rust/src/libcore/hashmap.rs

// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! An unordered map and set type implemented as hash tables
//!
//! The tables use a keyed hash with new random keys generated for each container, so the ordering
//! of a set of keys in a hash table is randomized.

use container::{Container, Mutable, Map, Set};
use cmp::{Eq, Equiv};
use hash::Hash;
use to_bytes::IterBytes;
use iter::BaseIter;
use hash::Hash;
use iter;
use option::{None, Option, Some};
use rand::RngUtil;
use rand;
use uint;
use vec;
use util::unreachable;

static INITIAL_CAPACITY: uint = 32u; // 2^5

struct Bucket<K,V> {
    hash: uint,
    key: K,
    value: V,
}

pub struct HashMap<K,V> {
    priv k0: u64,
    priv k1: u64,
    priv resize_at: uint,
    priv size: uint,
    priv buckets: ~[Option<Bucket<K, V>>],
}

// We could rewrite FoundEntry to have type Option<&Bucket<K, V>>
// which would be nifty
enum SearchResult {
    FoundEntry(uint), FoundHole(uint), TableFull
}

#[inline(always)]
fn resize_at(capacity: uint) -> uint {
    ((capacity as float) * 3. / 4.) as uint
}

pub fn linear_map_with_capacity<K:Eq + Hash,V>(
    initial_capacity: uint) -> HashMap<K, V> {
    let r = rand::task_rng();
    linear_map_with_capacity_and_keys(r.gen_u64(), r.gen_u64(),
                                      initial_capacity)
}

fn linear_map_with_capacity_and_keys<K:Eq + Hash,V>(
    k0: u64, k1: u64,
    initial_capacity: uint) -> HashMap<K, V> {
    HashMap {
        k0: k0, k1: k1,
        resize_at: resize_at(initial_capacity),
        size: 0,
        buckets: vec::from_fn(initial_capacity, |_| None)
    }
}

priv impl<K:Hash + IterBytes + Eq,V> HashMap<K, V> {
    #[inline(always)]
    fn to_bucket(&self, h: uint) -> uint {
        // A good hash function with entropy spread over all of the
        // bits is assumed. SipHash is more than good enough.
        h % self.buckets.len()
    }

    #[inline(always)]
    fn next_bucket(&self, idx: uint, len_buckets: uint) -> uint {
        let n = (idx + 1) % len_buckets;
        debug!("next_bucket(%?, %?) = %?", idx, len_buckets, n);
        n
    }

    #[inline(always)]
    fn bucket_sequence(&self, hash: uint,
                            op: &fn(uint) -> bool) -> uint {
        let start_idx = self.to_bucket(hash);
        let len_buckets = self.buckets.len();
        let mut idx = start_idx;
        loop {
            if !op(idx) {
                return idx;
            }
            idx = self.next_bucket(idx, len_buckets);
            if idx == start_idx {
                return start_idx;
            }
        }
    }

    #[inline(always)]
    fn bucket_for_key(&self, k: &K) -> SearchResult {
        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        self.bucket_for_key_with_hash(hash, k)
    }

    #[inline(always)]
    fn bucket_for_key_equiv<Q:Hash + IterBytes + Equiv<K>>(&self,
                                                           k: &Q)
                                                        -> SearchResult {
        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        self.bucket_for_key_with_hash_equiv(hash, k)
    }

    #[inline(always)]
    fn bucket_for_key_with_hash(&self,
                                hash: uint,
                                k: &K)
                             -> SearchResult {
        let _ = for self.bucket_sequence(hash) |i| {
            match self.buckets[i] {
                Some(ref bkt) => if bkt.hash == hash && *k == bkt.key {
                    return FoundEntry(i);
                },
                None => return FoundHole(i)
            }
        };
        TableFull
    }

    #[inline(always)]
    fn bucket_for_key_with_hash_equiv<Q:Equiv<K>>(&self,
                                                  hash: uint,
                                                  k: &Q)
                                               -> SearchResult {
        let _ = for self.bucket_sequence(hash) |i| {
            match self.buckets[i] {
                Some(ref bkt) => {
                    if bkt.hash == hash && k.equiv(&bkt.key) {
                        return FoundEntry(i);
                    }
                },
                None => return FoundHole(i)
            }
        };
        TableFull
    }

    /// Expand the capacity of the array to the next power of two
    /// and re-insert each of the existing buckets.
    #[inline(always)]
    fn expand(&mut self) {
        let new_capacity = self.buckets.len() * 2;
        self.resize(new_capacity);
    }

