How are Rust crates (e.g. num_cpus) implemented?

Question

I was wondering how are Rust crates are implemented.

For example, there is a crate named num_cpus. This crate has this basic method num_cpus::get() which tells number of CPUs in your computer.

My questions:

• How is the method num_cpus::get() implemented (is it done using another language?)
• Can the same result be achieved with plain Rust code without using any crates?

Answer 1

... in Rust. There's no reason to believe it'd be anything else.

You can also check this by just looking at the source code, easily done by:

1. Search crates.io for "num_cpus"..
2. Select the num_cpus crate.
3. Select "Repository" for the source code.
4. Open the only .rs source file in the repository, src/lib.rs.