#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>

unsigned long long hash_function(unsigned long long);

enum
{
    MIN_ARGS = 4
};

int
main(int argc, char *argv[])
{
    unsigned long long h;
    int count;
    if (argc < MIN_ARGS ||
            sscanf(argv[2], "%llx", &h) != 1 ||
            sscanf(argv[3], "%d", &count) != 1) {
        return 0;
    }

    int fd = open(argv[1], O_WRONLY | O_CREAT,
            S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
    if (fd == -1) {
        return 0;
    }

    int file_end = lseek(fd, 0, SEEK_END);
    for (int i = 0; i < count; ++i) {
        off_t offset = file_end + (count - i - 1) * sizeof(h);
        if (lseek(fd, offset, SEEK_SET) == -1 ||
            write(fd, &h, sizeof(h)) != sizeof(h)) {
            return 0;
        }

        h = hash_function(h);
    }

    close(fd);
    return 0;
}