coding

Converting Firefox HTML5 Parser: Java to C++

Mozilla engineers describe the technical process and challenges of converting the Firefox HTML5 parser from Java to C++ to improve browser performance and

Developers explore Firefox’s HTML5 parser conversion process using specific repository commands.

Repository Setup:

  • Clone: git clone https://github.com/mozilla/gecko-dev (8GB download)
  • Navigate: cd parser/html/java

Translation Commands:

  • make sync: Synchronizes Java source files
  • make translate: Converts Java to C++ automatically
  • git diff: Reviews generated C++ changes

Source Code Locations:

  • Java parser: parser/html/java/ in gecko-dev
  • Translation engine: htmlparser/cpptranslate/CppVisitor.java in github.com/validator/validator
  • W3C validator: validator.w3.org/nu/

Inspection: The process transforms Java class declarations into C++ header includes and preprocessor definitions through automated script execution.

This workflow demonstrates how Firefox maintains cross-language codebases, allowing developers to study production-grade transpilation systems that convert 15+ years of HTML parsing logic between languages.