VLCKit/Sources/VLCEventManager.m

/*****************************************************************************
 * VLCEventManager.m: VLCKit.framework VLCEventManager implementation
 *****************************************************************************
 * Copyright (C) 2007 Pierre d'Herbemont
 * Copyright (C) 2007 VLC authors and VideoLAN
 * $Id$
 *
 * Authors: Pierre d'Herbemont <pdherbemont # videolan.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

#import "VLCEventManager.h"
#import <pthread.h>

/**
 * Defines the type of interthread message on the queue.
 */
typedef enum
{
    VLCNotification,                //< Standard NSNotification.
    VLCObjectMethodWithObjectArg,   //< Method with an object argument.
    VLCObjectMethodWithArrayArg     //< Method with an array argument.
} message_type_t;

/**
 * Data structured used to enqueue messages onto the queue.
 */
typedef struct {
    id target;                      //< Target object that should receive the message (retained until method is called).
    SEL sel;                        //< A selector that identifies the message to be sent to the target.
    union u                         //< Object could either be a VLCNotification or other.
    {
        NSString * name;            //< Name to be used for NSNotification
        id object;                  //< Object argument to pass to the target via the selector.
    } u;
    message_type_t type;            //< Type of queued message.
} message_t;

@interface VLCEventManager (Private)
- (void)callDelegateOfObjectAndSendNotificationWithArgs:(NSData*)data;
- (void)callObjectMethodWithArgs:(NSData*)data;
- (void)callDelegateOfObject:(id) aTarget withDelegateMethod:(SEL)aSelector withNotificationName:(NSString *)aNotificationName;
- (pthread_cond_t *)signalData;
- (pthread_mutex_t *)queueLock;
- (NSMutableArray *)messageQueue;
- (NSMutableArray *)pendingMessagesOnMainThread;
- (NSLock *)pendingMessagesLock;

- (void)addMessageToHandleOnMainThread:(NSData *)messageAsData;
@end

/**
 * Provides a function for the main entry point for the dispatch thread.  It dispatches any messages that is queued.
 * \param user_data Pointer to the VLCEventManager instance that instiated this thread.
 */
static void * EventDispatcherMainLoop(void * user_data)
{
    VLCEventManager * self = user_data;

    for (;;) {
        NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
        message_t * message, * message_newer = NULL;
        NSData * dataMessage;

        /* Sleep a bit not to flood the interface */
        usleep(300);

        /* Wait for some data */

        pthread_mutex_lock([self queueLock]);
        /* Wait until we have something on the queue */
        while ([[self messageQueue] count] <= 0)
            pthread_cond_wait([self signalData], [self queueLock]);

        //if ([[self messageQueue] count] % 100 == 0 || [[self messageQueue] count] < 100)
          //  VKLog(@"[EVENT_MANAGER] On the stack we have %d elements", [[self messageQueue] count]);

        /* Get the first object off the queue. */
        dataMessage = [[[self messageQueue] lastObject] retain];    // Released in 'call'
        [[self messageQueue] removeLastObject];
        message = (message_t *)[dataMessage bytes];

        /* Remove duplicate notifications (keep the newest one). */
        if (message->type == VLCNotification) {
            NSInteger last_match_msg = -1;
            for (NSInteger i = [[self messageQueue] count]-1; i >= 0; i-- ) {
                message_newer = (message_t *)[(NSData *)[self messageQueue][i] bytes];
                if (message_newer->type == VLCNotification &&
                    message_newer->target == message->target &&
                    [message_newer->u.name isEqualToString:message->u.name]) {
                    if (last_match_msg >= 0) {
                        message_t * msg = (message_t *)[(NSData *)[self messageQueue][last_match_msg] bytes];
                        [msg->u.name release];
                        [[self messageQueue] removeObjectAtIndex:last_match_msg];
                    }
                    last_match_msg = i;
                }
            }
            if (last_match_msg >= 0) {
                // newer notification detected, ignore current one
                [message->u.name release];
                [dataMessage release];
                [pool release];
                pthread_mutex_unlock([self queueLock]);
                continue;
            }
        } else if (message->type == VLCObjectMethodWithArrayArg) {
            NSMutableArray * newArg = nil;

