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