Writing and Reading Sections of .e57 File

[JonKirkland]

Hello,
Currently I only know how to read and write e57 files while storing the data for an entire file in a buffer. Since I have some large .e57's I would like to work with, I was wondering if it was possible to:
Read from 0-5 million points, write 5 million points, then read from 5-10 million points etc. not so much memory is being used.
Looking at the docs I saw CompressedVectorReader.seek(), but I was not able to get this working for me. I have also not been able to find any example in the tests. If you anyone could outline a way for this to be done I would greatly appreciate it.

[asmaloney]

The code for seek() looks like this:

   void CompressedVectorReaderImpl::seek( uint64_t /*recordNumber*/ )
   {
      checkImageFileOpen( __FILE__, __LINE__, static_cast<const char *>( __FUNCTION__ ) );

      // !!! implement
      throw E57_EXCEPTION1( ErrorNotImplemented );
   }

This is related to #79 - though you are also asking for a batch/streaming interface.

(I've mentioned in other places that I started a new implementation from scratch a while ago. I'd implemented batched reading the way you describe because I think it makes a lot of sense!)

[JonKirkland]

Sorry to revive this, but is the fact that libe57 uses Xerces preventing file streaming? I'm just curious as I've been using this library a lot and have started to poke around the code to gain a better understanding.
Great project btw.

[asmaloney]

is the fact that libe57 uses Xerces preventing file streaming?

Nope - that's a separate issue. The issue with Xerces is that it is like using a sledgehammer to push a tack into cork - and it's been a constant source of problems to include & build. A small simple implementation like pugixml would be better. The structure of libE57Format's code, however, makes replacing the XML a fair bit of work.

For streaming, I think it would be possible to implement CompressedVectorReaderImpl::seek and use it somehow (which I believe was the original intent), but not efficiently because the library doesn't implement certain features from the standard (e.g. indexing).