iOS AudioSession Getting all USB Audio Ouputs

gistfile1.c

/* print a CFNumber */
void printCfNumber(CFNumberRef cfNum) {
	SInt32 s;
	if(!CFNumberGetValue(cfNum, kCFNumberSInt32Type, &s)) {
		printf("***CFNumber overflow***");
		return;
	}
	printf("%d", (int)s);
}


void GetAudioOutputRoutes(){
    //get all available output destination
    UInt32 size = sizeof(CFArrayRef);
    CFArrayRef audioOutputRoutes;
    
    OSStatus err = AudioSessionGetProperty(kAudioSessionProperty_OutputDestinations, &size, &audioOutputRoutes);
    
    if (err == noErr){
        CFIndex i, c = CFArrayGetCount(audioOutputRoutes);
        CFDictionaryRef audioOutput;
        
        for (i=0; i<c; i++) {
            audioOutput = (CFDictionaryRef)CFArrayGetValueAtIndex(audioOutputRoutes, i);

            CFNumberRef routeId = (CFNumberRef)CFDictionaryGetValue(audioOutput, kAudioSession_OutputDestinationKey_ID);
            CFStringRef routeDescription = (CFStringRef)CFDictionaryGetValue(audioOutput, kAudioSession_OutputDestinationKey_Description);
            
            printCfNumber(routeId);
            const char *bytes;
            
            //haven't worked out how to print out the CFString yet.
            bytes = CFStringGetCStringPtr(routeDescription, kCFStringEncodingMacRoman);
            
            printf(bytes);
            
        }
    }
}