/**
 * @see #hasOutputChanged(ChannelHandlerContext, boolean)
 */
private void initOutputChanged(ChannelHandlerContext ctx) {
    if (observeOutput) {
        Channel channel = ctx.channel();
        Unsafe unsafe = channel.unsafe();
        ChannelOutboundBuffer buf = unsafe.outboundBuffer();

        if (buf != null) {
            lastMessageHashCode = System.identityHashCode(buf.current());
            lastPendingWriteBytes = buf.totalPendingWriteBytes();
        }
    }
}
 

/**
 * Returns {@code true} if and only if the {@link IdleStateHandler} was constructed
 * with {@link #observeOutput} enabled and there has been an observed change in the
 * {@link ChannelOutboundBuffer} between two consecutive calls of this method.
 * 如果且仅当IdleStateHandler被构造为启用了observeOutput并且该方法的两个连续调用之间的ChannelOutboundBuffer中出现了观察到的更改时，返回true。
 *
 * https://github.com/netty/netty/issues/6150
 */
private boolean hasOutputChanged(ChannelHandlerContext ctx, boolean first) {
    if (observeOutput) {

        // We can take this shortcut if the ChannelPromises that got passed into write()
        // appear to complete. It indicates "change" on message level and we simply assume
        // that there's change happening on byte level. If the user doesn't observe channel
        // writability events then they'll eventually OOME and there's clearly a different
        // problem and idleness is least of their concerns.
        if (lastChangeCheckTimeStamp != lastWriteTime) {
            lastChangeCheckTimeStamp = lastWriteTime;

            // But this applies only if it's the non-first call.
            if (!first) {
                return true;
            }
        }

        Channel channel = ctx.channel();
        Unsafe unsafe = channel.unsafe();
        ChannelOutboundBuffer buf = unsafe.outboundBuffer();

        if (buf != null) {
            int messageHashCode = System.identityHashCode(buf.current());
            long pendingWriteBytes = buf.totalPendingWriteBytes();

            if (messageHashCode != lastMessageHashCode || pendingWriteBytes != lastPendingWriteBytes) {
                lastMessageHashCode = messageHashCode;
                lastPendingWriteBytes = pendingWriteBytes;

                if (!first) {
                    return true;
                }
            }
        }
    }

    return false;
}