source: MondoRescue/branches/2.2.5/mindi-busybox/util-linux/mkswap.c

/* vi: set sw=4 ts=4: */
/* mkswap.c - format swap device (Linux v1 only)
 *
 * Copyright 2006 Rob Landley <rob@landley.net>
 *
 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
 */

#include "libbb.h"

int mkswap_main(int argc, char **argv);
int mkswap_main(int argc, char **argv)
{
    int fd, pagesize;
    off_t len;
    unsigned int hdr[129];

    // No options supported.

    if (argc != 2) bb_show_usage();

    // Figure out how big the device is and announce our intentions.

    fd = xopen(argv[1], O_RDWR);
    len = fdlength(fd);
    pagesize = getpagesize();
    printf("Setting up swapspace version 1, size = %"OFF_FMT"d bytes\n",
            len - pagesize);

    // Make a header.

    memset(hdr, 0, sizeof(hdr));
    hdr[0] = 1;
    hdr[1] = (len / pagesize) - 1;

    // Write the header.  Sync to disk because some kernel versions check
    // signature on disk (not in cache) during swapon.

    xlseek(fd, 1024, SEEK_SET);
    xwrite(fd, hdr, sizeof(hdr));
    xlseek(fd, pagesize-10, SEEK_SET);
    xwrite(fd, "SWAPSPACE2", 10);
    fsync(fd);

    if (ENABLE_FEATURE_CLEAN_UP) close(fd);

    return 0;
}