79 lines
3.4 KiB
Swift
79 lines
3.4 KiB
Swift
//
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// Copyright 2024 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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//
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import notify
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/// Wrapper around notify to provide more ergonomic support to swift for cross-process notification
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/// handling.
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///
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/// > Note: The original ObjC implementation of this code did not check the status result codes
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/// > from the `notify_*` functions so we have kept that same behavior here. It may be advisable
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/// > to change these to throwing at some point in the future and throw an error if the result code
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/// > is not `NOTIFY_STATUS_OK`.
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public enum DarwinNotificationCenter {
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public typealias ObserverToken = Int32
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public static let invalidObserverToken: ObserverToken = NOTIFY_TOKEN_INVALID
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/// Determines if an observer token is valid for a current registration.
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/// Negative integers are never valid. A positive or zero value is valid
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/// if the current process has a registration associated with the given value.
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///
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/// - Parameter observer: The token returned by ``addObserver(name:queue:block:)``
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/// - Returns: `true` iff the given `observer` is valid
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public static func isValid(_ observer: ObserverToken) -> Bool {
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return notify_is_valid_token(observer)
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}
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/// Post a darwin notification that can be listened for from other processes.
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///
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/// - Parameter name: The name of the notification to post.
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public static func postNotification(name: DarwinNotificationName) {
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_ = notify_post(name.rawValue)
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}
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/// Add an observer for a darwin notification of the given name.
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///
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/// - Parameter name: The name of the notification to listen for.
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/// - Parameter queue: The queue to call back on.
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/// - Parameter block: The block to call back. Includes the observer token as an input parameter to allow
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/// removing the observer after receipt.
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/// - Returns: An ``ObserverToken`` that can be used to remove this observer.
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public static func addObserver(name: DarwinNotificationName, queue: DispatchQueue, block: @escaping (ObserverToken) -> Void) -> ObserverToken {
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var observer = Self.invalidObserverToken
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_ = notify_register_dispatch(name.rawValue, &observer, queue, block)
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return observer
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}
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/// Stops listening for notifications registered by the given observer token.
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///
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/// - Parameter observer: The token returned by ``addObserver(name:queue:block:)`` for the notification you want to stop listening
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/// for.
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public static func removeObserver(_ observer: ObserverToken) {
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guard isValid(observer) else {
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owsFailDebug("Invalid observer token.")
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return
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}
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_ = notify_cancel(observer)
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}
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/// Retrieves the state for a given observer. This value can be set and read from
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/// any process listening for this notification. Note: ``setState(_:observer:)`` and ``getState(observer:)``
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/// are vulnerable to races.
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///
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/// - Parameter observer: The token returned by ``addObserver(name:queue:block:)`` for the notification you want to get state for.
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/// - Returns: The state fetched from the observer.
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public static func getState(observer: ObserverToken) -> UInt64 {
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guard isValid(observer) else {
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owsFailDebug("Invalid observer token.")
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return 0
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}
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var result: UInt64 = 0
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_ = notify_get_state(observer, &result)
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return result
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}
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}
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