osom_lib_prng/prngs/
splitmix.rs

1#![allow(
2    clippy::cast_possible_truncation,
3    clippy::cast_possible_wrap,
4)]
5
6use core::ops::RangeBounds;
7
8use osom_lib_reprc::macros::reprc;
9
10use crate::{
11    prngs::helpers::{
12        fill_raw_from_array_generator, generate_f32_in_range, generate_f64_in_range, generate_i32_in_range,
13        generate_i64_in_range, generate_u32_in_range, generate_u64_in_range
14    },
15    traits::{PRNConcreteBoundedGenerator, PRNConcreteGenerator, PRNGenerator, Seedable},
16};
17
18/// The Rust imlementation of `SplitMix64` algorithm. It is good
19/// for generating seeds and good enough general purpose PRNG.
20#[derive(Debug, PartialEq, Eq, Clone, Copy)]
21#[reprc]
22#[repr(transparent)]
23#[must_use]
24pub struct SplitMix64 {
25    state: u64
26}
27
28impl SplitMix64 {
29    /// Creates a new [`SplitMix64`] from a seed.
30    #[inline(always)]
31    pub const fn with_seed(seed: u64) -> Self {
32        let state = if seed != 0 { seed } else { 1 };
33        Self { state }
34    }
35
36    /// Generates a new pseudo-random u64.
37    pub const fn next(&mut self) -> u64 {
38        self.state = self.state.wrapping_add(0x9e3779b97f4a7c15);
39        let mut result = self.state;
40        result = (result ^ (result >> 30)).wrapping_mul(0xbf58476d1ce4e5b9);
41        result = (result ^ (result >> 27)).wrapping_mul(0x94d049bb133111eb);
42        result ^ (result >> 31)
43    }
44}
45
46impl Seedable<u64> for SplitMix64 {
47    fn with_seed(seed: u64) -> Self {
48        Self::with_seed(seed)
49    }
50}
51
52impl PRNGenerator for SplitMix64 {
53    unsafe fn fill_raw(&mut self, dst_ptr: *mut u8, dst_len: usize) {
54        fill_raw_from_array_generator(|| self.next().to_be_bytes(), dst_ptr, dst_len);
55    }
56}
57
58impl PRNConcreteGenerator<SplitMix64> for bool {
59    fn generate(generator: &mut SplitMix64) -> Self {
60        (generator.next() & 1) == 1
61    }
62}
63
64impl<const N: usize> PRNConcreteGenerator<SplitMix64> for [u8; N] {
65    fn generate(generator: &mut SplitMix64) -> Self {
66        let mut item = core::mem::MaybeUninit::<Self>::uninit();
67        unsafe {
68            generator.fill_raw(item.as_mut_ptr().cast(), size_of::<Self>());
69            item.assume_init()
70        }
71    }
72}
73
74impl PRNConcreteGenerator<SplitMix64> for u8 {
75    fn generate(generator: &mut SplitMix64) -> Self {
76        u8::from_le_bytes(generator.generate::<[u8; 1]>())
77    }
78}
79
80impl PRNConcreteGenerator<SplitMix64> for i8 {
81    fn generate(generator: &mut SplitMix64) -> Self {
82        i8::from_le_bytes(generator.generate::<[u8; 1]>())
83    }
84}
85
86
87impl PRNConcreteGenerator<SplitMix64> for u32 {
88    fn generate(generator: &mut SplitMix64) -> Self {
89        u32::from_le_bytes(generator.generate::<[u8; 4]>())
90    }
91}
92
93impl PRNConcreteGenerator<SplitMix64> for i32 {
94    fn generate(generator: &mut SplitMix64) -> Self {
95        i32::from_le_bytes(generator.generate::<[u8; 4]>())
96    }
97}
98
99impl PRNConcreteGenerator<SplitMix64> for u64 {
100    fn generate(generator: &mut SplitMix64) -> Self {
101        u64::from_le_bytes(generator.generate::<[u8; 8]>())
102    }
103}
104
105impl PRNConcreteGenerator<SplitMix64> for i64 {
106    fn generate(generator: &mut SplitMix64) -> Self {
107        i64::from_le_bytes(generator.generate::<[u8; 8]>())
108    }
109}
110
111impl PRNConcreteBoundedGenerator<SplitMix64> for u32 {
112    fn generate<TBounds: RangeBounds<Self>>(generator: &mut SplitMix64, range: TBounds) -> Self {
113        generate_u32_in_range(generator, range)
114    }
115}
116
117impl PRNConcreteBoundedGenerator<SplitMix64> for u64 {
118    fn generate<TBounds: RangeBounds<Self>>(generator: &mut SplitMix64, range: TBounds) -> Self {
119        generate_u64_in_range(generator, range)
120    }
121}
122
123impl PRNConcreteBoundedGenerator<SplitMix64> for i32 {
124    fn generate<TBounds: RangeBounds<Self>>(generator: &mut SplitMix64, range: TBounds) -> Self {
125        generate_i32_in_range(generator, range)
126    }
127}
128
129impl PRNConcreteBoundedGenerator<SplitMix64> for i64 {
130    fn generate<TBounds: RangeBounds<Self>>(generator: &mut SplitMix64, range: TBounds) -> Self {
131        generate_i64_in_range(generator, range)
132    }
133}
134
135impl PRNConcreteBoundedGenerator<SplitMix64> for f32 {
136    fn generate<TBounds: RangeBounds<Self>>(generator: &mut SplitMix64, range: TBounds) -> Self {
137        generate_f32_in_range(generator, range)
138    }
139}
140
141impl PRNConcreteBoundedGenerator<SplitMix64> for f64 {
142    fn generate<TBounds: RangeBounds<Self>>(generator: &mut SplitMix64, range: TBounds) -> Self {
143        generate_f64_in_range(generator, range)
144    }
145}
osom_lib_prng/prngs/splitmix.rs

osom_lib_prng/prngs/
splitmix.rs