    /// Expands the capacity of the array and re-insert each of the
    /// existing buckets.
    fn resize(&mut self, new_capacity: uint) {
        let old_capacity = self.buckets.len();
        self.resize_at = resize_at(new_capacity);

        let mut old_buckets = vec::from_fn(new_capacity, |_| None);
        self.buckets <-> old_buckets;

        self.size = 0;
        for uint::range(0, old_capacity) |i| {
            let mut bucket = None;
            bucket <-> old_buckets[i];
            self.insert_opt_bucket(bucket);
        }
    }

    fn insert_opt_bucket(&mut self, bucket: Option<Bucket<K, V>>) {
        match bucket {
            Some(Bucket{hash: hash, key: key, value: value}) => {
                self.insert_internal(hash, key, value);
            }
            None => {}
        }
    }

    #[cfg(stage0)]
    #[inline(always)]
    fn value_for_bucket(&self, idx: uint) -> &'self V {
        match self.buckets[idx] {
            Some(ref bkt) => &bkt.value,
            None => fail!(~"HashMap::find: internal logic error"),
        }
    }

    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    #[inline(always)]
    fn value_for_bucket<'a>(&'a self, idx: uint) -> &'a V {
        match self.buckets[idx] {
            Some(ref bkt) => &bkt.value,
            None => fail!(~"HashMap::find: internal logic error"),
        }
    }

    #[cfg(stage0)]
    #[inline(always)]
    fn mut_value_for_bucket(&mut self, idx: uint) -> &'self mut V {
        match self.buckets[idx] {
            Some(ref mut bkt) => &mut bkt.value,
            None => unreachable()
        }
    }

    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    #[inline(always)]
    fn mut_value_for_bucket<'a>(&'a mut self, idx: uint) -> &'a mut V {
        match self.buckets[idx] {
            Some(ref mut bkt) => &mut bkt.value,
            None => unreachable()
        }
    }

    /// Inserts the key value pair into the buckets.
    /// Assumes that there will be a bucket.
    /// True if there was no previous entry with that key
    fn insert_internal(&mut self, hash: uint, k: K, v: V) -> bool {
        match self.bucket_for_key_with_hash(hash, &k) {
            TableFull => { fail!(~"Internal logic error"); }
            FoundHole(idx) => {
                debug!("insert fresh (%?->%?) at idx %?, hash %?",
                       k, v, idx, hash);
                self.buckets[idx] = Some(Bucket{hash: hash, key: k,
                                                value: v});
                self.size += 1;
                true
            }
            FoundEntry(idx) => {
                debug!("insert overwrite (%?->%?) at idx %?, hash %?",
                       k, v, idx, hash);
                self.buckets[idx] = Some(Bucket{hash: hash, key: k,
                                                value: v});
                false
            }
        }
    }

    fn pop_internal(&mut self, hash: uint, k: &K) -> Option<V> {
        // Removing from an open-addressed hashtable
        // is, well, painful.  The problem is that
        // the entry may lie on the probe path for other
        // entries, so removing it would make you think that
        // those probe paths are empty.
        //
        // To address this we basically have to keep walking,
        // re-inserting entries we find until we reach an empty
        // bucket.  We know we will eventually reach one because
        // we insert one ourselves at the beginning (the removed
        // entry).
        //
        // I found this explanation elucidating:
        // http://www.maths.lse.ac.uk/Courses/MA407/del-hash.pdf
        let mut idx = match self.bucket_for_key_with_hash(hash, k) {
            TableFull | FoundHole(_) => return None,
            FoundEntry(idx) => idx
        };

        let len_buckets = self.buckets.len();
        let mut bucket = None;
        self.buckets[idx] <-> bucket;

        let value = match bucket {
            None => None,
            Some(bucket) => {
                let Bucket{value: value, _} = bucket;
                Some(value)
            },
        };

        /* re-inserting buckets may cause changes in size, so remember
        what our new size is ahead of time before we start insertions */
        let size = self.size - 1;
        idx = self.next_bucket(idx, len_buckets);
        while self.buckets[idx].is_some() {
            let mut bucket = None;
            bucket <-> self.buckets[idx];
            self.insert_opt_bucket(bucket);
            idx = self.next_bucket(idx, len_buckets);
        }
        self.size = size;

        value
    }

    fn search(&self, hash: uint,
              op: &fn(x: &Option<Bucket<K, V>>) -> bool) {
        let _ = self.bucket_sequence(hash, |i| op(&self.buckets[i]));
    }
}

impl<K:Hash + IterBytes + Eq,V> Container for HashMap<K, V> {
    /// Return the number of elements in the map
    fn len(&const self) -> uint { self.size }

