32_led.c

/* example from http://barnyard.syr.edu/quickies/led.c */

/* led.c: print out number as if on 7 line led display. I.e., write integer
   given on command line like this:  
     _   _       _  
  |  _|  _| |_| |_  
  | |_   _|   |  _| etc.

   We assume the terminal behaves like a classical teletype. So the top
   lines of all digits have to be printed first, then the middle lines of
   all digits, etc.

        By Terry R. McConnell

  compile: cc -o led led.c
 
  If you just want to link in the subroutine print_led that does all the
  work, compile with -DNO_MAIN, and declare the following in any source file
  that uses the call:

  extern void print_led(unsigned long x, char *buf);

  Bug: you cannot call repeatedly to print more than one number to a line.
  That would require curses or some other terminal API that allows moving the
  cursor to a previous line.

 */



#include <stdlib.h>
#include <stdio.h>

#define MAX_DIGITS 32
#define NO_MAIN


/* Print the top line of the digit d into buffer. 
   Does not null terminate buffer. */

void topline(int d, char *p){

        *p++ = ' ';
        switch(d){

                 /* all these have _ on top line */

                case 0:
                case 2:
                case 3:
                case 5:
                case 7:
                case 8:
                case 9:
                        *p++ = '_';
                        break;
                default:
                        *p++=' ';
        
        }
        *p++=' ';
}

/* Print the middle line of the digit d into the buffer. 
   Does not null terminate. */

void midline(int d, char *p){

        switch(d){
                
                /* those that have leading | on middle line */

                case 0:
                case 4:
                case 5:
                case 6:
                case 8:
                case 9:
                        *p++='|';
                        break;
                default:
                        *p++=' ';       
        }
        switch(d){

                /* those that have _ on middle line */

                case 2:
                case 3:
                case 4:
                case 5:
                case 6:
                case 8:
                case 9:
                        *p++='_';
                        break;
                default:
                        *p++=' ';

        }
        switch(d){

                /* those that have closing | on middle line */

                case 0:
                case 1:
                case 2:
                case 3:
                case 4:
                case 7:
                case 8:
                case 9:
                        *p++='|';
                        break;
                default:
                        *p++=' ';
                        
        }
}

/* Print the bottom line of the digit d. Does not null terminate. */

void botline(int d, char *p){


        switch(d){

                /* those that have leading | on bottom line */
                
                case 0:
                case 2:
                case 6:
                case 8:
                        *p++='|';
                        break;
                default:
                        *p++=' ';       
        }
        switch(d){

                /* those that have _ on bottom line */

                case 0:
                case 2:
                case 3:
                case 5:
                case 6:
                case 8:
                        *p++='_';
                        break;
                default:
                        *p++=' ';

        }
        switch(d){

                /* those that have closing | on bottom line */

                case 0:
                case 1:
                case 3:
                case 4:
                case 5:
                case 6:
                case 7:
                case 8:
                case 9:
                        *p++='|';
                        break;
                default:
                        *p++=' ';
                        
        }
}

/* Write the led representation of integer to string buffer. */

void print_led(unsigned long x, char *buf)
{

        int i=0,n;
        static int d[MAX_DIGITS];


        /* extract digits from x */

        n = ( x == 0L ? 1 : 0 );  /* 0 is a digit, hence a special case */

        while(x){
                d[n++] = (int)(x%10L);
                if(n >= MAX_DIGITS)break;
                x = x/10L;
        }

        /* print top lines of all digits */

        for(i=n-1;i>=0;i--){
                topline(d[i],buf);
                buf += 3;
                *buf++=' ';
        }
        *buf++='\n'; /* move teletype to next line */

        /* print middle lines of all digits */

        for(i=n-1;i>=0;i--){
                midline(d[i],buf);
                buf += 3;
                *buf++=' ';
        }
        *buf++='\n';
        
        /* print bottom lines of all digits */

        for(i=n-1;i>=0;i--){
                botline(d[i],buf);
                buf += 3;
                *buf++=' ';
        }
        *buf++='\n';
        *buf='\0';
}

int main()
{
        char buf[5*MAX_DIGITS];
        print_led(1234567, buf);
        printf("%s\n",buf);

    return 0;
}

#ifndef NO_MAIN
int main(int argc, char **argv)
{

        int i=0,n;
        long x;
        static int d[MAX_DIGITS];
        char buf[5*MAX_DIGITS];

        if(argc != 2){
                fprintf(stderr,"led: usage: led integer\n");
                return 1;
        }

        /* fetch argument from command line */

        x = atol(argv[1]);

        /* sanity check */

        if(x<0){
                fprintf(stderr,"led: %d must be non-negative\n",x);
                return 1;
        }

        print_led(x,buf);
        printf("%s\n",buf);

        return 0;
        
}
#endif