use core::borrow::Borrow;
use core::cmp::Ordering;
use core::fmt::Debug;
use core::hash::{Hash, Hasher};
use core::iter::{FromIterator, Peekable, FusedIterator};
use core::marker::PhantomData;
use core::ops::Bound::{Excluded, Included, Unbounded};
use core::ops::{Index, RangeBounds};
use core::{fmt, intrinsics, mem, ptr};
use super::node::{self, Handle, NodeRef, marker, InsertResult::*, ForceResult::*};
use super::search::{self, SearchResult::*};
use UnderflowResult::*;
use Entry::*;
#[stable(feature = "rust1", since = "1.0.0")]
pub struct BTreeMap<K, V> {
    root: node::Root<K, V>,
    length: usize,
}
#[stable(feature = "btree_drop", since = "1.7.0")]
unsafe impl<#[may_dangle] K, #[may_dangle] V> Drop for BTreeMap<K, V> {
    fn drop(&mut self) {
        unsafe {
            drop(ptr::read(self).into_iter());
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
    fn clone(&self) -> BTreeMap<K, V> {
        fn clone_subtree<'a, K: Clone, V: Clone>(
            node: node::NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>
        ) -> BTreeMap<K, V>
        where K: 'a, V: 'a,
        {
            match node.force() {
                Leaf(leaf) => {
                    let mut out_tree = BTreeMap {
                        root: node::Root::new_leaf(),
                        length: 0,
                    };
                    {
                        let mut out_node = match out_tree.root.as_mut().force() {
                            Leaf(leaf) => leaf,
                            Internal(_) => unreachable!(),
                        };
                        let mut in_edge = leaf.first_edge();
                        while let Ok(kv) = in_edge.right_kv() {
                            let (k, v) = kv.into_kv();
                            in_edge = kv.right_edge();
                            out_node.push(k.clone(), v.clone());
                            out_tree.length += 1;
                        }
                    }
                    out_tree
                }
                Internal(internal) => {
                    let mut out_tree = clone_subtree(internal.first_edge().descend());
                    {
                        let mut out_node = out_tree.root.push_level();
                        let mut in_edge = internal.first_edge();
                        while let Ok(kv) = in_edge.right_kv() {
                            let (k, v) = kv.into_kv();
                            in_edge = kv.right_edge();
                            let k = (*k).clone();
                            let v = (*v).clone();
                            let subtree = clone_subtree(in_edge.descend());
                            
                            
                            let (subroot, sublength) = unsafe {
                                let root = ptr::read(&subtree.root);
                                let length = subtree.length;
                                mem::forget(subtree);
                                (root, length)
                            };
                            out_node.push(k, v, subroot);
                            out_tree.length += 1 + sublength;
                        }
                    }
                    out_tree
                }
            }
        }
        if self.len() == 0 {
            
            
            BTreeMap {
                root: node::Root::shared_empty_root(),
                length: 0,
            }
        } else {
            clone_subtree(self.root.as_ref())
        }
    }
}
impl<K, Q: ?Sized> super::Recover<Q> for BTreeMap<K, ()>
    where K: Borrow<Q> + Ord,
          Q: Ord
{
    type Key = K;
    fn get(&self, key: &Q) -> Option<&K> {
        match search::search_tree(self.root.as_ref(), key) {
            Found(handle) => Some(handle.into_kv().0),
            GoDown(_) => None,
        }
    }
    fn take(&mut self, key: &Q) -> Option<K> {
        match search::search_tree(self.root.as_mut(), key) {
            Found(handle) => {
                Some(OccupiedEntry {
                         handle,
                         length: &mut self.length,
                         _marker: PhantomData,
                     }
                     .remove_kv()
                     .0)
            }
            GoDown(_) => None,
        }
    }
    fn replace(&mut self, key: K) -> Option<K> {
        self.ensure_root_is_owned();
        match search::search_tree::<marker::Mut<'_>, K, (), K>(self.root.as_mut(), &key) {
            Found(handle) => Some(mem::replace(handle.into_kv_mut().0, key)),
            GoDown(handle) => {
                VacantEntry {
                    key,
                    handle,
                    length: &mut self.length,
                    _marker: PhantomData,
                }
                .insert(());
                None
            }
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Iter<'a, K: 'a, V: 'a> {
    range: Range<'a, K, V>,
    length: usize,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Iter<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_list().entries(self.clone()).finish()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Debug)]
pub struct IterMut<'a, K: 'a, V: 'a> {
    range: RangeMut<'a, K, V>,
    length: usize,
}
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IntoIter<K, V> {
    front: Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>,
    back: Handle<NodeRef<marker::Owned, K, V, marker::Leaf>, marker::Edge>,
    length: usize,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IntoIter<K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let range = Range {
            front: self.front.reborrow(),
            back: self.back.reborrow(),
        };
        f.debug_list().entries(range).finish()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Keys<'a, K: 'a, V: 'a> {
    inner: Iter<'a, K, V>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<K: fmt::Debug, V> fmt::Debug for Keys<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_list().entries(self.clone()).finish()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Values<'a, K: 'a, V: 'a> {
    inner: Iter<'a, K, V>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<K, V: fmt::Debug> fmt::Debug for Values<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_list().entries(self.clone()).finish()
    }
}
#[stable(feature = "map_values_mut", since = "1.10.0")]
#[derive(Debug)]
pub struct ValuesMut<'a, K: 'a, V: 'a> {
    inner: IterMut<'a, K, V>,
}
#[stable(feature = "btree_range", since = "1.17.0")]
pub struct Range<'a, K: 'a, V: 'a> {
    front: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
    back: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Range<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_list().entries(self.clone()).finish()
    }
}
#[stable(feature = "btree_range", since = "1.17.0")]
pub struct RangeMut<'a, K: 'a, V: 'a> {
    front: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
    back: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
    
