diff options
Diffstat (limited to 'usr.bin/caesar/caesar.c')
| -rw-r--r-- | usr.bin/caesar/caesar.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/usr.bin/caesar/caesar.c b/usr.bin/caesar/caesar.c new file mode 100644 index 0000000..b1f9920 --- /dev/null +++ b/usr.bin/caesar/caesar.c @@ -0,0 +1,159 @@ +/* + * 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 + * + * 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. + */ + +#if 0 +#ifndef lint +static const char copyright[] = +"@(#) Copyright (c) 1989, 1993\n\ + The Regents of the University of California. All rights reserved.\n"; +#endif /* not lint */ + +#ifndef lint +static const char sccsid[] = "@(#)caesar.c 8.1 (Berkeley) 5/31/93"; +#endif /* not lint */ +#endif +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <errno.h> +#include <math.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <ctype.h> +#include <unistd.h> + +#define LINELENGTH 2048 +#define ROTATE(ch, perm) \ + isascii(ch) ? ( \ + isupper(ch) ? ('A' + (ch - 'A' + perm) % 26) : \ + islower(ch) ? ('a' + (ch - 'a' + perm) % 26) : ch) : ch + +/* + * letter frequencies (taken from some unix(tm) documentation) + * (unix is a trademark of Bell Laboratories) + */ +static double stdf[26] = { + 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 void printit(char *); + +int +main(int argc, char **argv) +{ + int ch, dot, i, nread, winnerdot = 0; + char *inbuf; + int obs[26], try, winner; + + if (argc > 1) + printit(argv[1]); + + if (!(inbuf = malloc((size_t)LINELENGTH))) { + (void)fprintf(stderr, "caesar: out of memory.\n"); + exit(1); + } + + /* adjust frequency table to weight low probs REAL low */ + for (i = 0; i < 26; ++i) + stdf[i] = log(stdf[i]) + log(26.0 / 100.0); + + /* zero out observation table */ + bzero(obs, 26 * sizeof(int)); + + if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) { + (void)fprintf(stderr, "caesar: %s\n", strerror(errno)); + exit(1); + } + for (i = nread; i--;) { + ch = (unsigned char) inbuf[i]; + if (isascii(ch)) { + if (islower(ch)) + ++obs[ch - 'a']; + else if (isupper(ch)) + ++obs[ch - 'A']; + } + } + + /* + * now "dot" the freqs with the observed letter freqs + * and keep track of best fit + */ + for (try = winner = 0; try < 26; ++try) { /* += 13) { */ + dot = 0; + for (i = 0; i < 26; i++) + dot += obs[i] * stdf[(i + try) % 26]; + /* initialize winning score */ + if (try == 0) + winnerdot = dot; + if (dot > winnerdot) { + /* got a new winner! */ + winner = try; + winnerdot = dot; + } + } + + for (;;) { + for (i = 0; i < nread; ++i) { + ch = (unsigned char) inbuf[i]; + putchar(ROTATE(ch, winner)); + } + if (nread < LINELENGTH) + break; + if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) { + (void)fprintf(stderr, "caesar: %s\n", strerror(errno)); + exit(1); + } + } + exit(0); +} + +static void +printit(char *arg) +{ + int ch, rot; + + if ((rot = atoi(arg)) < 0) { + (void)fprintf(stderr, "caesar: bad rotation value.\n"); + exit(1); + } + while ((ch = getchar()) != EOF) + putchar(ROTATE(ch, rot)); + exit(0); +} |
