/* Fill a file with a sequence of byte values from 0 - 0xff */

#include <sys/param.h>
#include <sys/mman.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
main(int argc, char *argv[])
{
        size_t i, size;
        int fd;
        char *cp, *file;

        if (argc != 3) {
                fprintf(stderr, "Usage: %s <file> <file length in bytes>\n", argv[0]);
                exit(1);
        }
        file = argv[1];
        size = atol(argv[2]);

        if ((fd = open(file, O_RDWR | O_CREAT | O_TRUNC, 0600)) < 0)
                err(1, "%s", file);

        if (lseek(fd, size - 1, SEEK_SET) == -1)
                err(1, "lseek error");

        /* write a dummy byte at the last location */
        if (write(fd, "\0", 1) != 1)
                err(1, "write error");

        if ((cp = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0)) == MAP_FAILED)
                err(1, "mmap()");

        for (i = 0; i < size; i++)
                cp[i] = i & 0xff;

        if (munmap(cp, size) == -1)
                err(1, "munmap");
        close(fd);
}