> Value?) rethrows {
try self.lock.withLock {
let value = try body(self.underlying)
self.underlying = value
}
}
@discardableResult
public func memoize(body: () throws -> Value) rethrows -> Value {
if let value = self.get() {
return value
}
let value = try body()
self.lock.withLock {
self.underlying = value
}
return value
}
public func clear() {
self.lock.withLock {
self.underlying = nil
}
}
public func get() -> Value? {
self.lock.withLock {
self.underlying
}
}
public func get(default: Value) -> Value {
self.lock.withLock {
self.underlying ?? `default`
}
}
public func put(_ newValue: Value) {
self.lock.withLock {
self.underlying = newValue
}
}
public subscript<T>(dynamicMember keyPath: KeyPath<Value, T>) -> T? {
self.lock.withLock {
self.underlying?[keyPath: keyPath]
}
}
public subscript<T>(dynamicMember keyPath: WritableKeyPath<Value, T?>) -> T? {
get {
self.lock.withLock {
self.underlying?[keyPath: keyPath]
}
}
set {
self.lock.withLock {
if var value = self.underlying {
value[keyPath: keyPath] = newValue
}
}
}
}
}
extension ThreadSafeBox where Value == Int {
public func increment() {
self.lock.withLock {
if let value = self.underlying {
self.underlying = value + 1
}
}
}
public func decrement() {
self.lock.withLock {
if let value = self.underlying {
self.underlying = value - 1
}
}
}
}
extension ThreadSafeBox where Value == String {
public func append(_ value: String) {
self.mutate { existingValue in
if let existingValue {
return existingValue + value
} else {
return value
}
}
}
}
extension ThreadSafeBox: @unchecked Sendable where Value: Sendable {}
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