pull IndexList into crate, get_mut -> get

accounts-db/src/index_list.rs

@@ -0,0 +1,388 @@
+//! A doubly linked list, backed by a vector.
+
+use std::{
+    convert::TryFrom,
+    fmt::{Debug, Formatter},
+    mem,
+    num::NonZeroU32,
+};
+
+/// Vector index for the elements in the list. They are typically not
+/// squential.
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
+pub(crate) struct Index(Option<NonZeroU32>);
+
+impl Index {
+    #[inline]
+    pub(crate) fn new() -> Index {
+        Index(None)
+    }
+    #[inline]
+    /// Returns `true` for a valid index.
+    ///
+    /// A valid index can be used in IndexList method calls.
+    pub(crate) fn is_some(&self) -> bool {
+        self.0.is_some()
+    }
+    #[inline]
+    /// Returns `true` for an invalid index.
+    ///
+    /// An invalid index will always be ignored and have `None` returned from
+    /// any IndexList method call that returns something.
+    pub(crate) fn is_none(&self) -> bool {
+        self.0.is_none()
+    }
+    #[inline]
+    fn get(&self) -> Option<usize> {
+        Some(self.0?.get() as usize - 1)
+    }
+    #[inline]
+    fn set(mut self, index: Option<usize>) -> Self {
+        if let Some(n) = index {
+            if let Ok(num) = NonZeroU32::try_from(n as u32 + 1) {
+                self.0 = Some(num);
+            } else {
+                self.0 = None;
+            }
+        } else {
+            self.0 = None;
+        }
+        self
+    }
+}
+
+impl From<usize> for Index {
+    fn from(index: usize) -> Index {
+        Index::new().set(Some(index))
+    }
+}
+
+#[derive(Clone, Default)]
+struct IndexNode {
+    next: Index,
+    prev: Index,
+}
+
+impl IndexNode {
+    #[inline]
+    fn new() -> IndexNode {
+        IndexNode {
+            next: Index::new(),
+            prev: Index::new(),
+        }
+    }
+    #[inline]
+    fn new_next(&mut self, next: Index) -> Index {
+        mem::replace(&mut self.next, next)
+    }
+    #[inline]
+    fn new_prev(&mut self, prev: Index) -> Index {
+        mem::replace(&mut self.prev, prev)
+    }
+}
+
+#[derive(Clone, Default)]
+struct IndexEnds {
+    head: Index,
+    tail: Index,
+}
+
+impl IndexEnds {
+    #[inline]
+    fn new() -> Self {
+        IndexEnds {
+            head: Index::new(),
+            tail: Index::new(),
+        }
+    }
+    #[inline]
+    fn clear(&mut self) {
+        self.new_both(Index::new());
+    }
+    #[inline]
+    fn is_empty(&self) -> bool {
+        self.head.is_none()
+    }
+    #[inline]
+    fn new_head(&mut self, head: Index) -> Index {
+        mem::replace(&mut self.head, head)
+    }
+    #[inline]
+    fn new_tail(&mut self, tail: Index) -> Index {
+        mem::replace(&mut self.tail, tail)
+    }
+    #[inline]
+    fn new_both(&mut self, both: Index) {
+        self.head = both;
+        self.tail = both;
+    }
+}
+
+/// Doubly-linked list implemented in safe Rust.
+pub(crate) struct IndexList<T> {
+    elems: Vec<Option<T>>,
+    nodes: Vec<IndexNode>,
+    used: IndexEnds,
+    free: IndexEnds,
+    size: usize,
+}
+
+impl<T> Default for IndexList<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T> Debug for IndexList<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "IndexList")?;
+        Ok(())
+    }
+}
+
+impl<T> IndexList<T> {
+    /// Creates a new empty index list.
+    ///
+    /// Example:
+    /// ```rust
+    /// use index_list::IndexList;
+    ///
+    /// let list = IndexList::<u64>::new();
+    /// ```
+    pub(crate) fn new() -> Self {
+        IndexList {
+            elems: Vec::new(),
+            nodes: Vec::new(),
+            used: IndexEnds::new(),
+            free: IndexEnds::new(),
+            size: 0,
+        }
+    }
+    /// Clears the list be removing all elements, making it empty.
