This can be done by comparing user idle time with predefined amount of seconds, for which we are shure that user is left his place, usualy 300 or 600 seconds (5-10 minutes).

The idle time is stored as a property of the IOHIDSystem class; the name is HIDIdleTime. It’s stored as a 64-bit int, measured in nanoseconds. To figure out the idle time of the system we use IOKit. Here’s the code that will return how long user was inactive in seconds:

#include <IOKit/IOKitLib.h>
#include <CoreFoundation/CFNumber.h>

/**
Returns the number of seconds the machine has been idle or -1 if an error occurs.
The code is compatible with Tiger/10.4 and later (but not iOS).
*/
int64_t SystemIdleTime(void) {
	int64_t idlesecs = -1;
	io_iterator_t iter = 0;
	if (IOServiceGetMatchingServices(kIOMasterPortDefault, IOServiceMatching("IOHIDSystem"), &iter) == KERN_SUCCESS) {
		io_registry_entry_t entry = IOIteratorNext(iter);
		if (entry)  {
			CFMutableDictionaryRef dict = NULL;
			if (IORegistryEntryCreateCFProperties(entry, &dict, kCFAllocatorDefault, 0) == KERN_SUCCESS) {
				CFNumberRef obj = (CFNumberRef) CFDictionaryGetValue(dict, CFSTR("HIDIdleTime"));
				if (obj) {
					int64_t nanoseconds = 0;
					if (CFNumberGetValue(obj, kCFNumberSInt64Type, &nanoseconds)) {
						idlesecs = (nanoseconds / 1000000000); // Convert from nanoseconds to seconds.
					}
				}
				CFRelease(dict);
			}
			IOObjectRelease(entry);
		}
		IOObjectRelease(iter);
	}
	return idlesecs;
}



This code has been released as public domain, so you are free to copy it and use it for your own projects.

In the end I just want to point out the two things:

• If you need “user idle time” in other units then seconds, you need to change the divisor in line:

idlesecs = (nanoseconds / 1000000000); // Slower and accurate

• If you need dirty speedup of this code and you don’t need really accurate time you can change calculation from  to:

idlesecs = (nanoseconds >> 30); // Faster



Note: To use this code in X Code project, you need to add frameworks:

• IOKit.framework
• CoreFoundation.framework

DAEMON Tools is an advanced application for Microsoft Windows which provides optical media emulation. DAEMON Tools enables you to use your CD/DVD images as if they were already burned to CD/DVD.

There are three version of Daemon Tools software: Daemon Tools Pro Advanced, Daemon Tools Pro Standard and Daemon Tools Lite.

Version we are interested in is Daemon Tools Lite. It enables you to emulate up to 4 Virtual CD/DVD drives on your PC and to create image files from original disks inserted in physical drives.

This software is free if you going to use it at home personally and not for commercial purpose.

For more information about this software visit product page: Daemon Tools Lite.

Install Instructions

Here is the instruction how to install Daemon Tools Lite and how to mount image in Virtual Disk.

Step 1

Open http://www.daemon-tools.cc/eng/products/dtLite in your browser.

Click on a Download link at the end of the page.

Step 2

Start installation and install Daemon Tools Lite

Uncheck Browser’s Start Page

You can leave default location or you can select new one where you want program to be installed.

Select Don’t Intall if you don’t need Desktop Gadget

Mount Image Instructions

Step 3.

Double click DAEMON Tools Lite icon on your Desktop to start the program

DAEMON Tools Lite icon is show in taskbar.

Step 4.

Right click on DAEMON Tools icon in taskbar and select Virtual Devices > Add SCSI Virtual Device.

New Virtual drive is enabled and ready.

Step 5

Load image to created virtual drive. Right click om DAEMON Tools icon in taskbar and select Virtual Devices > Device X: No Media > Mount Image…

Select image dialog is opened. Browse for image file on your computer to load it to virtual drive.

Step 6

New Drive is now present in your Computer directory. Now you can use it as any other drive.