CFNotificationCenter.c

/*
 * Copyright (c) 2009 Stuart Crook.  All rights reserved.
 *
 * Created by Stuart Crook on 23/02/2009.
 * This source code is a reverse-engineered implementation of the notification center from
 * Apple's core foundation library.
 *
 * The PureFoundation code base consists of a combination of original code provided by contributors
 * and open-source code drawn from a nuber of other projects -- chiefly Cocotron (www.coctron.org)
 * and GNUStep (www.gnustep.org). Under the principal that the least-liberal licence trumps the others,
 * the PureFoundation project as a whole is released under the GNU Lesser General Public License (LGPL).
 * Where code has been included from other projects, that project's licence, along with a note of the
 * exact source (eg. file name) is included inline in the source.
 *
 * Since PureFoundation is a dynamically-loaded shared library, it is my interpretation of the LGPL
 * that any application linking to it is not automatically bound by its terms.
 *
 * See the text of the LGPL (from http://www.gnu.org/licenses/lgpl-3.0.txt, accessed 26/2/09):
 * 
 */

#include "CFNotificationCenter.h"
#include <CoreFoundation/CFPropertyList.h>
#include <CoreFoundation/CFNumber.h>
#include <CoreFoundation/CFMessagePort.h>
#include <CoreFoundation/CFStream.h>
#include <CoreFoundation/CFString.h>

#include <CoreFoundation/CFRuntime.h>
#include "CFPriv.h"
#include <CoreFoundation/CoreFoundation_Prefix.h>
#include "CFInternal.h"

#include <stdlib.h>
#include <stdio.h>
#if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_LINUX
#include <unistd.h>
#endif

#define CF_LOCAL_CENTER		0
#define CF_DIST_CENTER		1
#define CF_DARWIN_CENTER	2

#define CF_OBS_SIZE	32

typedef struct __CFObserver {
	//CFStringRef name; // can be NULL
	CFHashCode hash; // hashed string, for speed. can be NULL
	const void *object; // can be NULL
	const void *observer; // may be NULL
	CFNotificationCallback callback;
	CFNotificationSuspensionBehavior sb;
} __CFObserver;

struct __CFNotificationCenter {
	CFRuntimeBase _base;
	CFIndex type;
	CFIndex suspended; // <- move into base bits?
	CFIndex observers;
	CFIndex capacity;
	__CFObserver *obs;
	CFSpinLock_t lock;
};


// STRUCTURES FOR DISTRIBUTED CENTER HERE
// message ids recognised by ddistnoted
#define NOTIFICATION			0
#define REGISTER_PORT			1
#define UNREGISTER_PORT			2
#define REGISTER_NOTIFICATION	3
#define UNREGISTER_NOTIFICATION	4

#define CF_DIST_SIZE	32
#define CF_QUEUE_SIZE	32

typedef struct __CFDistNotification {
	CFHashCode hash;
	CFHashCode object;
	CFIndex count;
} __CFDistNotification;

typedef struct __CFQueueRecord {
	CFStringRef name;
	const void *object; // will be a CFStringRef...
	const void *observer;
	CFDictionaryRef userInfo;
	CFNotificationCallback callback;
} __CFQueueRecord;

typedef struct __CFDistributedCenterInfo {
	CFMessagePortRef local;
	CFMessagePortRef remote;
	long session;
	CFHashCode uid;
	CFRunLoopSourceRef rls;
	CFIndex count;
	CFIndex capacity;
	__CFDistNotification *nots;
	CFIndex queueCount;
	CFIndex queueCapacity;
	__CFQueueRecord *queue;
} __CFDistributedCenterInfo;

static __CFDistributedCenterInfo __CFDistInfo = { NULL, NULL, 0, 0, NULL, 0, 0, NULL, 0, 0, NULL };

// these structures come from the ddistnoted project -- beter keep their definitions synced
typedef struct dndNotReg {
	CFHashCode uid;
	CFHashCode name;
	CFHashCode object;
} dndNotReg;

typedef struct dndNotHeader {
	long session;
	CFHashCode name;
	CFHashCode object;
	CFIndex flags;
} dndNotHeader;

#if DEPLOYMENT_TARGET_MACOSX
#include <notify.h>
#include <CoreFoundation/CFMachPort.h>
#endif
/*
 *	Darwin notifications
 *
 *	There are two ways we could organise recieving notify messages via Mach ports. The
 *	method we are using here is to use a single port for all messages, with an int token
 *	in the message header used to identify the notification name.
 *
 *	The alternative, which we may have to consider if the number of notifications in
 *	general use swamps a single port's message queue, is to allocate one Mach port per
 *	notification name.
 */
#define CF_DARWIN_SIZE 32

typedef struct __CFDarwinNotifications {
	//CFStringRef name;
	CFHashCode hash;
	int token;
	CFIndex count;
} __CFDarwinNotifications;

typedef struct __CFDarwinCenterInfo {	
#if defined(__MACH__)
	CFMachPortRef port;
#endif
	CFRunLoopSourceRef rls;
	CFIndex count;
	CFIndex capacity;
	__CFDarwinNotifications *nots;
} __CFDarwinCenterInfo;

#if defined(__MACH__)
static __CFDarwinCenterInfo __CFDarwinInfo = { NULL, NULL, 0, 0, NULL };
#else
static __CFDarwinCenterInfo __CFDarwinInfo = { NULL, 0, 0, NULL };
#endif

// the task's singleton centres
static CFNotificationCenterRef __CFLocalCenter = NULL;
static CFNotificationCenterRef __CFDistributedCenter = NULL;
static CFNotificationCenterRef __CFDarwinCenter = NULL;

static CFMutableDictionaryRef __CFHashStore = NULL;


// these control access to the Get functions. access to individual structure are
//	embeded within those structures
static CFSpinLock_t __CFLocalCenterLock = CFSpinLockInit;
static CFSpinLock_t __CFDistributedCenterLock = CFSpinLockInit;
static CFSpinLock_t __CFDarwinCenterLock = CFSpinLockInit;

static CFSpinLock_t __CFHashStoreLock = CFSpinLockInit;

// store for our typeID
static CFTypeID __kCFNotificationCenterTypeID = _kCFRuntimeNotATypeID;