    /// Return true if the map contains no elements
    fn is_empty(&const self) -> bool { self.len() == 0 }
}

impl<K:Hash + IterBytes + Eq,V> Mutable for HashMap<K, V> {
    /// Clear the map, removing all key-value pairs.
    fn clear(&mut self) {
        for uint::range(0, self.buckets.len()) |idx| {
            self.buckets[idx] = None;
        }
        self.size = 0;
    }
}

impl<K:Hash + IterBytes + Eq,V> Map<K, V> for HashMap<K, V> {
    /// Return true if the map contains a value for the specified key
    fn contains_key(&self, k: &K) -> bool {
        match self.bucket_for_key(k) {
            FoundEntry(_) => {true}
            TableFull | FoundHole(_) => {false}
        }
    }

    /// Visit all key-value pairs
    #[cfg(stage0)]
    fn each(&self, blk: &fn(&'self K, &'self V) -> bool) {
        for uint::range(0, self.buckets.len()) |i| {
            for self.buckets[i].each |bucket| {
                if !blk(&bucket.key, &bucket.value) {
                    return;
                }
            }
        }
    }

    /// Visit all key-value pairs
    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn each<'a>(&'a self, blk: &fn(&'a K, &'a V) -> bool) {
        for uint::range(0, self.buckets.len()) |i| {
            for self.buckets[i].each |bucket| {
                if !blk(&bucket.key, &bucket.value) {
                    return;
                }
            }
        }
    }

    /// Visit all keys
    fn each_key(&self, blk: &fn(k: &K) -> bool) {
        self.each(|k, _| blk(k))
    }

    /// Visit all values
    #[cfg(stage0)]
    fn each_value(&self, blk: &fn(v: &V) -> bool) {
        self.each(|_, v| blk(v))
    }

    /// Visit all values
    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn each_value<'a>(&'a self, blk: &fn(v: &'a V) -> bool) {
        self.each(|_, v| blk(v))
    }

    /// Iterate over the map and mutate the contained values
    fn mutate_values(&mut self, blk: &fn(&K, &mut V) -> bool) {
        for uint::range(0, self.buckets.len()) |i| {
            match self.buckets[i] {
              Some(Bucket{key: ref key, value: ref mut value, _}) => {
                if !blk(key, value) { return }
              }
              None => ()
            }
        }
    }

    /// Return a reference to the value corresponding to the key
    #[cfg(stage0)]
    fn find(&self, k: &K) -> Option<&'self V> {
        match self.bucket_for_key(k) {
            FoundEntry(idx) => Some(self.value_for_bucket(idx)),
            TableFull | FoundHole(_) => None,
        }
    }

    /// Return a reference to the value corresponding to the key
    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn find<'a>(&'a self, k: &K) -> Option<&'a V> {
        match self.bucket_for_key(k) {
            FoundEntry(idx) => Some(self.value_for_bucket(idx)),
            TableFull | FoundHole(_) => None,
        }
    }

    /// Return a mutable reference to the value corresponding to the key
    #[cfg(stage0)]
    fn find_mut(&mut self, k: &K) -> Option<&'self mut V> {
        let idx = match self.bucket_for_key(k) {
            FoundEntry(idx) => idx,
            TableFull | FoundHole(_) => return None
        };
        unsafe {  // FIXME(#4903)---requires flow-sensitive borrow checker
            Some(::cast::transmute_mut_region(self.mut_value_for_bucket(idx)))
        }
    }

    /// Return a mutable reference to the value corresponding to the key
    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn find_mut<'a>(&'a mut self, k: &K) -> Option<&'a mut V> {
        let idx = match self.bucket_for_key(k) {
            FoundEntry(idx) => idx,
            TableFull | FoundHole(_) => return None
        };
        unsafe {  // FIXME(#4903)---requires flow-sensitive borrow checker
            Some(::cast::transmute_mut_region(self.mut_value_for_bucket(idx)))
        }
    }

