#include <sys/uio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <unistd.h>
#include <string.h>

void exit_error(char *str) {
    fputs(str, stderr);
    fputc('\n', stderr);
    exit(1);
}

void exit_perror(char *str) {
    perror(str);
    exit(1);
}

int main(int argc, char **argv) {
    int in_fd, out_fd;
    struct stat info;
    void *base_addr;
    char buf[600];
    struct iovec iov[2];
    int mode = 0;

    if (argc < 3)
        exit_error("Usage: writev-test copy infile outfile\n"
                   "       writev-test drop infile\n");

    if (!strcmp(argv[1], "copy")) {
        if (argc < 4)
            exit_error("Missing outfile argument\n");
        mode = 1;
    }
    else if (!strcmp(argv[1], "drop"))
        mode = 0;
    else
        exit_error("Unknown mode\n");

    in_fd = open(argv[2], O_RDONLY);
    if (in_fd < 0)
        exit_perror("open input");

    if (fstat(in_fd, &info) < 0)
        exit_perror("fstat");

    if (mode == 1) {

        base_addr = mmap(0, info.st_size, PROT_READ, MAP_SHARED, in_fd, 0);
        if (base_addr == MAP_FAILED)
            perror("mmap");

        if (read(in_fd, buf, 600) < 600)
            exit_perror("read");

        out_fd = open(argv[3], O_WRONLY|O_TRUNC|O_CREAT, 0666);
        if (out_fd < 0)
            exit_perror("open output");

        iov[0].iov_base = buf;
        iov[0].iov_len = 600;
        iov[1].iov_base = base_addr + 600;
        iov[1].iov_len = info.st_size - 600;
        if (writev(out_fd, iov, 2) < info.st_size)
            exit_perror("writev");

    } else {
        if (fsync(in_fd) < 0)
            perror("fsync");
        if (posix_fadvise(in_fd, 0, info.st_size, POSIX_FADV_DONTNEED) != 0)
            perror("posix_fadvise");
    }
    return 0;
}