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
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118

use rand::SeedableRng;
use rand_seeder::Seeder;
use rand_xoshiro::Xoshiro256StarStar;
use std::ops::{Deref, DerefMut};

#[cfg(all(feature = "bevy-nightly", not(feature = "bevy-stable")))]
use bevy_nightly as bevy;
#[cfg(all(feature = "bevy-stable", not(feature = "bevy-nightly")))]
use bevy_stable as bevy;

use bevy::prelude::*;

pub use rand::Rng as _;

/// `RngPlugin` allows you to inject a (optionally seeded) random number
/// generator into your systems.
///
/// Once the plugin is active, you can use `Local<bevy_rng::Rng>` to get the
/// rng instance.
///
/// Using `Local<T>` ensures you get a unique copy of the rng for each
/// individual system, which is important, because systems have no deterministic
/// order, which will result in non-deterministic rng results.
///
/// You are still responsible for deterministically generating random numbers
/// _inside_ an individual system, which (currently) means you can't generate
/// random numbers when iterating over entities, as entity iteration also isn't
/// ordered currently.
#[derive(Debug, Clone, Default, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct RngPlugin {
    seed: Option<Seed>,
}

impl From<String> for RngPlugin {
    fn from(seed: String) -> Self {
        Self {
            seed: Some(Seed::String(seed)),
        }
    }
}

impl From<&str> for RngPlugin {
    fn from(seed: &str) -> Self {
        Self {
            seed: Some(Seed::String(seed.to_owned())),
        }
    }
}

impl From<u64> for RngPlugin {
    fn from(seed: u64) -> Self {
        Self {
            seed: Some(Seed::Number(seed)),
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
enum Seed {
    Number(u64),
    String(String),
}

impl Plugin for RngPlugin {
    fn build(&self, app: &mut AppBuilder) {
        let rng = match &self.seed {
            Some(Seed::String(seed)) => Seeder::from(seed.as_str()).make_rng(),
            Some(Seed::Number(num)) => Xoshiro256StarStar::seed_from_u64(*num),
            None => Xoshiro256StarStar::from_entropy(),
        };

        #[cfg(all(feature = "bevy-nightly", not(feature = "bevy-stable")))]
        app.insert_resource(RootRng { rng });
        #[cfg(all(feature = "bevy-stable", not(feature = "bevy-nightly")))]
        app.add_resource(RootRng { rng });
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
struct RootRng {
    rng: Xoshiro256StarStar,
}

/// The Rng resource.
///
/// This wraps a random number generator.
///
/// See the `rand::Rng` trait for more details on how to generate random data.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Rng {
    inner: Xoshiro256StarStar,
}

impl Deref for Rng {
    type Target = Xoshiro256StarStar;

    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

impl DerefMut for Rng {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.inner
    }
}

impl FromResources for Rng {
    fn from_resources(resources: &Resources) -> Self {
        let inner = match resources.get_mut::<RootRng>() {
            Some(mut rng) => Xoshiro256StarStar::from_rng(&mut rng.deref_mut().rng)
                .expect("failed to create rng"),
            None => Xoshiro256StarStar::from_entropy(),
        };

        Self { inner }
    }
}