[Interest] json file handling

[Thiago Macieira]

On Wednesday 15 April 2015 19:28:49 Andre Somers wrote:
> On 15-4-2015 17:25, Thiago Macieira wrote:
> > On Wednesday 15 April 2015 16:36:15 André Somers wrote:
> >>> The dilemma I'm in is, how can I tell the json writer to "append" to a
> >>> current json file without loading the whole file back in memory (eg
> >>> read json from file->edit in Qt->write back to file). Because, after a
> >>> while, I suppose the file will get quite large.
> >> 
> >> I don't think JSON is particulary suitable for this kind of application
> >> (and neither is XML).
> > 
> > CBOR might be, since it does support "undefined length" maps and arrays.
> 
> I'm not familiar with that format, but I'll look it up. I guess the
> choice for JSON or XML is made due to convenience though, as classes to
> read and write these are readily available. I doubt the same can be said
> of CBOR.

RFC 7049.

> > As for XML, the format may not be suitable but QXmlStreamWriter is since
> > it
> > keeps the state of which tags it needs to close and allows you to simply
> > stream data into it. On the receiver side, QXmlStreamReader is capable of
> > receiving incomplete data and making the best it can with what has been
> > completed.
> 
> I'd expect a log-file like output to be well defined at any moment in
> time, or as close as possible to that. So, while QXmlStreamWriter is
> suitable, it does not produce a valid XML file until you finalize the
> write. That may not be what you want (even though QXmlStreamReader could
> be used to parse the incomplete file*).

Yeah, that makes sense. Then for CBOR you wouldn't have the array header (byte 
0x9f), but simply have a sequence of items.

Or your parser should recover from having an unterminated array.
-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center