static void H2_STREAM_OUT_LOG(int lvl, h2_stream *s, const char *tag)
{
    if (APLOG_C_IS_LEVEL(s->session->c, lvl)) {
        conn_rec *c = s->session->c;
        char buffer[4 * 1024];
        apr_size_t len, bmax = sizeof(buffer)/sizeof(buffer[0]);
        
        len = h2_util_bb_print(buffer, bmax, tag, "", s->out_buffer);
        ap_log_cerror(APLOG_MARK, lvl, 0, c, 
                      H2_STRM_MSG(s, "out-buffer(%s)"), len? buffer : "empty");
    }
}