UltraJSON is a high-performance JSON encoder/decoder library for Python, implemented entirely in C with Python bindings. It provides drop-in replacements for Python's standard json module (ujson.dumps, ujson.loads, ujson.dump, ujson.load) and offers configuration options for ASCII encoding, HTML character escaping, forward slash escaping, indentation, sorting keys, NaN/Infinity handling, and customizable separators. The library's core architecture consists of a hand-optimized C state machine for decoding and a recursive encoder that handles Python objects via a type-context system. It bundles a copy of the double-conversion library for precise floating-point serialization and uses a stack-first, heap-later buffer allocation strategy. Despite being in maintenance-only mode due to architectural security concerns, the codebase exhibits strong craftsmanship: meticulous memory management, comprehensive UTF-8 validation, support for surrogate pairs, fuzz testing with ref-count verification, and compatibility with CPython's free-threaded builds. The repository also includes extensive tests, benchmarks, and CI for multiple architectures and Python implementations (CPython, PyPy, GraalPy).
UTF8-CPP is a mature, header-only C++ library for encoding and decoding between UTF-8, UTF-16, and UTF-32 Unicode formats. It provides both checked (validating) and unchecked (fast) APIs for common operations such as iterating over code points, appending encoded sequences, converting between encodings, detecting invalid sequences, and replacing invalid sequences with a replacement character. The library is designed to be generic (works with any iterator model), portable across C++98/11/14/17/20, and lightweight (pay-only-for-what-you-use). It has a comprehensive test suite derived from Markus Kuhn's UTF-8 stress test and is widely used in open-source and commercial projects. The architecture is modular: core.h contains the low-level validation and encoding logic, checked.h adds exception-throwing wrappers, and unchecked.h provides non-throwing variants, with additional C++ standard edition-specific convenience overloads in cpp11.h, cpp17.h, and cpp20.h.
Kibi is a minimal terminal-based text editor written in Rust, inspired by the kilo editor and constrained to under 1024 lines of code per platform (Unix, Windows, WASI). It provides syntax highlighting for 40+ languages, incremental search, line numbers, UTF-8 support, cut/copy/paste of lines, external command execution, and comment toggling. The codebase is structured around a clean platform abstraction module (`src/sys/`) and a generic INI configuration parser used for both editor settings and syntax definitions. Core editing logic lives in `src/editor.rs`, with row management and render mapping in `src/row.rs`. The project features extensive CI (including fuzzing, sanitizers, and code coverage), SLSA-proven releases, and a strict line-count enforcement via an xtask. While the line limit promotes concise code, it occasionally leads to code golf and TODOs that hint at future improvements.
mPDF is a mature PHP library that generates PDF documents from UTF-8 encoded HTML content. It is not a standalone application but a dependency used within PHP projects (e.g., Laravel, Symfony) via Composer. The library parses HTML and CSS, handles complex typography (including bidirectional text, Indic and Myanmar scripts, hyphenation), and produces PDF output with support for barcodes, watermarks, forms, table of contents, PDF/A compliance, and encryption. The architecture follows a service-oriented pattern: the central `Mpdf` class orchestrates a set of specialized services (CSS parser, color converter, size converter, image processor, tag handlers, writers) assembled by a `ServiceFactory`. HTML tags are mapped to handler classes in `src/Tag/` that extend `BlockTag`, `InlineTag`, or `SubstituteTag`. PDF output is built by writer classes in `src/Writer/` that write raw PDF objects via a `BaseWriter`. External dependencies include FPDI for PDF import, PSR-3 logging, PSR-7 HTTP messages, and the `myclabs/deep-copy` library for table of contents page numbering. The library is extensively tested with over 200 unit tests and snapshot tests that compare generated PDFs against stored references.