json2xml-c

A dependency-free JSON-to-XML converter written in C23.

The behavior and compatibility cases are ported from vinitkumar/json2xml. The implementation is new, pure C, and does not embed Python or a third-party JSON parser.

Features

• Objects, arrays, strings, numbers, booleans, and null
• XML 1.0 validation and escaping
• UTF-8 and JSON Unicode escape handling, including surrogate pairs
• Type attributes and custom wrapper names
• Configurable root, pretty printing, item wrapping, and list headers
• @attrs, @val, and @flat compatibility
• CDATA output with safe ]]> splitting
• W3C XPath 3.1 JSON-to-XML mapping
• Library API and json2xml-c command
• No runtime dependencies

URL input from the Python command is intentionally not included. HTTPS would require a TLS dependency, which conflicts with this project's dependency-free scope. Read remote JSON with the HTTP client appropriate for your application, then pass the bytes to json2xml_convert.

Build

make
make test
make sanitize
make coverage

The build requires a C23 compiler and CMake. The coverage target uses Clang's llvm-cov and enforces 100% line and function coverage across production sources. Branch coverage is reported as an additional metric.

Benchmark

Install the current Rust-enabled Python package in an isolated environment, then run the reproducible in-process comparison:

python3 -m venv .benchmark-venv
.benchmark-venv/bin/pip install 'json2xml[fast]'
make benchmark PYTHON=.benchmark-venv/bin/python

The harness refuses to run unless the Python package reports the rust backend. It verifies byte-for-byte output parity before timing and reports both complete JSON parse-plus-serialize time and Rust serializer-only time. See BENCHMARKS.md for the latest recorded run.

Command line

./build/json2xml-c --no-pretty -s '{"name":"Ada","active":true}'
./build/json2xml-c data.json -o data.xml
cat data.json | ./build/json2xml-c -
./build/json2xml-c --xpath data.json

Run json2xml-c --help for all conversion flags.

Install a release binary

GitHub Releases provide native CLI archives for:

Operating system	x86-64 / AMD64	ARM64 / AArch64
Linux	linux-x86_64.tar.gz	linux-arm64.tar.gz
macOS	macos-x86_64.tar.gz	macos-arm64.tar.gz
Windows	windows-x86_64.zip	windows-arm64.zip

The x86-64 build works on 64-bit AMD and Intel processors. Linux executables are statically linked; macOS and Windows executables use their operating system's standard runtime.

Download the archive for your system and SHA256SUMS from the latest release. Verify the download before installing:

sha256sum -c SHA256SUMS --ignore-missing
# macOS also provides: shasum -a 256 -c SHA256SUMS

On Linux or macOS, extract the archive and copy the executable into PATH:

tar -xzf json2xml-c-*.tar.gz
sudo install -m 0755 json2xml-c-*/bin/json2xml-c /usr/local/bin/json2xml-c
json2xml-c --version

On Windows, expand the ZIP and copy bin\json2xml-c.exe to a directory in PATH. The initial macOS and Windows archives are unsigned, so those operating systems may display an unknown-publisher warning.

Pushing a version tag such as v0.1.0 builds and tests all six native targets, creates a GitHub release, and attaches the archives and checksum manifest. The tag version must match both CMakeLists.txt and JSON2XML_VERSION.

Library API

#include "json2xml.h"

#include <stdio.h>
#include <string.h>

int main(void)
{
    const char json[] = "{\"name\":\"Ada\"}";
    json2xml_options options = json2xml_options_default();
    json2xml_error error = {0};
    char *xml = NULL;
    size_t xml_len = 0;

    options.pretty = false;
    json2xml_status status = json2xml_convert(
        json, sizeof(json) - 1, &options, &xml, &xml_len, &error);
    if (status != JSON2XML_OK) {
        fprintf(stderr, "conversion failed at byte %zu: %s\n",
                error.offset, error.message);
        return 1;
    }

    fwrite(xml, 1, xml_len, stdout);
    json2xml_free(xml);
    return 0;
}

The input may contain embedded NUL bytes because its length is explicit. The returned XML is NUL-terminated for convenience; xml_len remains authoritative. Release it with json2xml_free.

Compatibility

The C tests use literal expected output derived from the Python project's functional suite. Python-only behavior—arbitrary Python object subclasses, runtime backend selection, URL fetching, and Python callbacks—has no direct C equivalent and is outside this API.

License

Apache License 2.0. See LICENSE and NOTICE.