NSConditionLock

A synchronization tool that combines a condition variable with an integer value. Used to synchronize threads based on state values.

Base Class

NSCondition

Instance Variables

mulle_atomic_pointer_t   _currentCondition;  // The current condition value

Methods

Initialization

• -initWithCondition: - Initialize with starting condition value

Condition Access

• -condition - Returns current condition value

Locking Operations

• -lockWhenCondition: - Acquires lock when condition matches value
• -mulleLockWhenNotCondition: - Acquires lock when condition doesn’t match value
• -tryLockWhenCondition: - Attempts to acquire lock if condition matches value
• -mulleTryLockWhenNotCondition: - Attempts to acquire lock if condition doesn’t match value
• -unlockWithCondition: - Releases lock and sets new condition value
• -mulleUnlockWithCondition:broadcast: - Releases lock, sets condition, optionally broadcasts

Usage Example

NSConditionLock *lock = [[NSConditionLock alloc] initWithCondition:0];

// Wait for condition 0
[lock lockWhenCondition:0];
// ... do work ...
[lock unlockWithCondition:1];  // Signal completion

// Wait for condition 1
[lock lockWhenCondition:1];
// ... do more work ...
[lock unlockWithCondition:2];

Important Notes

1. Thread Safety
   • All methods are thread-safe
   • Uses atomic operations for condition value
   • Inherits mutex and condition variable from NSCondition
2. Performance
   • Keep workload inside lock minimal
   • Other threads may deadlock in lockWhenCondition:beforeDate:
3. Implementation Details
   • Uses broadcast by default in unlockWithCondition:
   • Can control signal vs broadcast with mulleUnlockWithCondition:broadcast:
   • Condition value is stored atomically