// life-cycle stuff can wait for now
static const CFRuntimeClass __CFNotificationCenterClass = {
	0,
	"CFNotificationCenter",
	NULL,	// init
	NULL,	// copy
	NULL, //__CFDataDeallocate,
	NULL, //__CFDataEqual,
	NULL, //__CFDataHash,
	NULL,	// 
	NULL, //__CFDataCopyDescription
};

__private_extern__ void __CFNotificationCenterInitialize(void) 
{
	__kCFNotificationCenterTypeID = _CFRuntimeRegisterClass(&__CFNotificationCenterClass);
	__CFHashStore = CFDictionaryCreateMutable( kCFAllocatorDefault, 0, NULL, NULL );
}

CFTypeID CFNotificationCenterGetTypeID(void) { return __kCFNotificationCenterTypeID; }

/*
 *	The __CFAdd and Remove functions take an optional callback of this type which is called once
 *	for each observer added or removed. It runs under the current spinlock and gets over the
 *	problem of returning a list of notification to remove from the RemoveEvery function
 */
typedef void (*__CFAdderCallBack)( CFStringRef name, CFHashCode hash, CFHashCode object );
typedef void (*__CFRemoverCallBack)( CFHashCode name, CFHashCode object );


/*
 *	Declaration of functions internal to this file
 */
CFNotificationCenterRef __CFCreateCenter( CFIndex type );

void __CFAddObserver( CFNotificationCenterRef center, const void *observer, CFNotificationCallback callBack, CFStringRef name, const void *object, CFNotificationSuspensionBehavior suspensionBehavior, __CFAdderCallBack cb );
void __CFRemoveObserver( CFNotificationCenterRef center, const void *observer, CFHashCode name, const void *object, __CFRemoverCallBack cb );
void __CFRemoveEveryObserver( CFNotificationCenterRef center, const void *observer, __CFRemoverCallBack cb );
void __CFInvokeCallBacks( CFNotificationCenterRef center, CFHashCode name, CFStringRef nameReturn, const void *object, const void *objectReturn, CFDictionaryRef userInfo, Boolean deliverNow );

//void __PFPostLocalNotification( PFNotificationCenterRef center, CFStringRef name, const void *object, CFDictionaryRef userInfo );
void __CFPostDistributedNotification( CFNotificationCenterRef center, CFStringRef name, CFStringRef object, CFDictionaryRef userInfom, CFOptionFlags options );
void __CFPostDarwinNotification( CFNotificationCenterRef center, CFStringRef name );

void __CFAddQueue( CFStringRef name, const void *object, const void *observer, CFDictionaryRef userInfo, CFNotificationCallback callback, Boolean coalesce );
void __CFDeliverQueue( void );

Boolean _CFNotificationCenterIsSuspended( CFNotificationCenterRef center );
void _CFNotificationCenterSetSuspended( CFNotificationCenterRef center, Boolean suspended );

#if DEPLOYMENT_TARGET_MACOSX
void __CFDarwinCallBack(CFMachPortRef port, void *msg, CFIndex size, void *info);
#endif

/*
 *	Manage the message queue, which is used to store distributed notifications
 *	when delivery has been suspended.
 */
void __CFAddQueue( CFStringRef name, const void *object, const void *observer, CFDictionaryRef userInfo, CFNotificationCallback callback, Boolean coalesce )
{
	CFRetain(userInfo);
	__CFQueueRecord *queue = __CFDistInfo.queue;
	CFIndex count = __CFDistInfo.queueCount;
	
	if( coalesce ) // do we check for this notification in the queue?
	{
		while( count-- ) 
		{
			// we're looking for exactl matches on name, object, observer and callback
			if( (queue->name == name) && (queue->object == object) 
			   && (queue->observer == observer) && (queue->callback == callback) )
			{
				CFRelease(queue->userInfo);
				queue->userInfo = userInfo;
				break;
			}
			
			queue++;
		}
	}
	
	// either we're not coalescing or this notification wasn't already enqueued
	if( __CFDistInfo.count == __CFDistInfo.capacity )
	{
		__CFDistInfo.capacity += CF_QUEUE_SIZE;
		__CFDistInfo.queue = (__CFQueueRecord*)realloc( __CFDistInfo.queue, (CF_QUEUE_SIZE * sizeof(__CFQueueRecord)) );
		if( __CFDistInfo.queue == NULL ) return;
	}

	queue = __CFDistInfo.queue + __CFDistInfo.queueCount;
	
	queue->name = name;
	queue->object = object;
	queue->observer = observer;
	queue->callback = callback;
	queue->userInfo = userInfo;
	
	__CFDistInfo.queueCount++;
}

void __CFDeliverQueue( void )
{
	CFIndex count = __CFDistInfo.queueCount;
	__CFQueueRecord *queue = __CFDistInfo.queue;
	
	while( count-- ) 
	{
		queue->callback( (CFNotificationCenterRef)__CFDistributedCenter, (void*)queue->observer, queue->name, queue->object, queue->userInfo );
		CFRelease(queue->userInfo);
		
		queue->name = NULL;
		queue->object = NULL;
		queue->observer = NULL;
		queue->callback = NULL;
		queue->userInfo = NULL;
	}
	
	__CFDistInfo.queueCount = 0;
}


/*
 *	Set the suspended condition of the distributed notification centre (only). At the
 *	moment these will be left as no-ops, to be activated when we write the 
 *	NSDitributedNotificationCenter class (which provides -setSuspended: and -suspended
 *	methods).
 *
 *	The docs suggested that these functions existed, and running nm over CoreFoundation
 *	revealed their names. I'm just guessing their prototypes at the moment, and hoping
 *	that nothing tries to call them directly.
 */
Boolean _CFNotificationCenterIsSuspended( CFNotificationCenterRef center ) { return center->suspended; }

void _CFNotificationCenterSetSuspended( CFNotificationCenterRef center, Boolean suspended )
{ 
	if( center->type == CF_DIST_CENTER ) // only suspendable type
	{
		__CFSpinLock(&center->lock);
		if( center->suspended != suspended ) // changing state?
		{
			center->suspended = suspended;
			// have we just un-suspended and are there notifications to deliver?
			if( !suspended && (__CFDistInfo.queueCount != 0) ) 
				__CFDeliverQueue();
		}
		__CFSpinUnlock(&center->lock);
	}
}

