/*
 *      $OpenBSD: locate.bigram.c,v 1.16 2019/01/17 06:15:44 tedu Exp $
 *
 * Copyright (c) 1995 Wolfram Schneider <wosch@FreeBSD.org>. Berlin.
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * James A. Woods.
 *
 * 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.
 */

/*
 *  bigram < sorted_file_names | sort -nr |
 *      awk 'NR <= 128 { printf $2 }' > bigrams
 *
 * List bigrams for 'updatedb' script.
 * Use 'code' to encode a file using this output.
 */

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <unistd.h>
#include <err.h>
#include "locate.h"

u_char buf1[PATH_MAX] = " ";
u_char buf2[PATH_MAX];
u_int bigram[UCHAR_MAX + 1][UCHAR_MAX + 1];

int
main(void)
{
        u_char *cp;
        u_char *oldpath = buf1, *path = buf2;
        u_int i, j;

        if (pledge("stdio", NULL) == -1)
                err(1, "pledge");

        while (fgets(path, sizeof(buf2), stdin) != NULL) {

                /*
                 * We don't need remove newline character '\n'.
                 * '\n' is less than ASCII_MIN and will be later
                 * ignored at output.
                 */


                /* skip longest common prefix */
                for (cp = path; *cp == *oldpath; cp++, oldpath++)
                        if (*cp == '\0')
                                break;

                while (*cp != '\0' && *(cp + 1) != '\0') {
                        bigram[(u_char)*cp][(u_char)*(cp + 1)]++;
                        cp += 2;
                }

                /* swap pointers */
                if (path == buf1) {
                        path = buf2;
                        oldpath = buf1;
                } else {
                        path = buf1;
                        oldpath = buf2;
                }
        }

        /* output, boundary check */
        for (i = ASCII_MIN; i <= ASCII_MAX; i++)
                for (j = ASCII_MIN; j <= ASCII_MAX; j++)
                        if (bigram[i][j] != 0)
                                (void)printf("%4u\t%c%c\n", bigram[i][j], i, j);

        exit(0);
}