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
92
93
94
95
96
97

#![no_std]

use core::marker::PhantomData;
use core::ptr;

pub trait Random: Sized {
    fn random<G: ?Sized + RandomGen>(g: &mut G) -> Self;
}

pub trait RandomGen {
    #[inline]
    fn gen_u32(&mut self) -> u32 { self.gen_u64() as u32 }
    #[inline]
    fn gen_u64(&mut self) -> u64 { (self.gen_u32() as u64) << 32 | (self.gen_u32() as u64) }
    #[inline]
    fn gen_f32(&mut self) -> f32 { (self.gen_u32() >>  8) as f32 / (1u64 << 24) as f32 }
    #[inline]
    fn gen_f64(&mut self) -> f64 { (self.gen_u64() >> 11) as f64 / (1u64 << 53) as f64 }
    #[inline]
    fn fill_bytes(&mut self, bs: &mut [u8]) {
        let mut p = bs.as_mut_ptr();
        let mut l = bs.len();
        loop { unsafe {
            if l >= 8 {
                let n = self.gen_u64();
                ptr::copy_nonoverlapping(&n as *const _ as *const u8, p, 8);
                p = p.offset(8);
                l -= 8;
            } else {
                let n = self.gen_u32();
                ptr::copy_nonoverlapping(&n as *const _ as *const u8, p, usize::min(4, l));
                if 4 >= l { return; }
                p = p.offset(4);
                l -= 4;
            }
        } }
    }
    #[inline]
    fn gen<A: Random>(&mut self) -> A { A::random(self) }
}

impl<'a, G: RandomGen> RandomGen for &'a mut G {
    #[inline] fn gen_u32(&mut self) -> u32 { G::gen_u32(self) }
    #[inline] fn gen_u64(&mut self) -> u64 { G::gen_u64(self) }
    #[inline] fn gen_f32(&mut self) -> f32 { G::gen_f32(self) }
    #[inline] fn gen_f64(&mut self) -> f64 { G::gen_f64(self) }
    #[inline] fn fill_bytes(&mut self, bs: &mut [u8]) { G::fill_bytes(self, bs) }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Stream<G, A>(G, PhantomData<A>);

impl<G, A> Stream<G, A> {
    #[inline]
    pub fn new(g: G) -> Self { Stream(g, PhantomData) }
}

impl<G: RandomGen, A: Random> Iterator for Stream<G, A> {
    type Item = A;
    #[inline]
    fn next(&mut self) -> Option<A> { Some(self.0.gen()) }
}

impl Random for u32 {
    #[inline]
    fn random<G: ?Sized + RandomGen>(g: &mut G) -> u32 { g.gen_u32() }
}

impl Random for u64 {
    #[inline]
    fn random<G: ?Sized + RandomGen>(g: &mut G) -> u64 { g.gen_u64() }
}

impl Random for i32 {
    #[inline]
    fn random<G: ?Sized + RandomGen>(g: &mut G) -> i32 { g.gen_u32() as _ }
}

impl Random for i64 {
    #[inline]
    fn random<G: ?Sized + RandomGen>(g: &mut G) -> i64 { g.gen_u64() as _ }
}

impl Random for f32 {
    #[inline]
    fn random<G: ?Sized + RandomGen>(g: &mut G) -> f32 { g.gen_f32() }
}

impl Random for f64 {
    #[inline]
    fn random<G: ?Sized + RandomGen>(g: &mut G) -> f64 { g.gen_f64() }
}

pub trait Seedable<Seed>: RandomGen {
    fn reseed(&mut self, _: Seed);
    fn from_seed(_: Seed) -> Self;
}