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Backports the Swift 6 type Mutex<Value> to all Apple platforms that support OSAllocatedUnfairLock
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| // Backports the Swift 6 type Mutex<Value> to Swift 5 and all Darwin platforms via OSAllocatedUnfairLock. | |
| // Lightweight version of https://github.com/swhitty/swift-mutex | |
| // Feel free to use any part of this gist. | |
| // Note: ~Copyable are not supported | |
| #if compiler(>=6) | |
| @available(iOS, introduced: 16.0, deprecated: 18.0, message: "use Mutex from Synchronization module included with Swift 6") | |
| @available(macOS, introduced: 13.0, deprecated: 15.0, message: "use Mutex from Synchronization module included with Swift 6") | |
| public struct Mutex<Value>: @unchecked Sendable { | |
| let lock: OSAllocatedUnfairLock<Value> | |
| public init(_ initialValue: consuming sending Value) { | |
| self.lock = OSAllocatedUnfairLock(uncheckedState: initialValue) | |
| } | |
| public borrowing func withLock<Result, E: Error>( | |
| _ body: (inout sending Value) throws(E) -> sending Result | |
| ) throws(E) -> sending Result { | |
| do { | |
| return try lock.withLockUnchecked { value in | |
| nonisolated(unsafe) var copy = value | |
| defer { value = copy } | |
| return try Transferring(body(©)) | |
| }.value | |
| } catch let error as E { | |
| throw error | |
| } catch { | |
| preconditionFailure("cannot occur") | |
| } | |
| } | |
| public borrowing func withLockIfAvailable<Result, E>( | |
| _ body: (inout sending Value) throws(E) -> sending Result | |
| ) throws(E) -> sending Result? where E: Error { | |
| do { | |
| return try lock.withLockIfAvailableUnchecked { value in | |
| nonisolated(unsafe) var copy = value | |
| defer { value = copy } | |
| return try Transferring(body(©)) | |
| }?.value | |
| } catch let error as E { | |
| throw error | |
| } catch { | |
| preconditionFailure("cannot occur") | |
| } | |
| } | |
| } | |
| private struct Transferring<T> { | |
| nonisolated(unsafe) var value: T | |
| init(_ value: T) { | |
| self.value = value | |
| } | |
| } | |
| #else | |
| @available(macOS 13.0, iOS 16.0, *) | |
| public struct Mutex<Value>: @unchecked Sendable { | |
| let lock: OSAllocatedUnfairLock<Value> | |
| public init(_ initialValue: consuming Value) { | |
| self.lock = OSAllocatedUnfairLock(uncheckedState: initialValue) | |
| } | |
| public borrowing func withLock<Result>( | |
| _ body: (inout Value) throws -> Result | |
| ) rethrows -> Result { | |
| try lock.withLockUnchecked { | |
| return try body(&$0) | |
| } | |
| } | |
| public borrowing func withLockIfAvailable<Result>( | |
| _ body: (inout Value) throws -> Result | |
| ) rethrows -> Result? { | |
| try lock.withLockIfAvailableUnchecked { | |
| return try body(&$0) | |
| } | |
| } | |
| } | |
| #endif |
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