    /// Insert a key-value pair into the map. An existing value for a
    /// key is replaced by the new value. Return true if the key did
    /// not already exist in the map.
    fn insert(&mut self, k: K, v: V) -> bool {
        if self.size >= self.resize_at {
            // n.b.: We could also do this after searching, so
            // that we do not resize if this call to insert is
            // simply going to update a key in place.  My sense
            // though is that it's worse to have to search through
            // buckets to find the right spot twice than to just
            // resize in this corner case.
            self.expand();
        }

        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        self.insert_internal(hash, k, v)
    }

    /// Remove a key-value pair from the map. Return true if the key
    /// was present in the map, otherwise false.
    fn remove(&mut self, k: &K) -> bool {
        self.pop(k).is_some()
    }
}

pub impl<K: Hash + IterBytes + Eq, V> HashMap<K, V> {
    /// Create an empty HashMap
    fn new() -> HashMap<K, V> {
        HashMap::with_capacity(INITIAL_CAPACITY)
    }

    /// Create an empty HashMap with space for at least `n` elements in
    /// the hash table.
    fn with_capacity(capacity: uint) -> HashMap<K, V> {
        linear_map_with_capacity(capacity)
    }

    /// Reserve space for at least `n` elements in the hash table.
    fn reserve_at_least(&mut self, n: uint) {
        if n > self.buckets.len() {
            let buckets = n * 4 / 3 + 1;
            self.resize(uint::next_power_of_two(buckets));
        }
    }

    fn pop(&mut self, k: &K) -> Option<V> {
        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        self.pop_internal(hash, k)
    }

    fn swap(&mut self, k: K, v: V) -> Option<V> {
        // this could be faster.
        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        let old_value = self.pop_internal(hash, &k);

        if self.size >= self.resize_at {
            // n.b.: We could also do this after searching, so
            // that we do not resize if this call to insert is
            // simply going to update a key in place.  My sense
            // though is that it's worse to have to search through
            // buckets to find the right spot twice than to just
            // resize in this corner case.
            self.expand();
        }

        self.insert_internal(hash, k, v);

        old_value
    }

    /// Return the value corresponding to the key in the map, or insert
    /// and return the value if it doesn't exist.
    #[cfg(stage0)]
    fn find_or_insert(&mut self, k: K, v: V) -> &'self V {
        if self.size >= self.resize_at {
            // n.b.: We could also do this after searching, so
            // that we do not resize if this call to insert is
            // simply going to update a key in place.  My sense
            // though is that it's worse to have to search through
            // buckets to find the right spot twice than to just
            // resize in this corner case.
            self.expand();
        }

        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        let idx = match self.bucket_for_key_with_hash(hash, &k) {
            TableFull => fail!(~"Internal logic error"),
            FoundEntry(idx) => idx,
            FoundHole(idx) => {
                self.buckets[idx] = Some(Bucket{hash: hash, key: k,
                                     value: v});
                self.size += 1;
                idx
            },
        };

        unsafe { // FIXME(#4903)---requires flow-sensitive borrow checker
            ::cast::transmute_region(self.value_for_bucket(idx))
        }
    }

    /// Return the value corresponding to the key in the map, or insert
    /// and return the value if it doesn't exist.
    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn find_or_insert<'a>(&'a mut self, k: K, v: V) -> &'a V {
        if self.size >= self.resize_at {
            // n.b.: We could also do this after searching, so
            // that we do not resize if this call to insert is
            // simply going to update a key in place.  My sense
            // though is that it's worse to have to search through
            // buckets to find the right spot twice than to just
            // resize in this corner case.
            self.expand();
        }

        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        let idx = match self.bucket_for_key_with_hash(hash, &k) {
            TableFull => fail!(~"Internal logic error"),
            FoundEntry(idx) => idx,
            FoundHole(idx) => {
                self.buckets[idx] = Some(Bucket{hash: hash, key: k,
                                     value: v});
                self.size += 1;
                idx
            },
        };

        unsafe { // FIXME(#4903)---requires flow-sensitive borrow checker
            ::cast::transmute_region(self.value_for_bucket(idx))
        }
    }

    /// Return the value corresponding to the key in the map, or create,
    /// insert, and return a new value if it doesn't exist.
    #[cfg(stage0)]
    fn find_or_insert_with(&mut self, k: K, f: &fn(&K) -> V) -> &'self V {
        if self.size >= self.resize_at {
            // n.b.: We could also do this after searching, so
            // that we do not resize if this call to insert is
            // simply going to update a key in place.  My sense
            // though is that it's worse to have to search through
            // buckets to find the right spot twice than to just
            // resize in this corner case.
            self.expand();
        }

