LengthFieldBasedFrameDecoder
hezjing
hezjing at gmail.com
Mon Sep 28 00:06:15 EDT 2009
Hi Trustin and Netty contributors
I have to clarify that English is not my native language and so the previous
Javadoc could be good already.
Thanks for updating the Javadoc and it is definitely clearer than before (at
least to me).
In overall, I appreciate the way Javadoc is maintained. I particularly like
when there are some basic network details described in the Javadoc like the
packet fragmentation described in FrameDecoder. These are indeed very
helpful to novice network application developer.
Thank you!
2009/9/25 Trustin Lee (이희승) <trustin at gmail.com>
> Here's the revised Javadoc:
>
>
> http://fisheye.jboss.org/browse/Netty/trunk/src/main/java/org/jboss/netty/handler/codec/frame/LengthFieldBasedFrameDecoder.java?r=1741
>
> I'm sure it explains quite a lot about using LengthFieldBasedFrameDecoder
> now :)
>
> Let me know if you have anything to add.
>
> -- Trustin Lee, http://gleamynode.net/
>
>
>
> 2009/9/25 Trustin Lee (이희승) <trustin at gmail.com>:
> > Hmm, I want the Javadoc to be easily understandable without referring
> > to the source code. What would you suggest me to fix the
> > documentation?
> >
> > -- Trustin Lee, http://gleamynode.net/
> >
> > On Wed, Sep 23, 2009 at 3:02 PM, hezjing <hezjing at gmail.com> wrote:
> >> Yes, you're right.
> >> I should really create a decoder with
> LengthFieldBasedFrameDecoder(0xFFFF,
> >> 2, 2, 16, 0).
> >> I was having problem figuring the correct lengthAdjustment until I found
> the
> >> formula from the LengthFieldBasedFrameDecoder source code:
> >> frameLength += lengthAdjustment + lengthFieldEndOffset;
> >>
> >> Again, thanks for your help!
> >>
> >> On Mon, Sep 21, 2009 at 2:45 PM, Trustin Lee (이희승) <trustin at gmail.com>
> >> wrote:
> >>>
> >>> Not actually. It is supposed to work with either cases, as there are
> >>> lengthAdjustment and initialBytesToStrip.
> >>>
> >>> initialBytesToStrip should be 0 because you don't want the resulting
> >>> frame's header stripped out.
> >>>
> >>> lengthAdjustment could be 20 or something close to it because there's
> >>> an extra data between the length field and the payload.
> >>>
> >>> The Javadoc says:
> >>>
> >>> "It is particularly useful when you decode a binary message which has
> >>> an integer header field that represents the length of the message body
> >>> or the whole message."
> >>>
> >>> which means, it works regardless whether the length field includes the
> >>> header or not. Am I missing something? Could you suggest where to
> >>> improve?
> >>>
> >>> -- Trustin Lee, http://gleamynode.net/
> >>>
> >>>
> >>>
> >>> On Mon, Sep 21, 2009 at 3:24 PM, hezjing <hezjing at gmail.com> wrote:
> >>> > Hi Trustin
> >>> >
> >>> > In my case, the length field is the size of the payload (excluding
> the
> >>> > header).
> >>> >
> >>> > If I read the Javadoc correctly, the LengthFieldBasedFrameDecoder is
> >>> > applicable when the length field is the size of the header and
> payload
> >>> > right?
> >>> >
> >>> > :-)
> >>> >
> >>> > On Mon, Sep 21, 2009 at 9:39 AM, Trustin Lee (이희승) <
> trustin at gmail.com>
> >>> > wrote:
> >>> >>
> >>> >> Hi Hez,
> >>> >>
> >>> >> Thanks for closing this thread with a good answer and sorry that I'm
> >>> >> late.
> >>> >>
> >>> >> Do you find the Javadoc of LengthFieldBasedFrameDecoder difficult to
> >>> >> understand? I thought your use case is explained already there.
> Let
> >>> >> me know what you think so that we can improve the documentation.
> >>> >>
> >>> >> Cheers
> >>> >>
> >>> >> -- Trustin Lee, http://gleamynode.net/
> >>> >>
> >>> >>
> >>> >>
> >>> >> On Sun, Sep 20, 2009 at 9:12 PM, hezjing <hezjing at gmail.com> wrote:
> >>> >> > Hi Mike
> >>> >> > Hmmm ... do you mean the example of the frame like the following?
> >>> >> > <-- HEADER 20 bytes --><-- PAYLOAD 14 bytes -->
> >>> >> > +-------+---------+----+-----------------------+
> >>> >> > | | Length | | Payload |
> >>> >> > | | 0x000C | | |
> >>> >> > +-------+---------+----+-----------------------+
> >>> >> > Total frame size is 34 bytes.
> >>> >> > <-- HEADER 20 bytes --><-- PAYLOAD 100 bytes -->
> >>> >> > +-------+--------+-----+------------------------+
> >>> >> > | | Length | | Payload |
> >>> >> > | | 0x0064 | | |
> >>> >> > +-------+--------+-----+------------------------+
> >>> >> > Total frame size is 120 bytes.
