2014-03-06 18:34 GMT+08:00 Bjorn Reese :

On 03/03/2014 10:22 AM, Sebastian Theophil wrote:

But there are only two libraries AFAIK that parse JSON to C++ structs

...

using serialization adaptors:

Here is one that integrates with Boost.Serialization:

http://protoc.sourceforge.net/

You can parse JSON directly into C++ structures:

std::string input("[1,2,3]"); struct my_struct { int x, y, z; } result;

protoc::json::iarchive archive(input.begin(), input.end()); archive >> result;

or

std::string input("[1,2,3]"); std::vector<int> result;

protoc::json::iarchive archive(input.begin(), input.end()); archive >> result;

You can also parse generic JSON into a DOM based on boost::variant. I currently use dynamic-cpp:

http://dynamic-cpp.googlecode.com/

Parsing into this DOM follows the same pattern as above:

std::string input("[1,2,[3,4]]"); dynamic::var result;

protoc::json::iarchive archive(input.begin(), input.end()); archive >> dom;

The protoc project has a couple of other advantages: (1) it supports streaming, which means that you can parse or construct JSON without requiring all data to be in memory at once

I'm confused. Your json::iarchive takes iterators not istream. I see there's stream_oarchive but no stream_iarchive, something I missed? and (2) it supports various

binary encodings with a structure similar to JSON.

I really ought to write the documentation of this library...

After a glance at some of the tests, say, the 'person' example in oarchive_suite.cpp, I wonder why it outputs value as array instead of object: {"name": "Kant", "age": 127}

There has been a discussion about last year's GSoC mentioning further

...

desirable properties of a JSON library: http://boost.2283326.n4. nabble.com/JSON-Parser-GSoC-2013-td4645117.html

Indeed, and most of these desiderata still applies.

With the protoc library, we can focus on the integration with other Boost libraries, such as Boost.Fusion, or replacing the JSON implementation of Boost.PropertyTree.

Another suitable GSoC project (for the student who wants to do meta- programming) could be to write a more generic version of dynamic-cpp. I have already written parts of it.

What's the benefit of dynamic-cpp over Boost.Any? If you want more generic, I guess that's what Boost.TypeErasure is for.

On 03/06/2014 04:38 PM, Bjorn Reese wrote:

On 03/06/2014 02:35 PM, TONGARI J wrote:

...

I'm confused. Your json::iarchive takes iterators not istream. I see there's stream_oarchive but no stream_iarchive, something I missed?

I have not needed stream_iarchive so far. But you are right, it should be added.

It just occurred to me that the term "streaming" is ambiguous. When we talk about streaming parsers there are two interpretations: 1. The parser will read from an input stream and deliver the results in a DOM (or via a builder design pattern like SAX-style events.) The parser may block while waiting for the next data on the input stream. 2. The parser only returns the next element, so you have to put a loop around it to get a full parse. This is the StAX-style parsing [1]. When I mentioned that protoc is a streaming parser, I was thinking about the second category, whereas the stream archives belong to the first category, so I see the confusion now. I am going to change my vocabulary accordingly and refer to the second category as pull parsers from now on. [1] http://en.wikipedia.org/wiki/StAX