        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        let idx = match self.bucket_for_key_with_hash(hash, &k) {
            TableFull => fail!(~"Internal logic error"),
            FoundEntry(idx) => idx,
            FoundHole(idx) => {
                let v = f(&k);
                self.buckets[idx] = Some(Bucket{hash: hash, key: k,
                                     value: v});
                self.size += 1;
                idx
            },
        };

        unsafe { // FIXME(#4903)---requires flow-sensitive borrow checker
            ::cast::transmute_region(self.value_for_bucket(idx))
        }
    }

    /// Return the value corresponding to the key in the map, or create,
    /// insert, and return a new value if it doesn't exist.
    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn find_or_insert_with<'a>(&'a mut self, k: K, f: &fn(&K) -> V) -> &'a V {
        if self.size >= self.resize_at {
            // n.b.: We could also do this after searching, so
            // that we do not resize if this call to insert is
            // simply going to update a key in place.  My sense
            // though is that it's worse to have to search through
            // buckets to find the right spot twice than to just
            // resize in this corner case.
            self.expand();
        }

        let hash = k.hash_keyed(self.k0, self.k1) as uint;
        let idx = match self.bucket_for_key_with_hash(hash, &k) {
            TableFull => fail!(~"Internal logic error"),
            FoundEntry(idx) => idx,
            FoundHole(idx) => {
                let v = f(&k);
                self.buckets[idx] = Some(Bucket{hash: hash, key: k,
                                     value: v});
                self.size += 1;
                idx
            },
        };

        unsafe { // FIXME(#4903)---requires flow-sensitive borrow checker
            ::cast::transmute_region(self.value_for_bucket(idx))
        }
    }

    fn consume(&mut self, f: &fn(K, V)) {
        let mut buckets = ~[];
        self.buckets <-> buckets;
        self.size = 0;

        do vec::consume(buckets) |_, bucket| {
            match bucket {
                None => {},
                Some(bucket) => {
                    let Bucket{key: key, value: value, _} = bucket;
                    f(key, value)
                }
            }
        }
    }

    #[cfg(stage0)]
    fn get(&self, k: &K) -> &'self V {
        match self.find(k) {
            Some(v) => v,
            None => fail!(fmt!("No entry found for key: %?", k)),
        }
    }

    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn get<'a>(&'a self, k: &K) -> &'a V {
        match self.find(k) {
            Some(v) => v,
            None => fail!(fmt!("No entry found for key: %?", k)),
        }
    }

    /// Return true if the map contains a value for the specified key,
    /// using equivalence
    fn contains_key_equiv<Q:Hash + IterBytes + Equiv<K>>(&self, key: &Q)
                                                      -> bool {
        match self.bucket_for_key_equiv(key) {
            FoundEntry(_) => {true}
            TableFull | FoundHole(_) => {false}
        }
    }

    /// Return the value corresponding to the key in the map, using
    /// equivalence
    #[cfg(stage0)]
    fn find_equiv<Q:Hash + IterBytes + Equiv<K>>(&self, k: &Q)
                                              -> Option<&'self V> {
        match self.bucket_for_key_equiv(k) {
            FoundEntry(idx) => Some(self.value_for_bucket(idx)),
            TableFull | FoundHole(_) => None,
        }
    }

    /// Return the value corresponding to the key in the map, using
    /// equivalence
    #[cfg(stage1)]
    #[cfg(stage2)]
    #[cfg(stage3)]
    fn find_equiv<'a, Q:Hash + IterBytes + Equiv<K>>(
        &'a self, k: &Q) -> Option<&'a V>
    {
        match self.bucket_for_key_equiv(k) {
            FoundEntry(idx) => Some(self.value_for_bucket(idx)),
            TableFull | FoundHole(_) => None,
        }
    }
}

impl<K:Hash + IterBytes + Eq,V:Eq> Eq for HashMap<K, V> {
    fn eq(&self, other: &HashMap<K, V>) -> bool {
        if self.len() != other.len() { return false; }

        for self.each |key, value| {
            match other.find(key) {
                None => return false,
                Some(v) => if value != v { return false },
            }
        }

