oj_windows

A Windows-native, high-performance JSON parser and Object marshaller for Ruby.

oj_windows is a fork of Oj by Peter Ohler, adapted to build with the MSVC (mswin) Ruby toolchain. POSIX-specific code has been guarded or replaced with native Windows equivalents (pthread mutexes → Windows synchronization, timegm → _mkgmtime, guarded POSIX headers), and SIMD string scanning is enabled under MSVC.

Relationship to upstream Oj. Almost all of this code is Peter Ohler's. oj_windows exists only to provide a buildable Oj for Ruby compiled with the MSVC toolchain. It defines the same Oj module and the same public API, so it is a drop-in replacement for — and cannot be installed alongside — the upstream oj gem. If you use the standard RubyInstaller / MinGW Ruby, install the upstream oj gem instead (it builds there via the MSYS2 devkit); oj_windows is only needed for native MSVC (mswin) builds.

gem install oj_windows

Or in your Gemfile:

gem 'oj_windows'

require 'oj_windows'

# Dump Ruby objects to JSON
hash = { 'name' => 'oj_windows', 'version' => '3.17.2.1', 'windows' => true }
json = Oj.dump(hash)
# => {"name":"oj_windows","version":"3.16.14","windows":true}

# Load JSON back to Ruby objects  
data = Oj.load(json)
# => {"name"=>"oj_windows", "version"=>"3.16.14", "windows"=>true}

# Pretty print
puts Oj.dump(hash, indent: 2)

• SIMD-accelerated C extension compiled with MSVC (SSE2 string scanning on x86_64)
• Multiple Modes: Strict, Compat, Object, Custom, Rails, WAB, Null
• JSON Gem Compatibility: Drop-in replacement via Oj.mimic_JSON
• Rails Integration: :rails mode and Oj.optimize_rails for ActiveSupport/ActiveRecord (see note under Test Results)
• Streaming: SAJ and SC parsers for large documents
• Safe parsing: Oj::Parser.safe(max_depth:, max_array_size:, max_hash_size:, max_total_elements:) enforces limits on untrusted input
• StringWriter/StreamWriter: Efficient JSON generation

All tests pass on Windows MSVC Ruby 3.4.8:

Scope: This is the core suite run by test/test_all_no_rails.bat. Additional mode/parser tests (test_custom, test_null, test_wab, test_generate, test_parser_usual, test_integer_range, test_long_strings) also pass. A few files depend on POSIX fixtures or a specific working directory (test_realworld needs test/data/*.json; test_parser_saj's file test needs a local fixture) and are not part of this table. The Rails ActiveSupport/ActiveRecord suites require fork and are not run on Windows.

Skips (5): 3 require fork (test_various ×1, test_scp ×2), 1 needs a POSIX subprocess (test_writer), and 1 involves pre-1970 dates the Windows time API does not support (test_file).

oj_windows enables SIMD-accelerated string scanning on x86_64 (SSE2 by default — see InstallOptions). On string-heavy payloads this makes parsing roughly 20–25% faster than the scalar build that earlier versions shipped on MSVC.

A note on honest benchmarking: Ruby's bundled JSON::Ext is extremely well optimized and is competitive with — and on small, simple payloads can exceed — oj_windows on raw parse/dump throughput. Oj's value is less about winning a micro-benchmark and more about capabilities the JSON gem does not offer:

• Object mode — full Ruby object serialization/deserialization
• Rails / ActiveSupport integration (Oj.optimize_rails)
• Streaming parsers (SAJ, SCP) for large documents
• Custom serialization behavior and circular-reference handling

Benchmark your own representative payloads with the scripts in test/perf_*.rb rather than relying on synthetic numbers.

# Set default options
Oj.default_options = {
  mode: :compat,
  symbol_keys: true,
  indent: 2
}

# Check current options
Oj.default_options

• Options - Parse and dump options
• Modes - Detailed mode documentation
• Rails - Rails integration guide
• JsonGem - JSON gem compatibility
• Advanced - Advanced features

# Requires a Visual Studio (2019+) MSVC build environment. package_install.bat
# locates vcvars64.bat automatically via vswhere, so just run:
.\package_install.bat

If you prefer to set up the environment yourself, run the vcvars64.bat from your Visual Studio install (e.g. ...\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat) first, then bundle exec rake compile.

cd test
.\test_all_no_rails.bat

MIT License - See LICENSE for details.

Version 3.17.2.1 — based on Oj 3.17.2 by Peter Ohler (MIT).