gistfile1.m

- (NSArray *)arrayForReading
{
    NSArray * array;
    @synchronized (self) {
        array = [[_array retain] autorelease];
    }
    return array;
}

- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state objects:(id *)stackbuf count:(NSUInteger)len
{
    if (state->state == 0) {
        NSMutableData * subStateData = [NSMutableData dataWithLength:sizeof(NSFastEnumerationState)];
        state->state = (unsigned long)subStateData;
        state->extra[0] = (unsigned long)[self arrayForReading];
    }
    
    NSMutableData * subStateData = (NSMutableData *)state->state;
    NSArray * array = (NSArray *)state->extra[0];
    NSFastEnumerationState * subState = [subStateData mutableBytes];
    NSUInteger result = [array countByEnumeratingWithState:subState objects:stackbuf count:len];
    state->itemsPtr = subState->itemsPtr;
    state->mutationsPtr = subState->mutationsPtr;
    [subStateData self];
    return result;
}