src/joystick/darwin/SDL_sysjoystick.c

/*
	SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2012 Sam Lantinga

	This library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Library General Public
	License as published by the Free Software Foundation; either
	version 2 of the License, or (at your option) any later version.

	This library 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
	Library General Public License for more details.

	You should have received a copy of the GNU Library General Public
	License along with this library; if not, write to the Free
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

	Sam Lantinga
	slouken@libsdl.org
*/
#include "SDL_config.h"

#ifdef SDL_JOYSTICK_IOKIT

/* SDL joystick driver for Darwin / Mac OS X, based on the IOKit HID API */
/* Written 2001 by Max Horn */

#include <unistd.h>
#include <ctype.h>
#include <sysexits.h>
#include <mach/mach.h>
#include <mach/mach_error.h>
#include <IOKit/IOKitLib.h>
#include <IOKit/IOCFPlugIn.h>
#ifdef MACOS_10_0_4
#include <IOKit/hidsystem/IOHIDUsageTables.h>
#else
/* The header was moved here in Mac OS X 10.1 */
#include <Kernel/IOKit/hidsystem/IOHIDUsageTables.h>
#endif
#include <IOKit/hid/IOHIDLib.h>
#include <IOKit/hid/IOHIDKeys.h>
#include <CoreFoundation/CoreFoundation.h>
#include <Carbon/Carbon.h> /* for NewPtrClear, DisposePtr */

#include "SDL_joystick.h"
#include "../SDL_sysjoystick.h"
#include "../SDL_joystick_c.h"

struct recElement
{
	IOHIDElementCookie cookie;				/* unique value which identifies element, will NOT change */
	long min;								/* reported min value possible */
	long max;								/* reported max value possible */
#if 0
	/* TODO: maybe should handle the following stuff somehow? */

	long scaledMin;							/* reported scaled min value possible */
	long scaledMax;							/* reported scaled max value possible */
	long size;								/* size in bits of data return from element */
	Boolean relative;						/* are reports relative to last report (deltas) */
	Boolean wrapping;						/* does element wrap around (one value higher than max is min) */
	Boolean nonLinear;						/* are the values reported non-linear relative to element movement */
	Boolean preferredState;					/* does element have a preferred state (such as a button) */
	Boolean nullState;						/* does element have null state */
#endif /* 0 */

	/* runtime variables used for auto-calibration */
	long minReport;							/* min returned value */
	long maxReport;							/* max returned value */
	
	struct recElement * pNext;				/* next element in list */
};
typedef struct recElement recElement;

struct joystick_hwdata
{
	IOHIDDeviceInterface ** interface;		/* interface to device, NULL = no interface */

	char product[256];							/* name of product */
	long usage;								/* usage page from IOUSBHID Parser.h which defines general usage */
	long usagePage;							/* usage within above page from IOUSBHID Parser.h which defines specific usage */

	long axes;								/* number of axis (calculated, not reported by device) */
	long buttons;							/* number of buttons (calculated, not reported by device) */
	long hats;								/* number of hat switches (calculated, not reported by device) */
	long elements;							/* number of total elements (shouldbe total of above) (calculated, not reported by device) */

	recElement* firstAxis;
	recElement* firstButton;
	recElement* firstHat;

	int removed;
	int uncentered;

	struct joystick_hwdata* pNext;			/* next device */
};
typedef struct joystick_hwdata recDevice;


/* Linked list of all available devices */
static recDevice *gpDeviceList = NULL;


static void HIDReportErrorNum (char * strError, long numError)
{
	SDL_SetError(strError);
}

static void HIDGetCollectionElements (CFMutableDictionaryRef deviceProperties, recDevice *pDevice);

/* returns current value for element, polling element
 * will return 0 on error conditions which should be accounted for by application
 */

static SInt32 HIDGetElementValue (recDevice *pDevice, recElement *pElement)
{
	IOReturn result = kIOReturnSuccess;
	IOHIDEventStruct hidEvent;
	hidEvent.value = 0;
	
	if (NULL != pDevice && NULL != pElement && NULL != pDevice->interface)
	{
		result = (*(pDevice->interface))->getElementValue(pDevice->interface, pElement->cookie, &hidEvent);
		if (kIOReturnSuccess == result)
		{
			/* record min and max for auto calibration */
			if (hidEvent.value < pElement->minReport)
				pElement->minReport = hidEvent.value;
			if (hidEvent.value > pElement->maxReport)
				pElement->maxReport = hidEvent.value;
		}
	}

