* {
* assert(c == b->reader);
* b->len = sizeof(b->inbuf);
* return io_read_partial(c, b->inbuf, &b->len, wake_writer, b);
* }
*
* {
* assert(c == b->reader);
* b->len = sizeof(b->inbuf);
* return io_read_partial(c, b->inbuf, &b->len, wake_writer, b);
* }
*