/*
 *cuecat.c  22 Sept 2000  Stephen Satchell -- add interpretation of cue 
 *cuecat.c  21 Sept 2000  by Stephen Satchell
 *
 * This program takes keystrokes from stdin, interprets them according
 * to the research described in the programmer's essay on decoding
 * the CueCat's output, and emits information on stdout.
 *
 * The intent of this source module is to illustrate the techniques
 * described in the associated essay regarding the decoding and
 * decryption of Digital Convergence Inc. CueCat barcode wands.
 *
 * USE AT YOUR OWN RISK.  NO WARRANTY IS OFFERED.
 *
 * Copyright 2000 Stephen Satchell -- all rights reserved
 *
 * Anyone is free to link to this source code, and to download and
 * use the source code for non-commercial purposes.
 *  
 * Reproduction, but not for profit, of this source code is hereby granted.  
 * Any commercial use of the software requires that appropriate rights be 
 * secured from the author at slashdot@fluent-access.com.
 */

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define XOR ('C')

static int c;
static char string[80];

static int
get_cat (void)
{
    c = getchar ();
    switch (c)
	{
	default:
	    {
		return;
	    }
	case '+':
	    {
		c = ',';
		return;
	    }
	case '/':
	    {
		c = '-';
		return;
	    }
	}
}

static int
get_64 (void)
{
    static
	const
	char map[66] = "abcdefghijklmnopqrstuvwxyz"

	"ABCDEFGHIJKLMNOPQRSTUVWXYZ" "0123456789" ",-\0";
    int w = 0;
    const char *p;

    for (p = map; *p && ((unsigned) (*p) != (unsigned) (c)); p++)
	{
	}
    if (*p)
	{
	    w = p - map;
	    get_cat ();
	}
    return w;
}

int
get_byte (int digit_number)
{
    int w = 0;
    static int hold;

    if (!hold)
	{
	    if ((c == '.') || (c == '\n') || (c == EOF))
		{
		    return 0;
		}
	}
    switch (digit_number)
	{
	case 0:
	    {
		w = get_64 () << 2;
		hold = get_64 ();
		w = w | ((hold >> 4) & 0x03);
		hold = hold & 0x0F;
		return w ^ XOR;
	    }
	case 1:
	    {
		w = ((hold << 4) & 0xF0);
		hold = get_64 ();
		w = w | ((hold >> 2) & 0x0F);
		hold = hold & 0x03;
		return w ^ XOR;
	    }
	case 2:
	    {
		w = ((hold << 6) & 0xC0);
		hold = get_64 ();
		w = w | ((hold >> 0) & 0x3F);
		hold = 0;
		return w ^ XOR;
	    }
	default:
	    {
		return 0;
	    }
	}
}

void
swallow_dot (void)
{
    if (c == '.')
	{
	    get_cat ();
	}
    return;
}

void
process_code (void (*f) (int))
{
    int digit;
    int limit = 60;

    digit = 0;
    memset(string, 0, sizeof(string));
    while ((c != '.') && (c != '\n') && (c != EOF) && limit)
	{
	    (*f) (get_byte (digit));
	    digit = (digit + 1) % 3;
	    limit--;
	}

    if (digit)
	{
	    (*f) (get_byte (digit));
#if 0
	    printf (" [%d]", digit);
#endif
	}
    swallow_dot ();
    return;
}

void
print_code (int code)
{
    char *p;
    if (isprint (code))
	{
	    printf ("%c", code);
	}
    else
	{
	    printf ("\\x%02.2X", code);
	}
    p = strchr(string, 0);
    if (p - string < sizeof(string) - 2)
    	{
	    *p++ = code;
	    *p   = '\0';
	}
	
    return;
}

int
main (void)
{
    int digit;
    int cue;
    int cuetype;

    while (1)
	{
	    printf("Ready to scan (type 'q' and ENTER to quit\n");
	    get_cat ();
	    if (tolower (c) == 'q')
		{
		    return 0;
		}

	    /* swallow the header dot */
	    printf ("\nheader=");
	    process_code (print_code);

	    /*get the device ID */
	    printf ("\ndevid=");
	    process_code (print_code);

	    /*get the code type */
	    printf ("\ncodetype=");
	    process_code (print_code);
	    cue = ((string[0] == 'C') && (string[1] == 'C'));
	    cuetype = string[2];
#if 0
	    printf(" %1.64s", string);
#endif

	    /*get the barcode */
	    printf ("\nbarcode=");
	    process_code (print_code);
	    if (cue)
	        {
		static const
		char xlate[108] =
		    " !\"#$%&'()"  /* 00-09 */
		    "*+,-./0123"   /* 10-19 */
		    "456789:;<="   /* 20-29 */
		    ">?@ABCDEFG"   /* 30-39 */
		    "HIJKLMNOPQ"   /* 40-49 */
		    "RSTUVWXYZ["   /* 50-59 */
		    "\\]^_`abcde"  /* 60-69 */
		    "fghijklmno"   /* 70-79 */
		    "pqrstuvwxy"   /* 80-89 */
		    "z{|}~"        /* 90-99 */
		    ;
		char *p;
		int i;
		
		printf(", cue=C");
		p = strchr(xlate, cuetype);
		if (p)
		    {
		        printf(" %02.2d", p - xlate);
		    }
		for (i=0; (i < sizeof(string)) && (string[i]); i++)
		    {
		        p = strchr(xlate, string[i]);
			if (p)
			    {
			        printf(" %02.2d", p - xlate);
			    }
		    }
		}

	    /*get anything that follows */
	    printf ("\ntrailer=");
	    process_code (print_code);
	    putchar ('\n');
	}
}