+    ///
+    /// Example:
+    /// ```rust
+    /// # use index_list::IndexList;
+    /// # let mut list = IndexList::<u64>::new();
+    /// list.clear();
+    /// assert!(list.is_empty());
+    /// ```
+    #[inline]
+    pub(crate) fn clear(&mut self) {
+        self.elems.clear();
+        self.nodes.clear();
+        self.used.clear();
+        self.free.clear();
+        self.size = 0;
+    }
+    /// Returns `true` if the index is valid.
+    #[inline]
+    pub(crate) fn is_index_used(&self, index: Index) -> bool {
+        self.get(index).is_some()
+    }
+    /// Returns the index of the first element, or `None` if the list is empty.
+    ///
+    /// Example:
+    /// ```rust
+    /// # use index_list::IndexList;
+    /// # let list = IndexList::<u64>::new();
+    /// let index = list.first_index();
+    /// ```
+    #[inline]
+    pub(crate) fn first_index(&self) -> Index {
+        self.used.head
+    }
+    /// Get a reference to the first element data, or `None`.
+    ///
+    /// Example:
+    /// ```rust
+    /// # use index_list::IndexList;
+    /// # let list = IndexList::<u64>::new();
+    /// let data = list.get_first();
+    /// ```
+    #[inline]
+    pub(crate) fn get_first(&self) -> Option<&T> {
+        self.get(self.first_index())
+    }
+    /// Get an immutable reference to the element data at the index, or `None`.
+    ///
+    /// Example:
+    /// ```rust
+    /// # use index_list::IndexList;
+    /// # let list = IndexList::<u64>::new();
+    /// # let index = list.first_index();
+    /// let data = list.get(index);
+    /// ```
+    #[inline]
+    pub(crate) fn get(&self, index: Index) -> Option<&T> {
+        let ndx = index.get().unwrap_or(usize::MAX);
+        self.elems.get(ndx)?.as_ref()
+    }
+    /// Insert a new element at the end.
+    ///
+    /// It is typically not necessary to store the index, as the data will be
+    /// there when walking the list.
+    ///
+    /// Example:
+    /// ```rust
+    /// # use index_list::IndexList;
+    /// # let mut list = IndexList::<u64>::new();
+    /// let index = list.insert_last(42);
+    /// ```
+    pub(crate) fn insert_last(&mut self, elem: T) -> Index {
+        let this = self.new_node(Some(elem));
+        self.linkin_last(this);
+        this
+    }
+    /// Remove the element at the index and return its data.
+    ///
+    /// Example:
+    /// ```rust
+    /// # use index_list::IndexList;
+    /// # let mut list = IndexList::from(&mut vec!["A", "B", "C"]);
+    /// # let mut index = list.first_index();
+    /// # index = list.next_index(index);
+    /// let data = list.remove(index);
+    /// # assert_eq!(data, Some("B"));
+    /// ```
+    pub(crate) fn remove(&mut self, index: Index) -> Option<T> {
+        let elem_opt = self.remove_elem_at_index(index);
+        if elem_opt.is_some() {
+            self.linkout_used(index);
+            self.linkin_free(index);
+        }
+        elem_opt
+    }
+
+    /// Move the element at the index to the end.
+    /// The index remains the same.
