/*% cc -O -K -i -s -o fortune %
*/
/*
 * Fetch a fortune from the Fortunes file by randomly seeking
 *  within that file and then searching for the Nth next fortune,
 *  ( 0 <= N <= 15).   If EOF is reached, rewind and continue.
 *  This two step process minimizes file i/o while making the frequency
 *  of each fortune realtively independent of the size of its predecessors.
 *
 * Display the selected fortune, replacing @ characters with newlines.
 * This format (single line fortunes) allows foreign fortunes to be
 * merged into a local file with common lines deleted by sort -u
 *
 * If called with any argument, repeat until killed.
 *
 */
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>

char *Fortunes = "fortunes";

#define LEN 2048
char line[LEN];

main(argc, argv)
char **argv;
{
	long p;
	register l;
	register char *q;
	time_t t;
	FILE *f;
	struct stat sbuf;
	char *fortenv;

	if ( (fortenv = getenv ("FORTUNES")) != NULL )
		Fortunes = fortenv;
		
	if (argc >= 3 && !strcmp(argv[1], "-f")) {
		Fortunes = argv[2]; argv += 2; argc -= 2;
	}
	f = fopen(Fortunes, "r");
	if (f == NULL) {
		write(1,"Memory fault -- core dumped\n", 29);
		exit(1);
	}
	time(&t);
	srand(getpid() ^ (int)((t>>16) ^ t));
	fstat(fileno(f), &sbuf);
	do {
		p = rand() % sbuf.st_size;
		fseek(f, p, 0);
		for (l=((rand())&07); l-- >= 0; ) {
			fgets(line, LEN, f);
			if (fgets(line, LEN, f) == NULL || line[0] == 0) {
				rewind(f);
				fgets(line, LEN, f);
			}
		}
		for(q = line; *q++;)
			if ( *q  == '@')
				*q = '\n';
		l = (q - line) -1;
		write(1, line, l);
	} while (argc > 1);
	exit(0);
}

char *
fgets(s, n, f)
register char *s;
register n;
FILE *f;
{
	register c;
	register char *p;

	p=s;
	while (--n>0) {
		if ((c = getc(f)) == EOF)
			break;
		if ((*s++ = c) == '\n')
			break;
	}
	*s = 0;
	if (p == s)
		return NULL;
	return p;
}