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https://github.com/tgockel/json-voorhees

A killer modern C++ library for interacting with JSON.
https://github.com/tgockel/json-voorhees

c-plus-plus json json-serialization

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A killer modern C++ library for interacting with JSON.

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JSON Voorhees

=============



Yet another [JSON][JSON] library for C++.

This one touts new C++11 features for developer-friendliness, an extremely slow-speed parser and no dependencies beyond

 a compliant compiler.

If you love Doxygen, check out the [documentation](http://tgockel.github.io/json-voorhees/).



Features include (but are not necessarily limited to):



 - Simple

   - A `value` should not feel terribly different from a C++ Standard Library container

   - Write valid JSON with `operator<<`

   - Simple JSON parsing with `parse`

   - Reasonable error messages when parsing fails

   - Full support for Unicode-filled JSON (encoded in UTF-8 in C++)

 - Efficient

   - Minimal overhead to store values (a `value` is 16 bytes on a 64-bit platform)

   - No-throw move semantics wherever possible

 - Easy

   - Convert a `value` into a C++ type using `extract`

   - Encode a C++ type into a value using `to_json`

 - Safe

   - In the best case, illegal code should fail to compile

   - An illegal action should throw an exception

   - Almost all utility functions have a [strong exception guarantee](http://www.gotw.ca/gotw/082.htm)

 - Stable

   - Worry less about upgrading -- the API and ABI will not change out from under you

 - Documented

   - Consumable by human beings

   - Answers questions you might actually ask

 - Compiler support

     - GCC (4.8+)

     - Clang++ (3.3+)



[![Build Status](https://travis-ci.org/tgockel/json-voorhees.svg?branch=master)](https://travis-ci.org/tgockel/json-voorhees)

[![Coverage Status](https://coveralls.io/repos/tgockel/json-voorhees/badge.svg?branch=master&service=github)](https://coveralls.io/github/tgockel/json-voorhees?branch=master)

[![Flattr this git repo](http://api.flattr.com/button/flattr-badge-large.png)](https://flattr.com/submit/auto?user_id=tgockel&url=https://github.com/tgockel/json-voorhees&title=json-voorhees&language=c++&tags=github&category=software)



![JSON Conversions](https://raw.githubusercontent.com/tgockel/json-voorhees/master/doc/conversions.png)



Compile and Install

-------------------



JSON Voorhees uses [CMake](http://www.cmake.org/) as the automatic configuration software.

On Linux or Mac OSX, if you have `boost`, `cmake`, `g++` and `make` installed, simply:



    $> cmake .

    $> make

    $> sudo make install



If you want to customize your compilation or installation, see the options in `CMakeLists.txt` for easy-to-use

 configuration options.



If you are on Windows, you can also use CMake if you want.

However, it is probably easier to use the provided Visual Studio project files in `msvc/vs2015` to get going.

Hitting F5 should perform a NuGet restore, then compile and run all the unit tests.



### Arch Linux



If you use [Arch Linux](https://www.archlinux.org/), JSON Voorhees is easily installable via AUR.

The "latest stable" is called [json-voorhees](https://aur.archlinux.org/packages/json-voorhees), while there is a "close

 to tip" package called [json-voorhees-git](https://aur.archlinux.org/packages/json-voorhees-git).

With Arch, installation is as easy as `yaourt json-voorhees`!



Future

------



Future planned features can be found on the [issue tracker][future-features].



License

-------



Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with

the License. You may obtain a copy of the License at



  [http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0)



Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on

an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the

specific language governing permissions and limitations under the License.



Miscellaneous

=============



Compiler Support

----------------



 - Supported

     - GCC 4.8+

     - Clang 3.3+

 - Experimental

     - MSVC 14.0 CTP5+ (Visual C++ 2015)



Versioning

----------



Like every software system ever, JSON Voorhees describes versions in 3 part [semantic versioning](http://semver.org/):

 `${major}.${minor}.${patch}`.

The version components changing have very specific meanings:



 - `major`: There are no guarantees whatsoever across major releases.

 - `minor`: For a given minor release, all code is forward-compatible source-code compliant.

            That means code written against version 1.1 can be recompiled against version 1.4 and continue to work.

            No guarantees are made for going backwards (version 1.4 might have added new functions).

 - `patch`: Code is ABI-compatible across patch.

                  Library *A* built against JSON Voorhees 1.2.4 should be able to pass a `jsonv::value` to library *B*

                   built against JSON Voorhees 1.2.9.

                  Any change to publicly-visible data structures or calling conventions will correspond to a bump in the

                   minor version.



The preceding statements are not true if the version is suffixed with `-preN`.

These values are "pre-release" and are allowed to do whatever they feel like before a release.



When developing code, follow this simple workflow to determine which version components need to change:



 1. *Will this change force users to change their source code?*

    If yes, bump the `major` version.

 2. *Will this change force users to recompile to continue to work?*

    If yes, bump the `minor` version.

 3. *Will this change the behavior in any way?*

    If yes, bump the `patch` version.

 4. *Did I only change comments or rearrange code positioning (indentation, etc)?*

    If yes, you do not need to update any part of the version.

 5. *Did I miss something?*

    Yes. Go back to #1 and try again.



Character Encoding

------------------



This library assumes you [really love UTF-8][utf8].

When parsing JSON, this library happily assumes all sequences of bytes from C++ are UTF-8 encoded strings; it assumes

 you also want UTF-8 encoded strings when converting from JSON in C++ land; and it assumes the non-ASCII contents of a

 source string should be treated as UTF-8.

If you wish to use some other encoding format for your `std::string`, there is no convenient way to do that beyond

 conversion at every use site.

