✨ More methods (in particular partialeq and clone)

src/lib.rs

@@ -1,6 +1,21 @@
+#![feature(type_alias_impl_trait)]
+
 use std::cell::{Cell, UnsafeCell};
 use std::fmt::{self, Debug};
-
+use std::ops::{Deref, DerefMut};
+
+///
+/// # Safety
+///
+/// The following invariants are enforced by the code:
+///
+/// - (I) mutable guards (`RefMut`) may only be created if `vec.mut_borrow.is_none()` and `vec.borrows == 0`
+/// - (II) when a mutable guard is created, `vec.mut_borrow` is set to `Some(index)`
+/// - (III) when a mutable guard is dropped, `vec.mut_borrow` may be set back to `None`
+/// - (IV) a mutable reference may only be created if:
+///     - (IV-a) exclusive access to the `VecCell` is guaranteed (`&mut VecCell`)
+///     - (IV-b) it is created from a mutable guard, and the mutable guard's lifetime does not exceed that of the mutable guard
+#[derive(Debug)]
 pub struct VecCell<T> {
     mut_borrow: Cell<Option<usize>>,
     borrows: Cell<usize>,
@@ -41,6 +56,36 @@ impl<T> VecCell<T> {
         self.inner.len()
     }
 
+    #[inline]
+    pub fn capacity(&self) -> usize {
+        self.inner.capacity()
+    }
+
+    #[inline]
+    pub fn reserve(&mut self, additional: usize) {
+        self.inner.reserve(additional);
+    }
+
+    #[inline]
+    pub fn remove(&mut self, index: usize) -> T {
+        self.inner.remove(index).into_inner()
+    }
+
+    #[inline]
+    pub fn swap_remove(&mut self, index: usize) -> T {
+        self.inner.swap_remove(index).into_inner()
+    }
+
+    #[inline]
+    pub fn inner(&self) -> &Vec<UnsafeCell<T>> {
+        &self.inner
+    }
+
+    #[inline]
+    pub fn inner_mut(&mut self) -> &mut Vec<UnsafeCell<T>> {
+        &mut self.inner
+    }
+
     pub fn borrows(&self) -> usize {
         self.borrows.get()
     }
@@ -77,15 +122,113 @@ impl<T> VecCell<T> {
     pub unsafe fn get_mut_unchecked(&self, index: usize) -> &mut T {
         &mut *self.inner.get_unchecked(index).get()
     }
+
+    pub fn iter<'b>(&'b self) -> impl Iterator<Item = VecRef<'b, T>> {
+        self.into_iter()
+    }
+
+    pub fn iter_mut<'b>(&'b mut self) -> impl Iterator<Item = &'b mut T> {
+        self.inner.iter_mut().map(UnsafeCell::get_mut)
+    }
+}
+
+impl<'a, T: 'a> IntoIterator for &'a VecCell<T> {
+    type Item = VecRef<'a, T>;
+    type IntoIter = impl Iterator<Item = Self::Item>;
+
+    /// # Panics
+    ///
+    /// Panics if a value is currently mutably borrowed
+    fn into_iter(self) -> Self::IntoIter {
+        (0..self.len()).map(|index| {
+            self.get(index).expect("An element of VecCell is currently mutably borrowed")
+        })
+    }
+}
+
+impl<T> IntoIterator for VecCell<T> {
+    type Item = T;
+    type IntoIter = impl Iterator<Item = Self::Item>;
+
+    /// # Panics
+    ///
+    /// Panics if a value is currently mutably borrowed
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.into_iter().map(|x| x.into_inner())
+    }
+}
+
+impl<T: Clone> Clone for VecCell<T> {
+    /// # Panics
+    ///
+    /// Panics if a value is currently mutably borrowed
+    fn clone(&self) -> Self {
+        VecCell {
+            inner: self.into_iter().map(|x| UnsafeCell::new((*x).clone())).collect::<Vec<_>>(),
+            mut_borrow: Cell::new(None),
+            borrows: Cell::new(0),
+        }
+    }
+}
+
+impl<T: PartialEq> PartialEq for VecCell<T> {
+    /// # Panics
+    ///
+    /// Panics if a value in `self` or `other` is currently mutably borrowed when it is encountered in the comparison.
+    fn eq(&self, other: &Self) -> bool {
+        if self.len() != other.len() {
+            return false
+        }
+
+        for (s, o) in self.iter().zip(other.iter()) {
+            if *s != *o {
+                return false
+            }
+        }
+
+        true
+    }
+}
+
+impl<T: PartialEq> PartialEq<Vec<T>> for VecCell<T> {
+    /// # Panics
+    ///
+    /// Panics if a value in `self` is currently mutably borrowed when it is encountered in the comparison.
+    fn eq(&self, other: &Vec<T>) -> bool {
+        if self.len() != other.len() {
+            return false
+        }
+
+        for (s, o) in self.iter().zip(other.iter()) {
+            if *s != *o {
+                return false
+            }
+        }
+
+        true
+    }
 }
 
