[systemd-devel] [PATCH 2/5] shared/json: JSON parser + number tokenizer bugfix

Pavel Odvody podvody at redhat.com
Fri May 15 08:05:32 PDT 2015


On Fri, 2015-05-15 at 16:12 +0200, Lennart Poettering wrote:
> On Fri, 15.05.15 16:03, Pavel Odvody (podvody at redhat.com) wrote:
> 
> > On Fri, 2015-05-15 at 15:23 +0200, Lennart Poettering wrote:
> > > On Thu, 07.05.15 17:47, Pavel Odvody (podvody at redhat.com) wrote:
> > > 
> > > Hmm, so if I grok this right, then this at's a DOM-like ("object
> > > model") parser for json, where we previously hat a SAX-like ("stream")
> > > parser only. What's the rationale for this? Why doesn't the stream
> > > parser suffice?
> > > 
> > > I intentionally opted for a stream parser when I wrote the code, and
> > > that#s actually the primary reason why i roleld my own parser here,
> > > instead of using some existing library....
> > > 
> > 
> > Hmm, I'd call it lexer/tokenizer, since the burden of syntactic analysis
> > is on the user. The parser is actually rather thin wrapper around
> > json_tokenize.
> > 
> > Rationale: the v2 manifest (also) contains embedded JSON documents and
> > is itself versioned, so it will change sooner or later.
> > I believe that parsing the manifest, or any "decently" complex JSON
> > document, using the stream parser would yield equal or bigger chunk of
> > code than generic DOM parser + few lines that consume it's API.
> 
> Can you give an example of these embedded JSON documents?
> 
> Couldn't this part be handled nicely by providing a call that skips
> nicely over json objects we don't want to process?
> 
> Lennart
> 

http://pastebin.com/rrkVxHzT

Yes, it could be handled, but I wouldn't call it nicely :)
Since there's a lot of nested objects / arrays I guess that you'd need
to do the syntactic analysis anyway. It'd be even worse in case some
values would shadow the key names, or some part of the document were
re-ordered.

-- 
Pavel Odvody <podvody at redhat.com>
Software Engineer - EMEA ENG Developer Experience
5EC1 95C1 8E08 5BD9 9BBF 9241 3AFA 3A66 024F F68D
Red Hat Czech s.r.o., Purky┼łova 99/71, 612 45, Brno

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: This is a digitally signed message part
URL: <http://lists.freedesktop.org/archives/systemd-devel/attachments/20150515/e3aab15e/attachment-0001.sig>


More information about the systemd-devel mailing list