{"id":182325,"date":"2026-06-25T20:48:38","date_gmt":"2026-06-25T18:48:38","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/proekt-rars-podgotovil-svobodnuyu-realizacziyu-rar-s-podderzhkoj-sozdaniya-arhivov"},"modified":"2026-06-25T20:48:38","modified_gmt":"2026-06-25T18:48:38","slug":"proekt-rars-podgotovil-svobodnuyu-realizacziyu-rar-s-podderzhkoj-sozdaniya-arhivov","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/proekt-rars-podgotovil-svobodnuyu-realizacziyu-rar-s-podderzhkoj-sozdaniya-arhivov","title":{"rendered":"The rars project has prepared a free implementation of RAR with support for archive creation.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"
The rars project has been introduced, developing a free implementation of tools for the RAR format, written in Rust, supporting not only extraction but also the creation of RAR archives. The tools support both early RAR 1.3\/1.4 formats with the signature 'RE~^' and the latest RAR 7 version. Advanced operations such as volume splitting, password protection, header encryption, comment attachment, RARVM filters, indexes for quick opening, and mechanisms for data recovery are available. The code is distributed under the MIT and Apache-2.0 licenses. Bindings for the Python language have been prepared based on the PyO3 library, implementing an API in the style of rarfile for browsing, testing, and extracting archives, as well as an API in the style of RarBuilder for creating or repackaging archives.<\/p>\n
The feature of this project is that it implements RAR format handling without using the unrar utility code, which is distributed under a non-free license that prohibits the use of unrar code to recreate the RAR compression algorithm or develop RAR-compatible archivers. Due to this restriction, most free archivers were limited to RAR file extraction features, while proprietary tools from RARLAB had to be used to create RAR archives.<\/p>\n
A separate repository, rar-research, has been created where specifications for RAR formats 1.3\/1.4, 1.5-4.x, and 5.0\/7.0 are published, as well as notes on the algorithms, filters, integrity checking and recovery methods, encryption, volume splitting, and protection mechanisms used. Since there was no official complete specification at the time of the rars project's creation, the documentation was reconstructed from unpacker code, old implementations, test archives, and analysis of binary versions of RAR for DOS and Windows.<\/p>\n
The implementation was created using OpenAI Codex 5.5 and Claude Opus 4.7 AI tools during free time over approximately five weeks. In the first phase, the models were applied to systematize information about the format and fill in gaps in the description, after which code was generated in Rust based on the reconstructed specification. To clarify the specification and refine the implementation, the functionality was tested on real archives and compared with reference implementations.<\/p>\n
It is noted that AI tools performed well in translating formal descriptions into code and in the routine implementation of a large volume of functionality, but they were unable to provide architectural oversight. Without strict supervision, the AI models tended to bypass tests, complicate the code, and overlook obvious issues affecting usability. According to the author, in a project of this scale, tests, documentation, and comments became not just tools for verification, but also a way to guide the generation of code in the right direction.<\/p>\n
The development was accelerated after the introduction of the OpenAI Codex '\/goal' mode, allowing the AI agent to work on a single task for an extended period, compressing context and continuing execution after overflow. In this mode, Codex worked several times for over 6 hours and once for about 16 hours, implementing a significant portion of the remaining functionality, such as data recovery, encryption, and multi-volume archives. With a substantial token subsidy, \u00a340 was spent.<\/p>\n
In terms of compression level, rars lags behind WinRAR by an average of 5-10%. When it comes to compression and extraction speed, rars is significantly slower than WinRAR due to a lack of full optimizations. However, the project already features the '--features fast' mode, applying SIMD-based optimizations to speed up compression and extraction, but relying on the experimental API std::simd, available only in test builds of the Rust tools. The '--features parallel' mode is also implemented, utilizing the Rayon library for parallelizing the compression of individual files.<\/p>\n