tagged_vec/

lib.rs

//! An alternative to the standard libraries' [`Vec`] which is indexed with a custom type instead of [`usize`].
//!
//! This is useful to catch errors like using the wrong variable to index the vector.

#![warn(missing_docs)]

use std::{
    marker::PhantomData,
    ops::{Bound, RangeBounds},
};

use mapped_range_bounds::MappedRangeBounds;

#[cfg(feature = "binary-io")]
mod binary_io;
mod mapped_range_bounds;
#[cfg(test)]
mod tests;
mod trait_impls;

/// A [`Vec`] wrapper that allows indexing only via the given `Index` type.
///
/// For actual operation, `Index` must implement [`From<usize>`] and [`Into<usize>`].
pub struct TaggedVec<Index, Value> {
    index_type: PhantomData<Index>,
    vec: Vec<Value>,
}

impl<Index, Value> TaggedVec<Index, Value> {
    /// Creates a new empty `TaggedVec`.
    pub fn new() -> Self {
        Self::default()
    }

    /// Creates a new empty `TaggedVec` with at least the specified capacity.
    pub fn with_capacity(capacity: usize) -> Self {
        Self {
            index_type: PhantomData,
            vec: Vec::with_capacity(capacity),
        }
    }

    /// Returns the number of elements in the `TaggedVec`.
    pub fn len(&self) -> usize {
        self.vec.len()
    }

    /// Returns `true` if the `TaggedVec` contains no elements.
    pub fn is_empty(&self) -> bool {
        self.vec.is_empty()
    }

    /// Returns the total number of elements the `TaggedVec` can hold without reallocating.
    pub fn capacity(&self) -> usize {
        self.vec.capacity()
    }

    /// Returns the untagged slice of the `Vec` underlying this `TaggedVec`.
    pub fn as_untagged_slice(&self) -> &[Value] {
        &self.vec
    }

    /// Returns the untagged mutable slice of the `Vec` underlying this `TaggedVec`.
    pub fn as_untagged_mut_slice(&mut self) -> &mut [Value] {
        &mut self.vec
    }

    /// Inserts the given value at the back of the `TaggedVec`, returning its index.
    pub fn push(&mut self, value: Value) -> Index
    where
        Index: From<usize>,
    {
        let index = self.vec.len().into();
        self.vec.push(value);
        index
    }

    /// Insert a single value into the `TaggedVec` by constructing it in place.
    ///
    /// This method allows to create the value while already knowing its index.
    /// Returns the index.
    pub fn push_in_place(&mut self, value: impl FnOnce(Index) -> Value) -> Index
    where
        Index: From<usize>,
    {
        let index = self.vec.len();
        self.vec.push(value(index.into()));
        index.into()
    }

    /// Removes the value at the back of the `TaggedVec` and returns it with its index.
    pub fn pop(&mut self) -> Option<(Index, Value)>
    where
        Index: From<usize>,
    {
        if let Some(value) = self.vec.pop() {
            Some((self.vec.len().into(), value))
        } else {
            None
        }
    }

    /// Inserts the given `value` at position `index`, shifting all existing values in range `index..` one position to the right.
    pub fn insert(&mut self, index: Index, value: Value)
    where
        Index: Into<usize>,
    {
        self.vec.insert(index.into(), value);
    }

    /// See [`Vec::splice`].
    pub fn splice<I: IntoIterator<Item = Value>>(
        &mut self,
        range: impl RangeBounds<Index>,
        replace_with: I,
    ) -> std::vec::Splice<'_, I::IntoIter>
    where
        usize: From<Index>,
        Index: Copy,
    {
        self.vec.splice(MappedRangeBounds::new(range), replace_with)
    }

    /// Retains only the values specified by the predicate.
    ///
    /// In other words, remove all values `v` for which `f(&v)` returns `false`.
    /// This method operates in place, visiting each value exactly once in the original order, and preserves the order of the retained values.
    pub fn retain(&mut self, f: impl FnMut(&Value) -> bool) {
        self.vec.retain(f);
    }

    /// Removes the elements at the specified indices, shifting other elements to the left to fill gaps as required.
    ///
    /// The provided indices must be sorted.
    pub fn remove_multi(&mut self, indices: impl IntoIterator<Item = Index>)
    where
        Index: Into<usize> + Clone,
    {
        let mut indices = indices.into_iter().peekable();
        let mut current_index = 0;
        self.vec.retain(|_| {
            if let Some(next_delete_index) = indices.peek() {
                let next_delete_index = next_delete_index.clone().into();
                let result = if next_delete_index == current_index {
                    indices.next();

                    if let Some(next_next_delete_index) = indices.peek() {
                        let next_next_delete_index: usize = next_next_delete_index.clone().into();
                        assert!(next_next_delete_index > next_delete_index);
                    }

                    false
                } else {
                    true
                };
                current_index += 1;
                result
            } else {
                true
            }
        });

        assert!(indices.next().is_none());
    }

    /// Returns a reference to the value at the given index, or `None` if the index is out of bounds.
    pub fn get(&self, index: Index) -> Option<&Value>
    where
        Index: Into<usize>,
    {
        self.vec.get(index.into())
    }

