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)
70 static double stdf[26] = {
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,
76 static void printit(char *);
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));