dump_devices_file.c

#include <stdlib.h>
#include <stdio.h>
#include <libnvpair.h>
#include <fcntl.h>
#include <strings.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <err.h>
#include <errno.h>

int
main(int argc, char *argv[])
{
        int fd;
        struct stat st;
        char *buf;
        size_t pos = 0;
        size_t rem;
        int e;

        if (argc != 2) {
                errx(1, "which file?");
        }

        if ((fd = open(argv[1], O_RDONLY)) < 0) {
                err(1, "open %s", argv[1]);
        }

        if (fstat(fd, &st) != 0) {
                err(1, "fstat %s", argv[1]);
        }

        rem = st.st_size;
        if ((buf = malloc(rem)) == NULL) {
                err(1, "malloc");
        }

        for (;;) {
                ssize_t rsz;

                if ((rsz = read(fd, buf + pos, rem)) < 0) {
                        if (errno == EINTR) {
                                continue;
                        }

                        err(1, "read %s", argv[1]);
                } else if (rsz == 0) {
                        if (rem != 0) {
                                errx(1, "file length changed?");
                        }

                        break;
                }

                rem -= rsz;
                pos += rsz;
        }

        /*
         * Look for the appropriate header:
         */
        if (st.st_size < 128) {
                errx(1, "file too short");
        }
        uint32_t magic;
        bcopy(buf, &magic, sizeof (magic));
        if (magic != 0xdeb1dcac) {
                errx(1, "magic %x was not %x", magic, 0xdeb1dcac);
        }
        int32_t version;
        bcopy(buf + 4, &version, sizeof (version));
        if (version != 1) {
                errx(1, "version %d was not %d", version, 1);
        }

        nvlist_t *nvl;
        if ((e = nvlist_unpack(buf + 128, st.st_size - 128, &nvl, 0)) != 0) {
                errno = e;
                err(1, "nvlist_unpack");
        }

        nvlist_print(stdout, nvl);

        free(buf);
        nvlist_free(nvl);
        (void) close(fd);
}