	/* auto user scale */
	return hidEvent.value;
}

static SInt32 HIDScaledCalibratedValue (recDevice *pDevice, recElement *pElement, long min, long max)
{
	float deviceScale = max - min;
	float readScale = pElement->maxReport - pElement->minReport;
	SInt32 value = HIDGetElementValue(pDevice, pElement);
	if (readScale == 0)
		return value; /* no scaling at all */
	else
		return ((value - pElement->minReport) * deviceScale / readScale) + min;
}


static void HIDRemovalCallback(void * target,
                               IOReturn result,
                               void * refcon,
                               void * sender)
{
	recDevice *device = (recDevice *) refcon;
	device->removed = 1;
	device->uncentered = 1;
}


/* Create and open an interface to device, required prior to extracting values or building queues.
 * Note: appliction now owns the device and must close and release it prior to exiting
 */

static IOReturn HIDCreateOpenDeviceInterface (io_object_t hidDevice, recDevice *pDevice)
{
	IOReturn result = kIOReturnSuccess;
	HRESULT plugInResult = S_OK;
	SInt32 score = 0;
	IOCFPlugInInterface ** ppPlugInInterface = NULL;
	
	if (NULL == pDevice->interface)
	{
		result = IOCreatePlugInInterfaceForService (hidDevice, kIOHIDDeviceUserClientTypeID,
													kIOCFPlugInInterfaceID, &ppPlugInInterface, &score);
		if (kIOReturnSuccess == result)
		{
			/* Call a method of the intermediate plug-in to create the device interface */
			plugInResult = (*ppPlugInInterface)->QueryInterface (ppPlugInInterface,
								CFUUIDGetUUIDBytes (kIOHIDDeviceInterfaceID), (void *) &(pDevice->interface));
			if (S_OK != plugInResult)
				HIDReportErrorNum ("Couldn't query HID class device interface from plugInInterface", plugInResult);
			(*ppPlugInInterface)->Release (ppPlugInInterface);
		}
		else
			HIDReportErrorNum ("Failed to create **plugInInterface via IOCreatePlugInInterfaceForService.", result);
	}
	if (NULL != pDevice->interface)
	{
		result = (*(pDevice->interface))->open (pDevice->interface, 0);
		if (kIOReturnSuccess != result)
			HIDReportErrorNum ("Failed to open pDevice->interface via open.", result);
		else
			(*(pDevice->interface))->setRemovalCallback (pDevice->interface, HIDRemovalCallback, pDevice, pDevice);

	}
	return result;
}

/* Closes and releases interface to device, should be done prior to exting application
 * Note: will have no affect if device or interface do not exist
 * application will "own" the device if interface is not closed
 * (device may have to be plug and re-plugged in different location to get it working again without a restart)
 */

static IOReturn HIDCloseReleaseInterface (recDevice *pDevice)
{
	IOReturn result = kIOReturnSuccess;
	
	if ((NULL != pDevice) && (NULL != pDevice->interface))
	{
		/* close the interface */
		result = (*(pDevice->interface))->close (pDevice->interface);
		if (kIOReturnNotOpen == result)
		{
			/* do nothing as device was not opened, thus can't be closed */
		}
		else if (kIOReturnSuccess != result)
			HIDReportErrorNum ("Failed to close IOHIDDeviceInterface.", result);
		/* release the interface */
		result = (*(pDevice->interface))->Release (pDevice->interface);
		if (kIOReturnSuccess != result)
			HIDReportErrorNum ("Failed to release IOHIDDeviceInterface.", result);
		pDevice->interface = NULL;
	}	
	return result;
}

/* extracts actual specific element information from each element CF dictionary entry */

static void HIDGetElementInfo (CFTypeRef refElement, recElement *pElement)
{
	long number;
	CFTypeRef refType;

	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementCookieKey));
	if (refType && CFNumberGetValue (refType, kCFNumberLongType, &number))
		pElement->cookie = (IOHIDElementCookie) number;
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementMinKey));
	if (refType && CFNumberGetValue (refType, kCFNumberLongType, &number))
		pElement->minReport = pElement->min = number;
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementMaxKey));
	if (refType && CFNumberGetValue (refType, kCFNumberLongType, &number))
		pElement->maxReport = pElement->max = number;
/*
	TODO: maybe should handle the following stuff somehow?

