Paxl

A high-performance XML to JSON parser implemented in WebAssembly.

Paxl parses XML documents and converts them into JSON objects with minimal overhead. It's designed for speed and efficiency, making it ideal for processing large XML files or high-throughput applications.

Features

• Fast: Optimized C code compiled to WebAssembly for maximum performance
• Lightweight: Zero dependencies in the runtime (yyjson is statically linked)
• Standards-compliant: Supports standard XML syntax including attributes, nested elements, and text content
• Node.js ready: Easy to use JavaScript API with ES modules support

Installation

npm install paxl

Usage

import { parse } from 'paxl';

const xml = `<root>
  <item id="1">
    <name>Example</name>
    <value>42</value>
  </item>
</root>`;

const json = parse(xml);
console.log(json);
// Output: {"children":[{"tagName":"item","attributes":{"id":"1"},"children":[{"tagName":"name","children":["Example"]},{"tagName":"value","children":["42"]}]}]}

JSON Output Format

Paxl converts XML to a JSON structure where:

• Elements become objects with a tagName property and optional attributes and children properties
• Text content is represented as strings in the children array
• Attributes are collected in an attributes object
• Nested elements are placed in the children array

Example:

<book id="123" category="fiction">
  <title>Sample Book</title>
  <author>John Doe</author>
</book>

Becomes:

{
  "children": [
    {
      "tagName": "book",
      "attributes": {
        "id": "123",
        "category": "fiction"
      },
      "children": [
        {
          "tagName": "title",
          "children": ["Sample Book"]
        },
        {
          "tagName": "author",
          "children": ["John Doe"]
        }
      ]
    }
  ]
}

Performance

Paxl is designed for high performance and typically outperforms pure JavaScript XML parsers. Benchmarks show significant speedups compared to alternatives like rapidx2j and txml.

Run the included benchmarks to see performance on your system:

node tests/perf_test.js

Building from Source

Paxl requires Emscripten to build. Make sure you have the Emscripten SDK installed and activated.

# Clone the repository
git clone https://github.com/eitanwass/paxl.git
cd paxl

# Build the WebAssembly module
make build

# Run tests
node tests/simple_test.js

Build Options

• DEBUG=y: Build with debug symbols and no optimizations
• W_ENTRY=y: Include a main function for CLI applications using WASM
• MAX_XML_DEPTH=256: Maximum XML nesting depth (default: 256)

Requirements

• Node.js >= 12.22.7
• Emscripten (for building from source)

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

Roadmap

XSD Validation is not planned! Roadmap of features and support I want to implement, in no particular order.

• CI/CD
  • [ ] CI run tests (actually write them this time)
  • [ ] CD Distributed build
• Tests
  • [ ] Valgrind tests!
  • [ ] Reach 100% coverage!
• [ ] typescript support!
• [ ] Non-string attributes
• [ ] Online performance or/and demo
• [ ] Remove yyjson for smaller in-house implementation (unused features)
• Options:
  • [ ] Single root option - eliminate top "children" element
  • [ ] Parse comments
  • [ ] Custom keys (e.g. tagName -> my_tag_name)
• Data validations? (Do we want that? Hit for performance)
  • [ ] Parse boolean values to correct form (e.g. False -> false)
• Performance
  • [ ] Parallel pass parsing
  • [ ] SIMD? (Is it even applicable in this case?)

License

Apache 2.0 license - see LICENSE file for details.

Credits

• Uses yyjson for JSON handling
• Built with Emscripten