        true
    }

    fn ne(&self, other: &HashMap<K, V>) -> bool { !self.eq(other) }
}

pub struct HashSet<T> {
    priv map: HashMap<T, ()>
}

impl<T:Hash + IterBytes + Eq> BaseIter<T> for HashSet<T> {
    /// Visit all values in order
    fn each(&self, f: &fn(&T) -> bool) { self.map.each_key(f) }
    fn size_hint(&self) -> Option<uint> { Some(self.len()) }
}

impl<T:Hash + IterBytes + Eq> Eq for HashSet<T> {
    fn eq(&self, other: &HashSet<T>) -> bool { self.map == other.map }
    fn ne(&self, other: &HashSet<T>) -> bool { self.map != other.map }
}

impl<T:Hash + IterBytes + Eq> Container for HashSet<T> {
    /// Return the number of elements in the set
    fn len(&const self) -> uint { self.map.len() }

    /// Return true if the set contains no elements
    fn is_empty(&const self) -> bool { self.map.is_empty() }
}

impl<T:Hash + IterBytes + Eq> Mutable for HashSet<T> {
    /// Clear the set, removing all values.
    fn clear(&mut self) { self.map.clear() }
}

impl<T:Hash + IterBytes + Eq> Set<T> for HashSet<T> {
    /// Return true if the set contains a value
    fn contains(&self, value: &T) -> bool { self.map.contains_key(value) }

    /// Add a value to the set. Return true if the value was not already
    /// present in the set.
    fn insert(&mut self, value: T) -> bool { self.map.insert(value, ()) }

    /// Remove a value from the set. Return true if the value was
    /// present in the set.
    fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }

    /// Return true if the set has no elements in common with `other`.
    /// This is equivalent to checking for an empty intersection.
    fn is_disjoint(&self, other: &HashSet<T>) -> bool {
        iter::all(self, |v| !other.contains(v))
    }

    /// Return true if the set is a subset of another
    fn is_subset(&self, other: &HashSet<T>) -> bool {
        iter::all(self, |v| other.contains(v))
    }

    /// Return true if the set is a superset of another
    fn is_superset(&self, other: &HashSet<T>) -> bool {
        other.is_subset(self)
    }

    /// Visit the values representing the difference
    fn difference(&self, other: &HashSet<T>, f: &fn(&T) -> bool) {
        for self.each |v| {
            if !other.contains(v) {
                if !f(v) { return }
            }
        }
    }

    /// Visit the values representing the symmetric difference
    fn symmetric_difference(&self,
                            other: &HashSet<T>,
                            f: &fn(&T) -> bool) {
        self.difference(other, f);
        other.difference(self, f);
    }

    /// Visit the values representing the intersection
    fn intersection(&self, other: &HashSet<T>, f: &fn(&T) -> bool) {
        for self.each |v| {
            if other.contains(v) {
                if !f(v) { return }
            }
        }
    }

    /// Visit the values representing the union
    fn union(&self, other: &HashSet<T>, f: &fn(&T) -> bool) {
        for self.each |v| {
            if !f(v) { return }
        }

        for other.each |v| {
            if !self.contains(v) {
                if !f(v) { return }
            }
        }
    }
}

pub impl <T:Hash + IterBytes + Eq> HashSet<T> {
    /// Create an empty HashSet
    fn new() -> HashSet<T> {
        HashSet::with_capacity(INITIAL_CAPACITY)
    }

    /// Create an empty HashSet with space for at least `n` elements in
    /// the hash table.
    fn with_capacity(capacity: uint) -> HashSet<T> {
        HashSet { map: HashMap::with_capacity(capacity) }
    }

    /// Reserve space for at least `n` elements in the hash table.
    fn reserve_at_least(&mut self, n: uint) {
        self.map.reserve_at_least(n)
    }

    /// Consumes all of the elements in the set, emptying it out
    fn consume(&mut self, f: &fn(T)) {
        self.map.consume(|k, _| f(k))
    }
}

#[test]
mod test_map {
    use container::{Container, Map, Set};
    use option::{None, Some};
    use super::*;
    use uint;

    #[test]
    fn test_insert() {
        let mut m = HashMap::new();
        assert!(m.insert(1, 2));
        assert!(m.insert(2, 4));
        assert!(*m.get(&1) == 2);
        assert!(*m.get(&2) == 4);
    }

    #[test]
    fn test_find_mut() {
        let mut m = HashMap::new();
        assert!(m.insert(1, 12));
        assert!(m.insert(2, 8));
        assert!(m.insert(5, 14));
        let new = 100;
        match m.find_mut(&5) {
            None => fail!(), Some(x) => *x = new
        }
        assert_eq!(m.find(&5), Some(&new));
    }

