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
|
// Copyright 2018 Developers of the Rand project.
//
// 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.
//! Mock random number generator
use rand_core::{RngCore, Error, impls};
/// A simple implementation of `RngCore` for testing purposes.
///
/// This generates an arithmetic sequence (i.e. adds a constant each step)
/// over a `u64` number, using wrapping arithmetic. If the increment is 0
/// the generator yields a constant.
///
/// ```
/// use rand::Rng;
/// use rand::rngs::mock::StepRng;
///
/// let mut my_rng = StepRng::new(2, 1);
/// let sample: [u64; 3] = my_rng.gen();
/// assert_eq!(sample, [2, 3, 4]);
/// ```
#[derive(Debug, Clone)]
pub struct StepRng {
v: u64,
a: u64,
}
impl StepRng {
/// Create a `StepRng`, yielding an arithmetic sequence starting with
/// `initial` and incremented by `increment` each time.
pub fn new(initial: u64, increment: u64) -> Self {
StepRng { v: initial, a: increment }
}
}
impl RngCore for StepRng {
#[inline]
fn next_u32(&mut self) -> u32 {
self.next_u64() as u32
}
#[inline]
fn next_u64(&mut self) -> u64 {
let result = self.v;
self.v = self.v.wrapping_add(self.a);
result
}
#[inline]
fn fill_bytes(&mut self, dest: &mut [u8]) {
impls::fill_bytes_via_next(self, dest);
}
#[inline]
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
self.fill_bytes(dest);
Ok(())
}
}
|