> >>> >> >
> >>> >> >
> >>> >> > On Sun, Sep 20, 2009 at 1:41 AM, Mike McGrady
> >>> >> > <mmcgrady at topiatechnology.com>
> >>> >> > wrote:
> >>> >> >>
> >>> >> >> Could you include an example write with this? The two together,
> I
> >>> >> >> suspect, will be most helpful to many people, including me.
> >>> >> >> Mike
> >>> >> >> On Sep 19, 2009, at 8:11 AM, hezjing wrote:
> >>> >> >>
> >>> >> >> Hi
> >>> >> >> To close this thread, my solution is to extends FrameDecoder like
> >>> >> >> the
> >>> >> >> following code:
> >>> >> >> @ChannelPipelineCoverage("all")
> >>> >> >> public class MyFrameDecoder extends FrameDecoder {
> >>> >> >> @Override
> >>> >> >> protected Object decode(ChannelHandlerContext ctx, Channel
> >>> >> >> channel,
> >>> >> >> ChannelBuffer buf) throws Exception {
> >>> >> >> // the length field is at 3rd and 4th octet
> >>> >> >> if (buf.readableBytes() < 4) {
> >>> >> >> return null;
> >>> >> >> }
> >>> >> >> // The length field is in the buffer.
> >>> >> >> buf.markReaderIndex();
> >>> >> >> ...
> >>> >> >> // Read the length field (the payload size)
> >>> >> >> int length = buf.readUnsignedShort();
> >>> >> >> // The actual frame size is header (20) + payload size
> >>> >> >> length += 20;
> >>> >> >> buf.resetReaderIndex();
> >>> >> >> if (buf.readableBytes() < length) {
> >>> >> >> return null;
> >>> >> >> }
> >>> >> >> ChannelBuffer frame = buf.readBytes(length);
> >>> >> >> return frame;
> >>> >> >> }
> >>> >> >> }
> >>> >> >>
> >>> >> >> Thank you!
> >>> >> >>
> >>> >> >> On Thu, Sep 10, 2009 at 9:23 PM, hezjing <hezjing at gmail.com>
> wrote:
> >>> >> >>>
> >>> >> >>> Hi
> >>> >> >>> I have a message containing a fixed length header of 20 bytes,
> >>> >> >>> followed
> >>> >> >>> by a payload of variable length.
> >>> >> >>> The header contains a 2 bytes length field, indicating the
> length
> >>> >> >>> of
> >>> >> >>> the
> >>> >> >>> payload (excluding the header).
> >>> >> >>> For example if the message has 10 bytes payload, then the entire
> >>> >> >>> frame
> >>> >> >>> length is 30 bytes (20 bytes header + 10 bytes of payload),
> >>> >> >>> and the length field is 10.
> >>> >> >>> May I know what is the parameter to
> >>> >> >>> create LengthFieldBasedFrameDecoder?
> >>> >> >>>
> >>> >> >>> Thank you!
> >>> >> >>>
> >>> >> >>> --
> >>> >> >>>
> >>> >> >>> Hez
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >> --
> >>> >> >>
> >>> >> >> Hez
> >>> >> >> _______________________________________________
> >>> >> >> netty-users mailing list
> >>> >> >> netty-users at lists.jboss.org
> >>> >> >> https://lists.jboss.org/mailman/listinfo/netty-users
> >>> >> >>
> >>> >> >> Mike McGrady
> >>> >> >> Principal Investigator AF081-028 AFRL SBIR
> >>> >> >> Senior Engineer
> >>> >> >> Topia Technology, Inc.
> >>> >> >> 1.253.720.3365
> >>> >> >> mmcgrady at topiatechnology.com
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >> _______________________________________________
> >>> >> >> netty-users mailing list
> >>> >> >> netty-users at lists.jboss.org
> >>> >> >> https://lists.jboss.org/mailman/listinfo/netty-users
> >>> >> >>
> >>> >> >
> >>> >> >
> >>> >> >
> >>> >> > --
> >>> >> >
> >>> >> > Hez
> >>> >> >
> >>> >> > _______________________________________________
> >>> >> > netty-users mailing list
> >>> >> > netty-users at lists.jboss.org
> >>> >> > https://lists.jboss.org/mailman/listinfo/netty-users
> >>> >> >
> >>> >> >
> >>> >>
> >>> >> _______________________________________________
> >>> >> netty-users mailing list
> >>> >> netty-users at lists.jboss.org
> >>> >> https://lists.jboss.org/mailman/listinfo/netty-users
> >>> >
> >>> >
> >>> >
> >>> > --
> >>> >
> >>> > Hez
> >>> >
> >>> > _______________________________________________
> >>> > netty-users mailing list
> >>> > netty-users at lists.jboss.org
> >>> > https://lists.jboss.org/mailman/listinfo/netty-users
> >>> >
> >>> >
> >>>
> >>> _______________________________________________
> >>> netty-users mailing list
> >>> netty-users at lists.jboss.org
> >>> https://lists.jboss.org/mailman/listinfo/netty-users
> >>
> >>
> >>
> >> --
> >>
> >> Hez
> >>
> >> _______________________________________________
> >> netty-users mailing list
> >> netty-users at lists.jboss.org
> >> https://lists.jboss.org/mailman/listinfo/netty-users
> >>
> >>
> >
>
> _______________________________________________
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>
--
Hez
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