libnoise 1.2.0

A simple, performant, and customizable procedural noise generation library.
Documentation 
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use super::math::{Vec2, Vec3, Vec4};
use rand::seq::SliceRandom;
use rand_chacha::{ChaCha12Rng, rand_core::SeedableRng};

/// A trait attached to valid seed types for noise sources.
///
/// This trait is implemented for `u64` and `[u8; 32]`. In doing so, both
/// approaches to seed the underlying RNG are exposed.
pub trait Seed {
    fn construct_rng(self) -> ChaCha12Rng;
}

impl Seed for u64 {
    fn construct_rng(self) -> ChaCha12Rng {
        ChaCha12Rng::seed_from_u64(self)
    }
}

impl Seed for [u8; 32] {
    fn construct_rng(self) -> ChaCha12Rng {
        ChaCha12Rng::from_seed(self)
    }
}

#[derive(Clone, Debug)]
pub(crate) struct PermutationTable {
    pub(crate) table: Vec<usize>,
}

impl PermutationTable {
    pub(crate) fn new(seed: impl Seed, w: usize, doubleup: bool) -> Self {
        let mut table = Vec::from_iter(0..w);
        let mut rng = seed.construct_rng();
        table.shuffle(&mut rng);
        if doubleup {
            table.extend_from_within(..);
        }
        table.shrink_to_fit();
        Self { table }
    }

    #[inline]
    pub(crate) unsafe fn get(&self, i: usize) -> usize {
        unsafe { *self.table.get_unchecked(i) }
    }

    #[inline]
    pub(crate) unsafe fn hash1d(&self, i: usize) -> usize {
        unsafe { self.get(i) }
    }

    #[inline]
    pub(crate) unsafe fn hash2d(&self, i: usize, j: usize) -> usize {
        unsafe { self.get(j + self.get(i)) }
    }

    #[inline]
    pub(crate) unsafe fn hash3d(&self, i: usize, j: usize, k: usize) -> usize {
        unsafe { self.get(k + self.get(j + self.get(i))) }
    }

    #[inline]
    pub(crate) unsafe fn hash4d(&self, i: usize, j: usize, k: usize, l: usize) -> usize {
        unsafe { self.get(l + self.get(k + self.get(j + self.get(i)))) }
    }

    #[inline]
    pub(crate) unsafe fn hash2d_vec(&self, value: Vec2<usize>) -> usize {
        unsafe { self.get(value.y + self.get(value.x)) }
    }

    #[inline]
    pub(crate) unsafe fn hash3d_vec(&self, value: Vec3<usize>) -> usize {
        unsafe { self.get(value.z + self.get(value.y + self.get(value.x))) }
    }

    #[inline]
    pub(crate) unsafe fn hash4d_vec(&self, value: Vec4<usize>) -> usize {
        unsafe { self.get(value.w + self.get(value.z + self.get(value.y + self.get(value.x)))) }
    }
}