.\" Man page generated from reStructuredText.
.
.TH "JANSSON" "3LIB" "October 28, 2014" "2.7" "Jansson"
.SH NAME
jansson \- Jansson Documentation
.sp
This is the documentation for \fI\%Jansson\fP 2.7, last updated October 28, 2014\&.
.SH INTRODUCTION
.sp
\fI\%Jansson\fP is a C library for encoding, decoding and manipulating JSON
data. Its main features and design principles are:
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.IP \(bu 2
Simple and intuitive API and data model
.IP \(bu 2
Comprehensive documentation
.IP \(bu 2
No dependencies on other libraries
.IP \(bu 2
Full Unicode support (UTF\-8)
.IP \(bu 2
Extensive test suite
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.sp
Jansson is licensed under the \fI\%MIT license\fP; see LICENSE in the
source distribution for details.
.sp
Jansson is used in production and its API is stable. It works on
numerous platforms, including numerous Unix like systems and Windows.
It\(aqs suitable for use on any system, including desktop, server, and
small embedded systems.
.SH CONTENTS
.SS Getting Started
.SS Compiling and Installing Jansson
.sp
The Jansson source is available at
\fI\%http://www.digip.org/jansson/releases/\fP\&.
.SS Unix\-like systems (including MinGW)
.sp
Unpack the source tarball and change to the source directory:
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.nf
.ft CW
bunzip2 \-c jansson\-2.7\&.tar.bz2 | tar xf \-
cd jansson\-2.7
.ft R
.fi
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.sp
The source uses GNU Autotools (\fI\%autoconf\fP, \fI\%automake\fP, \fI\%libtool\fP), so
compiling and installing is extremely simple:
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.nf
.ft CW
\&./configure
make
make check
make install
.ft R
.fi
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.sp
To change the destination directory (\fB/usr/local\fP by default), use
the \fB\-\-prefix=DIR\fP argument to \fB\&./configure\fP\&. See \fB\&./configure
\-\-help\fP for the list of all possible installation options. (There are
no options to customize the resulting Jansson binary.)
.sp
The command \fBmake check\fP runs the test suite distributed with
Jansson. This step is not strictly necessary, but it may find possible
problems that Jansson has on your platform. If any problems are found,
please report them.
.sp
If you obtained the source from a Git repository (or any other source
control system), there\(aqs no \fB\&./configure\fP script as it\(aqs not kept in
version control. To create the script, the build system needs to be
bootstrapped. There are many ways to do this, but the easiest one is
to use \fBautoreconf\fP:
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.nf
.ft CW
autoreconf \-vi
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.fi
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This command creates the \fB\&./configure\fP script, which can then be
used as described above.
.SS CMake (various platforms, including Windows)
.sp
Jansson can be built using \fI\%CMake\fP\&. Create a build directory for an
out\-of\-tree build, change to that directory, and run \fBcmake\fP (or \fBccmake\fP,
\fBcmake\-gui\fP, or similar) to configure the project.
.sp
See the examples below for more detailed information.
.sp
\fBNOTE:\fP
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In the below examples \fB\&..\fP is used as an argument for \fBcmake\fP\&.
This is simply the path to the jansson project root directory.
In the example it is assumed you\(aqve created a sub\-directory \fBbuild\fP
and are using that. You could use any path you want.
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.SS Unix (Make files)
.sp
Generating make files on unix:
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.nf
.ft CW
bunzip2 \-c jansson\-2.7\&.tar.bz2 | tar xf \-
cd jansson\-2.7

mkdir build
cd build
cmake .. # or \fBccmake ..()\fP for a GUI.
.ft R
.fi
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Then to build:
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.nf
.ft CW
make
make check
make install
.ft R
.fi
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.SS Windows (Visual Studio)
.sp
Creating Visual Studio project files from the command line:
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.nf
.ft CW
<unpack>
cd jansson\-2.7

md build
cd build
cmake \-G "Visual Studio 10" ..
.ft R
.fi
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You will now have a \fIVisual Studio Solution\fP in your build directory.
To run the unit tests build the \fBRUN_TESTS\fP project.
.sp
If you prefer a GUI the \fBcmake\fP line in the above example can
be replaced with:
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.nf
.ft CW
cmake\-gui ..
.ft R
.fi
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For command line help (including a list of available generators)
for \fI\%CMake\fP simply run:
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.nf
.ft CW
cmake
.ft R
.fi
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To list available \fI\%CMake\fP settings (and what they are currently set to)
for the project, run:
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.nf
.ft CW
cmake \-LH ..
.ft R
.fi
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.SS Mac OSX (Xcode)
.sp
If you prefer using Xcode instead of make files on OSX,
do the following. (Use the same steps as
for \fIUnix\fP):
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.nf
.ft CW
\&...
cmake \-G "Xcode" ..
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.fi
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.SS Additional CMake settings
.SS Shared library
.sp
By default the \fI\%CMake\fP project will generate build files for building the
static library. To build the shared version use:
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.nf
.ft CW
\&...
cmake \-DJANSSON_BUILD_SHARED_LIBS=1 ..
.ft R
.fi
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.SS Changing install directory (same as autoconf \-\-prefix)
.sp
Just as with the \fI\%autoconf\fP project you can change the destination directory
for \fBmake install\fP\&. The equivalent for autoconfs \fB\&./configure \-\-prefix\fP
in \fI\%CMake\fP is:
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.nf
.ft CW
\&...
cmake \-DCMAKE_INSTALL_PREFIX:PATH=/some/other/path ..
make install
.ft R
.fi
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.SS Android
.sp
Jansson can be built for Android platforms. Android.mk is in the
source root directory. The configuration header file is located in the
\fBandroid\fP directory in the source distribution.
.SS Other Systems
.sp
On non Unix\-like systems, you may be unable to run the \fB\&./configure\fP
script. In this case, follow these steps. All the files mentioned can
be found in the \fBsrc/\fP directory.
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.IP 1. 3
Create \fBjansson_config.h\fP (which has some platform\-specific
parameters that are normally filled in by the \fB\&./configure\fP
script). Edit \fBjansson_config.h.in\fP, replacing all \fB@variable@\fP
placeholders, and rename the file to \fBjansson_config.h\fP\&.
.IP 2. 3
Make \fBjansson.h\fP and \fBjansson_config.h\fP available to the
compiler, so that they can be found when compiling programs that
use Jansson.
.IP 3. 3
Compile all the \fB\&.c\fP files (in the \fBsrc/\fP directory) into a
library file. Make the library available to the compiler, as in
step 2.
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.SS Building the Documentation
.sp
(This subsection describes how to build the HTML documentation you are
currently reading, so it can be safely skipped.)
.sp
Documentation is in the \fBdoc/\fP subdirectory. It\(aqs written in
\fI\%reStructuredText\fP with \fI\%Sphinx\fP annotations. To generate the HTML
documentation, invoke:
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.nf
.ft CW
make html
.ft R
.fi
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and point your browser to \fBdoc/_build/html/index.html\fP\&. \fI\%Sphinx\fP 1.0
or newer is required to generate the documentation.
.SS Compiling Programs that Use Jansson
.sp
Jansson involves one C header file, \fBjansson.h\fP, so it\(aqs enough
to put the line
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.nf
.ft CW
#include <jansson.h>
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.fi
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in the beginning of every source file that uses Jansson.
.sp
There\(aqs also just one library to link with, \fBlibjansson\fP\&. Compile and
link the program as follows:
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.nf
.ft CW
cc \-I/usr/include/jansson \-o prog prog.c \-ljansson
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.fi
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Starting from version 1.2, there\(aqs also support for \fI\%pkg\-config\fP:
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.nf
.ft CW
cc \-o prog prog.c \(gapkg\-config \-\-cflags \-\-libs jansson\(ga
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.fi
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.SS Upgrading from 1.x
.sp
This chapter lists the backwards incompatible changes introduced in
Jansson 2.0, and the steps that are needed for upgrading your code.
.sp
\fBThe incompatibilities are not dramatic.\fP The biggest change is that
all decoding functions now require and extra parameter. Most programs
can be modified to work with 2.0 by adding a \fB0\fP as the second
parameter to all calls of \fBjson_loads()\fP, \fBjson_loadf()\fP
and \fBjson_load_file()\fP\&.
.SS Compatibility
.sp
Jansson 2.0 is backwards incompatible with the Jansson 1.x releases.
It is ABI incompatible, i.e. all programs dynamically linking to the
Jansson library need to be recompiled. It\(aqs also API incompatible,
i.e. the source code of programs using Jansson 1.x may need
modifications to make them compile against Jansson 2.0.
.sp
All the 2.x releases are guaranteed to be backwards compatible for
both ABI and API, so no recompilation or source changes are needed
when upgrading from 2.x to 2.y.
.SS List of Incompatible Changes
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.TP
.B \fBDecoding flags\fP
For future needs, a \fBflags\fP parameter was added as the second
parameter to all decoding functions, i.e. \fBjson_loads()\fP,
\fBjson_loadf()\fP and \fBjson_load_file()\fP\&. All calls to
these functions need to be changed by adding a \fB0\fP as the second
argument. For example:
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.nf
.ft CW
/* old code */
json_loads(input, &error);

/* new code */
json_loads(input, 0, &error);
.ft R
.fi
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.TP
.B \fBUnderlying type of JSON integers\fP
The underlying C type of JSON integers has been changed from
\fBint\fP to the widest available signed integer type, i.e.
\fBlong long\fP or \fBlong\fP, depending on whether
\fBlong long\fP is supported on your system or not. This makes
the whole 64\-bit integer range available on most modern systems.
.sp
\fBjansson.h\fP has a typedef \fBjson_int_t\fP to the underlying
integer type. \fBint\fP should still be used in most cases when
dealing with smallish JSON integers, as the compiler handles
implicit type coercion. Only when the full 64\-bit range is needed,
\fBjson_int_t\fP should be explicitly used.
.TP
.B \fBMaximum encoder indentation depth\fP
The maximum argument of the \fBJSON_INDENT()\fP macro has been
changed from 255 to 31, to free up bits from the \fBflags\fP
parameter of \fBjson_dumps()\fP, \fBjson_dumpf()\fP and
\fBjson_dump_file()\fP\&. If your code uses a bigger indentation
than 31, it needs to be changed.
.TP
.B \fBUnsigned integers in API functions\fP
Version 2.0 unifies unsigned integer usage in the API. All uses of
\fBunsigned int\fP and \fBunsigned long\fP have been replaced
with \fBsize_t\fP\&. This includes flags, container sizes, etc.
This should not require source code changes, as both
\fBunsigned int\fP and \fBunsigned long\fP are usually
compatible with \fBsize_t\fP\&.
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.SS Tutorial
.sp
In this tutorial, we create a program that fetches the latest commits
of a repository in \fI\%GitHub\fP over the web. \fI\%GitHub API\fP uses JSON, so
the result can be parsed using Jansson.
.sp
To stick to the the scope of this tutorial, we will only cover the the
parts of the program related to handling JSON data. For the best user
experience, the full source code is available:
\fBgithub_commits.c\fP\&. To compile it (on Unix\-like systems with
gcc), use the following command:
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.nf
.ft CW
gcc \-o github_commits github_commits.c \-ljansson \-lcurl
.ft R
.fi
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\fI\%libcurl\fP is used to communicate over the web, so it is required to
compile the program.
.sp
The command line syntax is:
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.nf
.ft CW
github_commits USER REPOSITORY
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.fi
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\fBUSER\fP is a GitHub user ID and \fBREPOSITORY\fP is the repository
name. Please note that the GitHub API is rate limited, so if you run
the program too many times within a short period of time, the sever
starts to respond with an error.
.SS The GitHub Repo Commits API
.sp
The \fI\%GitHub Repo Commits API\fP is used by sending HTTP requests to
URLs like \fBhttps://api.github.com/repos/USER/REPOSITORY/commits\fP,
where \fBUSER\fP and \fBREPOSITORY\fP are the GitHub user ID and the name
of the repository whose commits are to be listed, respectively.
.sp
GitHub responds with a JSON array of the following form:
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.nf
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[
    {
        "sha": "<the commit ID>",
        "commit": {
            "message": "<the commit message>",
            <more fields, not important to this tutorial...>
        },
        <more fields...>
    },
    {
        "sha": "<the commit ID>",
        "commit": {
            "message": "<the commit message>",
            <more fields...>
        },
        <more fields...>
    },
    <more commits...>
]
.ft R
.fi
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In our program, the HTTP request is sent using the following
function:
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.nf
.ft CW
static char *request(const char *url);
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.fi
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It takes the URL as a parameter, preforms a HTTP GET request, and
returns a newly allocated string that contains the response body. If
the request fails, an error message is printed to stderr and the
return value is \fINULL\fP\&. For full details, refer to \fBthe code\fP, as the actual implementation is not important
here.
.SS The Program
.sp
First the includes:
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.nf
.ft CW
#include <string.h>
#include <jansson.h>
.ft R
.fi
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Like all the programs using Jansson, we need to include
\fBjansson.h\fP\&.
.sp
The following definitions are used to build the GitHub API request
URL:
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.nf
.ft CW
#define URL_FORMAT   "https://api.github.com/repos/%s/%s/commits"
#define URL_SIZE     256
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.fi
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The following function is used when formatting the result to find the
first newline in the commit message:
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.nf
.ft CW
/* Return the offset of the first newline in text or the length of
   text if there\(aqs no newline */
static int newline_offset(const char *text)
{
    const char *newline = strchr(text, \(aq\en\(aq);
    if(!newline)
        return strlen(text);
    else
        return (int)(newline \- text);
}
.ft R
.fi
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The main function follows. In the beginning, we first declare a bunch
of variables and check the command line parameters:
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int main(int argc, char *argv[])
{
    size_t i;
    char *text;
    char url[URL_SIZE];

    json_t *root;
    json_error_t error;

