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|
/* 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
/* vim: set expandtab ts=4 sw=3 sts=3 tw=80 :*/
|
