Rust CString drop benchmark

drop-bench.rs

extern crate time;
extern crate rand;

use time::precise_time_ns;
use rand::Rng;

use std::ffi::CString;

fn main() { 
    println!("Baseline 1: empty String");
    bench3::<String>(String::new());
    println!("Baseline 2: hello world String");
    bench3::<String>(String::from("Hello, World"));

    println!("Bench 1: empty CString");
    bench3::<CString>(CString::new("").unwrap());
    println!("Bench 2: hello world CString");
    bench3::<CString>(CString::new("Hello, World").unwrap());
}

fn bench3<T: Clone>(x: T) {
    let t = bench_drop(&x);
    println!("ns per iter = {}", t / 1_000_000);
    let t = bench_drop(&x);
    println!("ns per iter = {}", t / 1_000_000);
    let t = bench_drop(&x);
    println!("ns per iter = {}\n", t / 1_000_000);
}

fn bench_drop<T: Clone>(x: &T) -> u64 {
    let mut xs: Vec<T> = vec![x.clone(); 1_000_000];
    rand::weak_rng().shuffle(&mut xs);

    let start = precise_time_ns();
    for x in xs {
        drop(x)
    }
    let end = precise_time_ns();
    end - start
}