doWrite() — netty Function Reference

Source Code

transport-classes-epoll/src/main/java/io/netty/channel/epoll/AbstractEpollStreamChannel.java lines 422–458

    @Override
    protected void doWrite(ChannelOutboundBuffer in) throws Exception {
        int writeSpinCount = config().getWriteSpinCount();
        do {
            final int msgCount = in.size();
            // Do gathering write if the outbound buffer entries start with more than one ByteBuf.
            if (msgCount > 1 && in.current() instanceof ByteBuf) {
                writeSpinCount -= doWriteMultiple(in);
            } else if (msgCount == 0) {
                // Wrote all messages.
                clearFlag(Native.EPOLLOUT);
                // Return here so we not set the EPOLLOUT flag.
                return;
            } else {  // msgCount == 1
                writeSpinCount -= doWriteSingle(in);
            }

            // We do not break the loop here even if the outbound buffer was flushed completely,
            // because a user might have triggered another write and flush when we notify his or her
            // listeners.
        } while (writeSpinCount > 0);

        if (writeSpinCount == 0) {
            // It is possible that we have set EPOLLOUT, woken up by EPOLL because the socket is writable, and then use
            // our write quantum. In this case we no longer want to set the EPOLLOUT flag because the socket is still
            // writable (as far as we know). We will find out next time we attempt to write if the socket is writable
            // and set the EPOLLOUT if necessary.
            clearFlag(Native.EPOLLOUT);

            // We used our writeSpin quantum, and should try to write again later.
            eventLoop().execute(flushTask);
        } else {
            // Underlying descriptor can not accept all data currently, so set the EPOLLOUT flag to be woken up
            // when it can accept more data.
            setFlag(Native.EPOLLOUT);
        }
    }