/*
 *	Strings (names for all notifications, and objects from distributed observers) are
 *	stored as hashes in the look-up tables, with strings stored in the __CFHashStore
 *	dictionary
 *
 *	Strings are copied into the dictionary. At present, they are never removed.
 */
CFHashCode __CFNCHash( CFStringRef string );
CFStringRef __CFNCUnhash( CFHashCode hash );

// this should maybe be called "hashAndStore" - use CFHash() for just the hash
CFHashCode __CFNCHash( CFStringRef string )
{
	if( string == NULL ) return 0;
	CFHashCode hash = CFHash(string);
	__CFSpinLock(&__CFHashStoreLock);
	if( !CFDictionaryContainsKey(__CFHashStore, (const void *)hash) )
		CFDictionaryAddValue( __CFHashStore, (const void *)hash, CFStringCreateCopy( kCFAllocatorDefault, string) );
	__CFSpinUnlock(&__CFHashStoreLock);
	return hash;
}

CFStringRef __CFNCUnhash( CFHashCode hash ) 
{ 
	CFStringRef string;
	__CFSpinLock(&__CFHashStoreLock);
	if( hash == 0 )
		string = NULL;
	else
		string = (CFStringRef)CFDictionaryGetValue(__CFHashStore, (const void *)hash);
	__CFSpinUnlock(&__CFHashStoreLock);
	return string;
}

/*
 *	Basic diagnostic functions
 */
#include <stdio.h>

void __CFCenterDiag( CFNotificationCenterRef c );
void __CFObserverDiag( __CFObserver o );

void __CFCenterDiag( CFNotificationCenterRef c )
{
	//printf("centre: type = %d, observers = %d, capacity = %d, obs at 0x%X\n", c->type, c->observers, c->capacity, c->obs);
}

void __CFObserverDiag( __CFObserver o )
{
	//printf("observer: hash = %u, object = 0x%X, observer = 0x%X, callback to 0x%X, sb = %d\n", o.hash, o.object, o.observer, o.callback, o.sb);
}
// END DIAGNOSTIC FUNCTIONS


/*
 *	Add or remove a notification from the table of distributed notifications we are
 *	monitoring. When the first notification with a unique signature is added (or the
 *	last is removed) we make a call to the ddistnoted daemon to register (or unregister)
 *	for that notification.
 *
 *	When the first monitored notification is added (or the last is removed) we add the
 *	message port source to (or remove it from) the main runloop.
 */

#if DEPLOYMENT_TARGET_MACOSX
CFDataRef __CFDistRecieve( CFMessagePortRef local, SInt32 msgid, CFDataRef data, void *info );
#endif
void __CFDistAddNotification( CFStringRef name, CFHashCode hash, CFHashCode object );
void __CFDistRemoveNotification( CFHashCode hash, CFHashCode object );

#if DEPLOYMENT_TARGET_MACOSX
/*
 *	recieves messages from the ddistnoted daemon
 *
 *	In a later version we're going to have to take note of the centre's suspended
 *	state, queuing and coalescing messages as needed
 */
CFDataRef __CFDistRecieve( CFMessagePortRef local, SInt32 msgid, CFDataRef data, void *info )
{
	//printf("local port done got a message.\n");

	// center hasn't been created at the time the callback's set, so just as easier to pull in the global
	CFNotificationCenterRef center = __CFDistributedCenter;
	
	CFIndex length = CFDataGetLength(data);
	if( length < sizeof(dndNotHeader) ) return NULL;

	CFReadStreamRef rs = CFReadStreamCreateWithBytesNoCopy( kCFAllocatorDefault, CFDataGetBytePtr(data), length, NULL );
	CFReadStreamOpen(rs);
	
	dndNotHeader header;
	CFReadStreamRead( rs, (UInt8 *)&header, sizeof(dndNotHeader) );

	//printf("\tmessage name = %u, object = %u, flags = %u\n", header.name, header.object, header.flags);

	// the rest of the data contains an array: [name, object, userInfo] with kCFBooleanFalse representing
	//	a missing object or userInfo
	CFPropertyListRef array = NULL;
	CFIndex format = kCFPropertyListBinaryFormat_v1_0;
	array = CFPropertyListCreateFromStream( kCFAllocatorDefault, rs, 0, kCFPropertyListImmutable, &format, NULL );
	if( (array == NULL) || (CFGetTypeID(array) != CFArrayGetTypeID()) ) return NULL;
	
	// now recover and set up the arguments to invoke callbacks. If either name or object hasn't been
	//	encountered (and hashed) before, add it to the hash store now, so that coalescing based on 
	//	pointers will work later. If it ever needs to.
	CFStringRef name; 
	if( (name = __CFNCUnhash(header.name)) == NULL ) // we haven't met this name before
	{
		__CFNCHash( CFArrayGetValueAtIndex(array, 0) );
		name = __CFNCUnhash(header.name);
	}
	
	CFStringRef object;
	if( header.object == 0 ) 
		object = NULL;
	else
		if( (object = __CFNCUnhash(header.object)) == NULL )
		{
			__CFNCHash( CFArrayGetValueAtIndex(array, 1) );
			object = __CFNCUnhash(header.object);
		}
	
	CFPropertyListRef userInfo = CFArrayGetValueAtIndex(array, 2);
	if( CFGetTypeID(userInfo) != CFDictionaryGetTypeID() ) userInfo = NULL;
	
	// we deliver now if the centre isn't suspended or the messages header says we should
	Boolean deliverNow = header.flags | kCFNotificationDeliverImmediately;

	__CFInvokeCallBacks(center, header.name, name, (const void *)header.object, (const void *)object, userInfo, deliverNow);

	if( userInfo != NULL ) CFRelease(userInfo);
	return NULL;
}
#endif

/*
 *	Add a notification to the table of registered notifications, optionally registering it with
 *	the ddistnoted daemon and adding the local message port's source to the main runloop
 *
 *	We can ignore name.
 */
void __CFDistAddNotification( CFStringRef name, CFHashCode hash, CFHashCode object )
{
	//fprintf(stderr, "register distributed notification %8X, %8X\n", hash, object);

