Add Duration from nanos u128

[omanirudh]

What does this PR do?

This draft PR adds the Duration::from_nanos_u128 function to handle durations that exceed the range of u64, allowing for time spans greater than ~584 years.

Motivation

The current Duration API does not support creating durations from nanoseconds represented as u128. This addition addresses that limitation.

Tracking Issue

Fixes #139201

Details

• Introduced Duration::from_nanos_u128 as a const fn similar to other functions in the file.

• Ensured safety by validating the nanoseconds before using unsafe code.

• To do : complete the documentation and examples for the new function.

  r? @RalfJung

[rustbot]

r? @tgross35

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[RalfJung]

Thanks for taking this over!
However, this needs a libs reviewer. I just proposed the API. :)

r? libs

[omanirudh]

Thanks for taking this over! However, this needs a libs reviewer. I just proposed the API. :)

r? libs

Happy to take this up. noted.

[tgross35]

    /// Creates a new Duration from the specified number of nanoseconds.
    ///
    /// Use this function if you need to specify time greater than what can fit in u64 
    /// (around 584 years).

Nanoseconds is one word, summary line needs to be separate from the rest of the description, and I don't think we need to say the number of years twice.

[tgross35]

Needs the #![feature(...)] gate to work, also has a trailing newline.

[omanirudh]

Hey @tgross35 thanks for the review.
will make changes and get get back.

[tgross35]

@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[rust-log-analyzer]

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[RUSTC-TIMING] build_script_build test:false 0.172
[RUSTC-TIMING] cc test:false 0.572
   Compiling compiler_builtins v0.1.152
[RUSTC-TIMING] build_script_build test:false 0.279
error[E0015]: cannot call non-const associated function `<u64 as TryFrom<u128>>::try_from` in constant functions
   --> library/core/src/time.rs:327:20
    |
327 |         let secs = u64::try_from(nanos / NANOS_PER_SEC).unwrap_or(u64::MAX);
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants

error[E0015]: cannot call non-const method `result::Result::<u64, TryFromIntError>::unwrap_or` in constant functions
   --> library/core/src/time.rs:327:57
    |
327 |         let secs = u64::try_from(nanos / NANOS_PER_SEC).unwrap_or(u64::MAX);
    |                                                         ^^^^^^^^^^^^^^^^^^^
    |
    = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants

For more information about this error, try `rustc --explain E0015`.