vidya/crates/renderer_resources/src/util.rs

pub(crate) mod weak_vec {
    #![allow(dead_code)]
    //! Module containing the [`WeakVec`] API.

    use std::{sync::Weak, vec::Vec};

    /// An optimized container for `Weak` references of `T` that minimizes reallocations by
    /// dropping older elements that no longer have strong references to them.
    #[derive(Debug)]
    pub(crate) struct WeakVec<T> {
        inner: Vec<Weak<T>>,
    }

    impl<T> Default for WeakVec<T> {
        fn default() -> Self {
            Self {
                inner: Default::default(),
            }
        }
    }

    impl<T> WeakVec<T> {
        pub(crate) fn new() -> Self {
            Self { inner: Vec::new() }
        }

        /// Pushes a new element to this collection.
        ///
        /// If the inner Vec needs to be reallocated, we will first drop older elements that
        /// no longer have strong references to them.
        pub(crate) fn push(&mut self, value: Weak<T>) {
            if self.inner.len() == self.inner.capacity() {
                // Iterating backwards has the advantage that we don't do more work than we have to.
                for i in (0..self.inner.len()).rev() {
                    if self.inner[i].strong_count() == 0 {
                        self.inner.swap_remove(i);
                    }
                }

                // Make sure our capacity is twice the number of live elements.
                // Leaving some spare capacity ensures that we won't re-scan immediately.
                self.inner.reserve_exact(self.inner.len());
            }

            self.inner.push(value);
        }
    }

    pub(crate) struct WeakVecIter<T> {
        inner: std::vec::IntoIter<Weak<T>>,
    }

    impl<T> Iterator for WeakVecIter<T> {
        type Item = Weak<T>;
        fn next(&mut self) -> Option<Self::Item> {
            self.inner.next()
        }
    }

    impl<T> IntoIterator for WeakVec<T> {
        type Item = Weak<T>;
        type IntoIter = WeakVecIter<T>;
        fn into_iter(self) -> Self::IntoIter {
            WeakVecIter {
                inner: self.inner.into_iter(),
            }
        }
    }
}

pub(crate) use weak_vec::WeakVec;

pub fn eq_f32(lhs: f32, rhs: f32) -> bool {
    use core::num::FpCategory::*;
    match (lhs.classify(), rhs.classify()) {
        (Zero, Zero) | (Nan, Nan) => true,
        (Infinite, Infinite) => lhs.signum() == rhs.signum(),
        _ => lhs == rhs,
    }
}

pub fn ord_f32(lhs: f32, rhs: f32) -> core::cmp::Ordering {
    use core::cmp::Ordering;
    use core::num::FpCategory::*;
    match (lhs.classify(), rhs.classify()) {
        (Zero, Zero) | (Nan, Nan) => Ordering::Equal,
        (Infinite, Infinite) => {
            core::cmp::PartialOrd::partial_cmp(&lhs.signum(), &rhs.signum()).unwrap()
        }
        _ => core::cmp::PartialOrd::partial_cmp(&lhs, &rhs).unwrap(),
    }
}

pub fn hash_f32<H: std::hash::Hasher>(state: &mut H, f: f32) {
    use std::hash::Hash;
    let classify = f.classify();
    match classify {
        std::num::FpCategory::Nan => (classify as u8).hash(state),
        std::num::FpCategory::Infinite | std::num::FpCategory::Zero => {
            (classify as u8, f.signum() as i8).hash(state)
        }
        std::num::FpCategory::Subnormal | std::num::FpCategory::Normal => f.to_bits().hash(state),
    }
}

#[repr(transparent)]
#[derive(Debug, Clone, Copy)]
pub struct F32(f32);

impl F32 {
    #[inline]
    pub fn from_bits(bits: u32) -> Self {
        Self(f32::from_bits(bits))
    }
    #[inline]
    pub fn into_bits(self) -> u32 {
        self.0.to_bits()
    }
}

impl From<f32> for F32 {
    fn from(value: f32) -> Self {
        Self(value)
    }
}
impl From<F32> for f32 {
    fn from(value: F32) -> Self {
        value.0
    }
}

impl std::ops::Deref for F32 {
    type Target = f32;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl std::ops::DerefMut for F32 {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl PartialEq for F32 {
    fn eq(&self, other: &Self) -> bool {
        eq_f32(self.0, other.0)
    }
}

impl Eq for F32 {}

impl PartialOrd for F32 {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(ord_f32(self.0, other.0))
    }
}

impl Ord for F32 {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        ord_f32(self.0, other.0)
    }
}

impl core::hash::Hash for F32 {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        hash_f32(state, self.0)
    }
}