	CFIndex count = __CFDistInfo.count;
	__CFDistNotification *nots = __CFDistInfo.nots;
	
	while( count-- ) 
	{
		while( nots->count == 0 ) nots++; // count == 0 is the empty record marker
		
		if( (nots->hash == hash) && (nots->object == object) )
		{
			nots->count++;
			return;
		}
		
		nots++;
	}
	
	// we need to register for this notification
	dndNotReg info = { __CFDistInfo.uid, hash, object };
	CFDataRef data = CFDataCreate( kCFAllocatorDefault, (const UInt8 *)&info, sizeof(dndNotReg) );
#if DEPLOYMENT_TARGET_MACOSX
	SInt32 result = CFMessagePortSendRequest( __CFDistInfo.remote, REGISTER_NOTIFICATION, data, 1.0, 0.0, NULL, NULL );
#else
   SInt32 result = 0;
#endif
	CFRelease(data);
	if(result != kCFMessagePortSuccess) return;

	if( __CFDistInfo.count == __CFDistInfo.capacity )
	{
		fprintf(stderr, "Increasing capacity of dist notification list\n");
		__CFDistInfo.capacity += CF_DIST_SIZE;
		__CFDistInfo.nots = (__CFDistNotification*)realloc( __CFDistInfo.nots, (__CFDistInfo.capacity * sizeof(__CFDistNotification)) );
		if( __CFDistInfo.nots == NULL ) return;
		
		// because I'm unsure if realloc zeroes the new memory...
		nots = __CFDistInfo.nots + __CFDistInfo.count;
		for( int i = 0; i < CF_DIST_SIZE; i++ ) (nots++)->count = 0;
		
		nots = __CFDistInfo.nots + __CFDistInfo.count;
	}
	else
	{
		nots =  __CFDistInfo.nots;
		while( nots->count != 0 ) nots++;
	}
	
	nots->hash = hash;
	nots->object = object;
	nots->count = 1;
	
	if( 0 == __CFDistInfo.count++ ) 
		CFRunLoopAddSource( CFRunLoopGetMain(), __CFDistInfo.rls, kCFRunLoopCommonModes );

	//fprintf(stderr, "added notification (no.%d) and leaving\n", __CFDistInfo.count);
}

void __CFDistRemoveNotification( CFHashCode hash, CFHashCode object )
{
	//fprintf(stderr, "dist remove notification\n");

	CFIndex count = __CFDistInfo.count;
	__CFDistNotification *nots = __CFDistInfo.nots;
	
	while( count-- )
	{
		while( nots->count == 0 ) nots++; // count == 0 is the empty record marker

		if( (nots->hash == hash) && (nots->object == object) )
		{
			if( 0 == --nots->count )
			{
				dndNotReg info = { __CFDistInfo.uid, hash, object };
				CFDataRef data = CFDataCreate( kCFAllocatorDefault, (const UInt8 *)&info, sizeof(dndNotReg) );
				if( data != NULL )
				{
#if DEPLOYMENT_TARGET_MACOSX
					CFMessagePortSendRequest(__CFDistInfo.remote, UNREGISTER_NOTIFICATION, data, 1.0, 1.0, NULL, NULL);
#endif
					CFRelease(data);
				}
				
				nots->hash = 0;
				nots->object = 0;
				
				if( 0 == --__CFDistInfo.count ) 
					CFRunLoopRemoveSource( CFRunLoopGetMain(), __CFDistInfo.rls, kCFRunLoopCommonModes );
			}
			return;
		}		
		nots++;
	}

	//fprintf(stderr, "dist remove notification done\n");
}


/*
 *	Functions used to add and remove notifications to the list we are monitoring and register
 *	with notifyd to recieve them. We track how many times each is added and removed, so we can 
 *	unregister for notifications when they're no-longer needed. As above, assumes the structure 
 *	is spinlocked.
 */
void __CFDarwinAddNotification( CFStringRef name, CFHashCode hash, CFHashCode ignored );
void __CFDarwinRemoveNotification( CFHashCode hash, CFHashCode ignored );

void __CFDarwinAddNotification( CFStringRef name, CFHashCode hash, CFHashCode ignored )
{
	//CFHashCode hash = CFHash(name);
	CFIndex count = __CFDarwinInfo.count;
	__CFDarwinNotifications *nots = __CFDarwinInfo.nots;
	
	while( count-- )
	{
		while( nots->hash == 0 ) nots++;
		
		if( nots->hash == hash ) // already registered for this notification
		{
			nots->count++;
			return;
		}
		
		nots++;
	}
	
	// haven't registered for this notification yet
	CFIndex length = CFStringGetLength(name);
   STACK_BUFFER_DECL(char, buffer, ++length);
	CFStringGetCString(name, buffer, length, kCFStringEncodingASCII);
	int token = 0;
#if DEPLOYMENT_TARGET_MACOSX
	mach_port_t port = CFMachPortGetPort(__CFDarwinInfo.port);
	
	if( 0 != notify_register_mach_port(buffer, &port, NOTIFY_REUSE, &token) ) return;
#endif

	if( __CFDarwinInfo.count == __CFDarwinInfo.capacity )
	{
		__CFDarwinInfo.capacity += CF_DARWIN_SIZE;
		__CFDarwinInfo.nots = (__CFDarwinNotifications*)realloc( __CFDarwinInfo.nots, ( __CFDarwinInfo.capacity * sizeof(__CFDarwinNotifications)));
		if( __CFDarwinInfo.nots == NULL ) return;
		
		// because I'm unsure if realloc zeroes the new memory...
		nots = __CFDarwinInfo.nots + __CFDarwinInfo.count;
		for( int i = 0; i < CF_DARWIN_SIZE; i++ ) (nots++)->hash = 0;
		
		nots = __CFDarwinInfo.nots + __CFDarwinInfo.count;
	}
	else
	{
		nots = __CFDarwinInfo.nots;
		while( nots->hash != 0 ) nots++;
	}
	
	nots->hash = hash;
	//nots->name = name;
	nots->token = token;
	nots->count = 1;
	
	if( 0 == __CFDarwinInfo.count++ ) 
		CFRunLoopAddSource( CFRunLoopGetMain(), __CFDarwinInfo.rls, kCFRunLoopCommonModes );
}

void __CFDarwinRemoveNotification( CFHashCode hash, CFHashCode ignored )
{
	//CFHashCode hash = CFHash(name);
	CFIndex count = __CFDarwinInfo.count;
	__CFDarwinNotifications *nots = __CFDarwinInfo.nots;
	
	while( count-- )
	{
		while( nots->hash == 0 ) nots++;
		
		if( nots->hash == hash )
		{
			if( nots->count-- > 1 ) return; // still want to recieve the notification
			