    _marker: PhantomData<&'a mut (K, V)>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for RangeMut<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let range = Range {
            front: self.front.reborrow(),
            back: self.back.reborrow(),
        };
        f.debug_list().entries(range).finish()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
pub enum Entry<'a, K: 'a, V: 'a> {
    
    #[stable(feature = "rust1", since = "1.0.0")]
    Vacant(#[stable(feature = "rust1", since = "1.0.0")]
           VacantEntry<'a, K, V>),
    
    #[stable(feature = "rust1", since = "1.0.0")]
    Occupied(#[stable(feature = "rust1", since = "1.0.0")]
             OccupiedEntry<'a, K, V>),
}
#[stable(feature= "debug_btree_map", since = "1.12.0")]
impl<K: Debug + Ord, V: Debug> Debug for Entry<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match *self {
            Vacant(ref v) => f.debug_tuple("Entry")
                              .field(v)
                              .finish(),
            Occupied(ref o) => f.debug_tuple("Entry")
                                .field(o)
                                .finish(),
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
pub struct VacantEntry<'a, K: 'a, V: 'a> {
    key: K,
    handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
    length: &'a mut usize,
    
    _marker: PhantomData<&'a mut (K, V)>,
}
#[stable(feature= "debug_btree_map", since = "1.12.0")]
impl<K: Debug + Ord, V> Debug for VacantEntry<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("VacantEntry")
         .field(self.key())
         .finish()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
pub struct OccupiedEntry<'a, K: 'a, V: 'a> {
    handle: Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::KV>,
    length: &'a mut usize,
    
    _marker: PhantomData<&'a mut (K, V)>,
}
#[stable(feature= "debug_btree_map", since = "1.12.0")]
impl<K: Debug + Ord, V: Debug> Debug for OccupiedEntry<'_, K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("OccupiedEntry")
         .field("key", self.key())
         .field("value", self.get())
         .finish()
    }
}
struct MergeIter<K, V, I: Iterator<Item = (K, V)>> {
    left: Peekable<I>,
    right: Peekable<I>,
}
impl<K: Ord, V> BTreeMap<K, V> {
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn new() -> BTreeMap<K, V> {
        BTreeMap {
            root: node::Root::shared_empty_root(),
            length: 0,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn clear(&mut self) {
        *self = BTreeMap::new();
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn get<Q: ?Sized>(&self, key: &Q) -> Option<&V>
        where K: Borrow<Q>,
              Q: Ord
    {
        match search::search_tree(self.root.as_ref(), key) {
            Found(handle) => Some(handle.into_kv().1),
            GoDown(_) => None,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[unstable(feature = "map_get_key_value", issue = "49347")]
    pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)>
        where K: Borrow<Q>,
              Q: Ord
    {
        match search::search_tree(self.root.as_ref(), k) {
            Found(handle) => Some(handle.into_kv()),
            GoDown(_) => None,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn contains_key<Q: ?Sized>(&self, key: &Q) -> bool
        where K: Borrow<Q>,
              Q: Ord
    {
        self.get(key).is_some()
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn get_mut<Q: ?Sized>(&mut self, key: &Q) -> Option<&mut V>
        where K: Borrow<Q>,
              Q: Ord
    {
        match search::search_tree(self.root.as_mut(), key) {
            Found(handle) => Some(handle.into_kv_mut().1),
            GoDown(_) => None,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn insert(&mut self, key: K, value: V) -> Option<V> {
        match self.entry(key) {
            Occupied(mut entry) => Some(entry.insert(value)),
            Vacant(entry) => {
                entry.insert(value);
                None
            }
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn remove<Q: ?Sized>(&mut self, key: &Q) -> Option<V>
        where K: Borrow<Q>,
              Q: Ord
    {
        match search::search_tree(self.root.as_mut(), key) {
            Found(handle) => {
                Some(OccupiedEntry {
                         handle,
                         length: &mut self.length,
                         _marker: PhantomData,
                     }
                     .remove())
            }
            GoDown(_) => None,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "btree_append", since = "1.11.0")]
    pub fn append(&mut self, other: &mut Self) {
        
        if other.len() == 0 {
            return;
        }
        
        if self.len() == 0 {
            mem::swap(self, other);
            return;
        }
        
        let self_iter = mem::replace(self, BTreeMap::new()).into_iter();
        let other_iter = mem::replace(other, BTreeMap::new()).into_iter();
        let iter = MergeIter {
            left: self_iter.peekable(),
            right: other_iter.peekable(),
        };
        