	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementScaledMinKey));
	if (refType && CFNumberGetValue (refType, kCFNumberLongType, &number))
		pElement->scaledMin = number;
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementScaledMaxKey));
	if (refType && CFNumberGetValue (refType, kCFNumberLongType, &number))
		pElement->scaledMax = number;
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementSizeKey));
	if (refType && CFNumberGetValue (refType, kCFNumberLongType, &number))
		pElement->size = number;
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementIsRelativeKey));
	if (refType)
		pElement->relative = CFBooleanGetValue (refType);
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementIsWrappingKey));
	if (refType)
		pElement->wrapping = CFBooleanGetValue (refType);
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementIsNonLinearKey));
	if (refType)
		pElement->nonLinear = CFBooleanGetValue (refType);
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementHasPreferedStateKey));
	if (refType)
		pElement->preferredState = CFBooleanGetValue (refType);
	refType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementHasNullStateKey));
	if (refType)
		pElement->nullState = CFBooleanGetValue (refType);
*/
}			

/* examines CF dictionary vlaue in device element hierarchy to determine if it is element of interest or a collection of more elements
 * if element of interest allocate storage, add to list and retrieve element specific info
 * if collection then pass on to deconstruction collection into additional individual elements
 */

static void HIDAddElement (CFTypeRef refElement, recDevice* pDevice)
{
	recElement* element = NULL;
	recElement** headElement = NULL;
	long elementType, usagePage, usage;
	CFTypeRef refElementType = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementTypeKey));
	CFTypeRef refUsagePage = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementUsagePageKey));
	CFTypeRef refUsage = CFDictionaryGetValue (refElement, CFSTR(kIOHIDElementUsageKey));


	if ((refElementType) && (CFNumberGetValue (refElementType, kCFNumberLongType, &elementType)))
	{
		/* look at types of interest */
		if ((elementType == kIOHIDElementTypeInput_Misc) || (elementType == kIOHIDElementTypeInput_Button) ||
			(elementType == kIOHIDElementTypeInput_Axis))
		{
			if (refUsagePage && CFNumberGetValue (refUsagePage, kCFNumberLongType, &usagePage) &&
				refUsage && CFNumberGetValue (refUsage, kCFNumberLongType, &usage))
			{
				switch (usagePage) /* only interested in kHIDPage_GenericDesktop and kHIDPage_Button */
				{
					case kHIDPage_GenericDesktop:
						{
							switch (usage) /* look at usage to determine function */
							{
								case kHIDUsage_GD_X:
								case kHIDUsage_GD_Y:
								case kHIDUsage_GD_Z:
								case kHIDUsage_GD_Rx:
								case kHIDUsage_GD_Ry:
								case kHIDUsage_GD_Rz:
								case kHIDUsage_GD_Slider:
								case kHIDUsage_GD_Dial:
								case kHIDUsage_GD_Wheel:
									element = (recElement *) NewPtrClear (sizeof (recElement));
									if (element)
									{
										pDevice->axes++;
										headElement = &(pDevice->firstAxis);
									}
								break;
								case kHIDUsage_GD_Hatswitch:
									element = (recElement *) NewPtrClear (sizeof (recElement));
									if (element)
									{
										pDevice->hats++;
										headElement = &(pDevice->firstHat);
									}
								break;
							}							
						}
						break;
					case kHIDPage_Button:
						element = (recElement *) NewPtrClear (sizeof (recElement));
						if (element)
						{
							pDevice->buttons++;
							headElement = &(pDevice->firstButton);
						}
						break;
					case kHIDPage_Simulation:
                        {
                            switch (usage) /* look at usage to determine function */
                            {
                                case kHIDUsage_Sim_Rudder:
                                case kHIDUsage_Sim_Throttle:
                                    element = (recElement *) NewPtrClear (sizeof (recElement));
                                    if (element)
                                    {
                                        pDevice->axes++;
                                        headElement = &(pDevice->firstAxis);
                                    }
                                    break;
                            }							
                        }
						break;
					default:
						break;
				}
			}
		}
		else if (kIOHIDElementTypeCollection == elementType)
			HIDGetCollectionElements ((CFMutableDictionaryRef) refElement, pDevice);
	}

	if (element && headElement) /* add to list */
	{
		pDevice->elements++;
		if (NULL == *headElement)
			*headElement = element;
		else
		{
			recElement *elementPrevious, *elementCurrent;
			elementCurrent = *headElement;
			while (elementCurrent)
			{
				elementPrevious = elementCurrent;
				elementCurrent = elementPrevious->pNext;
			}
			elementPrevious->pNext = element;
		}
		element->pNext = NULL;
		HIDGetElementInfo (refElement, element);
	}
}

/* collects information from each array member in device element list (each array memeber = element) */

static void HIDGetElementsCFArrayHandler (const void * value, void * parameter)
{
	if (CFGetTypeID (value) == CFDictionaryGetTypeID ())
		HIDAddElement ((CFTypeRef) value, (recDevice *) parameter);
}

/* handles retrieval of element information from arrays of elements in device IO registry information */

static void HIDGetElements (CFTypeRef refElementCurrent, recDevice *pDevice)
{
	CFTypeID type = CFGetTypeID (refElementCurrent);
	if (type == CFArrayGetTypeID()) /* if element is an array */
	{
		CFRange range = {0, CFArrayGetCount (refElementCurrent)};
		/* CountElementsCFArrayHandler called for each array member */
		CFArrayApplyFunction (refElementCurrent, range, HIDGetElementsCFArrayHandler, pDevice);
	}
}			

/* handles extracting element information from element collection CF types
 * used from top level element decoding and hierarchy deconstruction to flatten device element list
 */

static void HIDGetCollectionElements (CFMutableDictionaryRef deviceProperties, recDevice *pDevice)
{
	CFTypeRef refElementTop = CFDictionaryGetValue (deviceProperties, CFSTR(kIOHIDElementKey));
	if (refElementTop)
		HIDGetElements (refElementTop, pDevice);
}

/* use top level element usage page and usage to discern device usage page and usage setting appropriate vlaues in device record */

static void HIDTopLevelElementHandler (const void * value, void * parameter)
{
	CFTypeRef refCF = 0;
	if (CFGetTypeID (value) != CFDictionaryGetTypeID ())
		return;
	refCF = CFDictionaryGetValue (value, CFSTR(kIOHIDElementUsagePageKey));
	if (!CFNumberGetValue (refCF, kCFNumberLongType, &((recDevice *) parameter)->usagePage))
		SDL_SetError ("CFNumberGetValue error retrieving pDevice->usagePage.");
	refCF = CFDictionaryGetValue (value, CFSTR(kIOHIDElementUsageKey));
	if (!CFNumberGetValue (refCF, kCFNumberLongType, &((recDevice *) parameter)->usage))
		SDL_SetError ("CFNumberGetValue error retrieving pDevice->usage.");
}

/* extracts device info from CF dictionary records in IO registry */

static void HIDGetDeviceInfo (io_object_t hidDevice, CFMutableDictionaryRef hidProperties, recDevice *pDevice)
{
	CFMutableDictionaryRef usbProperties = 0;
	io_registry_entry_t parent1, parent2;
	
	/* Mac OS X currently is not mirroring all USB properties to HID page so need to look at USB device page also
	 * get dictionary for usb properties: step up two levels and get CF dictionary for USB properties
	 */
	if ((KERN_SUCCESS == IORegistryEntryGetParentEntry (hidDevice, kIOServicePlane, &parent1)) &&
		(KERN_SUCCESS == IORegistryEntryGetParentEntry (parent1, kIOServicePlane, &parent2)) &&
		(KERN_SUCCESS == IORegistryEntryCreateCFProperties (parent2, &usbProperties, kCFAllocatorDefault, kNilOptions)))
	{
		if (usbProperties)
		{
			CFTypeRef refCF = 0;
			/* get device info
			 * try hid dictionary first, if fail then go to usb dictionary
			 */
			
			
			/* get product name */
			refCF = CFDictionaryGetValue (hidProperties, CFSTR(kIOHIDProductKey));
			if (!refCF)
				refCF = CFDictionaryGetValue (usbProperties, CFSTR("USB Product Name"));
			if (refCF)
			{
				if (!CFStringGetCString (refCF, pDevice->product, 256, CFStringGetSystemEncoding ()))
					SDL_SetError ("CFStringGetCString error retrieving pDevice->product.");
			}
			
