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. All advertising materials mentioning features or use of this software
22 * must display the following acknowledgement:
23 * This product includes software developed by the University of
24 * California, Berkeley and its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 static const char copyright[] =
45 "@(#) Copyright (c) 1989, 1993\n\
46 The Regents of the University of California. All rights reserved.\n";
50 static const char sccsid[] = "@(#)caesar.c 8.1 (Berkeley) 5/31/93";
53 #include <sys/cdefs.h>
54 __FBSDID("$FreeBSD$");
64 #define LINELENGTH 2048
65 #define ROTATE(ch, perm) \
67 isupper(ch) ? ('A' + (ch - 'A' + perm) % 26) : \
68 islower(ch) ? ('a' + (ch - 'a' + perm) % 26) : ch) : ch
71 * letter frequencies (taken from some unix(tm) documentation)
72 * (unix is a trademark of Bell Laboratories)
75 7.97, 1.35, 3.61, 4.78, 12.37, 2.01, 1.46, 4.49, 6.39, 0.04,
76 0.42, 3.81, 2.69, 5.92, 6.96, 2.91, 0.08, 6.63, 8.77, 9.68,
77 2.62, 0.81, 1.88, 0.23, 2.07, 0.06,
83 main(int argc, char **argv)
85 int ch, dot, i, nread, winnerdot = 0;
87 int obs[26], try, winner;
92 if (!(inbuf = malloc((size_t)LINELENGTH))) {
93 (void)fprintf(stderr, "caesar: out of memory.\n");
97 /* adjust frequency table to weight low probs REAL low */
98 for (i = 0; i < 26; ++i)
99 stdf[i] = log(stdf[i]) + log(26.0 / 100.0);
101 /* zero out observation table */
102 bzero(obs, 26 * sizeof(int));
104 if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
105 (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
108 for (i = nread; i--;) {
109 ch = (unsigned char) inbuf[i];
113 else if (isupper(ch))
119 * now "dot" the freqs with the observed letter freqs
120 * and keep track of best fit
122 for (try = winner = 0; try < 26; ++try) { /* += 13) { */
124 for (i = 0; i < 26; i++)
125 dot += obs[i] * stdf[(i + try) % 26];
126 /* initialize winning score */
129 if (dot > winnerdot) {
130 /* got a new winner! */
137 for (i = 0; i < nread; ++i) {
138 ch = (unsigned char) inbuf[i];
139 putchar(ROTATE(ch, winner));
141 if (nread < LINELENGTH)
143 if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
144 (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
156 if ((rot = atoi(arg)) < 0) {
157 (void)fprintf(stderr, "caesar: bad rotation value.\n");
160 while ((ch = getchar()) != EOF)
161 putchar(ROTATE(ch, rot));