redoubt-alloc 0.1.0-rc.4

// Copyright (c) 2025-2026 Federico Hoerth <memparanoid@gmail.com>
// SPDX-License-Identifier: GPL-3.0-only
// See LICENSE in the repository root for full license text.

use redoubt_zero::{
    FastZeroizable, RedoubtZero, ZeroizationProbe, ZeroizeMetadata, ZeroizeOnDropSentinel,
};

use crate::error::RedoubtOptionError;

/// An optional value wrapper with automatic zeroization.
#[derive(RedoubtZero, Default)]
pub struct RedoubtOption<T>
where
    T: FastZeroizable + ZeroizeMetadata + ZeroizationProbe,
{
    inner: Option<T>,
    __sentinel: ZeroizeOnDropSentinel,
}

impl<T> RedoubtOption<T>
where
    T: FastZeroizable + ZeroizeMetadata + ZeroizationProbe,
{
    /// Returns a reference to the inner value, or an error if `None`.
    pub fn as_ref(&self) -> Result<&T, RedoubtOptionError> {
        self.inner.as_ref().ok_or(RedoubtOptionError::Empty)
    }

    /// Returns a mutable reference to the inner value, or an error if `None`.
    pub fn as_mut(&mut self) -> Result<&mut T, RedoubtOptionError> {
        self.inner.as_mut().ok_or(RedoubtOptionError::Empty)
    }

    /// Replaces the inner value with a new one, zeroizing both the old value and the source.
    pub fn replace(&mut self, value: &mut T)
    where
        T: Default,
    {
        // Zeroize old value if Some
        if let Some(old) = &mut self.inner {
            old.fast_zeroize();
        }

        // Move new value from source
        let mut new_value = T::default();
        unsafe {
            // SAFETY: Both pointers are valid and properly aligned
            core::ptr::swap_nonoverlapping(value, &mut new_value, 1);
        }
        self.inner = Some(new_value);

        // Zeroize source
        value.fast_zeroize();
    }

    /// Takes the value out of the option, leaving `None` in its place.
    pub fn take(&mut self) -> Result<T, RedoubtOptionError> {
        self.inner.take().ok_or(RedoubtOptionError::Empty)
    }

    /// Returns `true` if the option contains a value.
    pub fn is_some(&self) -> bool {
        self.inner.is_some()
    }

    /// Returns `true` if the option is `None`.
    pub fn is_none(&self) -> bool {
        self.inner.is_none()
    }

    /// Returns a reference to the inner `Option<T>`.
    #[inline(always)]
    pub fn as_option(&self) -> &Option<T> {
        &self.inner
    }

    /// Returns a mutable reference to the inner `Option<T>`.
    #[inline(always)]
    pub fn as_mut_option(&mut self) -> &mut Option<T> {
        &mut self.inner
    }
}