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use crate::data::arena::Index;
#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
#[derive(Clone, Debug)]
/// A container for data associated to item existing into another Arena.
pub struct Coarena<T> {
data: Vec<(u64, T)>,
}
impl<T> Coarena<T> {
/// A coarena with no element.
pub fn new() -> Self {
Self { data: Vec::new() }
}
/// Gets a specific element from the coarena, if it exists.
pub fn get(&self, index: Index) -> Option<&T> {
let (i, g) = index.into_raw_parts();
self.data
.get(i)
.and_then(|(gg, t)| if g == *gg { Some(t) } else { None })
}
/// Gets a mutable reference to a specific element from the coarena, if it exists.
pub fn get_mut(&mut self, index: Index) -> Option<&mut T> {
let (i, g) = index.into_raw_parts();
self.data
.get_mut(i)
.and_then(|(gg, t)| if g == *gg { Some(t) } else { None })
}
/// Inserts an element into this coarena.
pub fn insert(&mut self, a: Index, value: T)
where
T: Clone + Default,
{
let (i1, g1) = a.into_raw_parts();
if self.data.len() <= i1 {
self.data.resize(i1 + 1, (u32::MAX as u64, T::default()));
}
self.data[i1] = (g1, value);
}
/// Ensure that elements at the two given indices exist in this coarena, and return their reference.
///
/// Missing elements are created automatically and initialized with the `default` value.
pub fn ensure_pair_exists(&mut self, a: Index, b: Index, default: T) -> (&mut T, &mut T)
where
T: Clone,
{
let (i1, g1) = a.into_raw_parts();
let (i2, g2) = b.into_raw_parts();
assert_ne!(i1, i2, "Cannot index the same object twice.");
let (elt1, elt2) = if i1 > i2 {
if self.data.len() <= i1 {
self.data.resize(i1 + 1, (u32::MAX as u64, default.clone()));
}
let (left, right) = self.data.split_at_mut(i1);
(&mut right[0], &mut left[i2])
} else {
// i2 > i1
if self.data.len() <= i2 {
self.data.resize(i2 + 1, (u32::MAX as u64, default.clone()));
}
let (left, right) = self.data.split_at_mut(i2);
(&mut left[i1], &mut right[0])
};
if elt1.0 != g1 {
*elt1 = (g1, default.clone());
}
if elt2.0 != g2 {
*elt2 = (g2, default);
}
(&mut elt1.1, &mut elt2.1)
}
}
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