    if(argc != 3)
    {
        fprintf(stderr, "usage: %s USER REPOSITORY\en\en", argv[0]);
        fprintf(stderr, "List commits at USER\(aqs REPOSITORY.\en\en");
        return 2;
    }
.ft R
.fi
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Then we build the request URL using the user and repository names
given as command line parameters:
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.nf
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snprintf(url, URL_SIZE, URL_FORMAT, argv[1], argv[2]);
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.fi
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This uses the \fBURL_SIZE\fP and \fBURL_FORMAT\fP constants defined above.
Now we\(aqre ready to actually request the JSON data over the web:
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.nf
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text = request(url);
if(!text)
    return 1;
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.fi
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If an error occurs, our function \fBrequest\fP prints the error and
returns \fINULL\fP, so it\(aqs enough to just return 1 from the main
function.
.sp
Next we\(aqll call \fBjson_loads()\fP to decode the JSON text we got
as a response:
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.ft CW
root = json_loads(text, 0, &error);
free(text);

if(!root)
{
    fprintf(stderr, "error: on line %d: %s\en", error.line, error.text);
    return 1;
}
.ft R
.fi
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We don\(aqt need the JSON text anymore, so we can free the \fBtext\fP
variable right after decoding it. If \fBjson_loads()\fP fails, it
returns \fINULL\fP and sets error information to the \fBjson_error_t\fP
structure given as the second parameter. In this case, our program
prints the error information out and returns 1 from the main function.
.sp
Now we\(aqre ready to extract the data out of the decoded JSON response.
The structure of the response JSON was explained in section
\fI\%The GitHub Repo Commits API\fP\&.
.sp
We check that the returned value really is an array:
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.nf
.ft CW
if(!json_is_array(root))
{
    fprintf(stderr, "error: root is not an array\en");
    json_decref(root);
    return 1;
}
.ft R
.fi
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.sp
Then we proceed to loop over all the commits in the array:
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.nf
.ft CW
for(i = 0; i < json_array_size(root); i++)
{
    json_t *data, *sha, *commit, *message;
    const char *message_text;

    data = json_array_get(root, i);
    if(!json_is_object(data))
    {
        fprintf(stderr, "error: commit data %d is not an object\en", i + 1);
        json_decref(root);
        return 1;
    }
\&...
.ft R
.fi
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.sp
The function \fBjson_array_size()\fP returns the size of a JSON
array. First, we again declare some variables and then extract the
i\(aqth element of the \fBroot\fP array using \fBjson_array_get()\fP\&.
We also check that the resulting value is a JSON object.
.sp
Next we\(aqll extract the commit ID (a hexadecimal SHA\-1 sum),
intermediate commit info object, and the commit message from that
object. We also do proper type checks:
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.sp
.nf
.ft CW
    sha = json_object_get(data, "sha");
    if(!json_is_string(sha))
    {
        fprintf(stderr, "error: commit %d: sha is not a string\en", i + 1);
        json_decref(root);
        return 1;
    }

    commit = json_object_get(data, "commit");
    if(!json_is_object(commit))
    {
        fprintf(stderr, "error: commit %d: commit is not an object\en", i + 1);
        json_decref(root);
        return 1;
    }

    message = json_object_get(commit, "message");
    if(!json_is_string(message))
    {
        fprintf(stderr, "error: commit %d: message is not a string\en", i + 1);
        json_decref(root);
        return 1;
    }
\&...
.ft R
.fi
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.sp
And finally, we\(aqll print the first 8 characters of the commit ID and
the first line of the commit message. A C\-style string is extracted
from a JSON string using \fBjson_string_value()\fP:
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.sp
.nf
.ft CW
    message_text = json_string_value(message);
    printf("%.8s %.*s\en",
           json_string_value(id),
           newline_offset(message_text),
           message_text);
}
.ft R
.fi
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.sp
After sending the HTTP request, we decoded the JSON text using
\fBjson_loads()\fP, remember? It returns a \fInew reference\fP to the
JSON value it decodes. When we\(aqre finished with the value, we\(aqll need
to decrease the reference count using \fBjson_decref()\fP\&. This way
Jansson can release the resources:
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.nf
.ft CW
json_decref(root);
return 0;
.ft R
.fi
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.sp
For a detailed explanation of reference counting in Jansson, see
\fIapiref\-reference\-count\fP in \fIapiref\fP\&.
.sp
The program\(aqs ready, let\(aqs test it and view the latest commits in
Jansson\(aqs repository:
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.sp
.nf
.ft CW
$ ./github_commits akheron jansson
1581f26a Merge branch \(aq2.3\(aq
aabfd493 load: Change buffer_pos to be a size_t
bd72efbd load: Avoid unexpected behaviour in macro expansion
e8fd3e30 Document and tweak json_load_callback()
873eddaf Merge pull request #60 from rogerz/contrib
bd2c0c73 Ignore the binary test_load_callback
17a51a4b Merge branch \(aq2.3\(aq
09c39adc Add json_load_callback to the list of exported symbols
cbb80baf Merge pull request #57 from rogerz/contrib
040bd7b0 Add json_load_callback()
2637faa4 Make test stripping locale independent
<...>
.ft R
.fi
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.SS Conclusion
.sp
In this tutorial, we implemented a program that fetches the latest
commits of a GitHub repository using the GitHub Repo Commits API.
Jansson was used to decode the JSON response and to extract the commit
data.
.sp
This tutorial only covered a small part of Jansson. For example, we
did not create or manipulate JSON values at all. Proceed to
\fIapiref\fP to explore all features of Jansson.
.SS RFC Conformance
.sp
JSON is specified in \fI\%RFC 4627\fP, \fI"The application/json Media Type
for JavaScript Object Notation (JSON)"\fP\&.
.SS Character Encoding
.sp
Jansson only supports UTF\-8 encoded JSON texts. It does not support or
auto\-detect any of the other encodings mentioned in the RFC, namely
UTF\-16LE, UTF\-16BE, UTF\-32LE or UTF\-32BE. Pure ASCII is supported, as
it\(aqs a subset of UTF\-8.
.SS Strings
.sp
JSON strings are mapped to C\-style null\-terminated character arrays,
and UTF\-8 encoding is used internally.
.sp
All Unicode codepoints U+0000 through U+10FFFF are allowed in string
values. However, U+0000 is not allowed in object keys because of API
restrictions.
.sp
Unicode normalization or any other transformation is never performed
on any strings (string values or object keys). When checking for
equivalence of strings or object keys, the comparison is performed
byte by byte between the original UTF\-8 representations of the
strings.
.SS Numbers
.SS Real vs. Integer
.sp
JSON makes no distinction between real and integer numbers; Jansson
does. Real numbers are mapped to the \fBdouble\fP type and integers to
the \fBjson_int_t\fP type, which is a typedef of \fBlong long\fP or
\fBlong\fP, depending on whether \fBlong long\fP is supported by your
compiler or not.
.sp
A JSON number is considered to be a real number if its lexical
representation includes one of \fBe\fP, \fBE\fP, or \fB\&.\fP; regardless if
its actual numeric value is a true integer (e.g., all of \fB1E6\fP,
\fB3.0\fP, \fB400E\-2\fP, and \fB3.14E3\fP are mathematical integers, but
will be treated as real values). With the \fBJSON_DECODE_INT_AS_REAL\fP
decoder flag set all numbers are interpreted as real.
.sp
All other JSON numbers are considered integers.
.sp
When encoding to JSON, real values are always represented
with a fractional part; e.g., the \fBdouble\fP value 3.0 will be
represented in JSON as \fB3.0\fP, not \fB3\fP\&.
.SS Overflow, Underflow & Precision
.sp
Real numbers whose absolute values are too small to be represented in
a C \fBdouble\fP will be silently estimated with 0.0. Thus, depending on
platform, JSON numbers very close to zero such as 1E\-999 may result in
0.0.
.sp
Real numbers whose absolute values are too large to be represented in
a C \fBdouble\fP will result in an overflow error (a JSON decoding
error). Thus, depending on platform, JSON numbers like 1E+999 or
\-1E+999 may result in a parsing error.
.sp
Likewise, integer numbers whose absolute values are too large to be
represented in the \fBjson_int_t\fP type (see above) will result in an
overflow error (a JSON decoding error). Thus, depending on platform,
JSON numbers like 1000000000000000 may result in parsing error.
.sp
Parsing JSON real numbers may result in a loss of precision. As long
as overflow does not occur (i.e. a total loss of precision), the
rounded approximate value is silently used. Thus the JSON number
1.000000000000000005 may, depending on platform, result in the
\fBdouble\fP value 1.0.
.SS Signed zeros
.sp
JSON makes no statement about what a number means; however Javascript
(ECMAscript) does state that +0.0 and \-0.0 must be treated as being
distinct values, i.e. \-0.0 ≠ 0.0. Jansson relies on the
underlying floating point library in the C environment in which it is
compiled. Therefore it is platform\-dependent whether 0.0 and \-0.0 will
be distinct values. Most platforms that use the IEEE 754
floating\-point standard will support signed zeros.
.sp
Note that this only applies to floating\-point; neither JSON, C, or
IEEE support the concept of signed integer zeros.
.SS Types
.sp
No support is provided in Jansson for any C numeric types other than
\fBjson_int_t\fP and \fBdouble\fP\&. This excludes things such as unsigned
types, \fBlong double\fP, etc. Obviously, shorter types like \fBshort\fP,
\fBint\fP, \fBlong\fP (if \fBjson_int_t\fP is \fBlong long\fP) and \fBfloat\fP
are implicitly handled via the ordinary C type coercion rules (subject
to overflow semantics). Also, no support or hooks are provided for any
supplemental "bignum" type add\-on packages.
.SS Portability
.SS Thread safety
.sp
Jansson is thread safe and has no mutable global state. The only
exceptions are the hash function seed and memory allocation functions,
see below.
.sp
There\(aqs no locking performed inside Jansson\(aqs code, so a multithreaded
program must perform its own locking if JSON values are shared by
multiple threads. Jansson\(aqs reference counting semantics may make this
a bit harder than it seems, as it\(aqs possible to have a reference to a
value that\(aqs also stored inside a list or object. Modifying the
container (adding or removing values) may trigger concurrent access to
such values, as containers manage the reference count of their
contained values. Bugs involving concurrent incrementing or
decrementing of deference counts may be hard to track.
.sp
The encoding functions (\fBjson_dumps()\fP and friends) track
reference loops by modifying the internal state of objects and arrays.
For this reason, encoding functions must not be run on the same JSON
values in two separate threads at the same time. As already noted
above, be especially careful if two arrays or objects share their
contained values with another array or object.
.sp
If you want to make sure that two JSON value hierarchies do not
contain shared values, use \fBjson_deep_copy()\fP to make copies.
.SS Hash function seed
.sp
To prevent an attacker from intentionally causing large JSON objects
with specially crafted keys to perform very slow, the hash function
used by Jansson is randomized using a seed value. The seed is
automatically generated on the first explicit or implicit call to
\fBjson_object()\fP, if \fBjson_object_seed()\fP has not been
called beforehand.
.sp
The seed is generated by using operating system\(aqs entropy sources if
they are available (\fB/dev/urandom\fP, \fBCryptGenRandom()\fP). The
initialization is done in as thread safe manner as possible, by using
architecture specific lockless operations if provided by the platform
or the compiler.
.sp
If you\(aqre using threads, it\(aqs recommended to autoseed the hashtable
explicitly before spawning any threads by calling
\fBjson_object_seed(0)\fP , especially if you\(aqre unsure whether the
initialization is thread safe on your platform.
.SS Memory allocation functions
.sp
Memory allocation functions should be set at most once, and only on
program startup. See \fIapiref\-custom\-memory\-allocation\fP\&.
.SS Locale
.sp
Jansson works fine under any locale.
.sp
However, if the host program is multithreaded and uses \fBsetlocale()\fP
to switch the locale in one thread while Jansson is currently encoding
or decoding JSON data in another thread, the result may be wrong or
the program may even crash.
.sp
Jansson uses locale specific functions for certain string conversions
in the encoder and decoder, and then converts the locale specific
values to/from the JSON representation. This fails if the locale
changes between the string conversion and the locale\-to\-JSON
conversion. This can only happen in multithreaded programs that use
\fBsetlocale()\fP, because \fBsetlocale()\fP switches the locale for all
running threads, not only the thread that calls \fBsetlocale()\fP\&.
.sp
If your program uses \fBsetlocale()\fP as described above, consider
using the thread\-safe \fBuselocale()\fP instead.
.SS API Reference
.SS Preliminaries
.sp
All declarations are in \fBjansson.h\fP, so it\(aqs enough to
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
#include <jansson.h>
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
in each source file.
.sp
All constants are prefixed with \fBJSON_\fP (except for those describing
the library version, prefixed with \fBJANSSON_\fP). Other identifiers
are prefixed with \fBjson_\fP\&. Type names are suffixed with \fB_t\fP and
\fBtypedef\fP\(aqd so that the \fBstruct\fP keyword need not be used.
.SS Library Version
.sp
The Jansson version is of the form \fIA.B.C\fP, where \fIA\fP is the major
version, \fIB\fP is the minor version and \fIC\fP is the micro version. If the
micro version is zero, it\(aqs omitted from the version string, i.e. the
version string is just \fIA.B\fP\&.
.sp
When a new release only fixes bugs and doesn\(aqt add new features or
functionality, the micro version is incremented. When new features are
added in a backwards compatible way, the minor version is incremented
and the micro version is set to zero. When there are backwards
incompatible changes, the major version is incremented and others are
set to zero.
.sp
The following preprocessor constants specify the current version of
the library:
.INDENT 0.0
.TP
.B \fBJANSSON_MAJOR_VERSION\fP, \fBJANSSON_MINOR_VERSION\fP, \fBJANSSON_MICRO_VERSION\fP
Integers specifying the major, minor and micro versions,
respectively.
.TP
.B \fBJANSSON_VERSION\fP
A string representation of the current version, e.g. \fB"1.2.1"\fP or
\fB"1.3"\fP\&.
.TP
.B \fBJANSSON_VERSION_HEX\fP
A 3\-byte hexadecimal representation of the version, e.g.
\fB0x010201\fP for version 1.2.1 and \fB0x010300\fP for version 1.3.
This is useful in numeric comparisions, e.g.:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
#if JANSSON_VERSION_HEX >= 0x010300
/* Code specific to version 1.3 and above */
#endif
.ft R
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.SS Value Representation
.sp
The JSON specification (\fI\%RFC 4627\fP) defines the following data types:
\fIobject\fP, \fIarray\fP, \fIstring\fP, \fInumber\fP, \fIboolean\fP, and \fInull\fP\&. JSON
types are used dynamically; arrays and objects can hold any other data
type, including themselves. For this reason, Jansson\(aqs type system is
also dynamic in nature. There\(aqs one C type to represent all JSON
values, and this structure knows the type of the JSON value it holds.
.INDENT 0.0
.TP
.B json_t
This data structure is used throughout the library to represent all
JSON values. It always contains the type of the JSON value it holds
and the value\(aqs reference count. The rest depends on the type of the
value.
.UNINDENT
.sp
Objects of \fBjson_t\fP are always used through a pointer. There
are APIs for querying the type, manipulating the reference count, and
for constructing and manipulating values of different types.
.sp
Unless noted otherwise, all API functions return an error value if an
error occurs. Depending on the function\(aqs signature, the error value
is either \fINULL\fP or \-1. Invalid arguments or invalid input are
apparent sources for errors. Memory allocation and I/O operations may
also cause errors.
.SS Type
.sp
The type of a JSON value is queried and tested using the following
functions:
.INDENT 0.0
.TP
.B enum json_type
The type of a JSON value. The following members are defined:
.TS
center;
|l|.
_
T{
\fBJSON_OBJECT\fP
T}
_
T{
\fBJSON_ARRAY\fP
T}
_
T{
\fBJSON_STRING\fP
T}
_
T{
\fBJSON_INTEGER\fP
T}
_
T{
\fBJSON_REAL\fP
T}
_
T{
\fBJSON_TRUE\fP
T}
_
T{
\fBJSON_FALSE\fP
T}
_
T{
\fBJSON_NULL\fP
T}
_
.TE
.sp
These correspond to JSON object, array, string, number, boolean and
null. A number is represented by either a value of the type
\fBJSON_INTEGER\fP or of the type \fBJSON_REAL\fP\&. A true boolean value
is represented by a value of the type \fBJSON_TRUE\fP and false by a
value of the type \fBJSON_FALSE\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B int json_typeof(const json_t\fI\ *json\fP)
Return the type of the JSON value (a \fBjson_type\fP cast to
\fBint\fP). \fIjson\fP MUST NOT be \fINULL\fP\&. This function is actually
implemented as a macro for speed.
.UNINDENT
.INDENT 0.0
.TP
.B json_is_object(const json_t\fI\ *json\fP)
.TP
.B json_is_array(const json_t\fI\ *json\fP)
.TP
.B json_is_string(const json_t\fI\ *json\fP)
.TP
.B json_is_integer(const json_t\fI\ *json\fP)
.TP
.B json_is_real(const json_t\fI\ *json\fP)
.TP
.B json_is_true(const json_t\fI\ *json\fP)
.TP
.B json_is_false(const json_t\fI\ *json\fP)
.TP
.B json_is_null(const json_t\fI\ *json\fP)
These functions (actually macros) return true (non\-zero) for values
of the given type, and false (zero) for values of other types and
for \fINULL\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B json_is_number(const json_t\fI\ *json\fP)
Returns true for values of types \fBJSON_INTEGER\fP and
\fBJSON_REAL\fP, and false for other types and for \fINULL\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B json_is_boolean(const json_t\fI\ *json\fP)
Returns true for types \fBJSON_TRUE\fP and \fBJSON_FALSE\fP, and false
for values of other types and for \fINULL\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B json_boolean_value(const json_t\fI\ *json\fP)
Alias of \fBjson_is_true()\fP, i.e. returns 1 for \fBJSON_TRUE\fP
and 0 otherwise.
.sp
New in version 2.7.