        self.from_sorted_iter(iter);
        self.fix_right_edge();
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "btree_range", since = "1.17.0")]
    pub fn range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V>
        where T: Ord, K: Borrow<T>, R: RangeBounds<T>
    {
        let root1 = self.root.as_ref();
        let root2 = self.root.as_ref();
        let (f, b) = range_search(root1, root2, range);
        Range { front: f, back: b}
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "btree_range", since = "1.17.0")]
    pub fn range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<'_, K, V>
        where T: Ord, K: Borrow<T>, R: RangeBounds<T>
    {
        let root1 = self.root.as_mut();
        let root2 = unsafe { ptr::read(&root1) };
        let (f, b) = range_search(root1, root2, range);
        RangeMut {
            front: f,
            back: b,
            _marker: PhantomData,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
        
        self.ensure_root_is_owned();
        match search::search_tree(self.root.as_mut(), &key) {
            Found(handle) => {
                Occupied(OccupiedEntry {
                    handle,
                    length: &mut self.length,
                    _marker: PhantomData,
                })
            }
            GoDown(handle) => {
                Vacant(VacantEntry {
                    key,
                    handle,
                    length: &mut self.length,
                    _marker: PhantomData,
                })
            }
        }
    }
    fn from_sorted_iter<I: Iterator<Item = (K, V)>>(&mut self, iter: I) {
        self.ensure_root_is_owned();
        let mut cur_node = last_leaf_edge(self.root.as_mut()).into_node();
        
        for (key, value) in iter {
            
            if cur_node.len() < node::CAPACITY {
                cur_node.push(key, value);
            } else {
                
                let mut open_node;
                let mut test_node = cur_node.forget_type();
                loop {
                    match test_node.ascend() {
                        Ok(parent) => {
                            let parent = parent.into_node();
                            if parent.len() < node::CAPACITY {
                                
                                open_node = parent;
                                break;
                            } else {
                                
                                test_node = parent.forget_type();
                            }
                        }
                        Err(node) => {
                            
                            open_node = node.into_root_mut().push_level();
                            break;
                        }
                    }
                }
                
                let tree_height = open_node.height() - 1;
                let mut right_tree = node::Root::new_leaf();
                for _ in 0..tree_height {
                    right_tree.push_level();
                }
                open_node.push(key, value, right_tree);
                
                cur_node = last_leaf_edge(open_node.forget_type()).into_node();
            }
            self.length += 1;
        }
    }
    fn fix_right_edge(&mut self) {
        
        let mut cur_node = self.root.as_mut();
        while let Internal(internal) = cur_node.force() {
            
            let mut last_edge = internal.last_edge();
            let right_child_len = last_edge.reborrow().descend().len();
            if right_child_len < node::MIN_LEN {
                
                let mut last_kv = match last_edge.left_kv() {
                    Ok(left) => left,
                    Err(_) => unreachable!(),
                };
                last_kv.bulk_steal_left(node::MIN_LEN - right_child_len);
                last_edge = last_kv.right_edge();
            }
            
            cur_node = last_edge.descend();
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "btree_split_off", since = "1.11.0")]
    pub fn split_off<Q: ?Sized + Ord>(&mut self, key: &Q) -> Self
        where K: Borrow<Q>
    {
        if self.is_empty() {
            return Self::new();
        }
        let total_num = self.len();
        let mut right = Self::new();
        right.root = node::Root::new_leaf();
        for _ in 0..(self.root.as_ref().height()) {
            right.root.push_level();
        }
        {
            let mut left_node = self.root.as_mut();
            let mut right_node = right.root.as_mut();
            loop {
                let mut split_edge = match search::search_node(left_node, key) {
                    
                    Found(handle) => handle.left_edge(),
                    GoDown(handle) => handle,
                };
                split_edge.move_suffix(&mut right_node);
                match (split_edge.force(), right_node.force()) {
                    (Internal(edge), Internal(node)) => {
                        left_node = edge.descend();
                        right_node = node.first_edge().descend();
                    }
                    (Leaf(_), Leaf(_)) => {
                        break;
                    }
                    _ => {
                        unreachable!();
                    }
                }
            }
        }
        self.fix_right_border();
        right.fix_left_border();
        if self.root.as_ref().height() < right.root.as_ref().height() {
            self.recalc_length();
            right.length = total_num - self.len();
        } else {
            right.recalc_length();
            self.length = total_num - right.len();
        }
        right
    }
    
    fn recalc_length(&mut self) {
        fn dfs<'a, K, V>(
            node: NodeRef<marker::Immut<'a>, K, V, marker::LeafOrInternal>
        ) -> usize
        where K: 'a, V: 'a
        {
            let mut res = node.len();
            if let Internal(node) = node.force() {
                let mut edge = node.first_edge();
                loop {
                    res += dfs(edge.reborrow().descend());
                    match edge.right_kv() {
                        Ok(right_kv) => {
                            edge = right_kv.right_edge();
                        }
                        Err(_) => {
                            break;
                        }
                    }
                }
            }
            res
        }
        self.length = dfs(self.root.as_ref());
    }
    
