feat: improve and fix extended timestamp extra field parsing

[Its-Just-Nans]

An improvement over https://github.com/zip-rs/zip2/pull/697/changes

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the parsing of extended timestamps by introducing a more structured approach to flag handling and enhancing error detection. The changes ensure that the system gracefully handles malformed or incomplete timestamp data, preventing crashes and making the parsing logic more resilient and reliable.

Highlights

• Improved Extended Timestamp Parsing: Introduced a dedicated ExtendedTimestampFlags enum to clearly define and manage the flags associated with extended timestamps, replacing direct bitwise comparisons.
• Enhanced Error Handling: Implemented robust error handling using checked_sub for byte length calculations during parsing, preventing potential panics from subtraction overflows when encountering malformed or truncated extended timestamp data.
• New Test Coverage: Added a new test case, test_extended_timestamp_overflow, to specifically validate that truncated extended timestamps correctly return an error instead of causing a panic.

Changelog

• src/extra_fields/extended_timestamp.rs
  • Added ExtendedTimestampFlags enum and its associated impl blocks for clearer flag management.
  • Replaced direct bitwise operations for flag checking with the new ExtendedTimestampFlags::matching method.
  • Modified byte length decrement logic to use checked_sub for safer arithmetic, returning an error on underflow.
  • Included a new test test_extended_timestamp_overflow to verify the improved error handling for truncated data.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[amazon-q-developer]

This PR improves extended timestamp handling by adding overflow protection and refactoring flag checks. However, there's a critical logic error in the matching method (line 26) that prevents access time and creation time from being parsed correctly. The bitwise AND comparison checks for equality with 1, but AcTime and CrTime flags have values 2 and 4 respectively, causing these fields to always be skipped.

Critical issue:

• Line 26: Fix bitwise comparison to check != 0 instead of == 1

Once this is fixed, the overflow protection and test coverage additions are solid improvements.

---

You can now have the agent implement changes and create commits directly on your pull request's source branch. Simply comment with /q followed by your request in natural language to ask the agent to make changes.

[gemini-code-assist]

Code Review

This pull request improves robustness in parsing extended timestamps. The review identified a significant logic error in ExtendedTimestampFlags::matching that could lead to data integrity issues or security vulnerabilities due to incorrect bitmask validation. Additionally, an error message was found to be misleading, and a more accurate one is suggested. The PR also introduces ExtendedTimestampFlags for clarity and other minor improvements.

[Its-Just-Nans]

Note

I can still improve the code

Edit: done

[Its-Just-Nans]

btw i think this condition (which is forcing the modTime when len == 5) was incorrect

let mod_time = if (flags & 0b0000_0001_u8 == 0b0000_0001_u8) || len == 5 {}

[Pr0methean]

Could you please explain in the title what specific improvements this gives us from the user's perspective? Remember, a PR title is its CHANGELOG entry.

[Pr0methean]

One nitpick re naming convention; otherwise looks good.

Dismissing the review (now fixed) to be able to merge