#if defined(__MACH__)
			notify_cancel(nots->token);
#endif
			
			nots->hash = 0;
			//nots->name = NULL;
			nots->token = 0;
			nots->count = 0;
			
			if( --__CFDarwinInfo.count == 0 )
				CFRunLoopRemoveSource( CFRunLoopGetMain(), __CFDarwinInfo.rls, kCFRunLoopCommonModes );
			
			return;
		}
		nots++;
	}
}


/*
 *	Add the observer info into the table of observers for the notification center, growing the
 *	table if need be. Duplicate observers with identical signatures are allowed.
 */
void __CFAddObserver( CFNotificationCenterRef center, const void *observer, CFNotificationCallback callBack, CFStringRef name, const void *object, CFNotificationSuspensionBehavior suspensionBehavior, __CFAdderCallBack cb )
{
	__CFObserver *obs;
	
	__CFSpinLock(&center->lock);
	
	if( center->observers == center->capacity )
	{
		//fprintf(stderr, "increasing size of observer records for center type %d\n", center->type);
		center->capacity += CF_OBS_SIZE;
		center->obs = (__CFObserver*)realloc(center->obs, (center->capacity * sizeof(__CFObserver)));
		if( center->obs == NULL )
		{
			fprintf(stderr, "Couldn't realloc observer records for notification center type %d\n", center->type);
			__CFSpinUnlock(&center->lock);
			return; 
		}
		obs = center->obs + center->observers;
		// because I'm unsure if realloc zeroes the new memory...
		for( int i = 0; i < CF_OBS_SIZE; i++ ) (obs++)->callback = NULL;
		obs = center->obs + center->observers;
	}
	else
	{
		obs = center->obs;
		while( obs->callback != NULL ) obs++;
	}
	
	// hash and store the name
	CFHashCode hash = __CFNCHash(name);
	
	//obs->name = name;
	obs->hash = hash;
	obs->object = object;
	obs->observer = observer;
	obs->callback = callBack;
	obs->sb = suspensionBehavior;
	
	center->observers++;
	
	if( cb != NULL ) cb(name, hash, (CFHashCode)object);
	
	__CFSpinUnlock(&center->lock);
}

/*
 *	Remove the observer with the given signature from the notification center's table.
 */
void __CFRemoveObserver( CFNotificationCenterRef center, const void *observer, CFHashCode name, const void *object, __CFRemoverCallBack cb )
{
	__CFSpinLock(&center->lock);
	
	//CFHashCode hash = (name == NULL) ? 0 : CFHash(name);
	CFIndex count = center->observers;
	__CFObserver *obs = center->obs;
	
	while( count-- ) 
	{
		while( obs->callback == NULL ) obs++;
		
		if( (obs->observer == observer)
		   && /* match name hash */ ((name == 0) || (name == obs->hash))
		   && /* match object */((object == NULL) || (object == obs->object)) )
		{
			//obs->name = NULL;
			obs->hash = 0;
			obs->object = NULL;
			obs->observer = NULL;
			obs->callback = NULL;
			obs->sb = 0;
			center->observers--;
			
			if( cb != NULL ) cb(name, (CFHashCode)object);
		}
		
		obs++;
	}
	
	__CFSpinUnlock(&center->lock);
}

/*
 *	Remove every instance of the observer from the notification centre's table.
 */
void __CFRemoveEveryObserver( CFNotificationCenterRef center, const void *observer, __CFRemoverCallBack cb )
{
	__CFSpinLock(&center->lock);
	
	CFIndex count = center->observers;	
	__CFObserver *obs = center->obs;
	
	while( count-- )
	{
		while( obs->callback == NULL ) obs++;
		
		if( obs->observer == observer )
		{
			if( cb != NULL ) cb(obs->hash, (CFHashCode)obs->object);

			//obs->name = NULL;
			obs->hash = 0;
			obs->object = NULL;
			obs->observer = NULL;
			obs->callback = NULL;
			obs->sb = 0;
			center->observers--;
		}
		
		obs++;
	}
	
	__CFSpinUnlock(&center->lock);	
}

/*
 *	Invoke the callback functions for the observers whose signature match the arguments.
 *
 *	This is a general routine which handles the special suspension behaviour of the
 *	distributed centre at the cost of extra un-needed checks while processing local
 *	and Darwin centre notifications.
 *
 *	I'm not entirely sure whether notifications sent with kCFNotificationDeliverImmediately
 *	should behave like notifications delivered to suspended observers with the deliver
 *	immediately behaviour and flush the notification queue... so at the moment it just
 *	jumps the queue and is delivered on its own.
 *
 *	The name and object arguments are used to find matching observers, while the nameReturn
 *	and objectReturn are passed to the observer's callbacks or queued.
 *		Local:			object == objectReturn
 *		Distributed:	object == hash, objectReturn == CFStringRef
 *		Darwin:			object == objectReturn == NULL
 */
void __CFInvokeCallBacks( CFNotificationCenterRef center, CFHashCode name, CFStringRef nameReturn, const void *object, const void *objectReturn, CFDictionaryRef userInfo, Boolean deliverNow )
{
	__CFSpinLock(&center->lock);
		
	CFIndex count = center->observers;
	__CFObserver *obs = center->obs;
	
	//printf("A\n");
	//__CFCenterDiag(center);
	
	// process each observer in the table
	while( count-- )
	{
		//printf("B\n");
		
		// find a record with a non-NULL callback field
		while( obs->callback == NULL ) obs++;
		
		//printf("C\n");
		//__CFObserverDiag( *obs );
		
		//printf("observer: 0x%X\n");
		
