ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll);
ssize_t loop_write(int fd, const void *buf, size_t nbytes, bool do_poll);
ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll);
ssize_t loop_write(int fd, const void *buf, size_t nbytes, bool do_poll);