hash.c

/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *      The President and Fellows of Harvard College.
 *
 * 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 UNIVERSITY 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 UNIVERSITY 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.
 */

/*
 * hash: Takes a file and computes a "hash" value by adding together all
 * the values in the file mod some largish prime.
 *
 * Once the basic system calls are complete, this should work on any
 * file the system supports. However, it's probably of most use for
 * testing your file system code.
 *
 * This should really be replaced with a real hash, like MD5 or SHA-1.
 */

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <err.h>

#ifdef HOST
#include "hostcompat.h"
#endif

#define HASHP 104729

int
main(int argc, char *argv[])
{
        int fd;
        char readbuf[1];
        int j = 0;

#ifdef HOST
        hostcompat_init(argc, argv);
#endif

        if (argc != 2) {
                errx(1, "Usage: hash filename");
        }
        
        fd = open(argv[1], O_RDONLY, 0664);
        
        if (fd<0) { 
                err(1, "%s", argv[1]);
        }

        for (;;) {
                if (read(fd, readbuf, 1) <= 0) break;
                j = ((j*8) + (int) readbuf[0]) % HASHP;
        }

        close(fd);
        
        printf("Hash : %d\n", j);

        return 0;
}