    fn fix_top(&mut self) {
        loop {
            {
                let node = self.root.as_ref();
                if node.height() == 0 || node.len() > 0 {
                    break;
                }
            }
            self.root.pop_level();
        }
    }
    fn fix_right_border(&mut self) {
        self.fix_top();
        {
            let mut cur_node = self.root.as_mut();
            while let Internal(node) = cur_node.force() {
                let mut last_kv = node.last_kv();
                if last_kv.can_merge() {
                    cur_node = last_kv.merge().descend();
                } else {
                    let right_len = last_kv.reborrow().right_edge().descend().len();
                    
                    if right_len < node::MIN_LEN + 1 {
                        last_kv.bulk_steal_left(node::MIN_LEN + 1 - right_len);
                    }
                    cur_node = last_kv.right_edge().descend();
                }
            }
        }
        self.fix_top();
    }
    
    fn fix_left_border(&mut self) {
        self.fix_top();
        {
            let mut cur_node = self.root.as_mut();
            while let Internal(node) = cur_node.force() {
                let mut first_kv = node.first_kv();
                if first_kv.can_merge() {
                    cur_node = first_kv.merge().descend();
                } else {
                    let left_len = first_kv.reborrow().left_edge().descend().len();
                    if left_len < node::MIN_LEN + 1 {
                        first_kv.bulk_steal_right(node::MIN_LEN + 1 - left_len);
                    }
                    cur_node = first_kv.left_edge().descend();
                }
            }
        }
        self.fix_top();
    }
    