		// for an observer to qualify to recieve a notification, it need to match
		//	both name and object, taking into account the NULL-case "match any name
		//	or object"
		if( /* match name hash */ ((obs->hash == 0) || (obs->hash == name))
		   /* match object */ && ((obs->object == NULL) || (obs->object == object)) )
		{
			// found a match, now do we deliver the notification?
			if( deliverNow /* non-dist short-circuit */ || !center->suspended )
			{
				// CFMachPort source suggested unlocking before invoking callbacks
				__CFSpinUnlock(&center->lock);
				obs->callback((CFNotificationCenterRef)center, (void*)obs->observer, nameReturn, objectReturn, userInfo);
				__CFSpinLock(&center->lock);
			}
			else switch(obs->sb) 
			{
				case CFNotificationSuspensionBehaviorDrop: break;
				case CFNotificationSuspensionBehaviorCoalesce:
					__CFAddQueue( nameReturn, objectReturn, obs->observer, userInfo, obs->callback, TRUE );
					break;
				case CFNotificationSuspensionBehaviorHold:
					__CFAddQueue( nameReturn, objectReturn, obs->observer, userInfo, obs->callback, FALSE );
					break;
				case CFNotificationSuspensionBehaviorDeliverImmediately:
					if( __CFDistInfo.queueCount != 0 ) __CFDeliverQueue();
					obs->callback( (CFNotificationCenterRef)center, (void*)obs->observer, nameReturn, objectReturn, userInfo );
					break;
			}
		}
		
		obs++;
	}
	
	__CFSpinUnlock(&center->lock);
}


#if defined(__MACH__)
/*
 *	The CFMachPortCallBack invoked when a message arrives at the runloop from notifyd. The
 *	Darwin notification centre is passed in as the info... just because.
 */
void __CFDarwinCallBack(CFMachPortRef port, void *msg, CFIndex size, void *info)
{
	//printf("Got a message from a darwin port!\n");

	// first we retrieve the token associated with the notification
	int token = ((mach_msg_header_t *)msg)->msgh_id;

	// then we look for the matching record
	CFIndex count = __CFDarwinInfo.count;
	__CFDarwinNotifications *nots = __CFDarwinInfo.nots;
	
	while( count-- ) 
	{
		while( nots->hash == 0 ) nots++;
		
		if( nots->token == token ) // found it
		{
			count = -1;
			break;
		}
		
		nots++;
	}
	
	if( count != -1 ) return; // couldn't find the matching notification

	// then we send the notification to all the matching observers
	__CFInvokeCallBacks(__CFDarwinCenter, nots->hash, __CFNCUnhash(nots->hash), NULL, NULL, NULL, TRUE);
}
#endif

// shared creation method
CFNotificationCenterRef __CFCreateCenter( CFIndex type )
{
	// allocate the memory
	CFIndex size = sizeof(struct __CFNotificationCenter) - sizeof(CFRuntimeBase);
	struct __CFNotificationCenter *memory = (CFNotificationCenterRef)_CFRuntimeCreateInstance( kCFAllocatorDefault, __kCFNotificationCenterTypeID, size, NULL);
	if (NULL == memory) return NULL;
	
	memory->suspended = FALSE;
	memory->type = type;
   CF_SPINLOCK_INIT_FOR_STRUCTS(memory->lock);

	// allocate storage and set counters
	memory->observers = 0;
	memory->capacity = CF_OBS_SIZE;
	// IMPORTANT: after calloc, we assume memory is zeroed
	memory->obs = (__CFObserver*)calloc(CF_OBS_SIZE, sizeof(__CFObserver));
	
	if( memory->obs == NULL )
	{
		CFAllocatorDeallocate( kCFAllocatorDefault, memory );
		memory = NULL;
	}
	return memory;
}

/*
 *	The local notification center is used for synchronous intra-task communication and
 *	can always be created.
 */
CFNotificationCenterRef CFNotificationCenterGetLocalCenter(void) 
{
	__CFSpinLock(&__CFLocalCenterLock);
	if( __CFLocalCenter == NULL ) 
		__CFLocalCenter = __CFCreateCenter(CF_LOCAL_CENTER);
	__CFSpinUnlock(&__CFLocalCenterLock);
	return __CFLocalCenter;
}

/*
 *	The distributed center relies on the presence of a daemon (our ddistnoted on
 *	Darwin) to deliver inter-task notifications. This implementation tries to contact 
 *	it via CFMessagePort, and fails if a connection cannot be made.
 */
CFNotificationCenterRef CFNotificationCenterGetDistributedCenter(void) 
{
	//fprintf(stderr, "Entering CFNotificationCenterGetDistributedCenter()\n");

	__CFSpinLock(&__CFDistributedCenterLock);
	if( __CFDistributedCenter == NULL )
	{
		// generate a 'unique' port name for the current task
		char uname[128];
		//sprintf(uname, "ddistnoted-%s-%u", getprogname(), getpid());
		//printf("unique string is '%s'\n", uname);
		CFStringRef name = CFStringCreateWithCString( kCFAllocatorDefault, uname, kCFStringEncodingASCII );

		// create the local port now, because the daemon will look for it
		CFMessagePortContext context = { 0, NULL, NULL, NULL, NULL };
#if defined(__MACH__)
		CFMessagePortRef local = CFMessagePortCreateLocal( kCFAllocatorDefault, name, __CFDistRecieve, &context, NULL );
		
		if( local == NULL )
		{
			fprintf(stderr, "CFNC: Couldn't create a local message port.\n");
			__CFSpinUnlock(&__CFDistributedCenterLock);
			return NULL;
		}
#else
      CFMessagePortRef local = 0;
#endif
		
		//CFRunLoopSourceRef rls = 
		//CFRunLoopAddSource( CFRunLoopGetMain(), rls, kCFRunLoopCommonModes );
		
#if defined(DEPLOYMENT_TARGET_MACOSX)
		// create the remote port
		CFMessagePortRef remote = CFMessagePortCreateRemote( kCFAllocatorDefault, CFSTR("org.puredarwin.ddistnoted") );
		
		if( remote == NULL )
		{
			fprintf(stderr, "CFNC: Couldn't connect to message port.\n");
			__CFSpinUnlock(&__CFDistributedCenterLock);
			return NULL;
		}
#else
      CFMessagePortRef remote = 0;
#endif

		// squeeze our unique name, as ASCII, into a data object...
		CFIndex length = CFStringGetLength(name);
      STACK_BUFFER_DECL(UInt8, data, (++length + sizeof(long)));

		/*	Security sessions come via one of the security components, although
			I'm not sure which. Once we get everything working we may be able to
			actually get this working properly. */
		
		// if this isn't set -- and on other platforms -- we could maybe use userIds
#if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_LINUX
		long session = getuid();
#else
      long session = 0;
#endif
		
		if( session == 0 ) session = 1;
		
