ASSERT(!(con->mpbr_fs_len = 0));
static struct File_sect *httpd__fd_next(struct Con *con){  struct File_sect *fs = NULL;    ASSERT(con->fs &&         (con->fs_off <= con->fs_num) && (con->fs_num <= con->fs_sz));    if (++con->fs_off >= con->fs_num)  {    fs = &con->fs[con->fs_off - 1];    fs->len = 0;    if (fs->fd != -1)      close(fs->fd);    fs->fd = -1;    fs = con->fs;    fs->fd = -1;    fs->len = 0;        con->fs_off = 0;    con->fs_num = 0;    con->use_mpbr = FALSE;    if (con->mpbr_ct)      vstr_del(con->mpbr_ct, 1, con->mpbr_ct->len);    return (NULL);  }  /* only allow multipart/byterange atm. where all fd's are the same */  ASSERT(con->fs[con->fs_off - 1].fd == con->fs[con->fs_off].fd);    fs = &con->fs[con->fs_off];  if (con->use_posix_fadvise)    posix_fadvise64(fs->fd, fs->off, fs->len, POSIX_FADV_SEQUENTIAL);    return (fs);}