Coalesced Blocks

gistfile1.m

@interface GCDCoalescent : NSObject
- (void)dispatchOn:(dispatch_queue_t)queue after:(double)seconds block:(dispatch_block_t)block;
@end


@implementation GCDCoalescent
{
    uint64_t count;
}

- (void)dispatchOn:(dispatch_queue_t)queue after:(double)seconds block:(dispatch_block_t)block;
{
	uint64_t eventNumber = __sync_add_and_fetch(&count, 1);
	dispatch_after(dispatch_time(DISPATCH_TIME_NOW, seconds * NSEC_PER_SEC), queue, ^{
		if (count > eventNumber) return;
		block();
	});
}

@end




@interface GCDCoalescer : NSObject
+ (GCDCoalescer *)shared;
- (void)dispatch:(NSString *)identifier on:(dispatch_queue_t)queue after:(double)seconds block:(dispatch_block_t)block;
@end


@implementation GCDCoalescer
{
	NSLock * _lock;
	
	NSMutableArray * _tags;
	uint64_t * _counts;
	uint64_t _numCounts;
	uint64_t _capacity;
}


+ (GCDCoalescer *)shared;
{
	static GCDCoalescer * shared = nil;
	if (!shared) {
		shared = [[GCDCoalescer alloc] init];
	}
	return shared;
}


- (id)init;
{
	if (!(self = [super init])) {
		return nil;
	}
	
	_tags = [[NSMutableArray alloc] init];
	_lock = [[NSLock alloc] init];
	_capacity = 16;
	_counts = calloc(_capacity * sizeof(uint64_t), 1);
	_numCounts = 0;
	
	return self;
}


- (void)dealloc;
{
	if (_counts) free(_counts);
	[_tags release];
	[_lock release];
	[super dealloc];
}



- (void)dispatch:(NSString *)identifier on:(dispatch_queue_t)queue after:(double)seconds block:(dispatch_block_t)block;
{
	NSUInteger index = [_tags indexOfObject:identifier];
	if (index == NSNotFound) {
		index = _numCounts;
		
		if (_numCounts == _capacity) {
			[_lock lock];
			_capacity += 16;
			_counts = realloc(_counts, sizeof(uint64_t) * _capacity);
			[_lock unlock];
		}
		
		[_tags addObject:identifier];
		_counts[index] = 0;
		_numCounts++;
	}
	
	
	uint64_t eventNumber = __sync_add_and_fetch(_counts + index, 1);
	dispatch_after(dispatch_time(DISPATCH_TIME_NOW, seconds * NSEC_PER_SEC), queue, ^{
		uint64_t currentCount;
		
		[_lock lock];
		currentCount = _counts[index];
		[_lock unlock];
		
		if (currentCount > eventNumber) return;
		block();
	});
}

@end

Pushed A 0 at 74.9
Pushed A 1 at 75.1
Pushed B 2 at 75.9
Pushed B 3 at 76.0
Fired A 1 at 76.1
Pushed B 4 at 76.3
Pushed B 5 at 76.6
Pushed B 6 at 76.8
Pushed B 7 at 77.2
Pushed A 8 at 77.5
Pushed A 9 at 77.7
Pushed A 10 at 77.8
Pushed A 11 at 78.0
Pushed A 12 at 78.2
Fired B 7 at 78.2
Pushed A 13 at 78.3
Pushed A 14 at 78.5
Pushed A 15 at 78.7
Pushed A 16 at 78.8
Pushed A 17 at 79.0
Fired A 17 at 80.0