		//session = strtol( getenv("SECURITYSESSIONID"), NULL, 16 );
		*(long *)data = session;
		//printf("session id = %d\n", *(long *)data);
		
		// getsid() returns the same as getpid()...
		//printf("and getsid() reports %u\n", getsid(0));
		
		CFStringGetCString(name, (char *)(data + sizeof(long)), length, kCFStringEncodingASCII);
		CFDataRef dataOut = CFDataCreate( kCFAllocatorDefault, (const UInt8 *)data, (length + sizeof(long)) );
		//printf("'unique' name: '%s'\n", data);
		

		// ...send the register message...
		CFDataRef dataIn = NULL;
#if DEPLOYMENT_TARGET_MACOSX
		CFMessagePortSendRequest( remote, REGISTER_PORT, dataOut, 1.0, 1.0, kCFRunLoopDefaultMode, &dataIn);
#endif
		
		CFRelease(name);
		CFRelease(dataOut);

		if( (dataIn == NULL) || (CFDataGetLength(dataIn) == 0) ) return NULL;
		
		CFHashCode hash;
		CFRange range = { 0, sizeof(CFHashCode) };
		CFDataGetBytes(dataIn, range, (UInt8 *)&hash);
		
		//if( h2 == -1 ) return NULL;

		//printf("Worked. Our hash = %u, returned hash = %u\n", h1, h2);
		
		// that seemed to work, so we'll try to allocate the centre object
		__CFDistributedCenter = __CFCreateCenter(CF_DIST_CENTER);
		
		if( __CFDistributedCenter == NULL ) return NULL;
		
		__CFDistInfo.nots = (__CFDistNotification*)calloc(CF_DIST_SIZE, sizeof(__CFDistNotification));
		if( __CFDistInfo.nots == NULL ) return NULL;

		__CFDistInfo.queue = (__CFQueueRecord*)calloc(CF_QUEUE_SIZE, sizeof(__CFQueueRecord));
		if( __CFDistInfo.queue == NULL ) return NULL;

		__CFDistInfo.local = local;
		__CFDistInfo.remote = remote;
		__CFDistInfo.session = session;
		__CFDistInfo.uid = hash;
#if defined(DEPLOYMENT_TARGET_MACOSX)
		__CFDistInfo.rls = CFMessagePortCreateRunLoopSource( kCFAllocatorDefault, local, 0 );
// do we need an "added to runloop" flag?
#endif
		//__PFDistInfo.count = 0;
		__CFDistInfo.capacity = CF_DIST_SIZE;
		//__PFDistInfo.count = 0;
		__CFDistInfo.capacity = CF_QUEUE_SIZE;
	}
	__CFSpinUnlock(&__CFDistributedCenterLock);

	//fprintf(stderr, "Leaving CFNotificationCenterGetDistributedCenter()\n");

	return __CFDistributedCenter;
}

/*
 *	The Darwin notification center passes inter-task notifications via the notifyd 
 *	daemon, with which it comunicates using the functions in <notify.h> for sending
 *	and a runloop-attached Mach port for recieving. I think this is Darwin-specific,
 *	altough other BSDs may have a similar set-up.
 *
 *	We create the CFMachPort and its runloop source used for recieving messages here 
 *	so that they're available when observers are added.
 */
CFNotificationCenterRef CFNotificationCenterGetDarwinNotifyCenter(void) 
{
	__CFSpinLock(&__CFDarwinCenterLock);
	if( __CFDarwinCenter == NULL )
	{
		__CFDarwinCenter = __CFCreateCenter(CF_DARWIN_CENTER);

#if DEPLOYMENT_TARGET_MACOSX
		CFMachPortContext context = { 0, (void *)__CFDarwinCenter, NULL, NULL, NULL };
		__CFDarwinInfo.port = CFMachPortCreate( kCFAllocatorDefault, __CFDarwinCallBack, &context, NULL );
		__CFDarwinInfo.rls = CFMachPortCreateRunLoopSource( kCFAllocatorDefault, __CFDarwinInfo.port, 0 );
#endif
		
		__CFDarwinInfo.nots = (__CFDarwinNotifications*)calloc(CF_DARWIN_SIZE, sizeof(__CFDarwinNotifications));
		__CFDarwinInfo.count = 0;
		__CFDarwinInfo.capacity = CF_DARWIN_SIZE;
	}
	__CFSpinUnlock(&__CFDarwinCenterLock);
	return __CFDarwinCenter;
}



/*
 *	Add an observer to the notification centre. In the local case at least, the CF
 *	behaviour is to allow multiple indentical observers.
 */
void CFNotificationCenterAddObserver(CFNotificationCenterRef center, const void *observer, CFNotificationCallback callBack, CFStringRef name, const void *object, CFNotificationSuspensionBehavior suspensionBehavior) 
{ 
	// common causes of failure
	if( (center == NULL) || (CFGetTypeID(center) != __kCFNotificationCenterTypeID) || (callBack == NULL) || ((name == NULL) && (object == NULL)) ) 
		return;

	switch (center->type) 
	{
		case CF_LOCAL_CENTER:
			__CFAddObserver(center, observer, callBack, name, object, 0, NULL);
			break;
		
		case CF_DIST_CENTER:
			// For distributed centres, object should always be a string. We hash the string and use
			//	this value for all comparisons until notifications are delivered
			if( object != NULL )
			{
				if( CFGetTypeID((CFTypeRef)object) != CFStringGetTypeID() ) return;
				object = (const void *)__CFNCHash((CFStringRef)object);
			}
			__CFAddObserver(center, observer, callBack, name, object, suspensionBehavior, __CFDistAddNotification);
			break;
			
		case CF_DARWIN_CENTER:
			if( name == NULL ) return;
			__CFAddObserver(center, observer, callBack, name, NULL, 0, __CFDarwinAddNotification);
			break;
	}
}


/*
 *
 */
void CFNotificationCenterRemoveObserver(CFNotificationCenterRef center, const void *observer, CFStringRef name, const void *object) 
{ 
	if( (center == NULL) || (CFGetTypeID(center) != __kCFNotificationCenterTypeID) || (observer == NULL) || (center->observers == 0) ) 
		return;

