Common traits

[pitdicker]

As discussed in #13, this removes the Copy trait from Rng implementations, and adds Clone and Debug where needed.

The Debug implementations look like this:

OsRng {
    inner: OsGetrandomRng
}
StdRng {
    rng: IsaacWordRng(
        Isaac64Rng {}
    )
}
ThreadRng {
    rng: RefCell {
        value: ReseedingRng {
            rng: StdRng {
                rng: IsaacWordRng(
                    Isaac64Rng {}
                )
            },
            generation_threshold: 32768,
            bytes_generated: 0,
            reseeder: ReseedWithNew
        }
    }
}
ReadRng {
    reader: File {
        fd: 3,
        path: "/dev/urandom",
        read: true,
        write: false
    }
}
XorShiftRng {}
IsaacRng {}
Isaac64Rng {}
IsaacWordRng(
    Isaac64Rng {}
)
ChaChaRng {}
MockAddRng {
    v: 2,
    a: 1
}

(generated with)

    use NewSeeded;
    use std::fs::File;
    use {StdRng, OsRng, ReadRng};
    use prng::{XorShiftRng, IsaacRng, Isaac64Rng, IsaacWordRng, ChaChaRng};
    println!("Debug:");
    println!("{:#?}", OsRng::new().unwrap());
    println!("{:#?}", StdRng::new().unwrap());
    println!("{:#?}", thread_rng());
    {
        let file = File::open("/dev/random").unwrap();
        let mut rng = ReadRng::new(file);
    }
    println!("{:#?}", XorShiftRng::new().unwrap());
    println!("{:#?}", IsaacRng::new().unwrap());
    println!("{:#?}", Isaac64Rng::new().unwrap());
    println!("{:#?}", IsaacWordRng::new().unwrap());
    println!("{:#?}", ChaChaRng::new().unwrap());
    println!("{:#?}", ::rand_core::mock::MockAddRng::new(2u32, 1u32));

It is not easily possible to implement Clone for OsRng, because on some operating systems it needs to read from /dev/urandom, anf File does not implement Clone.

I also did not implement Clone for ReadRng. If it is initialized with a reference to the underlying reader, the clone would share the same reader, not a clone of it. That seems like an easy footgun to me.

[dhardy]

Nice print-out. Looks okay I guess.

In general cloning any external generator is problematic, 1st because the resource may not be "cloneable" and second because it might be expected that after let a = b.clone(); the following is true: a.next_u32() == b.next_u32(), which of course may not be the case for an external generator.

[pitdicker]

Wow that is fast :-). I will add your comment to the issue.