docs: add Doxygen comments for private functions (fixes #371)

[Ashish-coder-gif]

Summary

This pull request adds Doxygen documentation comments for private functions in the entry.c file.

Changes Made

• Added detailed Doxygen-style comments to private functions to improve code readability and maintainability.
• Ensured consistent formatting across all new comments.
• Verified that the documentation builds without errors using Doxygen.

Motivation

These updates address issue #371, which requested better documentation for private functions. Improved internal documentation will make it easier for contributors to understand and maintain the codebase.

Testing

• Built the project successfully after adding comments.
• Ran Doxygen to confirm all comments are properly recognized.

Related Issue

Fixes #371

[goatshriek]

As described in the issue, please cover a minimum of three functions, and include POSIX safety in each documentation block as done elsewhere in the project.

[goatshriek]

Checking in to see if you intend to continue this work, as described in the inactivity policy.