+    pub(crate) fn move_to_last(&mut self, index: Index) {
+        if self.is_index_used(index) {
+            // unlink where it is
+            self.linkout_used(index);
+            // insert it as last
+            self.linkin_last(index);
+        }
+    }
+
+    #[inline]
+    fn get_mut_indexnode(&mut self, at: usize) -> &mut IndexNode {
+        &mut self.nodes[at]
+    }
+    #[inline]
+    fn set_prev(&mut self, index: Index, new_prev: Index) -> Index {
+        if let Some(at) = index.get() {
+            self.get_mut_indexnode(at).new_prev(new_prev)
+        } else {
+            index
+        }
+    }
+    #[inline]
+    fn set_next(&mut self, index: Index, new_next: Index) -> Index {
+        if let Some(at) = index.get() {
+            self.get_mut_indexnode(at).new_next(new_next)
+        } else {
+            index
+        }
+    }
+    #[inline]
+    fn insert_elem_at_index(&mut self, this: Index, elem: Option<T>) {
+        if let Some(at) = this.get() {
+            self.elems[at] = elem;
+            self.size += 1;
+        }
+    }
+    #[inline]
+    fn remove_elem_at_index(&mut self, this: Index) -> Option<T> {
+        this.get().and_then(|at| {
+            self.size -= 1;
+            self.elems[at].take()
+        })
+    }
+    fn new_node(&mut self, elem: Option<T>) -> Index {
+        let reuse = self.free.head;
+        if reuse.is_some() {
+            self.insert_elem_at_index(reuse, elem);
+            self.linkout_free(reuse);
+            return reuse;
+        }
+        let pos = self.nodes.len();
+        self.nodes.push(IndexNode::new());
+        self.elems.push(elem);
+        self.size += 1;
+        Index::from(pos)
+    }
+    fn linkin_free(&mut self, this: Index) {
+        debug_assert!(!self.is_index_used(this));
+        let prev = self.free.tail;
+        self.set_next(prev, this);
+        self.set_prev(this, prev);
+        if self.free.is_empty() {
+            self.free.new_both(this);
+        } else {
+            let old_tail = self.free.new_tail(this);
+            debug_assert_eq!(old_tail, prev);
+        }
+    }
+    fn linkin_last(&mut self, this: Index) {
+        debug_assert!(self.is_index_used(this));
+        let prev = self.used.tail;
+        self.set_next(prev, this);
+        self.set_prev(this, prev);
+        if self.used.is_empty() {
+            self.used.new_both(this);
+        } else {
+            let old_tail = self.used.new_tail(this);
+            debug_assert_eq!(old_tail, prev);
+        }
+    }
+    // prev >< this >< next => prev >< next
+    fn linkout_node(&mut self, this: Index) -> (Index, Index) {
+        let next = self.set_next(this, Index::new());
+        let prev = self.set_prev(this, Index::new());
+        let old_prev = self.set_prev(next, prev);
+        if old_prev.is_some() {
+            debug_assert_eq!(old_prev, this);
+        }
+        let old_next = self.set_next(prev, next);
+        if old_next.is_some() {
+            debug_assert_eq!(old_next, this);
+        }
+        (prev, next)
+    }
+    fn linkout_used(&mut self, this: Index) {
+        let (prev, next) = self.linkout_node(this);
+        if next.is_none() {
+            let old_tail = self.used.new_tail(prev);
+            debug_assert_eq!(old_tail, this);
+        }
+        if prev.is_none() {
+            let old_head = self.used.new_head(next);
+            debug_assert_eq!(old_head, this);
+        }
+    }
+    fn linkout_free(&mut self, this: Index) {
+        let (prev, next) = self.linkout_node(this);
+        if next.is_none() {
+            let old_tail = self.free.new_tail(prev);
+            debug_assert_eq!(old_tail, this);
+        }
+        if prev.is_none() {
+            let old_head = self.free.new_head(next);
+            debug_assert_eq!(old_head, this);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use {super::*, std::mem::size_of};
+
+    #[test]
+    fn test_struct_sizes() {
+        assert_eq!(size_of::<Index>(), 4);
+        assert_eq!(size_of::<IndexNode>(), 8);
+        assert_eq!(size_of::<IndexEnds>(), 8);
+        assert_eq!(size_of::<IndexList<u32>>(), 72);
+    }
+}

accounts-db/src/lib.rs

@@ -30,6 +30,7 @@ pub mod contains;
 pub mod epoch_accounts_hash;
 pub mod hardened_unpack;
 pub mod in_mem_accounts_index;
+mod index_list;
 pub mod inline_spl_token;
 pub mod inline_spl_token_2022;
 pub mod nonce_info;