Test to see if Vec capacity can be trusted in Rust.

vectest.rs

fn main() {
    // This may take a while to run...
    let ten_mega_bytes: usize = 10_000_001;
    println!("Testing Vec `with_capacity`, `reserve`, and `reserve_exact` in range 0..{} (ten megabytes)", ten_mega_bytes);
    for i in 0..ten_mega_bytes {
        let mut with_capacity: Vec<u8> = Vec::with_capacity(i);
        let mut reserve: Vec<u8> = Vec::new();
        reserve.reserve(i);
        let mut reserve_exact: Vec<u8> = Vec::new();
        reserve_exact.reserve_exact(i);
        let with_cap_capacity = with_capacity.capacity();
        let reserve_capacity = reserve.capacity();
        let reserve_exact_capacity = reserve_exact.capacity();

        if with_cap_capacity != i {
            println!("Setting capacity with `with_capacity` failed, expected {}, but got: {}", i, with_cap_capacity);
        }

        if reserve_capacity != i {
            println!("Setting capacity with `reserve` failed, expected {}, but got: {}", i, reserve_capacity);
        }

        if reserve_exact_capacity != i {
            println!("Setting capacity with `reserve_exact` failed, expected {}, but got: {}", i, reserve_exact_capacity);
        }

        with_capacity.shrink_to_fit();
        reserve.shrink_to_fit();
        reserve_exact.shrink_to_fit();

        with_capacity.reserve_exact(i);
        reserve.reserve_exact(i);
        reserve_exact.reserve_exact(i);

        let with_cap_capacity = with_capacity.capacity();
        let reserve_capacity = reserve.capacity();
        let reserve_exact_capacity = reserve_exact.capacity();

        if with_cap_capacity != i {
            println!("Setting capacity with `reserve_exact` after shirnk failed, expected {}, but got: {}", i, with_cap_capacity);
        }

        if reserve_capacity != i {
            println!("Setting capacity with `reserve_exact` after shirnk failed, expected {}, but got: {}", i, reserve_capacity);
        }

        if reserve_exact_capacity != i {
            println!("Setting capacity with `reserve_exact` after shirnk failed, expected {}, but got: {}", i, reserve_exact_capacity);
        }

        with_capacity.shrink_to_fit();
        reserve.shrink_to_fit();
        reserve_exact.shrink_to_fit();

        with_capacity.reserve(i);
        reserve.reserve(i);
        reserve_exact.reserve(i);

        let with_cap_capacity = with_capacity.capacity();
        let reserve_capacity = reserve.capacity();
        let reserve_exact_capacity = reserve_exact.capacity();

        if with_cap_capacity != i {
            println!("Setting capacity with `reserve` after shirnk failed, expected {}, but got: {}", i, with_cap_capacity);
        }

        if reserve_capacity != i {
            println!("Setting capacity with `reserve` after shirnk failed, expected {}, but got: {}", i, reserve_capacity);
        }

        if reserve_exact_capacity != i {
            println!("Setting capacity with `reserve` after shirnk failed, expected {}, but got: {}", i, reserve_exact_capacity);
        }
    }
}