    #[test]
    fn test_insert_overwrite() {
        let mut m = HashMap::new();
        assert!(m.insert(1, 2));
        assert!(*m.get(&1) == 2);
        assert!(!m.insert(1, 3));
        assert!(*m.get(&1) == 3);
    }

    #[test]
    fn test_insert_conflicts() {
        let mut m = linear_map_with_capacity(4);
        assert!(m.insert(1, 2));
        assert!(m.insert(5, 3));
        assert!(m.insert(9, 4));
        assert!(*m.get(&9) == 4);
        assert!(*m.get(&5) == 3);
        assert!(*m.get(&1) == 2);
    }

    #[test]
    fn test_conflict_remove() {
        let mut m = linear_map_with_capacity(4);
        assert!(m.insert(1, 2));
        assert!(m.insert(5, 3));
        assert!(m.insert(9, 4));
        assert!(m.remove(&1));
        assert!(*m.get(&9) == 4);
        assert!(*m.get(&5) == 3);
    }

    #[test]
    fn test_is_empty() {
        let mut m = linear_map_with_capacity(4);
        assert!(m.insert(1, 2));
        assert!(!m.is_empty());
        assert!(m.remove(&1));
        assert!(m.is_empty());
    }

    #[test]
    fn test_pop() {
        let mut m = HashMap::new();
        m.insert(1, 2);
        assert!(m.pop(&1) == Some(2));
        assert!(m.pop(&1) == None);
    }

    #[test]
    fn test_swap() {
        let mut m = HashMap::new();
        assert!(m.swap(1, 2) == None);
        assert!(m.swap(1, 3) == Some(2));
        assert!(m.swap(1, 4) == Some(3));
    }

    #[test]
    fn test_find_or_insert() {
        let mut m = HashMap::new::<int, int>();
        assert!(m.find_or_insert(1, 2) == &2);
        assert!(m.find_or_insert(1, 3) == &2);
    }

    #[test]
    fn test_find_or_insert_with() {
        let mut m = HashMap::new::<int, int>();
        assert!(m.find_or_insert_with(1, |_| 2) == &2);
        assert!(m.find_or_insert_with(1, |_| 3) == &2);
    }

    #[test]
    fn test_consume() {
        let mut m = HashMap::new();
        assert!(m.insert(1, 2));
        assert!(m.insert(2, 3));
        let mut m2 = HashMap::new();
        do m.consume |k, v| {
            m2.insert(k, v);
        }
        assert!(m.len() == 0);
        assert!(m2.len() == 2);
        assert!(m2.get(&1) == &2);
        assert!(m2.get(&2) == &3);
    }

    #[test]
    fn test_iterate() {
        let mut m = linear_map_with_capacity(4);
        for uint::range(0, 32) |i| {
            assert!(m.insert(i, i*2));
        }
        let mut observed = 0;
        for m.each |k, v| {
            assert!(*v == *k * 2);
            observed |= (1 << *k);
        }
        assert!(observed == 0xFFFF_FFFF);
    }

    #[test]
    fn test_find() {
        let mut m = HashMap::new();
        assert!(m.find(&1).is_none());
        m.insert(1, 2);
        match m.find(&1) {
            None => fail!(),
            Some(v) => assert!(*v == 2)
        }
    }

    #[test]
    fn test_eq() {
        let mut m1 = HashMap::new();
        m1.insert(1, 2);
        m1.insert(2, 3);
        m1.insert(3, 4);

        let mut m2 = HashMap::new();
        m2.insert(1, 2);
        m2.insert(2, 3);

        assert!(m1 != m2);

        m2.insert(3, 4);

        assert!(m1 == m2);
    }

    #[test]
    fn test_expand() {
        let mut m = HashMap::new();

        assert!(m.len() == 0);
        assert!(m.is_empty());

        let mut i = 0u;
        let old_resize_at = m.resize_at;
        while old_resize_at == m.resize_at {
            m.insert(i, i);
            i += 1;
        }

        assert!(m.len() == i);
        assert!(!m.is_empty());
    }
}

#[test]
mod test_set {
    use super::*;
    use container::{Container, Map, Set};
    use vec;