    fn ensure_root_is_owned(&mut self) {
        if self.root.is_shared_root() {
            self.root = node::Root::new_leaf();
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K: 'a, V: 'a> IntoIterator for &'a BTreeMap<K, V> {
    type Item = (&'a K, &'a V);
    type IntoIter = Iter<'a, K, V>;
    fn into_iter(self) -> Iter<'a, K, V> {
        self.iter()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
    type Item = (&'a K, &'a V);
    fn next(&mut self) -> Option<(&'a K, &'a V)> {
        if self.length == 0 {
            None
        } else {
            self.length -= 1;
            unsafe { Some(self.range.next_unchecked()) }
        }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.length, Some(self.length))
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for Iter<'_, K, V> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Iter<'a, K, V> {
    fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
        if self.length == 0 {
            None
        } else {
            self.length -= 1;
            unsafe { Some(self.range.next_back_unchecked()) }
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
    fn len(&self) -> usize {
        self.length
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> Clone for Iter<'_, K, V> {
    fn clone(&self) -> Self {
        Iter {
            range: self.range.clone(),
            length: self.length,
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K: 'a, V: 'a> IntoIterator for &'a mut BTreeMap<K, V> {
    type Item = (&'a K, &'a mut V);
    type IntoIter = IterMut<'a, K, V>;
    fn into_iter(self) -> IterMut<'a, K, V> {
        self.iter_mut()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
    type Item = (&'a K, &'a mut V);
    fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
        if self.length == 0 {
            None
        } else {
            self.length -= 1;
            unsafe { Some(self.range.next_unchecked()) }
        }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.length, Some(self.length))
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K: 'a, V: 'a> DoubleEndedIterator for IterMut<'a, K, V> {
    fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
        if self.length == 0 {
            None
        } else {
            self.length -= 1;
            unsafe { Some(self.range.next_back_unchecked()) }
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
    fn len(&self) -> usize {
        self.length
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for IterMut<'_, K, V> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> IntoIterator for BTreeMap<K, V> {
    type Item = (K, V);
    type IntoIter = IntoIter<K, V>;
    fn into_iter(self) -> IntoIter<K, V> {
        let root1 = unsafe { ptr::read(&self.root).into_ref() };
        let root2 = unsafe { ptr::read(&self.root).into_ref() };
        let len = self.length;
        mem::forget(self);
        IntoIter {
            front: first_leaf_edge(root1),
            back: last_leaf_edge(root2),
            length: len,
        }
    }
}
#[stable(feature = "btree_drop", since = "1.7.0")]
impl<K, V> Drop for IntoIter<K, V> {
    fn drop(&mut self) {
        self.for_each(drop);
        unsafe {
            let leaf_node = ptr::read(&self.front).into_node();
            if leaf_node.is_shared_root() {
                return;
            }
            if let Some(first_parent) = leaf_node.deallocate_and_ascend() {
                let mut cur_node = first_parent.into_node();
                while let Some(parent) = cur_node.deallocate_and_ascend() {
                    cur_node = parent.into_node()
                }
            }
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> Iterator for IntoIter<K, V> {
    type Item = (K, V);
    fn next(&mut self) -> Option<(K, V)> {
        if self.length == 0 {
            return None;
        } else {
            self.length -= 1;
        }
        let handle = unsafe { ptr::read(&self.front) };
        let mut cur_handle = match handle.right_kv() {
            Ok(kv) => {
                let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
                let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
                self.front = kv.right_edge();
                return Some((k, v));
            }
            Err(last_edge) => unsafe {
                unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
            },
        };
        loop {
            match cur_handle.right_kv() {
                Ok(kv) => {
                    let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
                    let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
                    self.front = first_leaf_edge(kv.right_edge().descend());
                    return Some((k, v));
                }
                Err(last_edge) => unsafe {
                    cur_handle = unwrap_unchecked(last_edge.into_node().deallocate_and_ascend());
                },
            }
        }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.length, Some(self.length))
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
    fn next_back(&mut self) -> Option<(K, V)> {
        if self.length == 0 {
            return None;
        } else {
            self.length -= 1;
        }
        let handle = unsafe { ptr::read(&self.back) };
        let mut cur_handle = match handle.left_kv() {
            Ok(kv) => {
                let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
                let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
                self.back = kv.left_edge();
                return Some((k, v));
            }
            Err(last_edge) => unsafe {
                unwrap_unchecked(last_edge.into_node().deallocate_and_ascend())
            },
        };
        loop {
            match cur_handle.left_kv() {
                Ok(kv) => {
                    let k = unsafe { ptr::read(kv.reborrow().into_kv().0) };
                    let v = unsafe { ptr::read(kv.reborrow().into_kv().1) };
                    self.back = last_leaf_edge(kv.left_edge().descend());
                    return Some((k, v));
                }
                Err(last_edge) => unsafe {
                    cur_handle = unwrap_unchecked(last_edge.into_node().deallocate_and_ascend());
                },
            }
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> ExactSizeIterator for IntoIter<K, V> {
    fn len(&self) -> usize {
        self.length
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for IntoIter<K, V> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K, V> Iterator for Keys<'a, K, V> {
    type Item = &'a K;
    fn next(&mut self) -> Option<&'a K> {
        self.inner.next().map(|(k, _)| k)
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.inner.size_hint()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
    fn next_back(&mut self) -> Option<&'a K> {
        self.inner.next_back().map(|(k, _)| k)
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
    fn len(&self) -> usize {
        self.inner.len()
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for Keys<'_, K, V> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> Clone for Keys<'_, K, V> {
    fn clone(&self) -> Self {
        Keys { inner: self.inner.clone() }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K, V> Iterator for Values<'a, K, V> {
    type Item = &'a V;
    fn next(&mut self) -> Option<&'a V> {
        self.inner.next().map(|(_, v)| v)
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.inner.size_hint()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
    fn next_back(&mut self) -> Option<&'a V> {
        self.inner.next_back().map(|(_, v)| v)
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> ExactSizeIterator for Values<'_, K, V> {
    fn len(&self) -> usize {
        self.inner.len()
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for Values<'_, K, V> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K, V> Clone for Values<'_, K, V> {
    fn clone(&self) -> Self {
        Values { inner: self.inner.clone() }
    }
}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> Iterator for Range<'a, K, V> {
    type Item = (&'a K, &'a V);
    fn next(&mut self) -> Option<(&'a K, &'a V)> {
        if self.front == self.back {
            None
        } else {
            unsafe { Some(self.next_unchecked()) }
        }
    }
}
#[stable(feature = "map_values_mut", since = "1.10.0")]
impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
    type Item = &'a mut V;
    fn next(&mut self) -> Option<&'a mut V> {
        self.inner.next().map(|(_, v)| v)
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.inner.size_hint()
    }
}
#[stable(feature = "map_values_mut", since = "1.10.0")]
impl<'a, K, V> DoubleEndedIterator for ValuesMut<'a, K, V> {
    fn next_back(&mut self) -> Option<&'a mut V> {
        self.inner.next_back().map(|(_, v)| v)
    }
}
#[stable(feature = "map_values_mut", since = "1.10.0")]
impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
    fn len(&self) -> usize {
        self.inner.len()
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
impl<'a, K, V> Range<'a, K, V> {
    unsafe fn next_unchecked(&mut self) -> (&'a K, &'a V) {
        let handle = self.front;
        let mut cur_handle = match handle.right_kv() {
            Ok(kv) => {
                let ret = kv.into_kv();
                self.front = kv.right_edge();
                return ret;
            }
            Err(last_edge) => {
                let next_level = last_edge.into_node().ascend().ok();
                unwrap_unchecked(next_level)
            }
        };
        loop {
            match cur_handle.right_kv() {
                Ok(kv) => {
                    let ret = kv.into_kv();
                    self.front = first_leaf_edge(kv.right_edge().descend());
                    return ret;
                }
                Err(last_edge) => {
                    let next_level = last_edge.into_node().ascend().ok();
                    cur_handle = unwrap_unchecked(next_level);
                }
            }
        }
    }
}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> DoubleEndedIterator for Range<'a, K, V> {
    fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
        if self.front == self.back {
            None
        } else {
            unsafe { Some(self.next_back_unchecked()) }
        }
    }
}
impl<'a, K, V> Range<'a, K, V> {
    unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a V) {
        let handle = self.back;
        let mut cur_handle = match handle.left_kv() {
            Ok(kv) => {
                let ret = kv.into_kv();
                self.back = kv.left_edge();
                return ret;
            }
            Err(last_edge) => {
                let next_level = last_edge.into_node().ascend().ok();
                unwrap_unchecked(next_level)
            }
        };
        loop {
            match cur_handle.left_kv() {
                Ok(kv) => {
                    let ret = kv.into_kv();
                    self.back = last_leaf_edge(kv.left_edge().descend());
                    return ret;
                }
                Err(last_edge) => {
                    let next_level = last_edge.into_node().ascend().ok();
                    cur_handle = unwrap_unchecked(next_level);
                }
            }
        }
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for Range<'_, K, V> {}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<K, V> Clone for Range<'_, K, V> {
    fn clone(&self) -> Self {
        Range {
            front: self.front,
            back: self.back,
        }
    }
}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
    type Item = (&'a K, &'a mut V);
    fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
        if self.front == self.back {
            None
        } else {
            unsafe { Some(self.next_unchecked()) }
        }
    }
}
impl<'a, K, V> RangeMut<'a, K, V> {
    unsafe fn next_unchecked(&mut self) -> (&'a K, &'a mut V) {
        let handle = ptr::read(&self.front);
        let mut cur_handle = match handle.right_kv() {
            Ok(kv) => {
                self.front = ptr::read(&kv).right_edge();
                