-pub struct VecRef<'a, T> {
+impl<T> From<Vec<T>> for VecCell<T> {
+    fn from(vec: Vec<T>) -> Self {
+        VecCell {
+            inner: vec.into_iter().map(|x| UnsafeCell::new(x)).collect::<Vec<_>>(),
+            mut_borrow: Cell::new(None),
+            borrows: Cell::new(0),
+        }
+    }
+}
+
+pub struct VecRef<'a, T: ?Sized> {
     borrows: &'a Cell<usize>,
     value: &'a T,
 }
 
-impl<'a, T> VecRef<'a, T> {
+impl<'a, T: ?Sized> VecRef<'a, T> {
-    fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self> {
+    fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self>
+    where
+        T: Sized
+    {
         if vec.mut_borrow.get() == Some(index) {
             return None
         }
@@ -104,9 +247,23 @@ impl<'a, T> VecRef<'a, T> {
             }
         })
     }
+
+    pub fn get(&self) -> &T {
+        &*self.value
+    }
+
+    pub fn map<'b, U: ?Sized, F>(original: VecRef<'b, T>, f: F) -> VecRef<'b, U>
+    where
+        F: FnOnce(&T) -> &U
+    {
+        VecRef {
+            value: f(original.value),
+            borrows: original.borrows
+        }
+    }
 }
 
-impl<'a, T> std::ops::Deref for VecRef<'a, T> {
+impl<'a, T: ?Sized> Deref for VecRef<'a, T> {
     type Target = T;
 
     fn deref(&self) -> &Self::Target {
@@ -114,7 +271,7 @@ impl<'a, T> std::ops::Deref for VecRef<'a, T> {
     }
 }
 
-impl<'a, T> Drop for VecRef<'a, T> {
+impl<'a, T: ?Sized> Drop for VecRef<'a, T> {
     #[inline]
     fn drop(&mut self) {
         debug_assert!(self.borrows.get() > 0, "Borrow count was null yet there was still a borrow!");
@@ -122,7 +279,7 @@ impl<'a, T> Drop for VecRef<'a, T> {
     }
 }
 
-impl<'a, T: Debug> Debug for VecRef<'a, T> {
+impl<'a, T: Debug + Sized> Debug for VecRef<'a, T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("VecRef")
             .field(self.value)
@@ -130,13 +287,37 @@ impl<'a, T: Debug> Debug for VecRef<'a, T> {
     }
 }
 
-pub struct VecRefMut<'a, T> {
+impl<'a, T: PartialEq + ?Sized> PartialEq for VecRef<'a, T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.get() == other.get()
+    }
+}
+
+impl<'a, T: PartialEq + ?Sized> PartialEq<T> for VecRef<'a, T> {
+    fn eq(&self, other: &T) -> bool {
+        self.get() == other
+    }
+}
+
+pub struct VecRefMut<'a, T: ?Sized> {
     mut_borrow: &'a Cell<Option<usize>>,
     value: &'a mut T,
 }
 
