gistfile1.m

#import "MABaseFuture.h"
#import <libkern/OSAtomic.h>


@implementation MABaseFuture
@dynamic futureValue;
@synthesize futureHasResolved = _resolved;

- (id)futureValue 
{
    OSMemoryBarrier();
    return _resolved ? _value : nil;
}

- (void)setFutureValue: (id)value
{
    [value retain];
    [_value release];
    _value = value;
    OSMemoryBarrier();
    _resolved = YES;
    [_lock broadcast];
}

- (id)init
{
    _lock = [[NSCondition alloc] init];
    return self;
}

- (void)dealloc
{
    [_value release];
    [_lock release];
    [super dealloc];
}

- (void)waitForFutureResolution
{
    [_lock lock];
    while(!_resolved)      
        [_lock wait];
    [_lock unlock];
}

- (id)resolveFuture
{
    if (!_resolved) {
        switch (OSAtomicIncrement32(&_threads)) {
            case 1: // Start resolving process.
                [self resolveFutureUnlocked]; // Lock/unlock dance should be done inside the block
                break;
            default: // Wait until future is resolved.
                [self waitForFutureResolution];
                break;
        }
        OSAtomicDecrement32Barrier(&_threads);
    }
    return _value;
}

- (void)resolveFutureUnlocked 
{
    NSAssert1(NO, @"-[MABaseFuture resolveFutureUnlocked] called, this should never happen! Did you forget to implement -[%@ resolveFutureUnlocked]?", NSStringFromClass(isa));
    __builtin_unreachable();
}

- (Class)class
{
    Class c = [[self resolveFuture] class];
    if([NSStringFromClass(c) hasPrefix: @"NSCF"])
        return [c superclass];
    else
        return c;
}

@end