NSLock.md

NSLock

Basic mutex-based lock for thread synchronization in mulle-objc. Note that this may be too heavyweight for very contested locks - consider using mulle_thread_mutex_t directly in such cases.

Base Class

NSObject

Implemented Protocols

• NSLocking
• MulleObjCThreadSafe

Instance Variables

mulle_thread_mutex_t    _lock;  // The underlying mutex

Methods

All methods are marked with MULLE_OBJC_THREADSAFE_METHOD:

Initialization

• -init - Initializes the lock

Locking Operations

• -lock - Acquires the lock
• -unlock - Releases the lock
• -tryLock - Attempts to acquire lock without blocking, returns YES if successful
• -lockBeforeTimeInterval: - Attempts to acquire lock before given time interval expires

Usage Example

NSLock *lock = [NSLock new];

// Basic locking
[lock lock];
// ... critical section ...
[lock unlock];

// Using convenience macro
MulleObjCLockDo( lock)
{
   // ... critical section ...
}  // automatically unlocked

// Try lock without blocking
if ([lock tryLock])
{
   // ... got the lock ...
   [lock unlock];
}

// Lock with timeout
if ([lock lockBeforeTimeInterval:1.0])
{
   // ... got the lock ...
   [lock unlock];
}

Important Notes

1. Thread Safety

   • All methods are thread-safe
   • The lock itself provides thread safety for critical sections

2. Performance Considerations

   • Consider using mulle_thread_mutex_t directly for high-contention scenarios
   • The lockBeforeTimeInterval: method uses thread yielding for polling

3. Platform Specifics

   • Some platforms need explicit mutex cleanup in dealloc (controlled by MULLE_THREAD_MUTEX_NEEDS_DONE)