There is a [proposal][decode-non-utf8] to potentially address this.



On output, the system takes the "safe" route of using the numeric encoding for dealing with non-ASCII `std::string`s.

For example, the `std::string` for `"Travis Göckel"` (`"Travis G\xc3\xb6ckel"`) will be encoded in JSON as

 `"Travis G\u00f6ckel"`, despite the fact that the character `'ö'` is the most basic of the Unicode Basic Multilingual

 Planes.

This is generally considered the most compatible option, as (hopefully) every transport mechanism can gracefully

 transmit ASCII character sequences without molestation.

The drawback to this route is a needlessly lengthened resultant encoding if all components of the pipeline gracefully

 deal with UTF-8.

There is an [outstanding issue][encode-utf8] to address this shortcoming.



F.A.Q.

------



### What makes JSON Voorhees different from the other C++ JSON libraries?



JSON Voorhees was written for a C++ programmer who wants to be productive in this modern world.

What does that mean?

There are a *ton* of JSON libraries floating around touting how they are "modern" C++ and so on.

But who really cares?

JSON Voorhees puts the focus more on the resulting C++ than any "modern" feature set.

This means the library does not skip on string encoding details like having full support for [UTF-8][utf8].

Are there "modern" features?

Sure, but this library is *not* meant to be a gallery of them -- a good API should get out of your way and let you work.



Another thing JSON Voorhees does not attempt to do is be a lightweight library; in fact, it wants to be the kitchen sink

 for anything you want to do in JSON in your C++ application.

This means it is [*configurable*](https://github.com/tgockel/json-voorhees/blob/master/include/jsonv/config.hpp) for your

 needs.

That said, the library does not depend on strange environment settings, so you can still drop the `.cpp` and `.hpp` files

 into your own project if you want.



It also includes a powerful serialization framework for converting from JSON into C++ types and back again.

There is an extensible [Serialization Builder DSL](http://tgockel.github.io/json-voorhees/serialization_builder_dsl.html)

 to help you writing your application.

The serialization framework was designed with the modern application in mind -- you will like it or your money back!



### Why are `integer` and `decimal` distinct types?



The [JSON specification][JSON] only has a *number* type, whereas this library has `kind::integer` and `kind::decimal`.

Behavior between the two types should be fairly consistent -- comparisons between two different `kind`s should behave as

 you would expect (assuming you expect things like `value(1) == value(1.0)` and `value(2.0) < value(10)`).

If you wish for behavior more like JavaScript, feel free to only use `as_decimal()`.



The reason integer and decimal are not a single type is because of how people tend to use JSON in C++.

If you look at projects that consume JSON, they make a distinction between integer and decimal values.

Even in specification land, a distinction between the numeric type is pretty normal (for example:

 [Swagger](http://swagger.io/)).

To ultimately answer the question: integer and decimal are distinct types for the convenience of users.



### Why are `NaN` and `INFINITY` serialized as a `null`?



The [JSON specification][JSON] does *not* have support for non-finite floating-point numbers like `NaN` and infinity.

This means the `value` defined with `object({ { "nan", std::nan("") }, { "infinity", INFINITY } })` to get serialized as

 `{ "nan": null, "infinity": null }`.

While this seems to constitute a loss of information, not doing this would lead to the encoder outputting invalid JSON

 text, which is completely unacceptable (unfortunately, this is a *very common* mistake in JSON libraries).

If you want to check that there will be no information loss when encoding, use the utility funciton `validate`.



*Why not throw when encoding?*

One could imagine the `encoder::encode` throwing something like an `encode_error` instead of outputting `null` to the

 stream.

However, that would make `operator<<` a potentially-throwing operation, which is extremely uncommon and would be very

 surprizing (imagine if you tried to log a `value` and it threw).



*Why not throw when constructing the `value`?*

Instead of waiting for encoding time to do anything about the problem, the library could attack the issue at the source

 and throw an exception if someone says `value(INFINITY)`.

This was not chosen as the behavior, because non-finite values are only an issue in the string representation, which is

 not a problem if the `value` is never encoded.

You are free to use this JSON library without `parse` and `encode`, so it should not prevent an action simply because

 someone *might* use `encode`.



### Why are there so many corruption checks?



If you are looking through the implementation, you will find a ton of places where there are `default` cases in `switch`

 statements that should be impossible to hit without memory corruption.

This is because it is unclear what should happen when the library detects something like an invalid `kind`.

The library could `assert`, but that seems overbearing when there is a reasonable option to fall back to.

Alternatively, the library could throw in these cases, but that leads to innocuous-looking operations like `x == y`

 being able to throw, which is somewhat disconcerning.



### This is really helpful! Can I give you money?



I would be [Flattr-ed](https://flattr.com/submit/auto?user_id=tgockel&url=https://github.com/tgockel/json-voorhees&title=json-voorhees&language=c++&tags=github&category=software)!



### With such a cool name, do you have an equally cool logo?



Not really...



![JSON: Serialized Killer](https://raw.githubusercontent.com/tgockel/json-voorhees/master/doc/meme.jpg)



 [decode-non-utf8]: https://github.com/tgockel/json-voorhees/issues/10

    "Decode numeric encodings into arbitrarily encoded std::string"

 [encode-utf8]: https://github.com/tgockel/json-voorhees/issues/11

    "Issue 21: String encoding should allow UTF-8 output"

 [future-features]: https://github.com/tgockel/json-voorhees/issues?q=is%3Aopen+is%3Aissue+no%3Amilestone

    "Future features"

 [JSON]: http://www.json.org/

    "JSON Specification"

 [utf8]: http://www.utf8everywhere.org/

    "UTF8 Everywhere!"