Add ol.format.Binary

[twpayne]

This PR adds binary support to ol.Format.

Reading binary data is done using ArrayBuffers, if available, otherwise (i.e. on IE9) it falls back to using VBArray to create an Array.<number>, where each array element is a byte. This abstraction is handled by ol.binary.Buffer.

Right now, only sequential reading of binary data, byte-by-byte, is supported, via the ol.binary.IReader interface. If/when random access is needed, appropriate methods can be added to ol.binary.Buffer.

Right now, the only binary format in progress is TWKB. See #1615 and another PR about to be opened.

[elemoine]

It looks great already. I'm intereted in reviewing when this is ready.

[twpayne]

This PR (just ol.format.Binary) is ready, but I'm happy to wait until #1718 is complete to provide a demonstration case.

[twpayne]

Any objections to merging this? I've a load of branches that depend on this it's getting really awkward juggling them all.

[bartvde]

no objections from me

[elemoine]

+1

[nicklasaven]

Just a very small question.
Why not put more "readers" in this binary format. Now you have readByte, but you keep the varInt readers in the twkb format.
I mean varInt can be found in more formats than twkb that might be supported in the future like
google protobuf https://code.google.com/p/protobuf/
and
openstreetmap pbf files http://wiki.openstreetmap.org/wiki/PBF

Just a thought

[twpayne]

The readers are in ol.binary. The reason for this is that different binary formats require quite different access. For example, TWKB currently requires sequential access to the binary data, whereas other formats require (and can be made much faster with) random access.

[nicklasaven]

Ok, Interesting!
Will you elaborate this in the twkb-feedback? I haven't seen any way to get random access without fixed size numbers like in wkb or some sort of index. Or after parsing it into some structure on client side like JSON.

But the "much faster" aspect is of course very interesting :-)

[twpayne]

Yes, I'll open an issue on the TWKB repo for feedback and discussion.