.UNINDENT
.SS Reference Count
.sp
The reference count is used to track whether a value is still in use
or not. When a value is created, it\(aqs reference count is set to 1. If
a reference to a value is kept (e.g. a value is stored somewhere for
later use), its reference count is incremented, and when the value is
no longer needed, the reference count is decremented. When the
reference count drops to zero, there are no references left, and the
value can be destroyed.
.sp
The following functions are used to manipulate the reference count.
.INDENT 0.0
.TP
.B json_t *json_incref(json_t\fI\ *json\fP)
Increment the reference count of \fIjson\fP if it\(aqs not \fINULL\fP\&.
Returns \fIjson\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B void json_decref(json_t\fI\ *json\fP)
Decrement the reference count of \fIjson\fP\&. As soon as a call to
\fBjson_decref()\fP drops the reference count to zero, the value
is destroyed and it can no longer be used.
.UNINDENT
.sp
Functions creating new JSON values set the reference count to 1. These
functions are said to return a \fBnew reference\fP\&. Other functions
returning (existing) JSON values do not normally increase the
reference count. These functions are said to return a \fBborrowed
reference\fP\&. So, if the user will hold a reference to a value returned
as a borrowed reference, he must call \fBjson_incref()\fP\&. As soon as
the value is no longer needed, \fBjson_decref()\fP should be called
to release the reference.
.sp
Normally, all functions accepting a JSON value as an argument will
manage the reference, i.e. increase and decrease the reference count
as needed. However, some functions \fBsteal\fP the reference, i.e. they
have the same result as if the user called \fBjson_decref()\fP on
the argument right after calling the function. These functions are
suffixed with \fB_new\fP or have \fB_new_\fP somewhere in their name.
.sp
For example, the following code creates a new JSON array and appends
an integer to it:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
json_t *array, *integer;

array = json_array();
integer = json_integer(42);

json_array_append(array, integer);
json_decref(integer);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
Note how the caller has to release the reference to the integer value
by calling \fBjson_decref()\fP\&. By using a reference stealing
function \fBjson_array_append_new()\fP instead of
\fBjson_array_append()\fP, the code becomes much simpler:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
json_t *array = json_array();
json_array_append_new(array, json_integer(42));
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
In this case, the user doesn\(aqt have to explicitly release the
reference to the integer value, as \fBjson_array_append_new()\fP
steals the reference when appending the value to the array.
.sp
In the following sections it is clearly documented whether a function
will return a new or borrowed reference or steal a reference to its
argument.
.SS Circular References
.sp
A circular reference is created when an object or an array is,
directly or indirectly, inserted inside itself. The direct case is
simple:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
json_t *obj = json_object();
json_object_set(obj, "foo", obj);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
Jansson will refuse to do this, and \fBjson_object_set()\fP (and
all the other such functions for objects and arrays) will return with
an error status. The indirect case is the dangerous one:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
json_t *arr1 = json_array(), *arr2 = json_array();
json_array_append(arr1, arr2);
json_array_append(arr2, arr1);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
In this example, the array \fBarr2\fP is contained in the array
\fBarr1\fP, and vice versa. Jansson cannot check for this kind of
indirect circular references without a performance hit, so it\(aqs up to
the user to avoid them.
.sp
If a circular reference is created, the memory consumed by the values
cannot be freed by \fBjson_decref()\fP\&. The reference counts never
drops to zero because the values are keeping the references to each
other. Moreover, trying to encode the values with any of the encoding
functions will fail. The encoder detects circular references and
returns an error status.
.SS True, False and Null
.sp
These three values are implemented as singletons, so the returned
pointers won\(aqt change between invocations of these functions.
.INDENT 0.0
.TP
.B json_t *json_true(void)
Return value: New reference.
.sp
Returns the JSON true value.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_false(void)
Return value: New reference.
.sp
Returns the JSON false value.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_boolean(val)
Return value: New reference.
.sp
Returns JSON false if \fBval\fP is zero, and JSON true otherwise.
This is a macro, and equivalent to \fBval ? json_true() :
json_false()\fP\&.
.sp
New in version 2.4.

.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_null(void)
Return value: New reference.
.sp
Returns the JSON null value.
.UNINDENT
.SS String
.sp
Jansson uses UTF\-8 as the character encoding. All JSON strings must be
valid UTF\-8 (or ASCII, as it\(aqs a subset of UTF\-8). All Unicode
codepoints U+0000 through U+10FFFF are allowed, but you must use
length\-aware functions if you wish to embed NUL bytes in strings.
.INDENT 0.0
.TP
.B json_t *json_string(const char\fI\ *value\fP)
Return value: New reference.
.sp
Returns a new JSON string, or \fINULL\fP on error. \fIvalue\fP must be a
valid null terminated UTF\-8 encoded Unicode string.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_stringn(const char\fI\ *value\fP, size_t\fI\ len\fP)
Return value: New reference.
.sp
Like \fBjson_string()\fP, but with explicit length, so \fIvalue\fP may
contain null characters or not be null terminated.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_string_nocheck(const char\fI\ *value\fP)
Return value: New reference.
.sp
Like \fBjson_string()\fP, but doesn\(aqt check that \fIvalue\fP is valid
UTF\-8. Use this function only if you are certain that this really
is the case (e.g. you have already checked it by other means).
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_stringn_nocheck(const char\fI\ *value\fP, size_t\fI\ len\fP)
Return value: New reference.
.sp
Like \fBjson_string_nocheck()\fP, but with explicit length, so
\fIvalue\fP may contain null characters or not be null terminated.
.UNINDENT
.INDENT 0.0
.TP
.B const char *json_string_value(const json_t\fI\ *string\fP)
Returns the associated value of \fIstring\fP as a null terminated UTF\-8
encoded string, or \fINULL\fP if \fIstring\fP is not a JSON string.
.sp
The retuned value is read\-only and must not be modified or freed by
the user. It is valid as long as \fIstring\fP exists, i.e. as long as
its reference count has not dropped to zero.
.UNINDENT
.INDENT 0.0
.TP
.B size_t json_string_length(const json_t\fI\ *string\fP)
Returns the length of \fIstring\fP in its UTF\-8 presentation, or zero
if \fIstring\fP is not a JSON string.
.UNINDENT
.INDENT 0.0
.TP
.B int json_string_set(const json_t\fI\ *string\fP, const char\fI\ *value\fP)
Sets the associated value of \fIstring\fP to \fIvalue\fP\&. \fIvalue\fP must be a
valid UTF\-8 encoded Unicode string. Returns 0 on success and \-1 on
error.
.UNINDENT
.INDENT 0.0
.TP
.B int json_string_setn(json_t\fI\ *string\fP, const char\fI\ *value\fP, size_t\fI\ len\fP)
Like \fBjson_string_set()\fP, but with explicit length, so \fIvalue\fP
may contain null characters or not be null terminated.
.UNINDENT
.INDENT 0.0
.TP
.B int json_string_set_nocheck(const json_t\fI\ *string\fP, const char\fI\ *value\fP)
Like \fBjson_string_set()\fP, but doesn\(aqt check that \fIvalue\fP is
valid UTF\-8. Use this function only if you are certain that this
really is the case (e.g. you have already checked it by other
means).
.UNINDENT
.INDENT 0.0
.TP
.B int json_string_setn_nocheck(json_t\fI\ *string\fP, const char\fI\ *value\fP, size_t\fI\ len\fP)
Like \fBjson_string_set_nocheck()\fP, but with explicit length,
so \fIvalue\fP may contain null characters or not be null terminated.
.UNINDENT
.SS Number
.sp
The JSON specification only contains one numeric type, "number". The C
programming language has distinct types for integer and floating\-point
numbers, so for practical reasons Jansson also has distinct types for
the two. They are called "integer" and "real", respectively. For more
information, see \fIrfc\-conformance\fP\&.
.INDENT 0.0
.TP
.B json_int_t
This is the C type that is used to store JSON integer values. It
represents the widest integer type available on your system. In
practice it\(aqs just a typedef of \fBlong long\fP if your compiler
supports it, otherwise \fBlong\fP\&.
.sp
Usually, you can safely use plain \fBint\fP in place of
\fBjson_int_t\fP, and the implicit C integer conversion handles the
rest. Only when you know that you need the full 64\-bit range, you
should use \fBjson_int_t\fP explicitly.
.UNINDENT
.INDENT 0.0
.TP
.B \fBJSON_INTEGER_IS_LONG_LONG\fP
This is a preprocessor variable that holds the value 1 if
\fBjson_int_t\fP is \fBlong long\fP, and 0 if it\(aqs \fBlong\fP\&. It
can be used as follows:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
#if JSON_INTEGER_IS_LONG_LONG
/* Code specific for long long */
#else
/* Code specific for long */
#endif
.ft R
.fi
.UNINDENT
.UNINDENT
.TP
.B \fBJSON_INTEGER_FORMAT\fP
This is a macro that expands to a \fBprintf()\fP conversion
specifier that corresponds to \fBjson_int_t\fP, without the
leading \fB%\fP sign, i.e. either \fB"lld"\fP or \fB"ld"\fP\&. This macro
is required because the actual type of \fBjson_int_t\fP can be
either \fBlong\fP or \fBlong long\fP, and \fBprintf()\fP reuiqres
different length modifiers for the two.
.sp
Example:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
json_int_t x = 123123123;
printf("x is %" JSON_INTEGER_FORMAT "\en", x);
.ft R
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_integer(json_int_t\fI\ value\fP)
Return value: New reference.
.sp
Returns a new JSON integer, or \fINULL\fP on error.
.UNINDENT
.INDENT 0.0
.TP
.B json_int_t json_integer_value(const json_t\fI\ *integer\fP)
Returns the associated value of \fIinteger\fP, or 0 if \fIjson\fP is not a
JSON integer.
.UNINDENT
.INDENT 0.0
.TP
.B int json_integer_set(const json_t\fI\ *integer\fP, json_int_t\fI\ value\fP)
Sets the associated value of \fIinteger\fP to \fIvalue\fP\&. Returns 0 on
success and \-1 if \fIinteger\fP is not a JSON integer.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_real(double\fI\ value\fP)
Return value: New reference.
.sp
Returns a new JSON real, or \fINULL\fP on error.
.UNINDENT
.INDENT 0.0
.TP
.B double json_real_value(const json_t\fI\ *real\fP)
Returns the associated value of \fIreal\fP, or 0.0 if \fIreal\fP is not a
JSON real.
.UNINDENT
.INDENT 0.0
.TP
.B int json_real_set(const json_t\fI\ *real\fP, double\fI\ value\fP)
Sets the associated value of \fIreal\fP to \fIvalue\fP\&. Returns 0 on
success and \-1 if \fIreal\fP is not a JSON real.
.UNINDENT
.sp
In addition to the functions above, there\(aqs a common query function
for integers and reals:
.INDENT 0.0
.TP
.B double json_number_value(const json_t\fI\ *json\fP)
Returns the associated value of the JSON integer or JSON real
\fIjson\fP, cast to double regardless of the actual type. If \fIjson\fP is
neither JSON real nor JSON integer, 0.0 is returned.
.UNINDENT
.SS Array
.sp
A JSON array is an ordered collection of other JSON values.
.INDENT 0.0
.TP
.B json_t *json_array(void)
Return value: New reference.
.sp
Returns a new JSON array, or \fINULL\fP on error. Initially, the array
is empty.
.UNINDENT
.INDENT 0.0
.TP
.B size_t json_array_size(const json_t\fI\ *array\fP)
Returns the number of elements in \fIarray\fP, or 0 if \fIarray\fP is NULL
or not a JSON array.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_array_get(const json_t\fI\ *array\fP, size_t\fI\ index\fP)
Return value: Borrowed reference.
.sp
Returns the element in \fIarray\fP at position \fIindex\fP\&. The valid range
for \fIindex\fP is from 0 to the return value of
\fBjson_array_size()\fP minus 1. If \fIarray\fP is not a JSON array,
if \fIarray\fP is \fINULL\fP, or if \fIindex\fP is out of range, \fINULL\fP is
returned.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_set(json_t\fI\ *array\fP, size_t\fI\ index\fP, json_t\fI\ *value\fP)
Replaces the element in \fIarray\fP at position \fIindex\fP with \fIvalue\fP\&.
The valid range for \fIindex\fP is from 0 to the return value of
\fBjson_array_size()\fP minus 1. Returns 0 on success and \-1 on
error.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_set_new(json_t\fI\ *array\fP, size_t\fI\ index\fP, json_t\fI\ *value\fP)
Like \fBjson_array_set()\fP but steals the reference to \fIvalue\fP\&.
This is useful when \fIvalue\fP is newly created and not used after
the call.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_append(json_t\fI\ *array\fP, json_t\fI\ *value\fP)
Appends \fIvalue\fP to the end of \fIarray\fP, growing the size of \fIarray\fP
by 1. Returns 0 on success and \-1 on error.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_append_new(json_t\fI\ *array\fP, json_t\fI\ *value\fP)
Like \fBjson_array_append()\fP but steals the reference to
\fIvalue\fP\&. This is useful when \fIvalue\fP is newly created and not used
after the call.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_insert(json_t\fI\ *array\fP, size_t\fI\ index\fP, json_t\fI\ *value\fP)
Inserts \fIvalue\fP to \fIarray\fP at position \fIindex\fP, shifting the
elements at \fIindex\fP and after it one position towards the end of
the array. Returns 0 on success and \-1 on error.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_insert_new(json_t\fI\ *array\fP, size_t\fI\ index\fP, json_t\fI\ *value\fP)
Like \fBjson_array_insert()\fP but steals the reference to
\fIvalue\fP\&. This is useful when \fIvalue\fP is newly created and not used
after the call.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_remove(json_t\fI\ *array\fP, size_t\fI\ index\fP)
Removes the element in \fIarray\fP at position \fIindex\fP, shifting the
elements after \fIindex\fP one position towards the start of the array.
Returns 0 on success and \-1 on error. The reference count of the
removed value is decremented.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_clear(json_t\fI\ *array\fP)
Removes all elements from \fIarray\fP\&. Returns 0 on sucess and \-1 on
error. The reference count of all removed values are decremented.
.UNINDENT
.INDENT 0.0
.TP
.B int json_array_extend(json_t\fI\ *array\fP, json_t\fI\ *other_array\fP)
Appends all elements in \fIother_array\fP to the end of \fIarray\fP\&.
Returns 0 on success and \-1 on error.
.UNINDENT
.sp
The following macro can be used to iterate through all elements
in an array.
.INDENT 0.0
.TP
.B json_array_foreach(array, index, value)
Iterate over every element of \fBarray\fP, running the block
of code that follows each time with the proper values set to
variables \fBindex\fP and \fBvalue\fP, of types \fBsize_t\fP and
\fBjson_t *\fP respectively. Example:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
/* array is a JSON array */
size_t index;
json_t *value;

