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* Introduction:
JSON (JavaScript Object Notation) is a lightweight data-interchange format.
It can represent integer, real number, string, an ordered sequence of
value, and a collection of name/value pairs.
JsonCpp is a simple API to manipulate JSON value, handle serialization
and unserialization to string.
It can also preserve existing comment in unserialization/serialization steps,
making it a convenient format to store user input files.
Unserialization parsing is user friendly and provides precise error reports.
* Building/Testing:
JsonCpp uses Scons ( as a build system. Scons requires
python to be installed (
You download scons-local distribution from the following url:
Unzip it in the directory where you found this README file. Should be
at the same level as README.
python platform=PLTFRM [TARGET]
where PLTFRM may be one of:
suncc Sun C++ (Solaris)
vacpp Visual Age C++ (AIX)
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)
Notes: if you are building with Microsoft Visual Studio 2008, you need to
setup the environment by running vcvars32.bat (e.g. MSVC 2008 command prompt)
before running scons.
Adding platform is fairly simple. You need to change the Sconstruct file
to do so.
and TARGET may be:
check: build library and run unit tests.
* Running the test manually:
cd test
# This will run the Reader/Writer tests
python "path to jsontest.exe"
# This will run the Reader/Writer tests, using JSONChecker test suite
# (
# 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 --with-json-checker "path to jsontest.exe"
# This will run the unit tests (mostly Value)
python "path to test_lib_json.exe"
You can run the tests using valgrind:
python --valgrind "path to test_lib_json.exe"
* Building the documentation:
Run the python script from the top directory:
python --open --with-dot
See --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.
TESTNAME.expected file format:
- 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
(e.g. represented by either [] or {}).
- element path: '.' represented 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 test_complex_01.json and test_complex_01.expected to better understand
element path.
* Understanding reader/writer test output:
When a test is run, output files are generated aside 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.exe from reading test_complex_01.json
- test_complex_01.rewrite: JSON document written by jsontest.exe using the
Json::Value parsed from test_complex_01.json and serialized using
- test_complex_01.actual-rewrite: flattened JSON element tree produced by
jsontest.exe from reading test_complex_01.rewrite.
test_complex_01.process-output: jsontest.exe output, typically useful to
understand parsing error.
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