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. 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