json_array_foreach(array, index, value) {
    /* block of code that uses index and value */
}
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
The items are returned in increasing index order.
.sp
This macro expands to an ordinary \fBfor\fP statement upon
preprocessing, so its performance is equivalent to that of
hand\-written code using the array access functions.
The main advantage of this macro is that it abstracts
away the complexity, and makes for shorter, more
concise code.
.sp
New in version 2.5.

.UNINDENT
.SS Object
.sp
A JSON object is a dictionary of key\-value pairs, where the key is a
Unicode string and the value is any JSON value.
.sp
Even though NUL bytes are allowed in string values, they are not
allowed in object keys.
.INDENT 0.0
.TP
.B json_t *json_object(void)
Return value: New reference.
.sp
Returns a new JSON object, or \fINULL\fP on error. Initially, the
object is empty.
.UNINDENT
.INDENT 0.0
.TP
.B size_t json_object_size(const json_t\fI\ *object\fP)
Returns the number of elements in \fIobject\fP, or 0 if \fIobject\fP is not
a JSON object.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_object_get(const json_t\fI\ *object\fP, const char\fI\ *key\fP)
Return value: Borrowed reference.
.sp
Get a value corresponding to \fIkey\fP from \fIobject\fP\&. Returns \fINULL\fP if
\fIkey\fP is not found and on error.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_set(json_t\fI\ *object\fP, const char\fI\ *key\fP, json_t\fI\ *value\fP)
Set the value of \fIkey\fP to \fIvalue\fP in \fIobject\fP\&. \fIkey\fP must be a
valid null terminated UTF\-8 encoded Unicode string. If there
already is a value for \fIkey\fP, it is replaced by the new value.
Returns 0 on success and \-1 on error.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_set_nocheck(json_t\fI\ *object\fP, const char\fI\ *key\fP, json_t\fI\ *value\fP)
Like \fBjson_object_set()\fP, but doesn\(aqt check that \fIkey\fP is
valid UTF\-8. Use this function only if you are certain that this
really is the case (e.g. you have already checked it by other
means).
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_set_new(json_t\fI\ *object\fP, const char\fI\ *key\fP, json_t\fI\ *value\fP)
Like \fBjson_object_set()\fP but steals the reference to
\fIvalue\fP\&. This is useful when \fIvalue\fP is newly created and not used
after the call.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_set_new_nocheck(json_t\fI\ *object\fP, const char\fI\ *key\fP, json_t\fI\ *value\fP)
Like \fBjson_object_set_new()\fP, but doesn\(aqt check that \fIkey\fP is
valid UTF\-8. Use this function only if you are certain that this
really is the case (e.g. you have already checked it by other
means).
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_del(json_t\fI\ *object\fP, const char\fI\ *key\fP)
Delete \fIkey\fP from \fIobject\fP if it exists. Returns 0 on success, or
\-1 if \fIkey\fP was not found. The reference count of the removed value
is decremented.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_clear(json_t\fI\ *object\fP)
Remove all elements from \fIobject\fP\&. Returns 0 on success and \-1 if
\fIobject\fP is not a JSON object. The reference count of all removed
values are decremented.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_update(json_t\fI\ *object\fP, json_t\fI\ *other\fP)
Update \fIobject\fP with the key\-value pairs from \fIother\fP, overwriting
existing keys. Returns 0 on success or \-1 on error.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_update_existing(json_t\fI\ *object\fP, json_t\fI\ *other\fP)
Like \fBjson_object_update()\fP, but only the values of existing
keys are updated. No new keys are created. Returns 0 on success or
\-1 on error.
.sp
New in version 2.3.

.UNINDENT
.INDENT 0.0
.TP
.B int json_object_update_missing(json_t\fI\ *object\fP, json_t\fI\ *other\fP)
Like \fBjson_object_update()\fP, but only new keys are created.
The value of any existing key is not changed. Returns 0 on success
or \-1 on error.
.sp
New in version 2.3.

.UNINDENT
.sp
The following macro can be used to iterate through all key\-value pairs
in an object.
.INDENT 0.0
.TP
.B json_object_foreach(object, key, value)
Iterate over every key\-value pair of \fBobject\fP, running the block
of code that follows each time with the proper values set to
variables \fBkey\fP and \fBvalue\fP, of types \fBconst char *\fP and
\fBjson_t *\fP respectively. Example:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
/* obj is a JSON object */
const char *key;
json_t *value;

json_object_foreach(obj, key, value) {
    /* block of code that uses key and value */
}
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
The items are not returned in any particular order.
.sp
This macro expands to an ordinary \fBfor\fP statement upon
preprocessing, so its performance is equivalent to that of
hand\-written iteration code using the object iteration protocol
(see below). The main advantage of this macro is that it abstracts
away the complexity behind iteration, and makes for shorter, more
concise code.
.sp
New in version 2.3.

.UNINDENT
.sp
The following functions implement an iteration protocol for objects,
allowing to iterate through all key\-value pairs in an object. The
items are not returned in any particular order, as this would require
sorting due to the internal hashtable implementation.
.INDENT 0.0
.TP
.B void *json_object_iter(json_t\fI\ *object\fP)
Returns an opaque iterator which can be used to iterate over all
key\-value pairs in \fIobject\fP, or \fINULL\fP if \fIobject\fP is empty.
.UNINDENT
.INDENT 0.0
.TP
.B void *json_object_iter_at(json_t\fI\ *object\fP, const char\fI\ *key\fP)
Like \fBjson_object_iter()\fP, but returns an iterator to the
key\-value pair in \fIobject\fP whose key is equal to \fIkey\fP, or NULL if
\fIkey\fP is not found in \fIobject\fP\&. Iterating forward to the end of
\fIobject\fP only yields all key\-value pairs of the object if \fIkey\fP
happens to be the first key in the underlying hash table.
.UNINDENT
.INDENT 0.0
.TP
.B void *json_object_iter_next(json_t\fI\ *object\fP, void\fI\ *iter\fP)
Returns an iterator pointing to the next key\-value pair in \fIobject\fP
after \fIiter\fP, or \fINULL\fP if the whole object has been iterated
through.
.UNINDENT
.INDENT 0.0
.TP
.B const char *json_object_iter_key(void\fI\ *iter\fP)
Extract the associated key from \fIiter\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_object_iter_value(void\fI\ *iter\fP)
Return value: Borrowed reference.
.sp
Extract the associated value from \fIiter\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_iter_set(json_t\fI\ *object\fP, void\fI\ *iter\fP, json_t\fI\ *value\fP)
Set the value of the key\-value pair in \fIobject\fP, that is pointed to
by \fIiter\fP, to \fIvalue\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B int json_object_iter_set_new(json_t\fI\ *object\fP, void\fI\ *iter\fP, json_t\fI\ *value\fP)
Like \fBjson_object_iter_set()\fP, but steals the reference to
\fIvalue\fP\&. This is useful when \fIvalue\fP is newly created and not used
after the call.
.UNINDENT
.INDENT 0.0
.TP
.B void *json_object_key_to_iter(const char\fI\ *key\fP)
Like \fBjson_object_iter_at()\fP, but much faster. Only works for
values returned by \fBjson_object_iter_key()\fP\&. Using other keys
will lead to segfaults. This function is used internally to
implement \fBjson_object_foreach()\fP\&.
.sp
New in version 2.3.

.UNINDENT
.sp
The iteration protocol can be used for example as follows:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
/* obj is a JSON object */
const char *key;
json_t *value;

void *iter = json_object_iter(obj);
while(iter)
{
    key = json_object_iter_key(iter);
    value = json_object_iter_value(iter);
    /* use key and value ... */
    iter = json_object_iter_next(obj, iter);
}
.ft R
.fi
.UNINDENT
.UNINDENT
.INDENT 0.0
.TP
.B void json_object_seed(size_t\fI\ seed\fP)
Seed the hash function used in Jansson\(aqs hashtable implementation.
The seed is used to randomize the hash function so that an
attacker cannot control its output.
.sp
If \fIseed\fP is 0, Jansson generates the seed itselfy by reading
random data from the operating system\(aqs entropy sources. If no
entropy sources are available, falls back to using a combination
of the current timestamp (with microsecond precision if possible)
and the process ID.
.sp
If called at all, this function must be called before any calls to
\fBjson_object()\fP, either explicit or implicit. If this
function is not called by the user, the first call to
\fBjson_object()\fP (either explicit or implicit) seeds the hash
function. See \fIportability\-thread\-safety\fP for notes on thread
safety.
.sp
If repeatable results are required, for e.g. unit tests, the hash
function can be "unrandomized" by calling \fBjson_object_seed()\fP
with a constant value on program startup, e.g.
\fBjson_object_seed(1)\fP\&.
.sp
New in version 2.6.