			/* get usage page and usage */
			refCF = CFDictionaryGetValue (hidProperties, CFSTR(kIOHIDPrimaryUsagePageKey));
			if (refCF)
			{
				if (!CFNumberGetValue (refCF, kCFNumberLongType, &pDevice->usagePage))
					SDL_SetError ("CFNumberGetValue error retrieving pDevice->usagePage.");
				refCF = CFDictionaryGetValue (hidProperties, CFSTR(kIOHIDPrimaryUsageKey));
				if (refCF)
					if (!CFNumberGetValue (refCF, kCFNumberLongType, &pDevice->usage))
						SDL_SetError ("CFNumberGetValue error retrieving pDevice->usage.");
			}

			if (NULL == refCF) /* get top level element HID usage page or usage */
			{
				/* use top level element instead */
				CFTypeRef refCFTopElement = 0;
				refCFTopElement = CFDictionaryGetValue (hidProperties, CFSTR(kIOHIDElementKey));
				{
					/* refCFTopElement points to an array of element dictionaries */
					CFRange range = {0, CFArrayGetCount (refCFTopElement)};
					CFArrayApplyFunction (refCFTopElement, range, HIDTopLevelElementHandler, pDevice);
				}
			}

			CFRelease (usbProperties);
		}
		else
			SDL_SetError ("IORegistryEntryCreateCFProperties failed to create usbProperties.");

		if (kIOReturnSuccess != IOObjectRelease (parent2))
			SDL_SetError ("IOObjectRelease error with parent2.");
		if (kIOReturnSuccess != IOObjectRelease (parent1))
			SDL_SetError ("IOObjectRelease error with parent1.");
	}
}


static recDevice *HIDBuildDevice (io_object_t hidDevice)
{
	recDevice *pDevice = (recDevice *) NewPtrClear (sizeof (recDevice));
	if (pDevice)
	{
		/* get dictionary for HID properties */
		CFMutableDictionaryRef hidProperties = 0;
		kern_return_t result = IORegistryEntryCreateCFProperties (hidDevice, &hidProperties, kCFAllocatorDefault, kNilOptions);
		if ((result == KERN_SUCCESS) && hidProperties)
		{
			/* create device interface */
			result = HIDCreateOpenDeviceInterface (hidDevice, pDevice);
			if (kIOReturnSuccess == result)
			{
				HIDGetDeviceInfo (hidDevice, hidProperties, pDevice); /* hidDevice used to find parents in registry tree */
				HIDGetCollectionElements (hidProperties, pDevice);
			}
			else
			{
				DisposePtr((Ptr)pDevice);
				pDevice = NULL;
			}
			CFRelease (hidProperties);
		}
		else
		{
			DisposePtr((Ptr)pDevice);
			pDevice = NULL;
		}
	}
	return pDevice;
}

/* disposes of the element list associated with a device and the memory associated with the list
 */

static void HIDDisposeElementList (recElement **elementList)
{
	recElement *pElement = *elementList;
	while (pElement)
	{
		recElement *pElementNext = pElement->pNext;
		DisposePtr ((Ptr) pElement);
		pElement = pElementNext;
	}
	*elementList = NULL;
}

/* disposes of a single device, closing and releaseing interface, freeing memory fro device and elements, setting device pointer to NULL
 * all your device no longer belong to us... (i.e., you do not 'own' the device anymore)
 */

static recDevice *HIDDisposeDevice (recDevice **ppDevice)
{
	kern_return_t result = KERN_SUCCESS;
	recDevice *pDeviceNext = NULL;
	if (*ppDevice)
	{
		/* save next device prior to disposing of this device */
		pDeviceNext = (*ppDevice)->pNext;
		
		/* free element lists */
		HIDDisposeElementList (&(*ppDevice)->firstAxis);
		HIDDisposeElementList (&(*ppDevice)->firstButton);
		HIDDisposeElementList (&(*ppDevice)->firstHat);
		
		result = HIDCloseReleaseInterface (*ppDevice); /* function sanity checks interface value (now application does not own device) */
		if (kIOReturnSuccess != result)
			HIDReportErrorNum ("HIDCloseReleaseInterface failed when trying to dipose device.", result);
		DisposePtr ((Ptr)*ppDevice);
		*ppDevice = NULL;
	}
	return pDeviceNext;
}


