How to create a LibArchive archive on a directory path instead of a list of files?

Question

I've never used LibArchive before and am trying to use it to create a .tar archive of a directory, since it is installed on my remote compute instance.

LibArchive has an example of how to create an archive from a flat list of files (shown below). But I can't find any examples of how to actually create an archive from a directory path. During the "Extract" example from the same website, it appears everything is contained within the "archive_entry" struct but there doesn't appear to be a counterpart for Create.

void
write_archive(const char *outname, const char **filename)
{
  struct archive *a;
  struct archive_entry *entry;
  struct stat st;
  char buff[8192];
  int len;
  int fd;

  a = archive_write_new();
  archive_write_add_filter_gzip(a);
  archive_write_set_format_pax_restricted(a); // Note 1
  archive_write_open_filename(a, outname);
  while (*filename) {
    stat(*filename, &st);
    entry = archive_entry_new(); // Note 2
    archive_entry_set_pathname(entry, *filename);
    archive_entry_set_size(entry, st.st_size); // Note 3
    archive_entry_set_filetype(entry, AE_IFREG);
    archive_entry_set_perm(entry, 0644);
    archive_write_header(a, entry);
    fd = open(*filename, O_RDONLY);
    len = read(fd, buff, sizeof(buff));
    while ( len > 0 ) {
        archive_write_data(a, buff, len);
        len = read(fd, buff, sizeof(buff));
    }
    close(fd);
    archive_entry_free(entry);
    filename++;
  }
  archive_write_close(a); // Note 4
  archive_write_free(a); // Note 5
}

Answer 1

The archive_read_disk_descend function from the libtar api allows you to traverse a directory. It should be called before archive_write_header(a, entry); To use this function prior to starting the for loop you need to call struct archive *disk = archive_read_disk_new() in order to create an archive representing your disk.