MulleProxy.md

MulleProxy

A thread-safe proxy implementation that provides locking and access control for target objects.

Base Class

NSProxy

Instance Variables

NSRecursiveLock   *__lock;           // Recursive lock for thread safety
id                __target;          // The proxied object
IMP               __gain_imp;        // Cached method for gaining access
IMP               __relinquish_imp;  // Cached method for relinquishing access
NSUInteger        __taoStrategy;     // Thread access strategy

Methods

Initialization

• +proxyWithObject: - Creates and returns an autoreleased proxy with lock
• +locklessProxyWithObject: - Creates proxy without lock
• -initWithObject: - Initializes proxy with lock
• -initNoLockWithObject: - Initializes proxy without lock

Lock Operations

• -lock - Acquires the recursive lock
• -unlock - Releases the recursive lock
• -tryLock - Attempts to acquire lock without blocking

Lock Sharing

• -didShareRecursiveLock: - Called after lock sharing to update thread affinity
• -shareRecursiveLock: - Shares lock with another lock
• -shareRecursiveLockWithObject: - Shares lock with a MulleObject
• -shareRecursiveLockWithProxy: - Shares lock with another proxy

Thread Access (TAO) Support

All marked with MULLE_OBJC_THREADSAFE_METHOD:

• -mulleIsThreadSafe - Returns YES
• -mulleIsAccessible - Returns YES
• -mulleIsAccessibleByThread: - Returns YES
• -mulleTAOStrategy - Returns MulleObjCTAOKnownThreadSafe
• -mulleRelinquishAccess - Retains self
• -mulleGainAccess - Autoreleases self
• -mulleGainAccessWithTAOStrategy: - Autoreleases self
• -mulleRelinquishAccessWithTAOStrategy: - Retains self

Class and Protocol Introspection

All marked with MULLE_OBJC_THREADSAFE_METHOD:

• -class - Returns target's class
• -superclass - Returns target's superclass
• -isKindOfClass: - Forwards to target
• -isMemberOfClass: - Forwards to target
• -mulleContainsProtocol: - Forwards to target
• -conformsToProtocol: - Forwards to target

Method Introspection

All marked with MULLE_OBJC_THREADSAFE_METHOD:

• -methodForSelector: - Forwards to target
• -respondsToSelector: - Forwards to target
• -methodSignatureForSelector: - Forwards to target

Usage Example

// Create proxy with lock
id target = [MyObject new];
MulleProxy *proxy = [MulleProxy proxyWithObject:target];

// Use proxy - automatically locks/unlocks around method calls
[proxy doSomething];

// Share lock between proxies
MulleProxy *proxy2 = [MulleProxy proxyWithObject:target2];
[proxy2 shareRecursiveLockWithProxy:proxy];

Important Notes

1. Thread Safety

   • All methods are thread-safe
   • Uses recursive locking for method calls
   • Can share locks between proxies

2. Implementation Details

   • Forwards all unknown methods to target
   • Automatically locks around forwarded calls
   • Caches access method IMPs for performance

3. Exception Handling

   • Detects exceptions passing through proxy calls
   • Prevents potential deadlocks from exceptions
   • Raises internal inconsistency in debug builds