-impl<'a, T> VecRefMut<'a, T> {
+impl<'a, T: ?Sized> VecRefMut<'a, T> {
-    fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self> {
+    /// # Safety
+    ///
+    /// If this function returns Some(ref), then there are no mutable borrows of ∀x, vec.inner[x]:
+    /// by contradiction, let `B: 'b` be a mutable borrow of lifetime `'b`. By conjunction on (IV):
+    ///     - either `B` had exclusive access, in which case calling `VecCell::borrow_mut` is UB
+    ///     - either `B` was obtained from a guard `VecRefMut<'c>`, in which case `'c: 'b` and `vec.mut_borrow.is_some()`, which contradicts our assertion
+    ///
+    /// - The invariant (I) is upheld by the first assertion.
+    /// - The invariant (II) is upheld by this function, as it sets `vec.mut_borrow` to `Some(index)`.
+    fn new(vec: &'a VecCell<T>, index: usize) -> Option<Self>
+    where
+        T: Sized
+    {
         if vec.borrows.get() > 0 || vec.mut_borrow.get().is_some() {
             return None
         }
@@ -150,29 +331,48 @@ impl<'a, T> VecRefMut<'a, T> {
         Some(Self {
             mut_borrow: &vec.mut_borrow,
             value: unsafe {
-                // SAFETY: there are no mutable borrows of ∀x, vec.inner[x],
-                // and we set vec.mut_borrow to Some(index), guaranteeing no further aliasing
                 vec.get_mut_unchecked(index)
             }
         })
     }
+
+    pub fn get(&self) -> &T {
+        &*self.value
+    }
+
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut *self.value
+    }
+
+    // pub fn map<'b, U: ?Sized, F>(original: VecRefMut<'b, T>, f: F) -> VecRefMut<'b, U>
+    // where
+    //     F: FnOnce(&mut T) -> &mut U
+    // {
+    //     let VecRefMut { value, mut_borrow } = original;
+    //     VecRefMut {
+    //         value: f(value),
+    //         mut_borrow
+    //     }
+    // }
 }
 
-impl<'a, T> std::ops::Deref for VecRefMut<'a, T> {
+impl<'a, T: ?Sized> Deref for VecRefMut<'a, T> {
     type Target = T;
 
+    // SAFETY: Upholds invariant (IV)
     fn deref(&self) -> &Self::Target {
         self.value
     }
 }
 
-impl<'a, T> std::ops::DerefMut for VecRefMut<'a, T> {
+impl<'a, T: ?Sized> DerefMut for VecRefMut<'a, T> {
+    // SAFETY: Upholds invariant (IV)
     fn deref_mut(&mut self) -> &mut Self::Target {
         self.value
     }
 }
 
-impl<'a, T> Drop for VecRefMut<'a, T> {
+impl<'a, T: ?Sized> Drop for VecRefMut<'a, T> {
     #[inline]
     fn drop(&mut self) {
         debug_assert!(self.mut_borrow.get().is_some());
@@ -180,10 +380,141 @@ impl<'a, T> Drop for VecRefMut<'a, T> {
     }
 }
 
