segment/init.c

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/****************************************************************************
 *
 * MODULE:       segment
 * AUTHOR(S):    CERL
 *               Bernhard Reiter <bernhard intevation.de>, 
 *               Brad Douglas <rez touchofmadness.com>, 
 *               Glynn Clements <glynn gclements.plus.com>, 
 *               Markus Neteler <neteler itc.it>
 * PURPOSE:      Segment initialization routines
 * COPYRIGHT:    (C) 2000-2006 by the GRASS Development Team
 *
 *               This program is free software under the GNU General Public
 *               License (>=v2). Read the file COPYING that comes with GRASS
 *               for details.
 *
 *****************************************************************************/

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <grass/segment.h>


static int read_int(int, int *);

/* fd must be open for read and write */


int segment_init(SEGMENT * SEG, int fd, int nseg)
{
    SEG->open = 0;
    SEG->fd = fd;
    SEG->nseg = nseg;

    if (lseek(fd, 0L, SEEK_SET) < 0) {
        G_warning("segment_init: %s", strerror(errno));
        return -1;
    }

    /* read the header */
    if (!read_int(fd, &SEG->nrows)
        || !read_int(fd, &SEG->ncols)
        || !read_int(fd, &SEG->srows)
        || !read_int(fd, &SEG->scols)
        || !read_int(fd, &SEG->len))
        return -1;

    return segment_setup(SEG);
}


static int read_int(int fd, int *n)
{
    int bytes_read;

    if ((bytes_read = read(fd, n, sizeof(int))) == -1)
        G_warning("read_int: %s", strerror(errno));

    bytes_read = (bytes_read == sizeof(int));

    return bytes_read;
}