/* Function to scan the system for joysticks.
 * Joystick 0 should be the system default joystick.
 * This function should return the number of available joysticks, or -1
 * on an unrecoverable fatal error.
 */
int SDL_SYS_JoystickInit(void)
{
	IOReturn result = kIOReturnSuccess;
	mach_port_t masterPort = 0;
	io_iterator_t hidObjectIterator = 0;
	CFMutableDictionaryRef hidMatchDictionary = NULL;
	recDevice *device, *lastDevice;
	io_object_t ioHIDDeviceObject = 0;
	
	SDL_numjoysticks = 0;
	
	if (gpDeviceList)
	{
		SDL_SetError("Joystick: Device list already inited.");
		return -1;
	}
	
	result = IOMasterPort (bootstrap_port, &masterPort);
	if (kIOReturnSuccess != result)
	{
		SDL_SetError("Joystick: IOMasterPort error with bootstrap_port.");
		return -1;
	}

	/* Set up a matching dictionary to search I/O Registry by class name for all HID class devices. */
	hidMatchDictionary = IOServiceMatching (kIOHIDDeviceKey);
	if (hidMatchDictionary)
	{
		/* Add key for device type (joystick, in this case) to refine the matching dictionary. */
		
		/* NOTE: we now perform this filtering later
		UInt32 usagePage = kHIDPage_GenericDesktop;
		UInt32 usage = kHIDUsage_GD_Joystick;
		CFNumberRef refUsage = NULL, refUsagePage = NULL;

		refUsage = CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &usage);
		CFDictionarySetValue (hidMatchDictionary, CFSTR (kIOHIDPrimaryUsageKey), refUsage);
		refUsagePage = CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &usagePage);
		CFDictionarySetValue (hidMatchDictionary, CFSTR (kIOHIDPrimaryUsagePageKey), refUsagePage);
		*/
	}
	else
	{
		SDL_SetError("Joystick: Failed to get HID CFMutableDictionaryRef via IOServiceMatching.");
		return -1;
	}
	
	/*/ Now search I/O Registry for matching devices. */
	result = IOServiceGetMatchingServices (masterPort, hidMatchDictionary, &hidObjectIterator);
	/* Check for errors */
	if (kIOReturnSuccess != result)
	{
		SDL_SetError("Joystick: Couldn't create a HID object iterator.");
		return -1;
	}
	if (!hidObjectIterator) /* there are no joysticks */
	{
		gpDeviceList = NULL;
		SDL_numjoysticks = 0;
		return 0;
	}
	/* IOServiceGetMatchingServices consumes a reference to the dictionary, so we don't need to release the dictionary ref. */

	/* build flat linked list of devices from device iterator */

	gpDeviceList = lastDevice = NULL;
	
	while ((ioHIDDeviceObject = IOIteratorNext (hidObjectIterator)))
	{
		/* build a device record */
		device = HIDBuildDevice (ioHIDDeviceObject);
		if (!device)
			continue;

		/* dump device object, it is no longer needed */
		result = IOObjectRelease (ioHIDDeviceObject);
/*		if (KERN_SUCCESS != result)
			HIDReportErrorNum ("IOObjectRelease error with ioHIDDeviceObject.", result);
*/

		/* Filter device list to non-keyboard/mouse stuff */ 
		if ( (device->usagePage != kHIDPage_GenericDesktop) ||
		     ((device->usage != kHIDUsage_GD_Joystick &&
		      device->usage != kHIDUsage_GD_GamePad &&
		      device->usage != kHIDUsage_GD_MultiAxisController)) ) {

			/* release memory for the device */
			HIDDisposeDevice (&device);
			DisposePtr((Ptr)device);
			continue;
		}
		
		/* Add device to the end of the list */
		if (lastDevice)
			lastDevice->pNext = device;
		else
			gpDeviceList = device;
		lastDevice = device;
	}
	result = IOObjectRelease (hidObjectIterator); /* release the iterator */