                
                let (k, v) = kv.into_kv_mut();
                return (k, v); 
            }
            Err(last_edge) => {
                let next_level = last_edge.into_node().ascend().ok();
                unwrap_unchecked(next_level)
            }
        };
        loop {
            match cur_handle.right_kv() {
                Ok(kv) => {
                    self.front = first_leaf_edge(ptr::read(&kv).right_edge().descend());
                    
                    
                    let (k, v) = kv.into_kv_mut();
                    return (k, v); 
                }
                Err(last_edge) => {
                    let next_level = last_edge.into_node().ascend().ok();
                    cur_handle = unwrap_unchecked(next_level);
                }
            }
        }
    }
}
#[stable(feature = "btree_range", since = "1.17.0")]
impl<'a, K, V> DoubleEndedIterator for RangeMut<'a, K, V> {
    fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> {
        if self.front == self.back {
            None
        } else {
            unsafe { Some(self.next_back_unchecked()) }
        }
    }
}
#[stable(feature = "fused", since = "1.26.0")]
impl<K, V> FusedIterator for RangeMut<'_, K, V> {}
impl<'a, K, V> RangeMut<'a, K, V> {
    unsafe fn next_back_unchecked(&mut self) -> (&'a K, &'a mut V) {
        let handle = ptr::read(&self.back);
        let mut cur_handle = match handle.left_kv() {
            Ok(kv) => {
                self.back = ptr::read(&kv).left_edge();
                
                
                let (k, v) = kv.into_kv_mut();
                return (k, v); 
            }
            Err(last_edge) => {
                let next_level = last_edge.into_node().ascend().ok();
                unwrap_unchecked(next_level)
            }
        };
        loop {
            match cur_handle.left_kv() {
                Ok(kv) => {
                    self.back = last_leaf_edge(ptr::read(&kv).left_edge().descend());
                    
                    
                    let (k, v) = kv.into_kv_mut();
                    return (k, v); 
                }
                Err(last_edge) => {
                    let next_level = last_edge.into_node().ascend().ok();
                    cur_handle = unwrap_unchecked(next_level);
                }
            }
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
    fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
        let mut map = BTreeMap::new();
        map.extend(iter);
        map
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
    #[inline]
    fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
        for (k, v) in iter {
            self.insert(k, v);
        }
    }
}
#[stable(feature = "extend_ref", since = "1.2.0")]
impl<'a, K: Ord + Copy, V: Copy> Extend<(&'a K, &'a V)> for BTreeMap<K, V> {
    fn extend<I: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: I) {
        self.extend(iter.into_iter().map(|(&key, &value)| (key, value)));
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        for elt in self {
            elt.hash(state);
        }
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Ord, V> Default for BTreeMap<K, V> {
    
    fn default() -> BTreeMap<K, V> {
        BTreeMap::new()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: PartialEq, V: PartialEq> PartialEq for BTreeMap<K, V> {
    fn eq(&self, other: &BTreeMap<K, V>) -> bool {
        self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
    #[inline]
    fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
        self.iter().partial_cmp(other.iter())
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
    #[inline]
    fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
        self.iter().cmp(other.iter())
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Debug, V: Debug> Debug for BTreeMap<K, V> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_map().entries(self.iter()).finish()
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<K: Ord, Q: ?Sized, V> Index<&Q> for BTreeMap<K, V>
    where K: Borrow<Q>,
          Q: Ord
{
    type Output = V;
    
    
    
    
    