.UNINDENT
.SS Error reporting
.sp
Jansson uses a single struct type to pass error information to the
user. See sections \fIapiref\-decoding\fP, \fIapiref\-pack\fP and
\fIapiref\-unpack\fP for functions that pass error information using
this struct.
.INDENT 0.0
.TP
.B json_error_t
.INDENT 7.0
.TP
.B char text[]
The error message (in UTF\-8), or an empty string if a message is
not available.
.UNINDENT
.INDENT 7.0
.TP
.B char source[]
Source of the error. This can be (a part of) the file name or a
special identifier in angle brackers (e.g. \fB<string>\fP).
.UNINDENT
.INDENT 7.0
.TP
.B int line
The line number on which the error occurred.
.UNINDENT
.INDENT 7.0
.TP
.B int column
The column on which the error occurred. Note that this is the
\fIcharacter column\fP, not the byte column, i.e. a multibyte UTF\-8
character counts as one column.
.UNINDENT
.INDENT 7.0
.TP
.B size_t position
The position in bytes from the start of the input. This is
useful for debugging Unicode encoding problems.
.UNINDENT
.UNINDENT
.sp
The normal use of \fBjson_error_t\fP is to allocate it on the stack,
and pass a pointer to a function. Example:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
int main() {
    json_t *json;
    json_error_t error;

    json = json_load_file("/path/to/file.json", 0, &error);
    if(!json) {
        /* the error variable contains error information */
    }
    ...
}
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
Also note that if the call succeeded (\fBjson != NULL\fP in the above
example), the contents of \fBerror\fP are generally left unspecified.
The decoding functions write to the \fBposition\fP member also on
success. See \fIapiref\-decoding\fP for more info.
.sp
All functions also accept \fINULL\fP as the \fBjson_error_t\fP pointer,
in which case no error information is returned to the caller.
.SS Encoding
.sp
This sections describes the functions that can be used to encode
values to JSON. By default, only objects and arrays can be encoded
directly, since they are the only valid \fIroot\fP values of a JSON text.
To encode any JSON value, use the \fBJSON_ENCODE_ANY\fP flag (see
below).
.sp
By default, the output has no newlines, and spaces are used between
array and object elements for a readable output. This behavior can be
altered by using the \fBJSON_INDENT\fP and \fBJSON_COMPACT\fP flags
described below. A newline is never appended to the end of the encoded
JSON data.
.sp
Each function takes a \fIflags\fP parameter that controls some aspects of
how the data is encoded. Its default value is 0. The following macros
can be ORed together to obtain \fIflags\fP\&.
.INDENT 0.0
.TP
.B \fBJSON_INDENT(n)\fP
Pretty\-print the result, using newlines between array and object
items, and indenting with \fIn\fP spaces. The valid range for \fIn\fP is
between 0 and 31 (inclusive), other values result in an undefined
output. If \fBJSON_INDENT\fP is not used or \fIn\fP is 0, no newlines are
inserted between array and object items.
.sp
The \fBJSON_MAX_INDENT\fP constant defines the maximum indentation
that can be used, and its value is 31.
.sp
Changed in version 2.7: Added \fBJSON_MAX_INDENT\fP\&.

.TP
.B \fBJSON_COMPACT\fP
This flag enables a compact representation, i.e. sets the separator
between array and object items to \fB","\fP and between object keys
and values to \fB":"\fP\&. Without this flag, the corresponding
separators are \fB", "\fP and \fB": "\fP for more readable output.
.TP
.B \fBJSON_ENSURE_ASCII\fP
If this flag is used, the output is guaranteed to consist only of
ASCII characters. This is achived by escaping all Unicode
characters outside the ASCII range.
.TP
.B \fBJSON_SORT_KEYS\fP
If this flag is used, all the objects in output are sorted by key.
This is useful e.g. if two JSON texts are diffed or visually
compared.
.TP
.B \fBJSON_PRESERVE_ORDER\fP
If this flag is used, object keys in the output are sorted into the
same order in which they were first inserted to the object. For
example, decoding a JSON text and then encoding with this flag
preserves the order of object keys.
.TP
.B \fBJSON_ENCODE_ANY\fP
Specifying this flag makes it possible to encode any JSON value on
its own. Without it, only objects and arrays can be passed as the
\fIroot\fP value to the encoding functions.
.sp
\fBNote:\fP Encoding any value may be useful in some scenarios, but
it\(aqs generally discouraged as it violates strict compatiblity with
\fI\%RFC 4627\fP\&. If you use this flag, don\(aqt expect interoperatibility
with other JSON systems.
.sp
New in version 2.1.

.TP
.B \fBJSON_ESCAPE_SLASH\fP
Escape the \fB/\fP characters in strings with \fB\e/\fP\&.
.sp
New in version 2.4.

.TP
.B \fBJSON_REAL_PRECISION(n)\fP
Output all real numbers with at most \fIn\fP digits of precision. The
valid range for \fIn\fP is between 0 and 31 (inclusive), and other
values result in an undefined behavior.
.sp
By default, the precision is 17, to correctly and losslessly encode
all IEEE 754 double precision floating point numbers.
.sp
New in version 2.7.

.UNINDENT
.sp
The following functions perform the actual JSON encoding. The result
is in UTF\-8.
.INDENT 0.0
.TP
.B char *json_dumps(const json_t\fI\ *root\fP, size_t\fI\ flags\fP)
Returns the JSON representation of \fIroot\fP as a string, or \fINULL\fP on
error. \fIflags\fP is described above. The return value must be freed
by the caller using \fBfree()\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B int json_dumpf(const json_t\fI\ *root\fP, FILE\fI\ *output\fP, size_t\fI\ flags\fP)
Write the JSON representation of \fIroot\fP to the stream \fIoutput\fP\&.
\fIflags\fP is described above. Returns 0 on success and \-1 on error.
If an error occurs, something may have already been written to
\fIoutput\fP\&. In this case, the output is undefined and most likely not
valid JSON.
.UNINDENT
.INDENT 0.0
.TP
.B int json_dump_file(const json_t\fI\ *json\fP, const char\fI\ *path\fP, size_t\fI\ flags\fP)
Write the JSON representation of \fIroot\fP to the file \fIpath\fP\&. If
\fIpath\fP already exists, it is overwritten. \fIflags\fP is described
above. Returns 0 on success and \-1 on error.
.UNINDENT
.INDENT 0.0
.TP
.B json_dump_callback_t
A typedef for a function that\(aqs called by
\fBjson_dump_callback()\fP:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
typedef int (*json_dump_callback_t)(const char *buffer, size_t size, void *data);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
\fIbuffer\fP points to a buffer containing a chunk of output, \fIsize\fP is
the length of the buffer, and \fIdata\fP is the corresponding
\fBjson_dump_callback()\fP argument passed through.
.sp
On error, the function should return \-1 to stop the encoding
process. On success, it should return 0.
.sp
New in version 2.2.

.UNINDENT
.INDENT 0.0
.TP
.B int json_dump_callback(const json_t\fI\ *json\fP, json_dump_callback_t\fI\ callback\fP, void\fI\ *data\fP, size_t\fI\ flags\fP)
Call \fIcallback\fP repeatedly, passing a chunk of the JSON
representation of \fIroot\fP each time. \fIflags\fP is described above.
Returns 0 on success and \-1 on error.
.sp
New in version 2.2.

.UNINDENT
.SS Decoding
.sp
This sections describes the functions that can be used to decode JSON
text to the Jansson representation of JSON data. The JSON
specification requires that a JSON text is either a serialized array
or object, and this requirement is also enforced with the following
functions. In other words, the top level value in the JSON text being
decoded must be either array or object. To decode any JSON value, use
the \fBJSON_DECODE_ANY\fP flag (see below).
.sp
See \fIrfc\-conformance\fP for a discussion on Jansson\(aqs conformance
to the JSON specification. It explains many design decisions that
affect especially the behavior of the decoder.
.sp
Each function takes a \fIflags\fP parameter that can be used to control
the behavior of the decoder. Its default value is 0. The following
macros can be ORed together to obtain \fIflags\fP\&.
.INDENT 0.0
.TP
.B \fBJSON_REJECT_DUPLICATES\fP
Issue a decoding error if any JSON object in the input text
contains duplicate keys. Without this flag, the value of the last
occurence of each key ends up in the result. Key equivalence is
checked byte\-by\-byte, without special Unicode comparison
algorithms.
.sp
New in version 2.1.

.TP
.B \fBJSON_DECODE_ANY\fP
By default, the decoder expects an array or object as the input.
With this flag enabled, the decoder accepts any valid JSON value.
.sp
\fBNote:\fP Decoding any value may be useful in some scenarios, but
it\(aqs generally discouraged as it violates strict compatiblity with
\fI\%RFC 4627\fP\&. If you use this flag, don\(aqt expect interoperatibility
with other JSON systems.
.sp
New in version 2.3.

.TP
.B \fBJSON_DISABLE_EOF_CHECK\fP
By default, the decoder expects that its whole input constitutes a
valid JSON text, and issues an error if there\(aqs extra data after
the otherwise valid JSON input. With this flag enabled, the decoder
stops after decoding a valid JSON array or object, and thus allows
extra data after the JSON text.
.sp
Normally, reading will stop when the last \fB]\fP or \fB}\fP in the
JSON input is encountered. If both \fBJSON_DISABLE_EOF_CHECK\fP and
\fBJSON_DECODE_ANY\fP flags are used, the decoder may read one extra
UTF\-8 code unit (up to 4 bytes of input). For example, decoding
\fB4true\fP correctly decodes the integer 4, but also reads the
\fBt\fP\&. For this reason, if reading multiple consecutive values that
are not arrays or objects, they should be separated by at least one
whitespace character.
.sp
New in version 2.1.

.TP
.B \fBJSON_DECODE_INT_AS_REAL\fP
JSON defines only one number type. Jansson distinguishes between
ints and reals. For more information see \fIreal\-vs\-integer\fP\&.
With this flag enabled the decoder interprets all numbers as real
values. Integers that do not have an exact double representation
will silently result in a loss of precision. Integers that cause
a double overflow will cause an error.
.sp
New in version 2.5.

.TP
.B \fBJSON_ALLOW_NUL\fP
Allow \fB\eu0000\fP escape inside string values. This is a safety
measure; If you know your input can contain NUL bytes, use this
flag. If you don\(aqt use this flag, you don\(aqt have to worry about NUL
bytes inside strings unless you explicitly create themselves by
using e.g. \fBjson_stringn()\fP or \fBs#\fP format specifier for
\fBjson_pack()\fP\&.
.sp
Object keys cannot have embedded NUL bytes even if this flag is
used.
.sp
New in version 2.6.

.UNINDENT
.sp
Each function also takes an optional \fBjson_error_t\fP parameter
that is filled with error information if decoding fails. It\(aqs also
updated on success; the number of bytes of input read is written to
its \fBposition\fP field. This is especially useful when using
\fBJSON_DISABLE_EOF_CHECK\fP to read multiple consecutive JSON texts.
.sp
New in version 2.3: Number of bytes of input read is written to the \fBposition\fP field
of the \fBjson_error_t\fP structure.

.sp
If no error or position information is needed, you can pass \fINULL\fP\&.
.sp
The following functions perform the actual JSON decoding.
.INDENT 0.0
.TP
.B json_t *json_loads(const char\fI\ *input\fP, size_t\fI\ flags\fP, json_error_t\fI\ *error\fP)
Return value: New reference.
.sp
Decodes the JSON string \fIinput\fP and returns the array or object it
contains, or \fINULL\fP on error, in which case \fIerror\fP is filled with
information about the error. \fIflags\fP is described above.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_loadb(const char\fI\ *buffer\fP, size_t\fI\ buflen\fP, size_t\fI\ flags\fP, json_error_t\fI\ *error\fP)
Return value: New reference.
.sp
Decodes the JSON string \fIbuffer\fP, whose length is \fIbuflen\fP, and
returns the array or object it contains, or \fINULL\fP on error, in
which case \fIerror\fP is filled with information about the error. This
is similar to \fBjson_loads()\fP except that the string doesn\(aqt
need to be null\-terminated. \fIflags\fP is described above.
.sp
New in version 2.1.

.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_loadf(FILE\fI\ *input\fP, size_t\fI\ flags\fP, json_error_t\fI\ *error\fP)
Return value: New reference.
.sp
Decodes the JSON text in stream \fIinput\fP and returns the array or
object it contains, or \fINULL\fP on error, in which case \fIerror\fP is
filled with information about the error. \fIflags\fP is described
above.
.sp
This function will start reading the input from whatever position
the input file was, without attempting to seek first. If an error
occurs, the file position will be left indeterminate. On success,
the file position will be at EOF, unless \fBJSON_DISABLE_EOF_CHECK\fP
flag was used. In this case, the file position will be at the first
character after the last \fB]\fP or \fB}\fP in the JSON input. This
allows calling \fBjson_loadf()\fP on the same \fBFILE\fP object
multiple times, if the input consists of consecutive JSON texts,
possibly separated by whitespace.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_load_file(const char\fI\ *path\fP, size_t\fI\ flags\fP, json_error_t\fI\ *error\fP)
Return value: New reference.
.sp
Decodes the JSON text in file \fIpath\fP and returns the array or
object it contains, or \fINULL\fP on error, in which case \fIerror\fP is
filled with information about the error. \fIflags\fP is described
above.
.UNINDENT
.INDENT 0.0
.TP
.B json_load_callback_t
A typedef for a function that\(aqs called by
\fBjson_load_callback()\fP to read a chunk of input data:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
typedef size_t (*json_load_callback_t)(void *buffer, size_t buflen, void *data);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
\fIbuffer\fP points to a buffer of \fIbuflen\fP bytes, and \fIdata\fP is the
corresponding \fBjson_load_callback()\fP argument passed through.
.sp
On success, the function should return the number of bytes read; a
returned value of 0 indicates that no data was read and that the
end of file has been reached. On error, the function should return
\fB(size_t)\-1\fP to abort the decoding process.
.sp
New in version 2.4.

.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_load_callback(json_load_callback_t\fI\ callback\fP, void\fI\ *data\fP, size_t\fI\ flags\fP, json_error_t\fI\ *error\fP)
Return value: New reference.
.sp
Decodes the JSON text produced by repeated calls to \fIcallback\fP, and
returns the array or object it contains, or \fINULL\fP on error, in
which case \fIerror\fP is filled with information about the error.
\fIdata\fP is passed through to \fIcallback\fP on each call. \fIflags\fP is
described above.
.sp
New in version 2.4.

