Preliminary tests to implement drutil's optical disc drive numbering in C

disc_drive_numbers.c

#include <IOKit/IOKitLib.h>
#include <IOKit/IOBSD.h>
#include <IOKit/storage/IOCDMedia.h>
#include <IOKit/storage/IOCDBlockStorageDevice.h>
#include <CoreFoundation/CoreFoundation.h>

#define MAXPATHLEN 1024

static void find_cd_block_devices(io_iterator_t *deviceIterator)
{
	mach_port_t masterPort;
	CFMutableDictionaryRef classesToMatch;

	IOMasterPort(MACH_PORT_NULL, &masterPort);
	classesToMatch = IOServiceMatching(kIOCDBlockStorageDeviceClass);
	IOServiceGetMatchingServices(masterPort, classesToMatch, deviceIterator);
}

static int get_device_file_path(io_object_t nextMedia, char * deviceFilePath)
{
        CFTypeRef deviceFilePathAsCFString;

	*deviceFilePath = '\0';
        deviceFilePathAsCFString = IORegistryEntryCreateCFProperty(nextMedia,
				CFSTR(kIOBSDNameKey), kCFAllocatorDefault, 0);

	if (deviceFilePathAsCFString) {
		if (CFStringGetCString(deviceFilePathAsCFString, deviceFilePath,
			   MAXPATHLEN, kCFStringEncodingASCII))
			return 1;
		CFRelease(deviceFilePathAsCFString);
	}
	return 0;
}

static io_object_t get_media(io_object_t storageDevice)
{
	io_iterator_t childrenIterator;
	io_object_t nextChild;
	io_object_t mediaObject = IO_OBJECT_NULL;
	IORegistryEntryCreateIterator(storageDevice,
			kIOServicePlane, kIORegistryIterateRecursively,
			&childrenIterator);
	while ((nextChild = IOIteratorNext(childrenIterator))) {
		if (IOObjectConformsTo(nextChild, kIOCDMediaClass))
			mediaObject = nextChild;
		else
			IOObjectRelease(nextChild);
	}
	IOObjectRelease(childrenIterator);
	return mediaObject;
}

static void print_info_for_objects(io_iterator_t objectIterator)
{
	io_object_t nextObject;
	io_object_t mediaObject;
	io_name_t nodeName;
	char device_name[MAXPATHLEN+1] = "\0";
	int index = 0;

	while ((nextObject = IOIteratorNext(objectIterator))) {
		printf("drive %d", ++index);
		if ((mediaObject = get_media(nextObject))) {
			if (get_device_file_path(mediaObject, device_name))
				printf(": %s\n", device_name);
		} else
			printf("\n", ++index);
		IOObjectRelease(mediaObject);
		IOObjectRelease(nextObject);
	}
}

int main() {
	io_iterator_t driveIterator;

	find_cd_block_devices(&driveIterator);
	print_info_for_objects(driveIterator);

	IOObjectRelease(driveIterator);
}

Makefile

disc_drive_numbers: disc_drive_numbers.c
	${CC} $^ -framework CoreFoundation -framework IOKit -o $@