1 /* 2 * Copyright (c) 1989, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Rick Adams. 7 * 8 * Authors: 9 * Stan King, John Eldridge, based on algorithm suggested by 10 * Bob Morris 11 * 29-Sep-82 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 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. 28 * 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 39 * SUCH DAMAGE. 40 * 41 * $FreeBSD: src/games/caesar/caesar.c,v 1.8.2.1 2000/08/17 06:13:06 jhb Exp $ 42 * $DragonFly: src/games/caesar/caesar.c,v 1.4 2005/03/01 22:47:10 joerg Exp $ 43 * 44 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. 45 * @(#)caesar.c 8.1 (Berkeley) 5/31/93 46 * $FreeBSD: src/games/caesar/caesar.c,v 1.8.2.1 2000/08/17 06:13:06 jhb Exp $ 47 */ 48 49 #include <ctype.h> 50 #include <err.h> 51 #include <errno.h> 52 #include <math.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include <unistd.h> 57 58 #define LINELENGTH 2048 59 #define ROTATE(ch, perm) \ 60 isascii(ch) ? ( \ 61 isupper(ch) ? ('A' + (ch - 'A' + perm) % 26) : \ 62 islower(ch) ? ('a' + (ch - 'a' + perm) % 26) : ch) : ch 63 64 /* 65 * letter frequencies (taken from some unix(tm) documentation) 66 * (unix is a trademark of Bell Laboratories) 67 */ 68 static double stdf[26] = { 69 7.97, 1.35, 3.61, 4.78, 12.37, 2.01, 1.46, 4.49, 6.39, 0.04, 70 0.42, 3.81, 2.69, 5.92, 6.96, 2.91, 0.08, 6.63, 8.77, 9.68, 71 2.62, 0.81, 1.88, 0.23, 2.07, 0.06, 72 }; 73 74 static void printit(const char *); 75 76 int 77 main(int argc, char **argv) 78 { 79 int ch, dot, i, nread, winnerdot = 0; 80 char *inbuf; 81 int obs[26], try, winner; 82 83 /* revoke setgid privileges */ 84 setgid(getgid()); 85 86 if (argc > 1) 87 printit(argv[1]); 88 89 if ((inbuf = malloc(LINELENGTH)) == NULL) 90 err(1, "malloc failed"); 91 92 /* adjust frequency table to weight low probs REAL low */ 93 for (i = 0; i < 26; ++i) 94 stdf[i] = log(stdf[i]) + log(26.0 / 100.0); 95 96 /* zero out observation table */ 97 bzero(obs, 26 * sizeof(int)); 98 99 if ((nread = read(STDIN_FILENO, inbuf, LINELENGTH)) < 0) 100 err(1, "read failed"); 101 for (i = nread; i--;) { 102 ch = (unsigned char) inbuf[i]; 103 if (isascii(ch)) { 104 if (islower(ch)) 105 ++obs[ch - 'a']; 106 else if (isupper(ch)) 107 ++obs[ch - 'A']; 108 } 109 } 110 111 /* 112 * now "dot" the freqs with the observed letter freqs 113 * and keep track of best fit 114 */ 115 for (try = winner = 0; try < 26; ++try) { /* += 13) { */ 116 dot = 0; 117 for (i = 0; i < 26; i++) 118 dot += obs[i] * stdf[(i + try) % 26]; 119 /* initialize winning score */ 120 if (try == 0) 121 winnerdot = dot; 122 if (dot > winnerdot) { 123 /* got a new winner! */ 124 winner = try; 125 winnerdot = dot; 126 } 127 } 128 129 for (;;) { 130 for (i = 0; i < nread; ++i) { 131 ch = (unsigned char) inbuf[i]; 132 putchar(ROTATE(ch, winner)); 133 } 134 if (nread < LINELENGTH) 135 break; 136 if ((nread = read(STDIN_FILENO, inbuf, LINELENGTH)) < 0) 137 err(1, "read failed"); 138 } 139 exit(0); 140 } 141 142 static void 143 printit(const char *arg) 144 { 145 int ch, rot; 146 147 if ((rot = atoi(arg)) < 0) 148 errx(1, "bad rotation value"); 149 150 while ((ch = getchar()) != EOF) 151 putchar(ROTATE(ch, rot)); 152 exit(0); 153 } 154