Introduction
------------

[JSON][json-org] is a lightweight data-interchange format. It can represent
numbers, strings, ordered sequences of values, and collections of name/value
pairs.

[json-org]: http://json.org/

[JsonCpp][] is a C++ library that allows manipulating JSON values, including
serialization and deserialization to and from strings. It can also preserve
existing comment in unserialization/serialization steps, making it a convenient
format to store user input files.

[JsonCpp]: http://open-source-parsers.github.io/jsoncpp-docs/doxygen/index.html

## A note on backward-compatibility
* `1.y.z` is built with C++11.
* `0.y.z` can be used with older compilers.
* Major versions maintain binary-compatibility.

# Using JsonCpp in your project
-----------------------------
The recommended approach to integrating JsonCpp in your project is to include
the [amalgamated source](#generating-amalgamated-source-and-header) (a single 
`.cpp` file and two `.h` files) in your project, and compile and build as you 
would any other source file. This ensures consistency of compilation flags and
ABI compatibility, issues which arise when building shared or static 
libraries. See the next section for instructions.
  
The `include/` should be added to your compiler include path. Jsoncpp headers
should be included as follow:

    #include <json/json.h>

If JsonCpp was built as a dynamic library on Windows, then your project needs to
define the macro `JSON_DLL`.

Generating amalgamated source and header
----------------------------------------
JsonCpp is provided with a script to generate a single header and a single
source file to ease inclusion into an existing project. The amalgamated source
can be generated at any time by running the following command from the
top-directory (this requires Python 2.6):

    python amalgamate.py

It is possible to specify header name. See the `-h` option for detail.

By default, the following files are generated:
* `dist/jsoncpp.cpp`: source file that needs to be added to your project.
* `dist/json/json.h`: corresponding header file for use in your project. It is
  equivalent to including `json/json.h` in non-amalgamated source. This header
  only depends on standard headers.
* `dist/json/json-forwards.h`: header that provides forward declaration of all
  JsonCpp types.

The amalgamated sources are generated by concatenating JsonCpp source in the
correct order and defining the macro `JSON_IS_AMALGAMATION` to prevent inclusion
of other headers.

# Contributing to JsonCpp

Building and testing with CMake
-------------------------------
[CMake][] is a C++ Makefiles/Solution generator. It is usually available on most
Linux system as package. On Ubuntu:

    sudo apt-get install cmake

[CMake]: http://www.cmake.org

Note that Python is also required to run the JSON reader/writer tests. If
missing, the build will skip running those tests.

When running CMake, a few parameters are required:

* a build directory where the makefiles/solution are generated. It is also used
  to store objects, libraries and executables files.
* the generator to use: makefiles or Visual Studio solution? What version or
  Visual Studio, 32 or 64 bits solution? 

Steps for generating solution/makefiles using `cmake-gui`:

* Make "source code" point to the source directory.
* Make "where to build the binary" point to the directory to use for the build.
* Click on the "Grouped" check box.
* Review JsonCpp build options (tick `BUILD_SHARED_LIBS` to build as a
  dynamic library).
* Click the configure button at the bottom, then the generate button.
* The generated solution/makefiles can be found in the binary directory.

Alternatively, from the command-line on Unix in the source directory:

    mkdir -p build/debug
    cd build/debug
    cmake -DCMAKE_BUILD_TYPE=debug -DBUILD_STATIC_LIBS=ON -DBUILD_SHARED_LIBS=OFF -DARCHIVE_INSTALL_DIR=. -G "Unix Makefiles" ../..
    make

Running `cmake -h` will display the list of available generators (passed using
the `-G` option).

By default CMake hides compilation commands. This can be modified by specifying
`-DCMAKE_VERBOSE_MAKEFILE=true` when generating makefiles.

Building and testing with SCons
-------------------------------
**Note:** The SCons-based build system is deprecated. Please use CMake; see the
section above.

JsonCpp can use [Scons][] as a build system. Note that SCons requires Python to
be installed.

[SCons]: http://www.scons.org/

Invoke SCons as follows:

    scons platform=$PLATFORM [TARGET]

where `$PLATFORM` may be one of:

* `suncc`: Sun C++ (Solaris)
* `vacpp`: Visual Age C++ (AIX)
* `mingw`
* `msvc6`: Microsoft Visual Studio 6 service pack 5-6
* `msvc70`: Microsoft Visual Studio 2002
* `msvc71`: Microsoft Visual Studio 2003
* `msvc80`: Microsoft Visual Studio 2005
* `msvc90`: Microsoft Visual Studio 2008
* `linux-gcc`: Gnu C++ (linux, also reported to work for Mac OS X)

If you are building with Microsoft Visual Studio 2008, you need to set up the
environment by running `vcvars32.bat` (e.g. MSVC 2008 command prompt) before
running SCons.

## Running the tests manually
You need to run tests manually only if you are troubleshooting an issue.

In the instructions below, replace `path/to/jsontest` with the path of the
`jsontest` executable that was compiled on your platform.

    cd test
    # This will run the Reader/Writer tests
    python runjsontests.py path/to/jsontest
    
    # This will run the Reader/Writer tests, using JSONChecker test suite
    # (http://www.json.org/JSON_checker/).
    # Notes: not all tests pass: JsonCpp is too lenient (for example,
    # it allows an integer to start with '0'). The goal is to improve
    # strict mode parsing to get all tests to pass.
    python runjsontests.py --with-json-checker path/to/jsontest
    
    # This will run the unit tests (mostly Value)
    python rununittests.py path/to/test_lib_json
    
    # You can run the tests using valgrind:
    python rununittests.py --valgrind path/to/test_lib_json

## Running the tests using scons
Note that tests can be run using SCons using the `check` target:

    scons platform=$PLATFORM check

Building the documentation
--------------------------
Run the Python script `doxybuild.py` from the top directory:

    python doxybuild.py --doxygen=$(which doxygen) --open --with-dot

See `doxybuild.py --help` for options.

Adding a reader/writer test
---------------------------
To add a test, you need to create two files in test/data:

* a `TESTNAME.json` file, that contains the input document in JSON format.
* a `TESTNAME.expected` file, that contains a flatened representation of the
  input document.

The `TESTNAME.expected` file format is as follows:

* each line represents a JSON element of the element tree represented by the
  input document.
* each line has two parts: the path to access the element separated from the
  element value by `=`. Array and object values are always empty (i.e.
  represented by either `[]` or `{}`).
* element path: `.` represents the root element, and is used to separate object
  members. `[N]` is used to specify the value of an array element at index `N`.

See the examples `test_complex_01.json` and `test_complex_01.expected` to better
understand element paths.

Understanding reader/writer test output
---------------------------------------
When a test is run, output files are generated beside the input test files.
Below is a short description of the content of each file:

* `test_complex_01.json`: input JSON document.
* `test_complex_01.expected`: flattened JSON element tree used to check if
  parsing was corrected.
* `test_complex_01.actual`: flattened JSON element tree produced by `jsontest`
  from reading `test_complex_01.json`.
* `test_complex_01.rewrite`: JSON document written by `jsontest` using the
  `Json::Value` parsed from `test_complex_01.json` and serialized using
  `Json::StyledWritter`.
* `test_complex_01.actual-rewrite`: flattened JSON element tree produced by
  `jsontest` from reading `test_complex_01.rewrite`.
* `test_complex_01.process-output`: `jsontest` output, typically useful for
  understanding parsing errors.

License
-------
See the `LICENSE` file for details. In summary, JsonCpp is licensed under the
MIT license, or public domain if desired and recognized in your jurisdiction.