If Gloss is to decode incoming packet (byte array) in little-endian format it is straightforward: Wrap byte array into ByteBuffer b, invoke b.order(LITTLE_ENDIAN) and pass b to decode function that will return Clojure map of decoded values.
However, when outgoing packet byte array is to be produced from map of values, encode function will always return ByteBuffer in default big- endian format, so resulting byte array extracted form ByteBuffer using get() method will be incorrect. If Gloss is to support little-endian frames, it seems that endianness needs to be part of frame definition. In that case Gloss decode fun would refuse to accept ByteBuffers with wrong order() and encode fun will always generate the correct result. Zoka On Nov 25, 3:00 am, Zach Tellman <ztell...@gmail.com> wrote: > ByteBuffers have an order() method which allows you to toggle the > endianness. I haven't tested this, but since everything is built on > top of Java's ByteBuffer functionality it should be fine as long as > the ByteBuffers are correctly set and correctly ordered with respect > to each other. > > Zach > > On Nov 23, 2:52 pm, zoka <ztomi...@gmail.com> wrote: > > > JVM stores numbers in in big endian format - is there a way to process > > binary stream containing little endian numbers? > > > Zoka > > > On Nov 24, 7:24 am, Zach Tellman <ztell...@gmail.com> wrote: > > > > Good question. The solution didn't make the cut for my initial > > > release, but will be added soon. My plan is to have an (ordered- > > > map ...) frame which encodes and decodes the keys in the given order. > > > So for C interop, the frame would be > > > > (ordered-map :a :int16, :b :float32) > > > > An alternative would be to just turn any vector which is alternating > > > keys and types into an ordered-map, but that seems a bit too magical. > > > > Zach > > > > On Nov 23, 12:12 pm, Chris Perkins <chrisperkin...@gmail.com> wrote: > > > > > On Nov 23, 12:03 pm, Zach Tellman <ztell...@gmail.com> wrote: > > > > > > When writing Calx [1], I discovered it was a huge pain to deal with > > > > > mixed C datatypes in Java. When writing Aleph [2], I discovered the > > > > > problem increases by a factor of ten when dealing with streams of > > > > > bytes. In an attempt to alleviate my own pain, and hopefully help a > > > > > few other people out, I've written Gloss, which can transform a simple > > > > > byte-format specification into an encoder and streaming decoder. > > > > > > A full writeup can be found athttps://github.com/ztellman/gloss/wiki. > > > > > > A few people have already asked me how this differs from protocol > > > > > buffers, so I'll preemptively answer that protocol buffers are a fixed > > > > > format that cannot be used to interface with external systems. Gloss > > > > > is less performant than protocol buffers, but is also much less picky > > > > > about formats. > > > > > > If anyone has any questions, I'd be happy to answer them. > > > > > Looks very useful, Zach. Thanks. > > > > > I have a question. > > > > > I have only taken a quick look, so maybe I'm misunderstanding the > > > > intent, but it's not clear to me how you would use this for sending > > > > and receiving structured data from, say, a C program. > > > > > Taking your example from the wiki: > > > > > (def fr (compile-frame {:a :int16, :b :float32})) > > > > > Let's say I want to talk to a C program that speaks in structs, like > > > > this: > > > > > struct Foo { short a; float b; } > > > > > The problem is, the C program cares about order - the short comes > > > > before the float. How does the Clojure program know what order I need > > > > the fields in, since I have specified the format with a map; an > > > > unordered data structure? Is there another way to specify a structure > > > > where order of the fields matters? If so, why have two ways of doing > > > > it? Or am I just missing something? > > > > > Thanks, > > > > > - Chris > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
