2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
9 * Stan King, John Eldridge, based on algorithm suggested by
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. Neither the name of the University nor the names of its contributors
22 * may be used to endorse or promote products derived from this software
23 * without specific prior written permission.
25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 static const char copyright[] =
41 "@(#) Copyright (c) 1989, 1993\n\
42 The Regents of the University of California. All rights reserved.\n";
46 static const char sccsid[] = "@(#)caesar.c 8.1 (Berkeley) 5/31/93";
49 #include <sys/cdefs.h>
50 __FBSDID("$FreeBSD$");
60 #define LINELENGTH 2048
61 #define ROTATE(ch, perm) \
63 isupper(ch) ? ('A' + (ch - 'A' + perm) % 26) : \
64 islower(ch) ? ('a' + (ch - 'a' + perm) % 26) : ch) : ch
67 * letter frequencies (taken from some unix(tm) documentation)
68 * (unix is a trademark of Bell Laboratories)
71 7.97, 1.35, 3.61, 4.78, 12.37, 2.01, 1.46, 4.49, 6.39, 0.04,
72 0.42, 3.81, 2.69, 5.92, 6.96, 2.91, 0.08, 6.63, 8.77, 9.68,
73 2.62, 0.81, 1.88, 0.23, 2.07, 0.06,
79 main(int argc, char **argv)
81 int ch, dot, i, nread, winnerdot = 0;
83 int obs[26], try, winner;
88 if (!(inbuf = malloc((size_t)LINELENGTH))) {
89 (void)fprintf(stderr, "caesar: out of memory.\n");
93 /* adjust frequency table to weight low probs REAL low */
94 for (i = 0; i < 26; ++i)
95 stdf[i] = log(stdf[i]) + log(26.0 / 100.0);
97 /* zero out observation table */
98 bzero(obs, 26 * sizeof(int));
100 if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
101 (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
104 for (i = nread; i--;) {
105 ch = (unsigned char) inbuf[i];
109 else if (isupper(ch))
115 * now "dot" the freqs with the observed letter freqs
116 * and keep track of best fit
118 for (try = winner = 0; try < 26; ++try) { /* += 13) { */
120 for (i = 0; i < 26; i++)
121 dot += obs[i] * stdf[(i + try) % 26];
122 /* initialize winning score */
125 if (dot > winnerdot) {
126 /* got a new winner! */
133 for (i = 0; i < nread; ++i) {
134 ch = (unsigned char) inbuf[i];
135 putchar(ROTATE(ch, winner));
137 if (nread < LINELENGTH)
139 if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
140 (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
152 if ((rot = atoi(arg)) < 0) {
153 (void)fprintf(stderr, "caesar: bad rotation value.\n");
156 while ((ch = getchar()) != EOF)
157 putchar(ROTATE(ch, rot));