When you call ParseFromArray(), you must pass the exact size of the message
being parsed. You cannot simply give it the size of the buffer if there are
extra bytes after the end of the message.
What happened here is that the parser, after parsing the bytes of your
actual message, continued to interpret the following bytes as more data.
The next byte was a 1, which the parser thought was indicating the
beginning of a 64-bit fixed-width field with field number zero. Since your
message does not declare a field number zero (you actually aren't allowed
to), it treated this as an unknown field and stored the value in the
UnknownFieldSet. Later, when you serialized the message, the value in the
UnknownFieldSet was written out again.
The moral of the story is that you must transmit the size of your message
along with the data, so that you can pass it to ParseFromArray() on the
receiving end.
On Wed, Dec 17, 2008 at 2:22 PM, Ryan <ryanroll...@gmail.com> wrote:
>
> Ok - found it. The problem was not on the serialization but on the
> message creation/parsing. The buffer the C++ code was parsing the
> protocol buffer message from was not properly initialized causing the
> ByteSize() function to return an incorrect value based on the junk
> padded past the typical sentinel.
>
> I did a call to memset prior and all is good.
>
> Two additional thoughts:
>
> 1) I am surprised the C++ parsing succeeded?
>
> 2) Why was the serialization reproducing the bad input? I would think
> the process of Marshalling/Unmarshalling would of cleaned it up.
>
> On Dec 17, 10:48 am, Ryan <ryanroll...@gmail.com> wrote:
> > I will try. A good debugging step for myself if not anything else.
> > This system is of course distributed so it may be difficult to isolate
> > it down into something I can send you easily (also lots of
> > dependencies). I have been trying to identify the messages that are
> > causing this but it appears to be happening independent of the message
> > contents.
> >
> > In a particular sequence of messages the same messages always get the
> > erroneous bytes appended. However, if I take one of those messages and
> > send it independently - works fine.
> >
> > Weird...
> >
> > Thanks for the dialog.
> >
> > On Dec 17, 9:36 am, Kenton Varda <ken...@google.com> wrote:
> >
> > > If you write a program demonstrating the problem and send it to me, I
> can
> > > debug it.
> >
> > > On Wed, Dec 17, 2008 at 11:10 AM, Ryan <ryanroll...@gmail.com> wrote:
> >
> > > > char mess[MAX_MESSLEN] ;
> > > > .
> > > > //Load some properties for the group com call
> > > > .
> > > > .
> > > > bplMessage.SerializeToArray(mess,bplMessage.ByteSize());
> >
> > > > //what I am using to detect trailing bytes
> > > > for(int i =0; i< bplMessage.ByteSize();i++) {
> > > > std::cout << (int) mess[i] << std::endl;
> > > > }
> >
> > > > On Dec 17, 8:32 am, Kenton Varda <ken...@google.com> wrote:
> > > > > Hi Ryan,
> > > > > What does your code look like that calls SerializeToArray()? It
> should
> > > > be
> > > > > something like:
> >
> > > > > int size = message.ByteSize();
> > > > > char* array = new char[size];
> > > > > message.SerializeToArray(array, size);
> >
> > > > > On Tue, Dec 16, 2008 at 8:13 PM, Ryan <ryanroll...@gmail.com>
> wrote:
> >
> > > > > > I have been working with a Group Communication System and
> Protocol
> > > > > > Buffers.
> >
> > > > > > I have an issue where the C++ SerializeToArray call on one of my
> > > > > > messages is occasionally appending Bytes {1,0,0,0,0,0,0,0,0} to
> the
> > > > > > end of the returned character array?
> >
> > > > > > Any ideas on what might be causing this? I can
> Marshall/Unmarshall
> > > > > > fine using the java api but the C++ call above has the odd quirk
> > > > > > mentioned.
> >
> > > > > > The Java parsingFrom fails on the C++ generated messages that
> have the
> > > > > > above bytes appended.
> >
> > > > > > Any suggestions much appreciated.
> >
>
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