	/* Count the total number of devices we found */
	device = gpDeviceList;
	while (device)
	{
		SDL_numjoysticks++;
		device = device->pNext;
	}
	
	return SDL_numjoysticks;
}

/* Function to get the device-dependent name of a joystick */
const char *SDL_SYS_JoystickName(int index)
{
	recDevice *device = gpDeviceList;
	
	for (; index > 0; index--)
		device = device->pNext;

	return device->product;
}

/* Function to open a joystick for use.
 * The joystick to open is specified by the index field of the joystick.
 * This should fill the nbuttons and naxes fields of the joystick structure.
 * It returns 0, or -1 if there is an error.
 */
int SDL_SYS_JoystickOpen(SDL_Joystick *joystick)
{
	recDevice *device = gpDeviceList;
	int index;
	
	for (index = joystick->index; index > 0; index--)
		device = device->pNext;

	joystick->hwdata = device;
	joystick->name = device->product;

	joystick->naxes = device->axes;
	joystick->nhats = device->hats;
	joystick->nballs = 0;
	joystick->nbuttons = device->buttons;

	return 0;
}

/* Function to update the state of a joystick - called as a device poll.
 * This function shouldn't update the joystick structure directly,
 * but instead should call SDL_PrivateJoystick*() to deliver events
 * and update joystick device state.
 */
void SDL_SYS_JoystickUpdate(SDL_Joystick *joystick)
{
	recDevice *device = joystick->hwdata;
	recElement *element;
	SInt32 value, range;
	int i;

	if (device->removed)  /* device was unplugged; ignore it. */
	{
		if (device->uncentered)
		{
			device->uncentered = 0;

			/* Tell the app that everything is centered/unpressed... */
			for (i = 0; i < device->axes; i++)
				SDL_PrivateJoystickAxis(joystick, i, 0);

			for (i = 0; i < device->buttons; i++)
				SDL_PrivateJoystickButton(joystick, i, 0);

			for (i = 0; i < device->hats; i++)
				SDL_PrivateJoystickHat(joystick, i, SDL_HAT_CENTERED);
		}

		return;
	}

	element = device->firstAxis;
	i = 0;
	while (element)
	{
		value = HIDScaledCalibratedValue(device, element, -32768, 32767);
		if ( value != joystick->axes[i] )
			SDL_PrivateJoystickAxis(joystick, i, value);
		element = element->pNext;
		++i;
	}
	
	element = device->firstButton;
	i = 0;
	while (element)
	{
		value = HIDGetElementValue(device, element);
        if (value > 1)  /* handle pressure-sensitive buttons */
            value = 1;
		if ( value != joystick->buttons[i] )
			SDL_PrivateJoystickButton(joystick, i, value);
		element = element->pNext;
		++i;
	}
	    
	element = device->firstHat;
	i = 0;
	while (element)
	{
		Uint8 pos = 0;

		range = (element->max - element->min + 1);
		value = HIDGetElementValue(device, element) - element->min;
		if (range == 4) /* 4 position hatswitch - scale up value */
			value *= 2;
		else if (range != 8) /* Neither a 4 nor 8 positions - fall back to default position (centered) */
			value = -1;
		switch(value)
		{
			case 0:
				pos = SDL_HAT_UP;
				break;
			case 1:
				pos = SDL_HAT_RIGHTUP;
				break;
			case 2:
				pos = SDL_HAT_RIGHT;
				break;
			case 3:
				pos = SDL_HAT_RIGHTDOWN;
				break;
			case 4:
				pos = SDL_HAT_DOWN;
				break;
			case 5:
				pos = SDL_HAT_LEFTDOWN;
				break;
			case 6:
				pos = SDL_HAT_LEFT;
				break;
			case 7:
				pos = SDL_HAT_LEFTUP;
				break;
			default:
				/* Every other value is mapped to center. We do that because some
				 * joysticks use 8 and some 15 for this value, and apparently
				 * there are even more variants out there - so we try to be generous.
				 */
				pos = SDL_HAT_CENTERED;
				break;
		}
		if ( pos != joystick->hats[i] )
			SDL_PrivateJoystickHat(joystick, i, pos);
		element = element->pNext;
		++i;
	}
	
	return;
}

/* Function to close a joystick after use */
void SDL_SYS_JoystickClose(SDL_Joystick *joystick)
{
	/* Should we do anything here? */
	return;
}

/* Function to perform any system-specific joystick related cleanup */
void SDL_SYS_JoystickQuit(void)
{
	while (NULL != gpDeviceList)
		gpDeviceList = HIDDisposeDevice (&gpDeviceList);
}

#endif /* SDL_JOYSTICK_IOKIT */