1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91

// Copyright 2018 Developers of the Rand project.
// Copyright 2017-2018 The Rust Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Random number generation traits
//!
//! This crate is mainly of interest to crates publishing implementations of
//! [`RngCore`]. Other users are encouraged to use the [`rand`] crate instead
//! which re-exports the main traits and error types.
//!
//! [`RngCore`] is the core trait implemented by algorithmic pseudo-random number
//! generators and external random-number sources.
//!
//! [`SeedableRng`] is an extension trait for construction from fixed seeds and
//! other random number generators.
//!
//! [`Error`] is provided for error-handling. It is safe to use in `no_std`
//! environments.
//!
//! The [`impls`] and [`le`] sub-modules include a few small functions to assist
//! implementation of [`RngCore`].
//!
//! [`rand`]: https://docs.rs/rand

#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
       html_root_url = "https://rust-random.github.io/rand/")]

#![deny(missing_docs)]
#![deny(missing_debug_implementations)]
#![doc(test(attr(allow(unused_variables), deny(warnings))))]

#![cfg_attr(not(feature="std"), no_std)]

#[cfg(feature="std")] extern crate core;
extern crate rand_core as rand_core5;

pub use error::{ErrorKind, Error, Error5};

mod error;

pub use rand_core5::{block, le, impls};
pub use rand_core5::{CryptoRng, RngCore, SeedableRng};

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_seed_from_u64() {
        struct SeedableNum(u64);
        impl SeedableRng for SeedableNum {
            type Seed = [u8; 8];
            fn from_seed(seed: Self::Seed) -> Self {
                let mut x = [0u64; 1];
                le::read_u64_into(&seed, &mut x);
                SeedableNum(x[0])
            }
        }

        const N: usize = 8;
        const SEEDS: [u64; N] = [0u64, 1, 2, 3, 4, 8, 16, -1i64 as u64];
        let mut results = [0u64; N];
        for (i, seed) in SEEDS.iter().enumerate() {
            let SeedableNum(x) = SeedableNum::seed_from_u64(*seed);
            results[i] = x;
        }

        for (i1, r1) in results.iter().enumerate() {
            let weight = r1.count_ones();
            // This is the binomial distribution B(64, 0.5), so chance of
            // weight < 20 is binocdf(19, 64, 0.5) = 7.8e-4, and same for
            // weight > 44.
            assert!(weight >= 20 && weight <= 44);

            for (i2, r2) in results.iter().enumerate() {
                if i1 == i2 { continue; }
                let diff_weight = (r1 ^ r2).count_ones();
                assert!(diff_weight >= 20);
            }
        }

        // value-breakage test:
        assert_eq!(results[0], 5029875928683246316);
    }
}