    #[inline]
    fn index(&self, key: &Q) -> &V {
        self.get(key).expect("no entry found for key")
    }
}
fn first_leaf_edge<BorrowType, K, V>
    (mut node: NodeRef<BorrowType, K, V, marker::LeafOrInternal>)
     -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
    loop {
        match node.force() {
            Leaf(leaf) => return leaf.first_edge(),
            Internal(internal) => {
                node = internal.first_edge().descend();
            }
        }
    }
}
fn last_leaf_edge<BorrowType, K, V>
    (mut node: NodeRef<BorrowType, K, V, marker::LeafOrInternal>)
     -> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
    loop {
        match node.force() {
            Leaf(leaf) => return leaf.last_edge(),
            Internal(internal) => {
                node = internal.last_edge().descend();
            }
        }
    }
}
fn range_search<BorrowType, K, V, Q: ?Sized, R: RangeBounds<Q>>(
    root1: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
    root2: NodeRef<BorrowType, K, V, marker::LeafOrInternal>,
    range: R
)-> (Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>,
     Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge>)
        where Q: Ord, K: Borrow<Q>
{
    match (range.start_bound(), range.end_bound()) {
        (Excluded(s), Excluded(e)) if s==e =>
            panic!("range start and end are equal and excluded in BTreeMap"),
        (Included(s), Included(e)) |
        (Included(s), Excluded(e)) |
        (Excluded(s), Included(e)) |
        (Excluded(s), Excluded(e)) if s>e =>
            panic!("range start is greater than range end in BTreeMap"),
        _ => {},
    };
    let mut min_node = root1;
    let mut max_node = root2;
    let mut min_found = false;
    let mut max_found = false;
    let mut diverged = false;
    loop {
        let min_edge = match (min_found, range.start_bound()) {
            (false, Included(key)) => match search::search_linear(&min_node, key) {
                (i, true) => { min_found = true; i },
                (i, false) => i,
            },
            (false, Excluded(key)) => match search::search_linear(&min_node, key) {
                (i, true) => { min_found = true; i+1 },
                (i, false) => i,
            },
            (_, Unbounded) => 0,
            (true, Included(_)) => min_node.keys().len(),
            (true, Excluded(_)) => 0,
        };
        let max_edge = match (max_found, range.end_bound()) {
            (false, Included(key)) => match search::search_linear(&max_node, key) {
                (i, true) => { max_found = true; i+1 },
                (i, false) => i,
            },
            (false, Excluded(key)) => match search::search_linear(&max_node, key) {
                (i, true) => { max_found = true; i },
                (i, false) => i,
            },
            (_, Unbounded) => max_node.keys().len(),
            (true, Included(_)) => 0,
            (true, Excluded(_)) => max_node.keys().len(),
        };
        if !diverged {
            if max_edge < min_edge { panic!("Ord is ill-defined in BTreeMap range") }
            if min_edge != max_edge { diverged = true; }
        }
        let front = Handle::new_edge(min_node, min_edge);
        let back = Handle::new_edge(max_node, max_edge);
        match (front.force(), back.force()) {
            (Leaf(f), Leaf(b)) => {
                return (f, b);
            },
            (Internal(min_int), Internal(max_int)) => {
                min_node = min_int.descend();
                max_node = max_int.descend();
            },
            _ => unreachable!("BTreeMap has different depths"),
        };
    }
}
#[inline(always)]
unsafe fn unwrap_unchecked<T>(val: Option<T>) -> T {
    val.unwrap_or_else(|| {
        if cfg!(debug_assertions) {
            panic!("'unchecked' unwrap on None in BTreeMap");
        } else {
            intrinsics::unreachable();
        }
    })
}
impl<K, V> BTreeMap<K, V> {
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn iter(&self) -> Iter<'_, K, V> {
        Iter {
            range: Range {
                front: first_leaf_edge(self.root.as_ref()),
                back: last_leaf_edge(self.root.as_ref()),
            },
            length: self.length,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
        let root1 = self.root.as_mut();
        let root2 = unsafe { ptr::read(&root1) };
        IterMut {
            range: RangeMut {
                front: first_leaf_edge(root1),
                back: last_leaf_edge(root2),
                _marker: PhantomData,
            },
            length: self.length,
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
        Keys { inner: self.iter() }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn values<'a>(&'a self) -> Values<'a, K, V> {
        Values { inner: self.iter() }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "map_values_mut", since = "1.10.0")]
    pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
        ValuesMut { inner: self.iter_mut() }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn len(&self) -> usize {
        self.length
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }
}
impl<'a, K: Ord, V> Entry<'a, K, V> {
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn or_insert(self, default: V) -> &'a mut V {
        match self {
            Occupied(entry) => entry.into_mut(),
            Vacant(entry) => entry.insert(default),
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V {
        match self {
            Occupied(entry) => entry.into_mut(),
            Vacant(entry) => entry.insert(default()),
        }
    }
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "map_entry_keys", since = "1.10.0")]
    pub fn key(&self) -> &K {
        match *self {
            Occupied(ref entry) => entry.key(),
            Vacant(ref entry) => entry.key(),
        }
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "entry_and_modify", since = "1.26.0")]
    pub fn and_modify<F>(self, f: F) -> Self
        where F: FnOnce(&mut V)
    {
        match self {
            Occupied(mut entry) => {
                f(entry.get_mut());
                Occupied(entry)
            },
            Vacant(entry) => Vacant(entry),
        }
    }
}
impl<'a, K: Ord, V: Default> Entry<'a, K, V> {
    #[stable(feature = "entry_or_default", since = "1.28.0")]
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    pub fn or_default(self) -> &'a mut V {
        match self {
            Occupied(entry) => entry.into_mut(),
            Vacant(entry) => entry.insert(Default::default()),
        }
    }
}
impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "map_entry_keys", since = "1.10.0")]
    pub fn key(&self) -> &K {
        &self.key
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
    pub fn into_key(self) -> K {
        self.key
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn insert(self, value: V) -> &'a mut V {
        *self.length += 1;
        let out_ptr;
        let mut ins_k;
        let mut ins_v;
        let mut ins_edge;
        let mut cur_parent = match self.handle.insert(self.key, value) {
            (Fit(handle), _) => return handle.into_kv_mut().1,
            (Split(left, k, v, right), ptr) => {
                ins_k = k;
                ins_v = v;
                ins_edge = right;
                out_ptr = ptr;
                left.ascend().map_err(|n| n.into_root_mut())
            }
        };
        loop {
            match cur_parent {
                Ok(parent) => {
                    match parent.insert(ins_k, ins_v, ins_edge) {
                        Fit(_) => return unsafe { &mut *out_ptr },
                        Split(left, k, v, right) => {
                            ins_k = k;
                            ins_v = v;
                            ins_edge = right;
                            cur_parent = left.ascend().map_err(|n| n.into_root_mut());
                        }
                    }
                }
                Err(root) => {
                    root.push_level().push(ins_k, ins_v, ins_edge);
                    return unsafe { &mut *out_ptr };
                }
            }
        }
    }
}
impl<'a, K: Ord, V> OccupiedEntry<'a, K, V> {
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "map_entry_keys", since = "1.10.0")]
    pub fn key(&self) -> &K {
        self.handle.reborrow().into_kv().0
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "map_entry_recover_keys2", since = "1.12.0")]
    pub fn remove_entry(self) -> (K, V) {
        self.remove_kv()
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn get(&self) -> &V {
        self.handle.reborrow().into_kv().1
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn get_mut(&mut self) -> &mut V {
        self.handle.kv_mut().1
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn into_mut(self) -> &'a mut V {
        self.handle.into_kv_mut().1
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn insert(&mut self, value: V) -> V {
        mem::replace(self.get_mut(), value)
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    #[stable(feature = "rust1", since = "1.0.0")]
    pub fn remove(self) -> V {
        self.remove_kv().1
    }
    fn remove_kv(self) -> (K, V) {
        *self.length -= 1;
        let (small_leaf, old_key, old_val) = match self.handle.force() {
            Leaf(leaf) => {
                let (hole, old_key, old_val) = leaf.remove();
                (hole.into_node(), old_key, old_val)
            }
            Internal(mut internal) => {
                let key_loc = internal.kv_mut().0 as *mut K;
                let val_loc = internal.kv_mut().1 as *mut V;
                let to_remove = first_leaf_edge(internal.right_edge().descend()).right_kv().ok();
                let to_remove = unsafe { unwrap_unchecked(to_remove) };
                let (hole, key, val) = to_remove.remove();
                let old_key = unsafe { mem::replace(&mut *key_loc, key) };
                let old_val = unsafe { mem::replace(&mut *val_loc, val) };
                (hole.into_node(), old_key, old_val)
            }
        };
        
