On Mon, 1 Aug 2011, Colin Patrick McCabe wrote: > On Mon, Aug 1, 2011 at 9:24 AM, Tommi Virtanen > <tommi.virtanen@xxxxxxxxxxxxx> wrote: > > We've talked about generating/parsing JSON a few times, and how we've > > run into edge cases whenever we've rolled our own functions for that. > > I've mentioned this C library a few times, but I'm not sure if I've > > actually sent the link to anyone.. Here's a C library for > > generating/parsing JSON, written by an ex-cow-orker of mine. > > Hi TV, > > Jansson is a nice library. > > I would also like to mention JSON-C: http://oss.metaparadigm.com/json-c/ > I used this library in the Ceph collectd plugin to parse JSON and it > was very easy to use. One nice thing about JSON-C is that it is easy > to install on Debian, because there is already a package for it. > Hopefully the Jansson guys can get a package in there too eventually. FWIW Jansson is in wheezy now, but nothing newer. Anyway, I think our escaping problems are trivial enough to fix, we just need to merge the rgw and comomn/ implementations. Thanks! sage > One thing that neither Jansson nor JSON-C offer, to my knowledge, is > the ability to do SAX-style parsing of a JSON document. In other > words, to set up a bunch of function pointers and have them called at > various points during parsing. I did not personally feel the need for > this, since my JSON data was small enough that memory consumption was > a non-issue, but I guess someone else might. If Jansson wants to do > something to differentiate itself from the competition, that could be > it. > > I am not sure how I feel about using libraries to output (as opposed > to parse) JSON. There is a point where a task becomes simple enough > that using more libraries is an anti-pattern. For example, would you > use a library to output CSV? Probably not. The only thing you have to > remember is to properly do escaping. > > Another consideration is that the Formatter code in RGW can output > both XML or JSON, depending on what configuration the daemon is > running in. This is something that no libraries that I have seen have > offered. > > cheers, > Colin > > > > > One feedback I've received earlier was that the "DOM-style" > > architecture, where you build up the JSON object in-memory and then > > dump it out, is not always a good match. If you want to avoid that, > > you can pull off a trick like this pseudocode: > > > > write("{") > > json.dump(key) > > write(":") > > json.dump(value) > > write(",") > > json.dump(key2) > > write(":") > > json.dump(value2) > > write("}") > > > > The above still uses the library for proper string encoding etc, while > > letting you control the top-level structure explicitly. And it should > > be pretty easy to encapsulate the above in a convenience wrapper, to > > make streaming even nicer; something like this pseudocode: > > > > j = StreamingJSONObject(fd) > > j.dump(key, value) > > j.dump(key2, value2) > > j.close() > > -- > > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > >
