44 lines
1.7 KiB
Objective-C
44 lines
1.7 KiB
Objective-C
//
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// Copyright (c) 2021 Open Whisper Systems. All rights reserved.
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//
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#import <Foundation/Foundation.h>
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NS_ASSUME_NONNULL_BEGIN
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/// An Objective-C wrapper around os_unfair_lock. This is a non-FIFO, priority preserving lock. See: os/lock.h
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///
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/// @discussion Why is this necessary? os_unfair_lock has some unexpected behavior in Swift. These problems arise
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/// from Swift's handling of inout C structs. Passing the underlying struct as an inout parameter results in
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/// surprising Law of Exclusivity violations. There are two ways to work around this: Manually allocate heap storage
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/// in Swift or bridge to Objective-C. I figured bridging a simple struct is a bit easier to read.
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///
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/// Note: Errors with unfair lock are fatal and will terminate the process.
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NS_SWIFT_NAME(UnfairLock)
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@interface UnfairLock : NSObject <NSLocking>
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/// Locks the lock. Blocks if the lock is held by another thread.
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/// Forwards to os_unfair_lock_lock() defined in os/lock.h
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- (void)lock;
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/// Unlocks the lock. Fatal error if the lock is owned by another thread.
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/// Forwards to os_unfair_lock_unlock() defined in os/lock.h
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- (void)unlock;
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/// Attempts to lock the lock. Returns YES if the lock was successfully acquired.
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/// Forwards to os_unfair_lock_trylock() defined in os/lock.h
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- (BOOL)tryLock NS_SWIFT_NAME(tryLock());
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// Note: NS_SWIFT_NAME is required to prevent bridging from renaming to `try()`.
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/// Fatal assert that the lock is owned by the current thread.
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/// Forwards to os_unfair_lock_assert_owner defined in os/lock.h
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- (void)assertOwner;
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/// Fatal assert that the lock is not owned by the current thread.
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/// Forwards to os_unfair_lock_assert_not_owner defined in os/lock.h
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- (void)assertNotOwner;
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@end
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NS_ASSUME_NONNULL_END
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