	CFHashCode hash = (name == NULL) ? 0 : CFHash(name);
	
	switch(center->type) 
	{
		case CF_DIST_CENTER:
			if( object != NULL )
			{
				if( CFGetTypeID(object) != CFStringGetTypeID() ) return; // wouldn't have been added
				object = (void *)CFHash(object);
			}
			if( (name == NULL) && (object == NULL) ) 
				__CFRemoveEveryObserver(center, observer, __CFDistRemoveNotification);
			else
				__CFRemoveObserver(center, observer, hash, object, __CFDistRemoveNotification);
			break;
			
		case CF_LOCAL_CENTER:
			if( (name == NULL) && (object == NULL) ) 
				__CFRemoveEveryObserver(center, observer, NULL);
			else
				__CFRemoveObserver(center, observer, hash, object, NULL);
			break;
			
		case CF_DARWIN_CENTER:
			if( name == NULL )
				__CFRemoveEveryObserver(center, observer, __CFDarwinRemoveNotification);
			else
				__CFRemoveObserver(center, observer, hash, NULL, __CFDarwinRemoveNotification);
			break;
	}
}


/*
 *
 */
void CFNotificationCenterRemoveEveryObserver(CFNotificationCenterRef center, const void *observer) 
{ 
	if( (center == NULL) || (CFGetTypeID(center) != __kCFNotificationCenterTypeID) || (observer == NULL) || (center->observers == 0) )
		return;

	switch(center->type) 
	{
		case CF_LOCAL_CENTER:
			__CFRemoveEveryObserver(center, observer, NULL);
			break;
		case CF_DIST_CENTER:
			__CFRemoveEveryObserver(center, observer, __CFDistRemoveNotification);
			break;
		case CF_DARWIN_CENTER:
			__CFRemoveEveryObserver(center, observer, __CFDarwinRemoveNotification);
			break;
	}
}



/*
 *	Type-specific notification posting functions
 */


/*
 *	Post a notification to the ddistnoted daemon which runs the distributed
 *	notification centre.
 *
 *	ddistnoted uses name and object hashes, along with session ids, to route
 *	distributions. The data object contains a 3-item array containing the name,
 *	object string and userInfo dictionary. We have to send the name and object
 *	because an observer may not have previously hashed and stored either string.
 */
void __CFPostDistributedNotification( CFNotificationCenterRef center, CFStringRef name, CFStringRef object, CFDictionaryRef userInfo, CFOptionFlags options )
{
	CFPropertyListRef plist[3];
	plist[0] = name;
	
	// object must be a string when posting to a distributed centre
	CFHashCode objectHash;
	if(object == NULL)
	{
		objectHash = 0;
		plist[1] = kCFBooleanFalse; // used to signal a null entry
	}
	else 
	{
		if(CFGetTypeID(object) != CFStringGetTypeID()) return;
		objectHash = __CFNCHash(object);
		plist[1] = object;
	}

	plist[2] = (userInfo == NULL) ? (CFDictionaryRef)kCFBooleanFalse : userInfo;
	CFArrayRef array = CFArrayCreate( kCFAllocatorDefault, (const void **)&plist, 3, NULL );
	
	// we don't need to store the strings these hashes represent
	CFHashCode nameHash = CFHash(name);
	dndNotHeader info = { __CFDistInfo.session, nameHash, objectHash, options };
	
	CFWriteStreamRef ws = CFWriteStreamCreateWithAllocatedBuffers( kCFAllocatorDefault, kCFAllocatorDefault );
	CFWriteStreamOpen(ws);
	CFWriteStreamWrite( ws, (const UInt8 *)&info, sizeof(dndNotHeader) );

	// write the property list, but don't worry if an error occurs
	CFPropertyListWriteToStream( array, ws, kCFPropertyListBinaryFormat_v1_0, NULL );
	
	CFWriteStreamClose(ws);
	CFDataRef data = (CFDataRef)CFWriteStreamCopyProperty( ws, kCFStreamPropertyDataWritten );
	CFRelease(ws);
	CFRelease(array);
	
	if( data == NULL ) return;
	
#if DEPLOYMENT_TARGET_MACOSX
	CFMessagePortSendRequest( __CFDistInfo.remote, NOTIFICATION, data, 1.0, 1.0, NULL, NULL );
#endif
}


/*
 *	All things considered, posting Darwin/notifyd notifications is fairly painless.
 */
void __CFPostDarwinNotification( CFNotificationCenterRef center, CFStringRef name )
{
	CFIndex length = CFStringGetLength(name);
	if( length == 0 ) return;
   STACK_BUFFER_DECL(char, buffer, ++length);
	CFStringGetCString(name, buffer, length, kCFStringEncodingASCII);
#if defined(__MACH__)
	notify_post(buffer);
#endif
}


/*
 *	Post notification: Interprets the deliverImmediately flag and invokes the other
 *	post notification method.
 */
void CFNotificationCenterPostNotification(CFNotificationCenterRef center, CFStringRef name, const void *object, CFDictionaryRef userInfo, Boolean deliverImmediately) 
{ 
	CFOptionFlags options = deliverImmediately ? kCFNotificationDeliverImmediately : 0;
	return CFNotificationCenterPostNotificationWithOptions(center, name, object, userInfo, options);
}


/*
 *	Checks for some common reasons why posting a notification could fail, then invokes
 *	the centre-specific posting message with the required sub-set of arguments.
 */
void CFNotificationCenterPostNotificationWithOptions(CFNotificationCenterRef center, CFStringRef name, const void *object, CFDictionaryRef userInfo, CFOptionFlags options) 
{ 
	//fprintf(stderr, "Entering CFNotificationCenterPostNotificationWithOptions()\n");

	if( (center == NULL) || (CFGetTypeID(center) != __kCFNotificationCenterTypeID) || (name == NULL) )
		return;

	CFHashCode hash = (name == NULL) ? 0 : CFHash(name);
	
	if( (center->type == CF_LOCAL_CENTER) && (center->observers != 0) )
		return __CFInvokeCallBacks( center, hash, name, object, object, userInfo, TRUE );
	else if( center->type == CF_DIST_CENTER )
	{
		//return 
		__CFPostDistributedNotification( center, name, (CFStringRef)object, userInfo, options );
		//fprintf(stderr, "Leaving CFNotificationCenterPostNotificationWithOptions()\n");
		return;
	}
	else if( center->type == CF_DARWIN_CENTER )
		return __CFPostDarwinNotification( center, name );
}