    #[test]
    fn test_disjoint() {
        let mut xs = HashSet::new();
        let mut ys = HashSet::new();
        assert!(xs.is_disjoint(&ys));
        assert!(ys.is_disjoint(&xs));
        assert!(xs.insert(5));
        assert!(ys.insert(11));
        assert!(xs.is_disjoint(&ys));
        assert!(ys.is_disjoint(&xs));
        assert!(xs.insert(7));
        assert!(xs.insert(19));
        assert!(xs.insert(4));
        assert!(ys.insert(2));
        assert!(ys.insert(-11));
        assert!(xs.is_disjoint(&ys));
        assert!(ys.is_disjoint(&xs));
        assert!(ys.insert(7));
        assert!(!xs.is_disjoint(&ys));
        assert!(!ys.is_disjoint(&xs));
    }

    #[test]
    fn test_subset_and_superset() {
        let mut a = HashSet::new();
        assert!(a.insert(0));
        assert!(a.insert(5));
        assert!(a.insert(11));
        assert!(a.insert(7));

        let mut b = HashSet::new();
        assert!(b.insert(0));
        assert!(b.insert(7));
        assert!(b.insert(19));
        assert!(b.insert(250));
        assert!(b.insert(11));
        assert!(b.insert(200));

        assert!(!a.is_subset(&b));
        assert!(!a.is_superset(&b));
        assert!(!b.is_subset(&a));
        assert!(!b.is_superset(&a));

        assert!(b.insert(5));

        assert!(a.is_subset(&b));
        assert!(!a.is_superset(&b));
        assert!(!b.is_subset(&a));
        assert!(b.is_superset(&a));
    }

    #[test]
    fn test_intersection() {
        let mut a = HashSet::new();
        let mut b = HashSet::new();

        assert!(a.insert(11));
        assert!(a.insert(1));
        assert!(a.insert(3));
        assert!(a.insert(77));
        assert!(a.insert(103));
        assert!(a.insert(5));
        assert!(a.insert(-5));

        assert!(b.insert(2));
        assert!(b.insert(11));
        assert!(b.insert(77));
        assert!(b.insert(-9));
        assert!(b.insert(-42));
        assert!(b.insert(5));
        assert!(b.insert(3));

        let mut i = 0;
        let expected = [3, 5, 11, 77];
        for a.intersection(&b) |x| {
            assert!(vec::contains(expected, x));
            i += 1
        }
        assert!(i == expected.len());
    }

    #[test]
    fn test_difference() {
        let mut a = HashSet::new();
        let mut b = HashSet::new();

        assert!(a.insert(1));
        assert!(a.insert(3));
        assert!(a.insert(5));
        assert!(a.insert(9));
        assert!(a.insert(11));

        assert!(b.insert(3));
        assert!(b.insert(9));

        let mut i = 0;
        let expected = [1, 5, 11];
        for a.difference(&b) |x| {
            assert!(vec::contains(expected, x));
            i += 1
        }
        assert!(i == expected.len());
    }

    #[test]
    fn test_symmetric_difference() {
        let mut a = HashSet::new();
        let mut b = HashSet::new();

        assert!(a.insert(1));
        assert!(a.insert(3));
        assert!(a.insert(5));
        assert!(a.insert(9));
        assert!(a.insert(11));

        assert!(b.insert(-2));
        assert!(b.insert(3));
        assert!(b.insert(9));
        assert!(b.insert(14));
        assert!(b.insert(22));

        let mut i = 0;
        let expected = [-2, 1, 5, 11, 14, 22];
        for a.symmetric_difference(&b) |x| {
            assert!(vec::contains(expected, x));
            i += 1
        }
        assert!(i == expected.len());
    }

    #[test]
    fn test_union() {
        let mut a = HashSet::new();
        let mut b = HashSet::new();

        assert!(a.insert(1));
        assert!(a.insert(3));
        assert!(a.insert(5));
        assert!(a.insert(9));
        assert!(a.insert(11));
        assert!(a.insert(16));
        assert!(a.insert(19));
        assert!(a.insert(24));

        assert!(b.insert(-2));
        assert!(b.insert(1));
        assert!(b.insert(5));
        assert!(b.insert(9));
        assert!(b.insert(13));
        assert!(b.insert(19));

        let mut i = 0;
        let expected = [-2, 1, 3, 5, 9, 11, 13, 16, 19, 24];
        for a.union(&b) |x| {
            assert!(vec::contains(expected, x));
            i += 1
        }
        assert!(i == expected.len());
    }
}