protect overflow when computing expiration

[barkanido]

This change protects against overflow using 2 measures:

1. cache builders now won't build caches with time_tolive or
   time_to_idle higher than 1000 years.
2. for future computations, the internal Instant type will now only
   allow checked additions to force handling a possible overflow. in
   addition, an overflow is now an explicit panic instead of a silent
   overflow.

closes #52

[barkanido]

@tatsuya6502 can you help here?

cargo build --no-default-features --features future

fails here since the new code is located at common/time_atomic64.rs, which is not compiled when --no-default-features I have done this before noticing the "atomic64" feature flag, and because Instant was already there. WDYT? should I move it? how to go around this?

[tatsuya6502]

how to go around this?

The "atomic64" feature is used to select the source file for the time module. Some 32-bit platforms (MIPS and ARMv5) do not support AtomicU64 and some older versions of quanta crate will not compile. So Moka has two different implementations for time:

moka/src/common.rs

Lines 7 to 13 in 1074082

	// targe_has_atomic is more convenient but yet unstable (Rust 1.55)
	// https://github.com/rust-lang/rust/issues/32976
	// #[cfg_attr(target_has_atomic = "64", path = "common/time_atomic64.rs")]
	#[cfg_attr(feature = "atomic64", path = "common/time_atomic64.rs")]
	#[cfg_attr(not(feature = "atomic64"), path = "common/time_compat.rs")]
	pub(crate) mod time;

However, by a historical reason, these two source files (common/time_atomic64.rs and common/time_compat.rs) now have identical definitions for the following types:

pub(crate) type Instant = quanta::Instant;
pub(crate) type Clock = quanta::Clock;

#[cfg(test)]
pub(crate) type Mock = quanta::Mock;

Let's clean them up now. You can remove them from these source files, and put them to common.rs.

[tatsuya6502]

You can remove them from these source files, and put them to common.rs.

Or maybe rename the current time module to something else (e.g. atomic_time).

  #[cfg_attr(feature = "atomic64", path = "common/time_atomic64.rs")] 
  #[cfg_attr(not(feature = "atomic64"), path = "common/time_compat.rs")] 
- pub(crate) mod time;
+ pub(crate) mod atomic_time;

and delete Instant and Clock and Mock from these file.

Then create common/time.rs and put them.

[tatsuya6502]

For the Rustfmt warnings, please do the followings:

1. Make sure you have the latest stable version of Rust installed. (e.g. Run rustup update stable)
   • You will use Rust stable because Moka's GitHub Actions uses Rust stable for Rustfmt check.
2. At the package root directory (where Cargo.toml is stored), run cargo fmt.
   • This will reformat all Rust source files in the package.
3. Run cargo fmt -- --check; echo $? to verify code is formatted.
   • If code is formatted, it will only print the exit code 0, otherwise it will print diffs and then the exit code 1.

[tatsuya6502]

LGTM. Thanks a lot for your contribution!

I will take care of the Rustfmt diffs after merging.

[tatsuya6502]

Hi @barkanido, I noticed you are not on our contributors page. I wish everybody who contributed to this project should be on the page to get some credits.

I think this is because GitHub cannot locate your account from the email address used by your commits. As you can see, your name is not clickable on the list of your commits here, but my name (GitHub user name) is clickable on my commits here.

I think you will need to go to GitHub's settings -> email page, and add your email address there if you have not.

Thanks!

[barkanido]

done. Thanks @tatsuya6502 the commits are now clickable. the contributors' page is still not updated though. maybe it take time, idk.

[tatsuya6502]

Hi @barkanido, Thanks for updating your setting. I wrote to the GitHub support and told that the contributors' page was not updated. They fixed the problem by re-indexing the data. Now you are on the page!

From the GitHub support:

I have reindexed the Insight contributor's graph for the repository and the contributor's list now display correctly.

https://github.com/moka-rs/moka/graphs/contributors

Hope this helps!