            /* Collapse messages that takes array arg by sending one bigger array */
            for (NSInteger i = [[self messageQueue] count] - 1; i >= 0; i--) {
                message_newer = (message_t *)[(NSData *)[self messageQueue][i] bytes];
                if (message_newer->type == VLCObjectMethodWithArrayArg &&
                    message_newer->target == message->target &&
                    message_newer->sel == message->sel) {
                    if (!newArg) {
                        newArg = [NSMutableArray arrayWithArray:message->u.object];
                        [message->u.object release];
                    }

                    [newArg addObjectsFromArray:message_newer->u.object];
                    [message_newer->u.object release];
                    [[self messageQueue] removeObjectAtIndex:i];
                }
                /* It shouldn be a good idea not to collapse event with other kind of event in-between.
                 * This could be particulary problematic when the same object receive two related events
                 * (for instance Added and Removed).
                 * Ignore for now only if target is the same */
                else if (message_newer->target == message->target)
                    break;
            }

            if (newArg)
                message->u.object = [newArg retain];
        }

        [self addMessageToHandleOnMainThread:dataMessage];

        pthread_mutex_unlock([self queueLock]);

        if (message->type == VLCNotification)
            [self performSelectorOnMainThread:@selector(callDelegateOfObjectAndSendNotificationWithArgs:)
                                   withObject:dataMessage
                                waitUntilDone: NO];
        else
            [self performSelectorOnMainThread:@selector(callObjectMethodWithArgs:)
                                   withObject:dataMessage
                                waitUntilDone: YES];

        [pool release];
    }
    return nil;
}

@implementation VLCEventManager
+ (id)sharedManager
{
    static dispatch_once_t onceToken;
    static VLCEventManager *defaultManager = nil;
    dispatch_once(&onceToken, ^{
        defaultManager = [[VLCEventManager alloc] init];
    });

    return defaultManager;
}

- (void)dummy
{
    /* Put Cocoa in multithreaded mode by calling a dummy function */
}

- (id)init
{
    if (self = [super init]) {
        if (![NSThread isMultiThreaded]) {
            [NSThread detachNewThreadSelector:@selector(dummy) toTarget:self withObject:nil];
            NSAssert([NSThread isMultiThreaded], @"Can't put Cocoa in multithreaded mode");
        }

        messageQueue = [[NSMutableArray alloc] initWithCapacity:10];
        pendingMessagesOnMainThread = [[NSMutableArray alloc] initWithCapacity:10];
        pendingMessagesLock = [[NSLock alloc] init];

        pthread_mutex_init(&queueLock, NULL);
        pthread_cond_init(&signalData, NULL);
        pthread_create(&dispatcherThread, NULL, EventDispatcherMainLoop, self);
    }
    return self;
}

- (void)dealloc
{
    pthread_kill(dispatcherThread, SIGKILL);
    pthread_join(dispatcherThread, NULL);

    [messageQueue release];
    [pendingMessagesOnMainThread release];
    [super dealloc];
}

- (void)callOnMainThreadDelegateOfObject:(id)aTarget withDelegateMethod:(SEL)aSelector withNotificationName:(NSString *)aNotificationName
{
    /* Don't send on main thread before this gets sorted out */
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    message_t message =
    {
        aTarget,
        aSelector,
        [aNotificationName retain],
        VLCNotification
    };

    pthread_mutex_lock([self queueLock]);
    [[self messageQueue] insertObject:[NSData dataWithBytes:&message length:sizeof(message_t)] atIndex:0];
    pthread_cond_signal([self signalData]);
    pthread_mutex_unlock([self queueLock]);

