Which medium is this an issue for? As you note, for files and HTTP responses it's not a problem in practice. i'd guess nor for NFC tags nor QR codes.


On Sun, Jan 26, 2014 at 10:11 PM, Andreas Schildbach <andreas@schildbach.de> wrote:
I'm experimenting with BIP70/71 (payment protocol) usage in face to face
payments (more on that soon).

I've excountered an issue with the protobuf format. Protobufs are not
self-delimiting. That means if you're reading from an undelimited
stream, you will read endlessly because you don't know how much to read.

The current BIP70 implementations probably work because they're reading
either from a file or from an HTTP resource which sets the
Content-Length header. Trouble is the Content-Length header is optional,
and also there are many kinds of streams that don't have this built-in
delimiting mechanism.

The Java protobuf API solves this by offering delimited I/O, like

payment.writeDelimitedTo(os);

This writes the size of the message as a varint before writing the data.
I don't know about protobuf implementations for other languages but I'd
expect them to offer something compatible.

However, this leading varint is an incompatible change and would need to
be added to the spec.

I specifically encountered this with PaymentMessage and PaymentACK, but
it might be a good idea to apply this to all messages if any. Open for
discussion.


------------------------------------------------------------------------------
CenturyLink Cloud: The Leader in Enterprise Cloud Services.
Learn Why More Businesses Are Choosing CenturyLink Cloud For
Critical Workloads, Development Environments & Everything In Between.
Get a Quote or Start a Free Trial Today.
http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk
_______________________________________________
Bitcoin-development mailing list
Bitcoin-development@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bitcoin-development