implement Index<u8> for IDT instead of Index<usize>

[Freax13]

This pr changes the Idx type of InterruptDescriptorTable's Index implementation from usize to u8 as discussed in #285 (comment). u8 more accurately represents the index for an InterruptDescriptorTable which always has exactly 256 entries. This change also eliminates some out of bounds panics that were possible with usize.

There was some discussion following #95 (comment) on whether it would be possible to use SliceIndex now or in the future. Following this pr this is no longer useful because SliceIndex is based around only usize not u8. Since using SliceIndex is now out of question, there shouldn't be any objections to hard coding implementations based for the range types in core and so this pr provides those implementations as well.

[phil-opp]

Thanks a lot, looks good! I left some minor comments about the integer conversions, otherwise this seems ready to be merged.

there shouldn't be any objections to hard coding implementations based for the range types in core and so this pr provides those implementations as well.

Good idea!

[phil-opp]

@Freax13 Do you want to join our x86_64 maintenance team by any chance? Your contributions to this repo are very good and we could need some help with reviewing PRs and further progressing this crate.

[Freax13]

@Freax13 Do you want to join our x86_64 maintenance team by any chance? Your contributions to this repo are very good and we could need some help with reviewing PRs and further progressing this crate.

Sure, that sounds great! 🎉

[Freax13]

CI is failing because yesterdays nightly release broke const operands in asm (see rust-lang/rust#90348). They now require #![feature(asm_const)]. Luckily we only use those on the next branch, so the master branch and all releases on crates.io should be fine.

[phil-opp]

Ok great, invite sent. Welcome!

CI is failing because yesterdays nightly release broke const operands in asm (see rust-lang/rust#90348). They now require #![feature(asm_const)]. Luckily we only use those on the next branch, so the master branch and all releases on crates.io should be fine.

Thanks for investigating, sounds like asm! might be stabilized soon!

We can just switch on the new feature gates on the next branch then, right?

[Freax13]

Ok great, invite sent. Welcome!

Thanks!

We can just switch on the new feature gates on the next branch then, right?

Yes, I created a seperate pr for that: #320.

[Freax13]

After merging #320 and rebasing this now passes CI.