.UNINDENT
.SS Building Values
.sp
This section describes functions that help to create, or \fIpack\fP,
complex JSON values, especially nested objects and arrays. Value
building is based on a \fIformat string\fP that is used to tell the
functions about the expected arguments.
.sp
For example, the format string \fB"i"\fP specifies a single integer
value, while the format string \fB"[ssb]"\fP or the equivalent \fB"[s, s,
b]"\fP specifies an array value with two strings and a boolean as its
items:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
/* Create the JSON integer 42 */
json_pack("i", 42);

/* Create the JSON array ["foo", "bar", true] */
json_pack("[ssb]", "foo", "bar", 1);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
Here\(aqs the full list of format specifiers. The type in parentheses
denotes the resulting JSON type, and the type in brackets (if any)
denotes the C type that is expected as the corresponding argument or
arguments.
.INDENT 0.0
.TP
.B \fBs\fP (string) [const char *]
Convert a NULL terminated UTF\-8 string to a JSON string.
.TP
.B \fBs#\fP (string) [const char *, int]
Convert a UTF\-8 buffer of a given length to a JSON string.
.sp
New in version 2.5.

.TP
.B \fBs%\fP (string) [const char *, size_t]
Like \fBs#\fP but the length argument is of type \fBsize_t\fP\&.
.sp
New in version 2.6.

.TP
.B \fB+\fP [const char *]
Like \fBs\fP, but concatenate to the previous string. Only valid
after \fBs\fP, \fBs#\fP, \fB+\fP or \fB+#\fP\&.
.sp
New in version 2.5.

.TP
.B \fB+#\fP [const char *, int]
Like \fBs#\fP, but concatenate to the previous string. Only valid
after \fBs\fP, \fBs#\fP, \fB+\fP or \fB+#\fP\&.
.sp
New in version 2.5.

.TP
.B \fB+%\fP (string) [const char *, size_t]
Like \fB+#\fP but the length argument is of type \fBsize_t\fP\&.
.sp
New in version 2.6.

.TP
.B \fBn\fP (null)
Output a JSON null value. No argument is consumed.
.TP
.B \fBb\fP (boolean) [int]
Convert a C \fBint\fP to JSON boolean value. Zero is converted
to \fBfalse\fP and non\-zero to \fBtrue\fP\&.
.TP
.B \fBi\fP (integer) [int]
Convert a C \fBint\fP to JSON integer.
.TP
.B \fBI\fP (integer) [json_int_t]
Convert a C \fBjson_int_t\fP to JSON integer.
.TP
.B \fBf\fP (real) [double]
Convert a C \fBdouble\fP to JSON real.
.TP
.B \fBo\fP (any value) [json_t *]
Output any given JSON value as\-is. If the value is added to an
array or object, the reference to the value passed to \fBo\fP is
stolen by the container.
.TP
.B \fBO\fP (any value) [json_t *]
Like \fBo\fP, but the argument\(aqs reference count is incremented.
This is useful if you pack into an array or object and want to
keep the reference for the JSON value consumed by \fBO\fP to
yourself.
.TP
.B \fB[fmt]\fP (array)
Build an array with contents from the inner format string. \fBfmt\fP
may contain objects and arrays, i.e. recursive value building is
supported.
.TP
.B \fB{fmt}\fP (object)
Build an object with contents from the inner format string
\fBfmt\fP\&. The first, third, etc. format specifier represent a key,
and must be a string (see \fBs\fP, \fBs#\fP, \fB+\fP and \fB+#\fP above),
as object keys are always strings. The second, fourth, etc. format
specifier represent a value. Any value may be an object or array,
i.e. recursive value building is supported.
.UNINDENT
.sp
Whitespace, \fB:\fP and \fB,\fP are ignored.
.sp
The following functions compose the value building API:
.INDENT 0.0
.TP
.B json_t *json_pack(const char\fI\ *fmt\fP, \&...)
Return value: New reference.
.sp
Build a new JSON value according to the format string \fIfmt\fP\&. For
each format specifier (except for \fB{}[]n\fP), one or more arguments
are consumed and used to build the corresponding value. Returns
\fINULL\fP on error.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_pack_ex(json_error_t\fI\ *error\fP, size_t\fI\ flags\fP, const char\fI\ *fmt\fP, \&...)
.TP
.B json_t *json_vpack_ex(json_error_t\fI\ *error\fP, size_t\fI\ flags\fP, const char\fI\ *fmt\fP, va_list\fI\ ap\fP)
Return value: New reference.
.sp
Like \fBjson_pack()\fP, but an in the case of an error, an error
message is written to \fIerror\fP, if it\(aqs not \fINULL\fP\&. The \fIflags\fP
parameter is currently unused and should be set to 0.
.sp
As only the errors in format string (and out\-of\-memory errors) can
be caught by the packer, these two functions are most likely only
useful for debugging format strings.
.UNINDENT
.sp
More examples:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
/* Build an empty JSON object */
json_pack("{}");

/* Build the JSON object {"foo": 42, "bar": 7} */
json_pack("{sisi}", "foo", 42, "bar", 7);

/* Like above, \(aq:\(aq, \(aq,\(aq and whitespace are ignored */
json_pack("{s:i, s:i}", "foo", 42, "bar", 7);

/* Build the JSON array [[1, 2], {"cool": true}] */
json_pack("[[i,i],{s:b}]", 1, 2, "cool", 1);

/* Build a string from a non\-NUL terminated buffer */
char buffer[4] = {\(aqt\(aq, \(aqe\(aq, \(aqs\(aq, \(aqt\(aq};
json_pack("s#", buffer, 4);

/* Concatentate strings together to build the JSON string "foobarbaz" */
json_pack("s++", "foo", "bar", "baz");
.ft R
.fi
.UNINDENT
.UNINDENT
.SS Parsing and Validating Values
.sp
This section describes functions that help to validate complex values
and extract, or \fIunpack\fP, data from them. Like \fIbuilding values\fP, this is also based on format strings.
.sp
While a JSON value is unpacked, the type specified in the format
string is checked to match that of the JSON value. This is the
validation part of the process. In addition to this, the unpacking
functions can also check that all items of arrays and objects are
unpacked. This check be enabled with the format specifier \fB!\fP or by
using the flag \fBJSON_STRICT\fP\&. See below for details.
.sp
Here\(aqs the full list of format specifiers. The type in parentheses
denotes the JSON type, and the type in brackets (if any) denotes the C
type whose address should be passed.
.INDENT 0.0
.TP
.B \fBs\fP (string) [const char *]
Convert a JSON string to a pointer to a NULL terminated UTF\-8
string. The resulting string is extracted by using
\fBjson_string_value()\fP internally, so it exists as long as
there are still references to the corresponding JSON string.
.TP
.B \fBs%\fP (string) [const char *, size_t *]
Convert a JSON string to a pointer to a NULL terminated UTF\-8
string and its length.
.sp
New in version 2.6.

.TP
.B \fBn\fP (null)
Expect a JSON null value. Nothing is extracted.
.TP
.B \fBb\fP (boolean) [int]
Convert a JSON boolean value to a C \fBint\fP, so that \fBtrue\fP
is converted to 1 and \fBfalse\fP to 0.
.TP
.B \fBi\fP (integer) [int]
Convert a JSON integer to C \fBint\fP\&.
.TP
.B \fBI\fP (integer) [json_int_t]
Convert a JSON integer to C \fBjson_int_t\fP\&.
.TP
.B \fBf\fP (real) [double]
Convert a JSON real to C \fBdouble\fP\&.
.TP
.B \fBF\fP (integer or real) [double]
Convert a JSON number (integer or real) to C \fBdouble\fP\&.
.TP
.B \fBo\fP (any value) [json_t *]
Store a JSON value with no conversion to a \fBjson_t\fP pointer.
.TP
.B \fBO\fP (any value) [json_t *]
Like \fBO\fP, but the JSON value\(aqs reference count is incremented.
.TP
.B \fB[fmt]\fP (array)
Convert each item in the JSON array according to the inner format
string. \fBfmt\fP may contain objects and arrays, i.e. recursive
value extraction is supporetd.
.TP
.B \fB{fmt}\fP (object)
Convert each item in the JSON object according to the inner format
string \fBfmt\fP\&. The first, third, etc. format specifier represent
a key, and must be \fBs\fP\&. The corresponding argument to unpack
functions is read as the object key. The second fourth, etc.
format specifier represent a value and is written to the address
given as the corresponding argument. \fBNote\fP that every other
argument is read from and every other is written to.
.sp
\fBfmt\fP may contain objects and arrays as values, i.e. recursive
value extraction is supporetd.
.sp
New in version 2.3: Any \fBs\fP representing a key may be suffixed with a \fB?\fP to
make the key optional. If the key is not found, nothing is
extracted. See below for an example.

.TP
.B \fB!\fP
This special format specifier is used to enable the check that
all object and array items are accessed, on a per\-value basis. It
must appear inside an array or object as the last format specifier
before the closing bracket or brace. To enable the check globally,
use the \fBJSON_STRICT\fP unpacking flag.
.TP
.B \fB*\fP
This special format specifier is the opposite of \fB!\fP\&. If the
\fBJSON_STRICT\fP flag is used, \fB*\fP can be used to disable the
strict check on a per\-value basis. It must appear inside an array
or object as the last format specifier before the closing bracket
or brace.
.UNINDENT
.sp
Whitespace, \fB:\fP and \fB,\fP are ignored.
.sp
The following functions compose the parsing and validation API:
.INDENT 0.0
.TP
.B int json_unpack(json_t\fI\ *root\fP, const char\fI\ *fmt\fP, \&...)
Validate and unpack the JSON value \fIroot\fP according to the format
string \fIfmt\fP\&. Returns 0 on success and \-1 on failure.
.UNINDENT
.INDENT 0.0
.TP
.B int json_unpack_ex(json_t\fI\ *root\fP, json_error_t\fI\ *error\fP, size_t\fI\ flags\fP, const char\fI\ *fmt\fP, \&...)
.TP
.B int json_vunpack_ex(json_t\fI\ *root\fP, json_error_t\fI\ *error\fP, size_t\fI\ flags\fP, const char\fI\ *fmt\fP, va_list\fI\ ap\fP)
Validate and unpack the JSON value \fIroot\fP according to the format
string \fIfmt\fP\&. If an error occurs and \fIerror\fP is not \fINULL\fP, write
error information to \fIerror\fP\&. \fIflags\fP can be used to control the
behaviour of the unpacker, see below for the flags. Returns 0 on
success and \-1 on failure.
.UNINDENT
.sp
\fBNOTE:\fP
.INDENT 0.0
.INDENT 3.5
The first argument of all unpack functions is \fBjson_t *root\fP
instead of \fBconst json_t *root\fP, because the use of \fBO\fP format
specifier causes the reference count of \fBroot\fP, or some value
reachable from \fBroot\fP, to be increased. Furthermore, the \fBo\fP
format specifier may be used to extract a value as\-is, which allows
modifying the structure or contents of a value reachable from
\fBroot\fP\&.
.sp
If the \fBO\fP and \fBo\fP format specifiers are not used, it\(aqs
perfectly safe to cast a \fBconst json_t *\fP variable to plain
\fBjson_t *\fP when used with these functions.
.UNINDENT
.UNINDENT
.sp
The following unpacking flags are available:
.INDENT 0.0
.TP
.B \fBJSON_STRICT\fP
Enable the extra validation step checking that all object and
array items are unpacked. This is equivalent to appending the
format specifier \fB!\fP to the end of every array and object in the
format string.
.TP
.B \fBJSON_VALIDATE_ONLY\fP
Don\(aqt extract any data, just validate the JSON value against the
given format string. Note that object keys must still be specified
after the format string.
.UNINDENT
.sp
Examples:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
/* root is the JSON integer 42 */
int myint;
json_unpack(root, "i", &myint);
assert(myint == 42);

/* root is the JSON object {"foo": "bar", "quux": true} */
const char *str;
int boolean;
json_unpack(root, "{s:s, s:b}", "foo", &str, "quux", &boolean);
assert(strcmp(str, "bar") == 0 && boolean == 1);

/* root is the JSON array [[1, 2], {"baz": null} */
json_error_t error;
json_unpack_ex(root, &error, JSON_VALIDATE_ONLY, "[[i,i], {s:n}]", "baz");
/* returns 0 for validation success, nothing is extracted */

/* root is the JSON array [1, 2, 3, 4, 5] */
int myint1, myint2;
json_unpack(root, "[ii!]", &myint1, &myint2);
/* returns \-1 for failed validation */