    /// Returns an iterator over references to the entries of the `TaggedVec`.
    ///
    /// The `range` specifies which subset of the entries to iterate over.
    /// Iterating over a partial range with this argument is more efficient than iterating over the whole vector and skipping the unwanted entries, because the returned iterator does not support the skip optimisation.
    pub fn iter(
        &self,
        range: impl RangeBounds<Index>,
    ) -> impl DoubleEndedIterator<Item = (Index, &Value)> + ExactSizeIterator
    where
        Index: From<usize> + Copy,
        usize: From<Index>,
    {
        let range = MappedRangeBounds::new(range);
        let start_index_inclusive = match range.start_bound() {
            Bound::Included(index) => *index,
            Bound::Excluded(index) => (*index).checked_add(1).expect("start index overflow"),
            Bound::Unbounded => 0,
        };
        let end_index_exclusive = match range.end_bound() {
            Bound::Included(index) => (*index).checked_add(1).expect("end index overflow"),
            Bound::Excluded(index) => *index,
            Bound::Unbounded => self.vec.len(),
        };

        self.vec
            .iter()
            .enumerate()
            .skip(start_index_inclusive)
            .take(end_index_exclusive - start_index_inclusive)
            .map(|(index, value)| (index.into(), value))
    }

    /// Returns an iterator over mutable references to the entries of the `TaggedVec`.
    ///
    /// The `range` specifies which subset of the entries to iterate over.
    /// Iterating over a partial range with this argument is more efficient than iterating over the whole vector and skipping the unwanted entries, because the returned iterator does not support the skip optimisation.
    pub fn iter_mut(
        &mut self,
        range: impl RangeBounds<Index>,
    ) -> impl DoubleEndedIterator<Item = (Index, &mut Value)> + ExactSizeIterator
    where
        Index: From<usize> + Copy,
        usize: From<Index>,
    {
        let range = MappedRangeBounds::new(range);
        let start_index_inclusive = match range.start_bound() {
            Bound::Included(index) => *index,
            Bound::Excluded(index) => (*index).checked_add(1).expect("start index overflow"),
            Bound::Unbounded => 0,
        };
        let end_index_exclusive = match range.end_bound() {
            Bound::Included(index) => (*index).checked_add(1).expect("end index overflow"),
            Bound::Excluded(index) => *index,
            Bound::Unbounded => self.vec.len(),
        };

        self.vec
            .iter_mut()
            .enumerate()
            .skip(start_index_inclusive)
            .take(end_index_exclusive - start_index_inclusive)
            .map(|(index, value)| (index.into(), value))
    }

    /// Returns an iterator over references to the values of the `TaggedVec`.
    pub fn iter_values(&self) -> std::slice::Iter<'_, Value> {
        self.vec.iter()
    }

    /// Returns an iterator over mutable references to the values of the `TaggedVec`.
    pub fn iter_values_mut(&mut self) -> std::slice::IterMut<'_, Value> {
        self.vec.iter_mut()
    }

    /// Returns an iterator over the indices of the `TaggedVec`.
    ///
    /// The `range` specifies which subset of the entries to iterate over.
    /// Iterating over a partial range with this argument is more efficient than iterating over the whole vector and skipping the unwanted entries, because the returned iterator does not support the skip optimisation.
    pub fn iter_indices(
        &self,
        range: impl RangeBounds<Index>,
    ) -> impl DoubleEndedIterator<Item = Index> + ExactSizeIterator
    where
        Index: From<usize> + Copy,
        usize: From<Index>,
    {
        let range = MappedRangeBounds::new(range);
        let start_index_inclusive = match range.start_bound() {
            Bound::Included(index) => *index,
            Bound::Excluded(index) => (*index).checked_add(1).expect("start index overflow"),
            Bound::Unbounded => 0,
        };
        let end_index_exclusive = match range.end_bound() {
            Bound::Included(index) => (*index).checked_add(1).expect("end index overflow"),
            Bound::Excluded(index) => *index,
            Bound::Unbounded => self.vec.len(),
        };

        (start_index_inclusive..end_index_exclusive).map(Into::into)
    }

    /// Consumes the `TaggedVec`, returning an iterator over the entries.
    ///
    /// The `range` specifies which subset of the entries to iterate over.
    /// Iterating over a partial range with this argument is more efficient than iterating over the whole vector and skipping the unwanted entries, because the returned iterator does not support the skip optimisation.
    pub fn into_iter(
        self,
        range: impl RangeBounds<Index>,
    ) -> impl DoubleEndedIterator<Item = (Index, Value)> + ExactSizeIterator
    where
        Index: From<usize> + Copy,
        usize: From<Index>,
    {
        let range = MappedRangeBounds::new(range);
        let start_index_inclusive = match range.start_bound() {
            Bound::Included(index) => *index,
            Bound::Excluded(index) => (*index).checked_add(1).expect("start index overflow"),
            Bound::Unbounded => 0,
        };
        let end_index_exclusive = match range.end_bound() {
            Bound::Included(index) => (*index).checked_add(1).expect("end index overflow"),
            Bound::Excluded(index) => *index,
            Bound::Unbounded => self.vec.len(),
        };

        self.vec
            .into_iter()
            .enumerate()
            .skip(start_index_inclusive)
            .take(end_index_exclusive - start_index_inclusive)
            .map(|(index, value)| (index.into(), value))
    }

    /// Consumes the `TaggedVec`, returning an iterator over the values.
    pub fn into_values_iter(self) -> std::vec::IntoIter<Value> {
        self.vec.into_iter()
    }
}