Optimize archive structure

We want to improve both security and performance by optimizing data structure of archive file,
this includes:

- [ ] Sanity check based on checksum and/or some magic number
- [ ] Use array instead of linked list for better cache behavior

Start by locating the archive-format implementation and the current linked-list data structure. Define the checksum or magic-number validation and compare an array-based layout against the existing structure; done means the archive is sanity-checked and the revised layout improves cache behavior without compromising security.

Written by the indexing model from the issue text.