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Annotation of 43BSDReno/games/caesar/caesar.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1989 The Regents of the University of California.
        !             3:  * 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 are permitted provided
        !            14:  * that: (1) source distributions retain this entire copyright notice and
        !            15:  * comment, and (2) distributions including binaries display the following
        !            16:  * acknowledgement:  ``This product includes software developed by the
        !            17:  * University of California, Berkeley and its contributors'' in the
        !            18:  * documentation or other materials provided with the distribution and in
        !            19:  * all advertising materials mentioning features or use of this software.
        !            20:  * Neither the name of the University nor the names of its contributors may
        !            21:  * be used to endorse or promote products derived from this software without
        !            22:  * specific prior written permission.
        !            23:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            24:  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            25:  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            26:  */
        !            27: 
        !            28: #ifndef lint
        !            29: char copyright[] =
        !            30: "@(#) Copyright (c) 1989 The Regents of the University of California.\n\
        !            31:  All rights reserved.\n";
        !            32: #endif /* not lint */
        !            33: 
        !            34: #ifndef lint
        !            35: static char sccsid[] = "@(#)caesar.c   5.4 (Berkeley) 6/1/90";
        !            36: #endif /* not lint */
        !            37: 
        !            38: #include <math.h>
        !            39: #include <stdio.h>
        !            40: #include <ctype.h>
        !            41: #include <unistd.h>
        !            42: 
        !            43: #define        LINELENGTH      2048
        !            44: #define        ROTATE(ch, perm) \
        !            45:        isupper(ch) ? ('A' + (ch - 'A' + perm) % 26) : \
        !            46:            islower(ch) ? ('a' + (ch - 'a' + perm) % 26) : ch
        !            47: 
        !            48: /*
        !            49:  * letter frequencies (taken from some unix(tm) documentation)
        !            50:  * (unix is a trademark of Bell Laboratories)
        !            51:  */
        !            52: double stdf[26] = {
        !            53:        7.97, 1.35, 3.61, 4.78, 12.37, 2.01, 1.46, 4.49, 6.39, 0.04,
        !            54:        0.42, 3.81, 2.69, 5.92,  6.96, 2.91, 0.08, 6.63, 8.77, 9.68,
        !            55:        2.62, 0.81, 1.88, 0.23,  2.07, 0.06,
        !            56: };
        !            57: 
        !            58: main(argc, argv)
        !            59:        int argc;
        !            60:        char **argv;
        !            61: {
        !            62:        extern int errno;
        !            63:        register int ch, dot, i, nread, winnerdot;
        !            64:        register char *inbuf;
        !            65:        int obs[26], try, winner;
        !            66:        char *malloc(), *strerror();
        !            67: 
        !            68:        if (argc > 1)
        !            69:                printit(argv[1]);
        !            70: 
        !            71:        if (!(inbuf = malloc(LINELENGTH))) {
        !            72:                (void)fprintf(stderr, "caesar: out of memory.\n");
        !            73:                exit(1);
        !            74:        }
        !            75: 
        !            76:        /* adjust frequency table to weight low probs REAL low */
        !            77:        for (i = 0; i < 26; ++i)
        !            78:                stdf[i] = log(stdf[i]) + log(26.0 / 100.0);
        !            79: 
        !            80:        /* zero out observation table */
        !            81:        bzero(obs, 26 * sizeof(int));
        !            82: 
        !            83:        if ((nread = read(STDIN_FILENO, inbuf, LINELENGTH)) < 0) {
        !            84:                (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
        !            85:                exit(1);
        !            86:        }
        !            87:        for (i = nread; i--;) {
        !            88:                ch = inbuf[i];
        !            89:                if (islower(ch))
        !            90:                        ++obs[ch - 'a'];
        !            91:                else if (isupper(ch))
        !            92:                        ++obs[ch - 'A'];
        !            93:        }
        !            94: 
        !            95:        /*
        !            96:         * now "dot" the freqs with the observed letter freqs
        !            97:         * and keep track of best fit
        !            98:         */
        !            99:        for (try = winner = 0; try < 26; ++try) { /* += 13) { */
        !           100:                dot = 0;
        !           101:                for (i = 0; i < 26; i++)
        !           102:                        dot += obs[i] * stdf[(i + try) % 26];
        !           103:                /* initialize winning score */
        !           104:                if (try == 0)
        !           105:                        winnerdot = dot;
        !           106:                if (dot > winnerdot) {
        !           107:                        /* got a new winner! */
        !           108:                        winner = try;
        !           109:                        winnerdot = dot;
        !           110:                }
        !           111:        }
        !           112: 
        !           113:        for (;;) {
        !           114:                for (i = 0; i < nread; ++i) {
        !           115:                        ch = inbuf[i];
        !           116:                        putchar(ROTATE(ch, winner));
        !           117:                }
        !           118:                if (nread < LINELENGTH)
        !           119:                        break;
        !           120:                if ((nread = read(STDIN_FILENO, inbuf, LINELENGTH)) < 0) {
        !           121:                        (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
        !           122:                        exit(1);
        !           123:                }
        !           124:        }
        !           125:        exit(0);
        !           126: }
        !           127: 
        !           128: printit(arg)
        !           129:        char *arg;
        !           130: {
        !           131:        register int ch, rot;
        !           132: 
        !           133:        if ((rot = atoi(arg)) < 0) {
        !           134:                (void)fprintf(stderr, "caesar: bad rotation value.\n");
        !           135:                exit(1);
        !           136:        }
        !           137:        while ((ch = getchar()) != EOF)
        !           138:                putchar(ROTATE(ch, rot));
        !           139:        exit(0);
        !           140: }

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