====== Kassensystem ======
===== Linux Keyboard foo =====
http://www.kernel.org/doc/Documentation/input/input.txt

http://lxr.free-electrons.com/source/drivers/input/input.c
==== Scancode -> keycode ====
https://wiki.archlinux.org/index.php/Map_scancodes_to_keycodes

<code>
$ sudo /lib/udev/keymap -i /dev/input/by-id/usb-_USB_Keyboard-event-kbd
</code>

==== keycode -> keysym ====
http://linux.about.com/library/cmd/blcmdl5_keymaps.htm

<code>
$ sudo  loadkeys de

$ dumpkeys -f  | grep -i at
keycode  16 = +q               +Q               at               Control_q        Control_q        nul              Meta_q           Meta_Q           Meta_at          Meta_Control_q  
keycode  26 = at               backslash        VoidSymbol       VoidSymbol       VoidSymbol       VoidSymbol       Meta_at          Meta_backslash   VoidSymbol       VoidSymbol      
keycode  70 = Scroll_Lock      Show_Memory      Show_Registers   Show_State       VoidSymbol       VoidSymbol       Scroll_Lock      VoidSymbol       VoidSymbol       VoidSymbol      
keycode  86 = less             greater          bar              VoidSymbol       VoidSymbol       VoidSymbol       Meta_less        Meta_greater     Meta_bar         VoidSymbol      

$  dumpkeys -f  | grep -i "+e"
keycode  18 = +e               +E               currency         Control_e        Control_e        Control_e        Meta_e           Meta_E           Meta_e           Meta_Control_e  

</code>
===== Probleme =====
==== Veränderung von Preisen ====
Der Preis eines Produkts ändert sich ggf., der Preis in der Zahlungshistory der user muss aber gleich bleiben.
=== Antwort: Produkte mit Preis History ===
  * (+) Die Preisentwicklung kann verfolgt werden
  * (-) Hässliche/teure query

=== Antwort: Preis Kopieren ===
  * (+) Einfach zu implementieren
  * (*) Kein Speicherplatzverschwendung, da Preis klein

==== Ggf. mehr Barcodes pro Produkt ====
==== Storno alter Transaktionen ====
Soll ein Storno alter Transaktionen das Guthaben der Transaktionen von der Stornierten bis jetzt updaten oder als neuer Punkt auftauechen?



<code c>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <dirent.h>
#include <linux/input.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/select.h>
#include <sys/time.h>
#include <termios.h>
#include <signal.h>


/*
http://www.kernel.org/doc/Documentation/input/event-codes.txt
http://stackoverflow.com/questions/2547616/how-can-i-translate-linux-keycodes-from-dev-input-event-to-ascii-in-perl
http://www.linuxquestions.org/questions/programming-9/read-from-a-usb-barcode-scanner-that-simulates-a-keyboard-495358/
http://www.thelinuxdaily.com/2010/05/grab-raw-keyboard-input-from-event-device-node-devinputevent/
http://code.metager.de/source/xref/linux/udev/src/keymap/keymap.c#print_key
http://lxr.free-electrons.com/source/drivers/hid/hid-input.c
*/

int
main(int argc, char *argv[]) {
	struct input_event ev[64];
	int fd;
	int rd;
	size_t size = sizeof(struct input_event);
	char name[256] = "Unknown";
	char *device = NULL;
	
	//Setup check
	if(argv[1] == NULL) {
		printf("Please specify (on the command line) the path to the dev event interface devicen\n");
		exit (0);
	}
	
	if((getuid ()) != 0) {
		printf("You have to be root\n");
		exit (0);
	}
	
	if(argc > 1) {
		device = argv[1];
	}
	
	//Open Device
	if((fd = open (device, O_RDONLY)) == -1) {
		printf("%s is not a vaild device.n", device);
		exit(0);
	}
	
	//Print Device Name
	ioctl(fd, EVIOCGRAB, name);
	ioctl(fd, EVIOCGNAME (sizeof (name)), name);
	printf("Reading From : %s (%s)\n", device, name);

	while(1) {
		if((rd = read(fd, ev, size * 64)) < size) {
			printf("read()");
			exit (0);
		}
		
		for(int i = 0; i < rd / size; i++) {
			printf("-- %i: %u\t%u\t%i\n", i, ev[i].type, ev[i].code, ev[i].value);
		}
	}
	
	return 0;
} 
</code>