o3 0.25.0

shared-nothing primitives
Documentation 
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use std::num;

use crate::buffer::{bytes::window, write::consume};

/// One nonzero window capacity bounded by its owning window's ceiling.
#[repr(transparent)]
#[derive(Clone, Copy, PartialEq, Eq)]
pub(in crate::buffer) struct Capacity<const MAX: usize>(num::NonZero<u32>);

impl<const MAX: usize> Capacity<MAX> {
    const VALID: () = assert!(
        MAX <= u32::MAX as usize,
        "window capacity ceiling must fit u32"
    );

    pub(in crate::buffer) fn try_new(value: num::NonZero<usize>) -> Result<Self, consume::Error> {
        let () = Self::VALID;
        consume::Error::check(value.get(), MAX)?;
        let value = num::NonZero::<u32>::MIN.saturating_add(value.get() as u32 - 1);
        Ok(Self(value))
    }

    pub(in crate::buffer::bytes::window) fn try_extend(
        edit: &window::Edit<'_, (), MAX>,
        src: &[u8],
    ) -> Result<Self, consume::Error> {
        let len = (edit.state.head - *edit.tail) as usize;
        consume::Error::check(src.len(), MAX - len)?;
        Ok(Self(
            num::NonZero::<u32>::MIN.saturating_add((len + src.len()).saturating_sub(1) as u32),
        ))
    }

    pub(in crate::buffer) const fn get(self) -> u32 {
        self.0.get()
    }

    pub(in crate::buffer) const fn nonzero(self) -> num::NonZero<u32> {
        self.0
    }

    pub(in crate::buffer::bytes::window) fn grow(self, required: Self) -> Self {
        let ceiling = Self(num::NonZero::<u32>::MIN.saturating_add(MAX as u32 - 1));
        self.grow_to(required, ceiling)
    }

    /// Doubles this capacity within the owner's admitted ceiling.
    /// Both current and required capacities belong to that unchanged ceiling.
    pub(in crate::buffer) fn grow_to(self, required: Self, ceiling: Self) -> Self {
        let mut target = self.0;
        while target < required.0 {
            target = target.saturating_add(target.get()).min(ceiling.0);
        }
        Self(target)
    }
}

impl From<num::NonZero<u32>> for Capacity<{ u32::MAX as usize }> {
    fn from(value: num::NonZero<u32>) -> Self {
        Self(value)
    }
}

const _: () = {
    assert!(size_of::<Capacity<1>>() == size_of::<u32>());
    assert!(size_of::<Option<Capacity<1>>>() == size_of::<u32>());
};