    [pool release];
}

- (void)callOnMainThreadObject:(id)aTarget withMethod:(SEL)aSelector withArgumentAsObject:(id)arg
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    message_t message =
    {
        aTarget,
        aSelector,
        [arg retain],
        [arg isKindOfClass:[NSArray class]] ? VLCObjectMethodWithArrayArg : VLCObjectMethodWithObjectArg
    };

    pthread_mutex_lock([self queueLock]);
    [[self messageQueue] insertObject:[NSData dataWithBytes:&message length:sizeof(message_t)] atIndex:0];
    pthread_cond_signal([self signalData]);
    pthread_mutex_unlock([self queueLock]);

    [pool release];
}

- (void)cancelCallToObject:(id)target
{

    // Remove all queued message
    pthread_mutex_lock([self queueLock]);
    [pendingMessagesLock lock];

    NSMutableArray *queue = [self messageQueue];
    for (int i = [queue count] - 1; i >= 0; i--) {
        NSData *data = queue[i];
        message_t *message = (message_t *)[data bytes];
        if (message->target == target)
            [queue removeObjectAtIndex:i];
    }

    // Remove all pending messages
    NSMutableArray *messages = pendingMessagesOnMainThread;
    for (int i = [messages count] - 1; i >= 0; i--) {
        NSData *data = messages[i];
        message_t *message = (message_t *)[data bytes];

        if (message->target == target)
            [messages removeObjectAtIndex:i];
    }

    [pendingMessagesLock unlock];
    pthread_mutex_unlock([self queueLock]);

}
@end

@implementation VLCEventManager (Private)

- (void)addMessageToHandleOnMainThread:(NSData *)messageAsData
{
    [pendingMessagesLock lock];
    [pendingMessagesOnMainThread addObject:messageAsData];
    [pendingMessagesLock unlock];

}

- (BOOL)markMessageHandledOnMainThreadIfExists:(NSData *)messageAsData
{
    [pendingMessagesLock lock];
    BOOL cancelled = ![pendingMessagesOnMainThread containsObject:messageAsData];
    if (!cancelled)
        [pendingMessagesOnMainThread removeObject:messageAsData];
    [pendingMessagesLock unlock];

    return !cancelled;
}

- (void)callDelegateOfObjectAndSendNotificationWithArgs:(NSData*)data
{
    message_t * message = (message_t *)[data bytes];

    // Check that we were not cancelled, ie, target was released
    if ([self markMessageHandledOnMainThreadIfExists:data])
        [self callDelegateOfObject:message->target withDelegateMethod:message->sel withNotificationName:message->u.name];

    [message->u.name release];
    [data release];
}

- (void)callObjectMethodWithArgs:(NSData*)data
{
    message_t * message = (message_t *)[data bytes];

    // Check that we were not cancelled
    if ([self markMessageHandledOnMainThreadIfExists:data]) {
        void (*method)(id, SEL, id) = (void (*)(id, SEL, id))[message->target methodForSelector: message->sel];
        method(message->target, message->sel, message->u.object);
    }

    [message->u.object release];
    [data release];
}

- (void)callDelegateOfObject:(id)aTarget withDelegateMethod:(SEL)aSelector withNotificationName:(NSString *)aNotificationName
{
    [[NSNotificationCenter defaultCenter] postNotification: [NSNotification notificationWithName:aNotificationName object:aTarget]];

    id delegate = [aTarget delegate];
    if (!delegate || ![delegate respondsToSelector:aSelector])
        return;

    void (*method)(id, SEL, id) = (void (*)(id, SEL, id))[[aTarget delegate] methodForSelector: aSelector];
    method([aTarget delegate], aSelector, [NSNotification notificationWithName:aNotificationName object:aTarget]);
}

- (NSMutableArray *)messageQueue
{
    return messageQueue;
}

- (NSMutableArray *)pendingMessagesOnMainThread
{
    return pendingMessagesOnMainThread;
}

- (NSLock *)pendingMessagesLock
{
    return pendingMessagesLock;
}


- (pthread_cond_t *)signalData
{
    return &signalData;
}

- (pthread_mutex_t *)queueLock
{
    return &queueLock;
}
@end