        let mut cur_node = small_leaf.forget_type();
        while cur_node.len() < node::CAPACITY / 2 {
            match handle_underfull_node(cur_node) {
                AtRoot => break,
                EmptyParent(_) => unreachable!(),
                Merged(parent) => {
                    if parent.len() == 0 {
                        
                        parent.into_root_mut().pop_level();
                        break;
                    } else {
                        cur_node = parent.forget_type();
                    }
                }
                Stole(_) => break,
            }
        }
        (old_key, old_val)
    }
}
enum UnderflowResult<'a, K, V> {
    AtRoot,
    EmptyParent(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
    Merged(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
    Stole(NodeRef<marker::Mut<'a>, K, V, marker::Internal>),
}
fn handle_underfull_node<'a, K, V>(node: NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>)
                                   -> UnderflowResult<'a, K, V> {
    let parent = if let Ok(parent) = node.ascend() {
        parent
    } else {
        return AtRoot;
    };
    let (is_left, mut handle) = match parent.left_kv() {
        Ok(left) => (true, left),
        Err(parent) => {
            match parent.right_kv() {
                Ok(right) => (false, right),
                Err(parent) => {
                    return EmptyParent(parent.into_node());
                }
            }
        }
    };
    if handle.can_merge() {
        Merged(handle.merge().into_node())
    } else {
        if is_left {
            handle.steal_left();
        } else {
            handle.steal_right();
        }
        Stole(handle.into_node())
    }
}
impl<K: Ord, V, I: Iterator<Item = (K, V)>> Iterator for MergeIter<K, V, I> {
    type Item = (K, V);
    fn next(&mut self) -> Option<(K, V)> {
        let res = match (self.left.peek(), self.right.peek()) {
            (Some(&(ref left_key, _)), Some(&(ref right_key, _))) => left_key.cmp(right_key),
            (Some(_), None) => Ordering::Less,
            (None, Some(_)) => Ordering::Greater,
            (None, None) => return None,
        };
        
        
        match res {
            Ordering::Less => self.left.next(),
            Ordering::Greater => self.right.next(),
            Ordering::Equal => {
                self.left.next();
                self.right.next()
            }
        }
    }
}