NetBSD/games/caesar/caesar.c

219 lines
5.3 KiB
C

/* $NetBSD: caesar.c,v 1.22 2008/07/20 01:03:21 lukem Exp $ */
/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Rick Adams.
*
* Authors:
* Stan King, John Eldridge, based on algorithm suggested by
* Bob Morris
* 29-Sep-82
* Roland Illig, 2005
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
The Regents of the University of California. All rights reserved.");
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)caesar.c 8.1 (Berkeley) 5/31/93";
#else
__RCSID("$NetBSD: caesar.c,v 1.22 2008/07/20 01:03:21 lukem Exp $");
#endif
#endif /* not lint */
#include <err.h>
#include <errno.h>
#include <limits.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define NCHARS (1 << CHAR_BIT)
#define LETTERS (26)
/*
* letter frequencies (taken from some unix(tm) documentation)
* (unix is a trademark of Bell Laboratories)
*/
static const unsigned char upper[LETTERS] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
static const unsigned char lower[LETTERS] = "abcdefghijklmnopqrstuvwxyz";
static double stdf[LETTERS] = {
7.97, 1.35, 3.61, 4.78, 12.37, 2.01, 1.46, 4.49, 6.39, 0.04,
0.42, 3.81, 2.69, 5.92, 6.96, 2.91, 0.08, 6.63, 8.77, 9.68,
2.62, 0.81, 1.88, 0.23, 2.07, 0.06
};
static unsigned char rottbl[NCHARS];
static void
init_rottbl(int rot)
{
size_t i;
rot %= LETTERS; /* prevent integer overflow */
for (i = 0; i < NCHARS; i++)
rottbl[i] = (unsigned char)i;
for (i = 0; i < LETTERS; i++)
rottbl[upper[i]] = upper[(i + rot) % LETTERS];
for (i = 0; i < LETTERS; i++)
rottbl[lower[i]] = lower[(i + rot) % LETTERS];
}
static void
print_file(void)
{
int ch;
while ((ch = getchar()) != EOF) {
if (putchar(rottbl[ch]) == EOF) {
err(EXIT_FAILURE, "<stdout>");
/* NOTREACHED */
}
}
}
static void
print_array(const unsigned char *a, size_t len)
{
size_t i;
for (i = 0; i < len; i++) {
if (putchar(rottbl[a[i]]) == EOF) {
err(EXIT_FAILURE, "<stdout>");
/* NOTREACHED */
}
}
}
static int
get_rotation(const char *arg)
{
long rot;
char *endp;
errno = 0;
rot = strtol(arg, &endp, 10);
if (errno == 0 && (arg[0] == '\0' || *endp != '\0'))
errno = EINVAL;
if (errno == 0 && (rot < 0 || rot > INT_MAX))
errno = ERANGE;
if (errno)
err(EXIT_FAILURE, "Bad rotation value `%s'", arg);
return (int)rot;
}
static void
guess_and_rotate(void)
{
unsigned char inbuf[2048];
unsigned int obs[NCHARS];
size_t i, nread;
double dot, winnerdot;
int try, winner;
int ch;
/* adjust frequency table to weight low probs REAL low */
for (i = 0; i < LETTERS; i++)
stdf[i] = log(stdf[i]) + log(LETTERS / 100.0);
/* zero out observation table */
(void)memset(obs, 0, sizeof(obs));
for (nread = 0; nread < sizeof(inbuf); nread++) {
if ((ch = getchar()) == EOF)
break;
inbuf[nread] = (unsigned char) ch;
}
for (i = 0; i < nread; i++)
obs[inbuf[i]]++;
/*
* now "dot" the freqs with the observed letter freqs
* and keep track of best fit
*/
winner = 0;
winnerdot = 0.0;
for (try = 0; try < LETTERS; try++) {
dot = 0.0;
for (i = 0; i < LETTERS; i++)
dot += (obs[upper[i]] + obs[lower[i]])
* stdf[(i + try) % LETTERS];
if (try == 0 || dot > winnerdot) {
/* got a new winner! */
winner = try;
winnerdot = dot;
}
}
init_rottbl(winner);
print_array(inbuf, nread);
print_file();
}
int
main(int argc, char **argv)
{
if (argc == 1) {
guess_and_rotate();
} else if (argc == 2) {
init_rottbl(get_rotation(argv[1]));
print_file();
} else {
(void)fprintf(stderr, "usage: caesar [rotation]\n");
exit(EXIT_FAILURE);
/* NOTREACHED */
}
if (ferror(stdin)) {
errx(EXIT_FAILURE, "<stdin>");
/* NOTREACHED */
}
(void)fflush(stdout);
if (ferror(stdout)) {
errx(EXIT_FAILURE, "<stdout>");
/* NOTREACHED */
}
return 0;
}