/* root is an empty JSON object */
int myint = 0, myint2 = 0;
json_unpack(root, "{s?i, s?[ii]}",
            "foo", &myint1,
            "bar", &myint2, &myint3);
/* myint1, myint2 or myint3 is no touched as "foo" and "bar" don\(aqt exist */
.ft R
.fi
.UNINDENT
.UNINDENT
.SS Equality
.sp
Testing for equality of two JSON values cannot, in general, be
achieved using the \fB==\fP operator. Equality in the terms of the
\fB==\fP operator states that the two \fBjson_t\fP pointers point to
exactly the same JSON value. However, two JSON values can be equal not
only if they are exactly the same value, but also if they have equal
"contents":
.INDENT 0.0
.IP \(bu 2
Two integer or real values are equal if their contained numeric
values are equal. An integer value is never equal to a real value,
though.
.IP \(bu 2
Two strings are equal if their contained UTF\-8 strings are equal,
byte by byte. Unicode comparison algorithms are not implemented.
.IP \(bu 2
Two arrays are equal if they have the same number of elements and
each element in the first array is equal to the corresponding
element in the second array.
.IP \(bu 2
Two objects are equal if they have exactly the same keys and the
value for each key in the first object is equal to the value of the
corresponding key in the second object.
.IP \(bu 2
Two true, false or null values have no "contents", so they are equal
if their types are equal. (Because these values are singletons,
their equality can actually be tested with \fB==\fP\&.)
.UNINDENT
.sp
The following function can be used to test whether two JSON values are
equal.
.INDENT 0.0
.TP
.B int json_equal(json_t\fI\ *value1\fP, json_t\fI\ *value2\fP)
Returns 1 if \fIvalue1\fP and \fIvalue2\fP are equal, as defined above.
Returns 0 if they are inequal or one or both of the pointers are
\fINULL\fP\&.
.UNINDENT
.SS Copying
.sp
Because of reference counting, passing JSON values around doesn\(aqt
require copying them. But sometimes a fresh copy of a JSON value is
needed. For example, if you need to modify an array, but still want to
use the original afterwards, you should take a copy of it first.
.sp
Jansson supports two kinds of copying: shallow and deep. There is a
difference between these methods only for arrays and objects. Shallow
copying only copies the first level value (array or object) and uses
the same child values in the copied value. Deep copying makes a fresh
copy of the child values, too. Moreover, all the child values are deep
copied in a recursive fashion.
.INDENT 0.0
.TP
.B json_t *json_copy(json_t\fI\ *value\fP)
Return value: New reference.
.sp
Returns a shallow copy of \fIvalue\fP, or \fINULL\fP on error.
.UNINDENT
.INDENT 0.0
.TP
.B json_t *json_deep_copy(const json_t\fI\ *value\fP)
Return value: New reference.
.sp
Returns a deep copy of \fIvalue\fP, or \fINULL\fP on error.
.UNINDENT
.SS Custom Memory Allocation
.sp
By default, Jansson uses \fBmalloc()\fP and \fBfree()\fP for
memory allocation. These functions can be overridden if custom
behavior is needed.
.INDENT 0.0
.TP
.B json_malloc_t
A typedef for a function pointer with \fBmalloc()\fP\(aqs
signature:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
typedef void *(*json_malloc_t)(size_t);
.ft R
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.INDENT 0.0
.TP
.B json_free_t
A typedef for a function pointer with \fBfree()\fP\(aqs
signature:
.INDENT 7.0
.INDENT 3.5
.sp
.nf
.ft CW
typedef void (*json_free_t)(void *);
.ft R
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.INDENT 0.0
.TP
.B void json_set_alloc_funcs(json_malloc_t\fI\ malloc_fn\fP, json_free_t\fI\ free_fn\fP)
Use \fImalloc_fn\fP instead of \fBmalloc()\fP and \fIfree_fn\fP instead
of \fBfree()\fP\&. This function has to be called before any other
Jansson\(aqs API functions to ensure that all memory operations use
the same functions.
.UNINDENT
.sp
\fBExamples:\fP
.sp
Circumvent problems with different CRT heaps on Windows by using
application\(aqs \fBmalloc()\fP and \fBfree()\fP:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
json_set_alloc_funcs(malloc, free);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
Use the \fI\%Boehm\(aqs conservative garbage collector\fP for memory
operations:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
json_set_alloc_funcs(GC_malloc, GC_free);
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
Allow storing sensitive data (e.g. passwords or encryption keys) in
JSON structures by zeroing all memory when freed:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft CW
static void *secure_malloc(size_t size)
{
    /* Store the memory area size in the beginning of the block */
    void *ptr = malloc(size + 8);
    *((size_t *)ptr) = size;
    return ptr + 8;
}

static void secure_free(void *ptr)
{
    size_t size;

    ptr \-= 8;
    size = *((size_t *)ptr);

