games/caesar/caesar.c

   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
  42 #if 0
  43 #ifndef lint
  44 static const char copyright[] =
  45 "@(#) Copyright (c) 1989, 1993\n\
  46         The Regents of the University of California.  All rights reserved.\n";
  47 #endif /* not lint */
  48
  49 #ifndef lint
  50 static const char sccsid[] = "@(#)caesar.c    8.1 (Berkeley) 5/31/93";
  51 #endif /* not lint */
  52 #endif
  53 #include <sys/cdefs.h>
  54 __FBSDID("$FreeBSD$");
  55
  56 #include <errno.h>
  57 #include <math.h>
  58 #include <stdio.h>
  59 #include <stdlib.h>
  60 #include <string.h>
  61 #include <ctype.h>
  62 #include <unistd.h>
  63
  64 #define LINELENGTH      2048
  65 #define ROTATE(ch, perm) \
  66      isascii(ch) ? ( \
  67         isupper(ch) ? ('A' + (ch - 'A' + perm) % 26) : \
  68             islower(ch) ? ('a' + (ch - 'a' + perm) % 26) : ch) : ch
  69
  70 /*
  71  * letter frequencies (taken from some unix(tm) documentation)
  72  * (unix is a trademark of Bell Laboratories)
  73  */
  74 double stdf[26] = {
  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,
  78 };
  79
  80 void printit(char *);
  81
  82 int
  83 main(int argc, char **argv)
  84 {
  85         int ch, dot, i, nread, winnerdot = 0;
  86         char *inbuf;
  87         int obs[26], try, winner;
  88
  89         /* revoke setgid privileges */
  90         setgid(getgid());
  91
  92         if (argc > 1)
  93                 printit(argv[1]);
  94
  95         if (!(inbuf = malloc((size_t)LINELENGTH))) {
  96                 (void)fprintf(stderr, "caesar: out of memory.\n");
  97                 exit(1);
  98         }
  99
 100         /* adjust frequency table to weight low probs REAL low */
 101         for (i = 0; i < 26; ++i)
 102                 stdf[i] = log(stdf[i]) + log(26.0 / 100.0);
 103
 104         /* zero out observation table */
 105         bzero(obs, 26 * sizeof(int));
 106
 107         if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
 108                 (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
 109                 exit(1);
 110         }
 111         for (i = nread; i--;) {
 112                 ch = (unsigned char) inbuf[i];
 113                 if (isascii(ch)) {
 114                         if (islower(ch))
 115                                 ++obs[ch - 'a'];
 116                         else if (isupper(ch))
 117                                 ++obs[ch - 'A'];
 118                 }
 119         }
 120
 121         /*
 122          * now "dot" the freqs with the observed letter freqs
 123          * and keep track of best fit
 124          */
 125         for (try = winner = 0; try < 26; ++try) { /* += 13) { */
 126                 dot = 0;
 127                 for (i = 0; i < 26; i++)
 128                         dot += obs[i] * stdf[(i + try) % 26];
 129                 /* initialize winning score */
 130                 if (try == 0)
 131                         winnerdot = dot;
 132                 if (dot > winnerdot) {
 133                         /* got a new winner! */
 134                         winner = try;
 135                         winnerdot = dot;
 136                 }
 137         }
 138
 139         for (;;) {
 140                 for (i = 0; i < nread; ++i) {
 141                         ch = (unsigned char) inbuf[i];
 142                         putchar(ROTATE(ch, winner));
 143                 }
 144                 if (nread < LINELENGTH)
 145                         break;
 146                 if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
 147                         (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
 148                         exit(1);
 149                 }
 150         }
 151         exit(0);
 152 }
 153
 154 void
 155 printit(char *arg)
 156 {
 157         int ch, rot;
 158
 159         if ((rot = atoi(arg)) < 0) {
 160                 (void)fprintf(stderr, "caesar: bad rotation value.\n");
 161                 exit(1);
 162         }
 163         while ((ch = getchar()) != EOF)
 164                 putchar(ROTATE(ch, rot));
 165         exit(0);
 166 }