#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <linux/fadvise.h>

#define BUF_SIZE 8192

int main(int argc, char **argv)
{
    char buf[BUF_SIZE];
    struct stat st_buf;

    if (argc < 3) {
        fprintf(stderr, "usage: %s src out\n", argv[0]);
        exit(EXIT_SUCCESS);
    }

    char *src  = argv[1];
    char *dest = argv[2];
    assert(strcmp(src, dest) != 0);

    int srcfd = open(src, O_RDONLY, 0644);
    assert(srcfd >= 0);

#if USE_FADVISE
    posix_fadvise(srcfd, 0, 0, POSIX_FADV_SEQUENTIAL);
    posix_fadvise(srcfd, 0, 0, POSIX_FADV_NOREUSE);
#endif

    /* get permission */
    assert(fstat(srcfd, &st_buf) >= 0);

    int destfd = open(dest, O_WRONLY | O_CREAT, st_buf.st_mode);
    assert(destfd >= 0);

    int n = 0;
    while ((n = read(srcfd, buf, sizeof(buf))) > 0) {
        char *p = &buf[0];
        const char * const endp = buf + n;
        while (p < endp) {
            int num_bytes = write(destfd, p, endp - p);
            p += num_bytes;
        }
    }
    assert(n == 0);

    fsync(destfd);

    close(destfd);
    close(srcfd);

    exit(EXIT_SUCCESS);
}