-impl<'a, T: Debug> Debug for VecRefMut<'a, T> {
+impl<'a, T: Debug + Sized> Debug for VecRefMut<'a, T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("VecRefMut")
             .field(self.value)
             .finish()
     }
 }
+
+impl<'a, T: PartialEq + ?Sized> PartialEq for VecRefMut<'a, T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.get() == other.get()
+    }
+}
+
+impl<'a, T: PartialEq + ?Sized> PartialEq<T> for VecRefMut<'a, T> {
+    fn eq(&self, other: &T) -> bool {
+        self.get() == other
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_create_vec() {
+        let vec: VecCell<usize> = VecCell::new();
+        assert_eq!(vec.len(), 0);
+        let vec: VecCell<i8> = VecCell::new();
+        assert_eq!(vec.len(), 0);
+        let vec: VecCell<()> = VecCell::new();
+        assert_eq!(vec.len(), 0);
+
+        let vec: VecCell<usize> = VecCell::with_capacity(16);
+        assert_eq!(vec.len(), 0);
+        assert_eq!(vec.capacity(), 16);
+        let vec: VecCell<i8> = VecCell::with_capacity(16);
+        assert_eq!(vec.len(), 0);
+        assert_eq!(vec.capacity(), 16);
+        let vec: VecCell<()> = VecCell::with_capacity(16);
+        assert_eq!(vec.len(), 0);
+        assert_eq!(vec.capacity(), usize::MAX);
+
+
+        let vec: VecCell<usize> = VecCell::with_capacity(0);
+        assert_eq!(vec.len(), 0);
+        assert_eq!(vec.capacity(), 0);
+        let vec: VecCell<i8> = VecCell::with_capacity(0);
+        assert_eq!(vec.len(), 0);
+        assert_eq!(vec.capacity(), 0);
+        let vec: VecCell<()> = VecCell::with_capacity(0);
+        assert_eq!(vec.len(), 0);
+        assert_eq!(vec.capacity(), usize::MAX);
+    }
+
+    #[test]
+    fn test_push() {
+        let mut vec: VecCell<usize> = VecCell::with_capacity(1);
+        vec.push(0);
+        assert_eq!(vec.len(), 1);
+        vec.push(1);
+        assert_eq!(vec.len(), 2);
+        vec.push(2);
+        assert_eq!(vec.len(), 3);
+
+        assert_eq!(vec, vec![0, 1, 2]);
+    }
+
+    #[test]
+    fn test_pop() {
+        let mut vec: VecCell<usize> = VecCell::new();
+        vec.push(1);
+        assert_eq!(vec.len(), 1);
+        vec.push(2);
+        assert_eq!(vec.len(), 2);
+
+        assert_eq!(vec.pop(), Some(2));
+        assert_eq!(vec.len(), 1);
+        assert_eq!(vec.pop(), Some(1));
+        assert_eq!(vec.len(), 0);
+    }
+
+    #[test]
+    fn test_borrow() {
+        let mut vec: VecCell<usize> = VecCell::new();
+        vec.push(1);
+        vec.push(2);
+
+        let mut x = vec.borrow_mut(1).unwrap();
+
+        assert_eq!(vec.get(0).unwrap(), 1);
+        assert_eq!(vec.get(1), None);
+
+        *x = 3;
+
+        std::mem::drop(x);
+
+        assert_eq!(vec.get(1).unwrap(), 3);
+    }
+
+    #[test]
+    fn test_double_borrow() {
+        let mut vec: VecCell<usize> = VecCell::new();
+        vec.push(1);
+        vec.push(2);
+
+        let mut x = vec.borrow_mut(1).unwrap();
+        let y = vec.borrow_mut(0);
+
+        assert!(y.is_none());
+        assert_eq!(vec.mut_borrow(), Some(1));
+        assert!(vec.borrow_mut(1).is_none());
+        assert_eq!(vec.mut_borrow(), Some(1));
+
+        assert_eq!(vec.get(0).unwrap(), 1);
+        assert_eq!(vec.get(1), None);
+
+        *x = 3;
+
+        std::mem::drop(x);
+        std::mem::drop(y);
+
+        assert_eq!(vec.mut_borrow(), None);
+        assert_eq!(vec.get(1).unwrap(), 3);
+    }
+
+    #[test]
+    fn test_out_of_bounds() {
+        let mut vec: VecCell<usize> = VecCell::new();
+
+        assert!(vec.get(0).is_none());
+
+        vec.push(1);
+
+        assert!(vec.get(0).is_some());
+        assert!(vec.get(1).is_none());
+    }
+}