    guaranteed_memset(ptr, 0, size + 8);
    free(ptr);
}

int main()
{
    json_set_alloc_funcs(secure_malloc, secure_free);
    /* ... */
}
.ft R
.fi
.UNINDENT
.UNINDENT
.sp
For more information about the issues of storing sensitive data in
memory, see
\fI\%http://www.dwheeler.com/secure\-programs/Secure\-Programs\-HOWTO/protect\-secrets.html\fP\&.
The page also explains the \fBguaranteed_memset()\fP function used
in the example and gives a sample implementation for it.
.SS Changes in Jansson
.SS Version 2.7
.sp
Released 2014\-10\-02
.INDENT 0.0
.IP \(bu 2
New features:
.INDENT 2.0
.IP \(bu 2
\fBjson_pack()\fP and friends: Add format specifiers \fBs%\fP and \fB+%\fP
for a size_t string length (#141).
.IP \(bu 2
\fBjson_unpack()\fP and friends: Add format specifier \fBs%\fP for
unpacking the string length along with the string itself (#141).
.IP \(bu 2
Add length\-aware string constructors \fBjson_stringn()\fP and
\fBjson_stringn_nocheck()\fP, length\-aware string mutators
\fBjson_string_setn()\fP and \fBjson_string_setn_nocheck()\fP, and a
function for getting string\(aqs length \fBjson_string_length()\fP (#141,
#143).
.IP \(bu 2
Support \fB\eu0000\fP escapes in the decoder. The support can be
enabled by using the \fBJSON_ALLOW_NUL\fP decoding flag (#141).
.IP \(bu 2
Add \fBjson_boolean_value()\fP as an alias for \fBjson_is_true()\fP
(#146).
.IP \(bu 2
Add JSON_REAL_PRECISION encoding flag/macro for controlling real
number precision (#178).
.IP \(bu 2
Define the maximum indentation as JSON_MAX_INDENT (#191).
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Some malformed \fB\euNNNN\fP escapes could crash the decoder with an
assertion failure.
.IP \(bu 2
Avoid integer overflows with very long strings in UTF\-8 decoder and
hashtable.
.IP \(bu 2
Check for \fINULL\fP key in \fBjson_object_get()\fP and
\fBjson_object_del()\fP (#151).
.IP \(bu 2
Enhance hashtable seeding on Windows (#162).
.IP \(bu 2
\fBjson_unpack()\fP: Allow mixing JSON_STRICT with optional keys
(#162, #163).
.IP \(bu 2
Fix int/int32 mismatch (#142).
.IP \(bu 2
Parse subnormal numbers correctly (#202).
.UNINDENT
.IP \(bu 2
Build:
.INDENT 2.0
.IP \(bu 2
Remove VS2010 build files. CMake should be used on Windows instead
(#165).
.IP \(bu 2
Fix CMake build flags for MinGW (#193).
.IP \(bu 2
Add CMake config files for find_package. Rename config.h to
jansson_private_config.h (#157, #159).
.IP \(bu 2
Make Valgrind checks work with CMake (#160).
.IP \(bu 2
Fix feature checks to use correct __ATOMIC flags.
.IP \(bu 2
Fix CMake checks for uint16_t and uint8_t support (#177).
.IP \(bu 2
Make Jansson build on SmartOS/Solaris (#171).
.IP \(bu 2
Work around a GCC bug on Solaris (#175).
.IP \(bu 2
Fix autoreconf on Debian (#182).
.IP \(bu 2
Don\(aqt use GNU make specific export for global AM_CFLAGS (#203,
#204).
.IP \(bu 2
Fix building on Android using the supplied Android.mk (#166,
#174).
.IP \(bu 2
Android.mk: Add \-DHAVE_STDINT_H to LOCAL_CFLAGS (#200).
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Document JANSSON_BUILD_SHARED_LIBS CMake option (#187).
.UNINDENT
.IP \(bu 2
Tests:
.INDENT 2.0
.IP \(bu 2
Close file handles correctly (#198).
.UNINDENT
.IP \(bu 2
Other changes:
.INDENT 2.0
.IP \(bu 2
\fB\euNNNN\fP escapes are now encoded in upper case for better
readability.
.IP \(bu 2
Enable usage of AddressSanitizer (#180).
.UNINDENT
.UNINDENT
.SS Version 2.6
.sp
Released 2014\-02\-11
.INDENT 0.0
.IP \(bu 2
Security:
.INDENT 2.0
.IP \(bu 2
CVE\-2013\-6401: The hash function used by the hashtable
implementation has been changed, and is automatically seeded with
random data when the first JSON object is created. This prevents
an attacker from causing large JSON objects with specially crafted
keys perform poorly.
.UNINDENT
.IP \(bu 2
New features:
.INDENT 2.0
.IP \(bu 2
\fBjson_object_seed()\fP: Set the seed value of the hash function.
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Include CMake specific files in the release tarball.
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Fix tutorial source to send a User\-Agent header, which is now
required by the GitHub API.
.IP \(bu 2
Set all memory to zero in secure_free() example.
.UNINDENT
.UNINDENT
.SS Version 2.5
.sp
Released 2013\-09\-19
.INDENT 0.0
.IP \(bu 2
New features:
.INDENT 2.0
.IP \(bu 2
\fBjson_pack()\fP and friends: Add format specifiers \fBs#\fP, \fB+\fP and
\fB+#\fP\&.
.IP \(bu 2
Add \fBJSON_DECODE_INT_AS_REAL\fP decoding flag to treat all numbers
as real in the decoder (#123).
.IP \(bu 2
Add \fBjson_array_foreach()\fP, paralleling \fBjson_object_foreach()\fP
(#118).
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
\fBjson_dumps()\fP and friends: Don\(aqt crash if json is \fINULL\fP and
\fBJSON_ENCODE_ANY\fP is set.
.IP \(bu 2
Fix a theoretical integer overflow in \fBjsonp_strdup()\fP\&.
.IP \(bu 2
Fix \fBl_isxdigit()\fP macro (#97).
.IP \(bu 2
Fix an off\-by\-one error in \fBjson_array_remove()\fP\&.
.UNINDENT
.IP \(bu 2
Build:
.INDENT 2.0
.IP \(bu 2
Support CMake in addition to GNU Autotools (#106, #107, #112,
#115, #120, #127).
.IP \(bu 2
Support building for Android (#109).
.IP \(bu 2
Don\(aqt use \fB\-Werror\fP by default.
.IP \(bu 2
Support building and testing with VPATH (#93).
.IP \(bu 2
Fix compilation when \fBNDEBUG\fP is defined (#128)
.UNINDENT
.IP \(bu 2
Tests:
.INDENT 2.0
.IP \(bu 2
Fix a refleak in \fBtest/bin/json_process.c\fP\&.
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Clarify the return value of \fBjson_load_callback_t()\fP\&.
.IP \(bu 2
Document how to circumvent problems with separate heaps on Windows.
.IP \(bu 2
Fix memory leaks and warnings in \fBgithub_commits.c\fP\&.
.IP \(bu 2
Use \fBjson_decref()\fP properly in tutorial.
.UNINDENT
.IP \(bu 2
Other:
.INDENT 2.0
.IP \(bu 2
Make it possible to forward declare \fBstruct json_t\fP\&.
.UNINDENT
.UNINDENT
.SS Version 2.4
.sp
Released 2012\-09\-23
.INDENT 0.0
.IP \(bu 2
New features:
.INDENT 2.0
.IP \(bu 2
Add \fBjson_boolean()\fP macro that returns the JSON true or false
value based on its argument (#86).
.IP \(bu 2
Add \fBjson_load_callback()\fP that calls a callback function
repeatedly to read the JSON input (#57).
.IP \(bu 2
Add JSON_ESCAPE_SLASH encoding flag to escape all occurences of
\fB/\fP with \fB\e/\fP\&.
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Check for and reject NaN and Inf values for reals. Encoding these
values resulted in invalid JSON.
.IP \(bu 2
Fix \fBjson_real_set()\fP to return \-1 on error.
.UNINDENT
.IP \(bu 2
Build:
.INDENT 2.0
.IP \(bu 2
Jansson now builds on Windows with Visual Studio 2010, and
includes solution and project files in \fBwin32/vs2010/\fP
directory.
.IP \(bu 2
Fix build warnings (#77, #78).
.IP \(bu 2
Add \fB\-no\-undefined\fP to LDFLAGS (#90).
.UNINDENT
.IP \(bu 2
Tests:
.INDENT 2.0
.IP \(bu 2
Fix the symbol exports test on Linux/PPC64 (#88).
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Fix typos (#73, #84).
.UNINDENT
.UNINDENT
.SS Version 2.3.1
.sp
Released 2012\-04\-20
.INDENT 0.0
.IP \(bu 2
Build issues:
.INDENT 2.0
.IP \(bu 2
Only use \fBlong long\fP if \fBstrtoll()\fP is also available.
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Fix the names of library version constants in documentation. (#52)
.IP \(bu 2
Change the tutorial to use GitHub API v3. (#65)
.UNINDENT
.IP \(bu 2
Tests:
.INDENT 2.0
.IP \(bu 2
Make some tests locale independent. (#51)
.IP \(bu 2
Distribute the library exports test in the tarball.
.IP \(bu 2
Make test run on shells that don\(aqt support the \fBexport FOO=bar\fP
syntax.
.UNINDENT
.UNINDENT
.SS Version 2.3
.sp
Released 2012\-01\-27
.INDENT 0.0
.IP \(bu 2
New features:
.INDENT 2.0
.IP \(bu 2
\fBjson_unpack()\fP and friends: Add support for optional object keys
with the \fB{s?o}\fP syntax.
.IP \(bu 2
Add \fBjson_object_update_existing()\fP and
\fBjson_object_update_missing()\fP, for updating only existing keys or
only adding missing keys to an object. (#37)
.IP \(bu 2
Add \fBjson_object_foreach()\fP for more convenient iteration over
objects. (#45, #46)
.IP \(bu 2
When decoding JSON, write the number of bytes that were read from
input to \fBerror.position\fP also on success. This is handy with
\fBJSON_DISABLE_EOF_CHECK\fP\&.
.IP \(bu 2
Add support for decoding any JSON value, not just arrays or
objects. The support is enabled with the new \fBJSON_DECODE_ANY\fP
flag. Patch by Andrea Marchesini. (#4)
.UNINDENT
.IP \(bu 2
Bug fixes
.INDENT 2.0
.IP \(bu 2
Avoid problems with object\(aqs serial number growing too big. (#40,
#41)
.IP \(bu 2
Decoding functions now return NULL if the first argument is NULL.
Patch by Andrea Marchesini.
.IP \(bu 2
Include \fBjansson_config.h.win32\fP in the distribution tarball.
.IP \(bu 2
Remove \fB+\fP and leading zeros from exponents in the encoder.
(#39)
.IP \(bu 2
Make Jansson build and work on MinGW. (#39, #38)
.UNINDENT
.IP \(bu 2
Documentation
.INDENT 2.0
.IP \(bu 2
Note that the same JSON values must not be encoded in parallel by
separate threads. (#42)
.IP \(bu 2
Document MinGW support.
.UNINDENT
.UNINDENT
.SS Version 2.2.1
.sp
Released 2011\-10\-06
.INDENT 0.0
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Fix real number encoding and decoding under non\-C locales. (#32)
.IP \(bu 2
Fix identifier decoding under non\-UTF\-8 locales. (#35)
.IP \(bu 2
\fBjson_load_file()\fP: Open the input file in binary mode for maximum
compatiblity.
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Clarify the lifecycle of the result of the \fBs\fP fromat of
\fBjson_unpack()\fP\&. (#31)
.IP \(bu 2
Add some portability info. (#36)
.IP \(bu 2
Little clarifications here and there.
.UNINDENT
.IP \(bu 2
Other:
.INDENT 2.0
.IP \(bu 2
Some style fixes, issues detected by static analyzers.
.UNINDENT
.UNINDENT
.SS Version 2.2
.sp
Released 2011\-09\-03
.INDENT 0.0
.IP \(bu 2
New features:
.INDENT 2.0
.IP \(bu 2
\fBjson_dump_callback()\fP: Pass the encoder output to a callback
function in chunks.
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
\fBjson_string_set()\fP: Check that target is a string and value is
not NULL.
.UNINDENT
.IP \(bu 2
Other:
.INDENT 2.0
.IP \(bu 2
Documentation typo fixes and clarifications.
.UNINDENT
.UNINDENT
.SS Version 2.1
.sp
Released 2011\-06\-10
.INDENT 0.0
.IP \(bu 2
New features:
.INDENT 2.0
.IP \(bu 2
\fBjson_loadb()\fP: Decode a string with a given size, useful if the
string is not null terminated.
.IP \(bu 2
Add \fBJSON_ENCODE_ANY\fP encoding flag to allow encoding any JSON
value. By default, only arrays and objects can be encoded. (#19)
.IP \(bu 2
Add \fBJSON_REJECT_DUPLICATES\fP decoding flag to issue a decoding
error if any JSON object in the input contins duplicate keys. (#3)
.IP \(bu 2
Add \fBJSON_DISABLE_EOF_CHECK\fP decoding flag to stop decoding after a
valid JSON input. This allows other data after the JSON data.
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Fix an additional memory leak when memory allocation fails in
\fBjson_object_set()\fP and friends.
.IP \(bu 2
Clear errno before calling \fBstrtod()\fP for better portability. (#27)
.UNINDENT
.IP \(bu 2
Building:
.INDENT 2.0
.IP \(bu 2
Avoid set\-but\-not\-used warning/error in a test. (#20)
.UNINDENT
.IP \(bu 2
Other:
.INDENT 2.0
.IP \(bu 2
Minor clarifications to documentation.
.UNINDENT
.UNINDENT
.SS Version 2.0.1
.sp
Released 2011\-03\-31
.INDENT 0.0
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Replace a few \fBmalloc()\fP and \fBfree()\fP calls with their
counterparts that support custom memory management.
.IP \(bu 2
Fix object key hashing in json_unpack() strict checking mode.
.IP \(bu 2
Fix the parentheses in \fBJANSSON_VERSION_HEX\fP macro.
.IP \(bu 2
Fix \fBjson_object_size()\fP return value.
.IP \(bu 2
Fix a few compilation issues.
.UNINDENT
.IP \(bu 2
Portability:
.INDENT 2.0
.IP \(bu 2
Enhance portability of \fBva_copy()\fP\&.
.IP \(bu 2
Test framework portability enhancements.
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Distribute \fBdoc/upgrading.rst\fP with the source tarball.
.IP \(bu 2
Build documentation in strict mode in \fBmake distcheck\fP\&.
.UNINDENT
.UNINDENT
.SS Version 2.0
.sp
Released 2011\-02\-28
.sp
This release is backwards incompatible with the 1.x release series.
See the chapter "Upgrading from older versions" in documentation for
details.
.INDENT 0.0
.IP \(bu 2
Backwards incompatible changes:
.INDENT 2.0
.IP \(bu 2
Unify unsigned integer usage in the API: All occurences of
unsigned int and unsigned long have been replaced with size_t.
.IP \(bu 2
Change JSON integer\(aqs underlying type to the widest signed integer
type available, i.e. long long if it\(aqs supported, otherwise long.
Add a typedef json_int_t that defines the type.
.IP \(bu 2
Change the maximum indentation depth to 31 spaces in encoder. This
frees up bits from the flags parameter of encoding functions
\fBjson_dumpf()\fP, \fBjson_dumps()\fP and \fBjson_dump_file()\fP\&.
.IP \(bu 2
For future needs, add a flags parameter to all decoding functions
\fBjson_loadf()\fP, \fBjson_loads()\fP and \fBjson_load_file()\fP\&.
.UNINDENT
.IP \(bu 2
New features
.INDENT 2.0
.IP \(bu 2
\fBjson_pack()\fP, \fBjson_pack_ex()\fP, \fBjson_vpack_ex()\fP: Create JSON
values based on a format string.
.IP \(bu 2
\fBjson_unpack()\fP, \fBjson_unpack_ex()\fP, \fBjson_vunpack_ex()\fP: Simple
value extraction and validation functionality based on a format
string.
.IP \(bu 2
Add column, position and source fields to the \fBjson_error_t\fP
struct.
.IP \(bu 2
Enhance error reporting in the decoder.
.IP \(bu 2
\fBJANSSON_VERSION\fP et al.: Preprocessor constants that define the
library version.
.IP \(bu 2
\fBjson_set_alloc_funcs()\fP: Set custom memory allocation functions.
.UNINDENT
.IP \(bu 2
Fix many portability issues, especially on Windows.
.IP \(bu 2
Configuration
.INDENT 2.0
.IP \(bu 2
Add file \fBjansson_config.h\fP that contains site specific
configuration. It\(aqs created automatically by the configure script,
or can be created by hand if the configure script cannot be used.
The file \fBjansson_config.h.win32\fP can be used without
modifications on Windows systems.
.IP \(bu 2
Add a section to documentation describing how to build Jansson on
Windows.
.IP \(bu 2
Documentation now requires Sphinx 1.0 or newer.
.UNINDENT
.UNINDENT
.SS Version 1.3
.sp
Released 2010\-06\-13
.INDENT 0.0
.IP \(bu 2
New functions:
.INDENT 2.0
.IP \(bu 2
\fBjson_object_iter_set()\fP, \fBjson_object_iter_set_new()\fP: Change
object contents while iterating over it.
.IP \(bu 2
\fBjson_object_iter_at()\fP: Return an iterator that points to a
specific object item.
.UNINDENT
.IP \(bu 2
New encoding flags:
.INDENT 2.0
.IP \(bu 2
\fBJSON_PRESERVE_ORDER\fP: Preserve the insertion order of object
keys.
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Fix an error that occured when an array or object was first
encoded as empty, then populated with some data, and then
re\-encoded
.IP \(bu 2
Fix the situation like above, but when the first encoding resulted
in an error
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Clarify the documentation on reference stealing, providing an
example usage pattern
.UNINDENT
.UNINDENT
.SS Version 1.2.1
.sp
Released 2010\-04\-03
.INDENT 0.0
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Fix reference counting on \fBtrue\fP, \fBfalse\fP and \fBnull\fP
.IP \(bu 2
Estimate real number underflows in decoder with 0.0 instead of
issuing an error
.UNINDENT
.IP \(bu 2
Portability:
.INDENT 2.0
.IP \(bu 2
Make \fBint32_t\fP available on all systems
.IP \(bu 2
Support compilers that don\(aqt have the \fBinline\fP keyword
.IP \(bu 2
Require Autoconf 2.60 (for \fBint32_t\fP)
.UNINDENT
.IP \(bu 2
Tests:
.INDENT 2.0
.IP \(bu 2
Print test names correctly when \fBVERBOSE=1\fP
.IP \(bu 2
\fBtest/suites/api\fP: Fail when a test fails
.IP \(bu 2
Enhance tests for iterators
.IP \(bu 2
Enhance tests for decoding texts that contain null bytes
.UNINDENT
.IP \(bu 2
Documentation:
.INDENT 2.0
.IP \(bu 2
Don\(aqt remove \fBchanges.rst\fP in \fBmake clean\fP
.IP \(bu 2
Add a chapter on RFC conformance
.UNINDENT
.UNINDENT
.SS Version 1.2
.sp
Released 2010\-01\-21
.INDENT 0.0
.IP \(bu 2
New functions:
.INDENT 2.0
.IP \(bu 2
\fBjson_equal()\fP: Test whether two JSON values are equal
.IP \(bu 2
\fBjson_copy()\fP and \fBjson_deep_copy()\fP: Make shallow and deep copies
of JSON values
.IP \(bu 2
Add a version of all functions taking a string argument that
doesn\(aqt check for valid UTF\-8: \fBjson_string_nocheck()\fP,
\fBjson_string_set_nocheck()\fP, \fBjson_object_set_nocheck()\fP,
\fBjson_object_set_new_nocheck()\fP
.UNINDENT
.IP \(bu 2
New encoding flags:
.INDENT 2.0
.IP \(bu 2
\fBJSON_SORT_KEYS\fP: Sort objects by key
.IP \(bu 2
\fBJSON_ENSURE_ASCII\fP: Escape all non\-ASCII Unicode characters
.IP \(bu 2
\fBJSON_COMPACT\fP: Use a compact representation with all unneeded
whitespace stripped
.UNINDENT
.IP \(bu 2
Bug fixes:
.INDENT 2.0
.IP \(bu 2
Revise and unify whitespace usage in encoder: Add spaces between
array and object items, never append newline to output.
.IP \(bu 2
Remove const qualifier from the \fBjson_t\fP parameter in
\fBjson_string_set()\fP, \fBjson_integer_set()\fP and \fBjson_real_set()\fP\&.
.IP \(bu 2
Use \fBint32_t\fP internally for representing Unicode code points
(int is not enough on all platforms)
.UNINDENT
.IP \(bu 2
Other changes:
.INDENT 2.0
.IP \(bu 2
Convert \fBCHANGES\fP (this file) to reStructured text and add it to
HTML documentation
.IP \(bu 2
The test system has been refactored. Python is no longer required
to run the tests.
.IP \(bu 2
Documentation can now be built by invoking \fBmake html\fP
.IP \(bu 2
Support for pkg\-config
.UNINDENT
.UNINDENT
.SS Version 1.1.3
.sp
Released 2009\-12\-18
.INDENT 0.0
.IP \(bu 2
Encode reals correctly, so that first encoding and then decoding a
real always produces the same value
.IP \(bu 2
Don\(aqt export private symbols in \fBlibjansson.so\fP
.UNINDENT
.SS Version 1.1.2
.sp
Released 2009\-11\-08
.INDENT 0.0
.IP \(bu 2
Fix a bug where an error message was not produced if the input file
could not be opened in \fBjson_load_file()\fP
.IP \(bu 2
Fix an assertion failure in decoder caused by a minus sign without a
digit after it
.IP \(bu 2
Remove an unneeded include of \fBstdint.h\fP in \fBjansson.h\fP
.UNINDENT
.SS Version 1.1.1
.sp
Released 2009\-10\-26
.INDENT 0.0
.IP \(bu 2
All documentation files were not distributed with v1.1; build
documentation in make distcheck to prevent this in the future
.IP \(bu 2
Fix v1.1 release date in \fBCHANGES\fP
.UNINDENT
.SS Version 1.1
.sp
Released 2009\-10\-20
.INDENT 0.0
.IP \(bu 2
API additions and improvements:
.INDENT 2.0
.IP \(bu 2
Extend array and object APIs
.IP \(bu 2
Add functions to modify integer, real and string values
.IP \(bu 2
Improve argument validation
.IP \(bu 2
Use unsigned int instead of \fBuint32_t\fP for encoding flags
.UNINDENT
.IP \(bu 2
Enhance documentation
.INDENT 2.0
.IP \(bu 2
Add getting started guide and tutorial
.IP \(bu 2
Fix some typos
.IP \(bu 2
General clarifications and cleanup
.UNINDENT
.IP \(bu 2
Check for integer and real overflows and underflows in decoder
.IP \(bu 2
Make singleton values thread\-safe (\fBtrue\fP, \fBfalse\fP and \fBnull\fP)
.IP \(bu 2
Enhance circular reference handling
.IP \(bu 2
Don\(aqt define \fB\-std=c99\fP in \fBAM_CFLAGS\fP
.IP \(bu 2
Add C++ guards to \fBjansson.h\fP
.IP \(bu 2
Minor performance and portability improvements
.IP \(bu 2
Expand test coverage
.UNINDENT
.SS Version 1.0.4
.sp
Released 2009\-10\-11
.INDENT 0.0
.IP \(bu 2
Relax Autoconf version requirement to 2.59
.IP \(bu 2
Make Jansson compile on platforms where plain \fBchar\fP is unsigned
.IP \(bu 2
Fix API tests for object
.UNINDENT
.SS Version 1.0.3
.sp
Released 2009\-09\-14
.INDENT 0.0
.IP \(bu 2
Check for integer and real overflows and underflows in decoder
.IP \(bu 2
Use the Python json module for tests, or simplejson if the json
module is not found
.IP \(bu 2
Distribute changelog (this file)
.UNINDENT
.SS Version 1.0.2
.sp
Released 2009\-09\-08
.INDENT 0.0
.IP \(bu 2
Handle EOF correctly in decoder
.UNINDENT
.SS Version 1.0.1
.sp
Released 2009\-09\-04
.INDENT 0.0
.IP \(bu 2
Fixed broken \fBjson_is_boolean()\fP
.UNINDENT
.SS Version 1.0
.sp
Released 2009\-08\-25
.INDENT 0.0
.IP \(bu 2
Initial release
.UNINDENT
.INDENT 0.0
.IP \(bu 2
\fIgenindex\fP
.IP \(bu 2
\fIsearch\fP
.UNINDENT
.sp
.SH AUTHOR
Petri Lehtinen
.SH COPYRIGHT
2009-2014, Petri Lehtinen
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