434 lines
14 KiB
Rust
434 lines
14 KiB
Rust
/*!
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Sendable hash maps. Very much a work in progress.
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*/
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use cmp::Eq;
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use hash::Hash;
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use to_bytes::IterBytes;
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trait SendMap<K:Eq Hash, V: Copy> {
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// FIXME(#3148) ^^^^ once find_ref() works, we can drop V:copy
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fn insert(&mut self, +k: K, +v: V) -> bool;
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fn remove(&mut self, k: &K) -> bool;
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fn clear(&mut self);
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pure fn len(&const self) -> uint;
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pure fn is_empty(&const self) -> bool;
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fn contains_key(&const self, k: &K) -> bool;
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fn each_ref(&self, blk: fn(k: &K, v: &V) -> bool);
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fn each_key_ref(&self, blk: fn(k: &K) -> bool);
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fn each_value_ref(&self, blk: fn(v: &V) -> bool);
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fn find(&const self, k: &K) -> Option<V>;
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fn get(&const self, k: &K) -> V;
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}
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/// Open addressing with linear probing.
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mod linear {
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export LinearMap, linear_map, linear_map_with_capacity, public_methods;
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const initial_capacity: uint = 32u; // 2^5
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struct Bucket<K:Eq Hash,V> {
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hash: uint,
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key: K,
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value: V,
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}
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struct LinearMap<K:Eq Hash,V> {
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k0: u64,
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k1: u64,
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resize_at: uint,
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size: uint,
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buckets: ~[Option<Bucket<K,V>>],
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}
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// FIXME(#3148) -- we could rewrite found_entry
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// to have type option<&bucket<K,V>> which would be nifty
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// However, that won't work until #3148 is fixed
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enum SearchResult {
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FoundEntry(uint), FoundHole(uint), TableFull
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}
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fn resize_at(capacity: uint) -> uint {
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((capacity as float) * 3. / 4.) as uint
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}
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fn LinearMap<K:Eq Hash,V>() -> LinearMap<K,V> {
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linear_map_with_capacity(32)
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}
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fn linear_map_with_capacity<K:Eq Hash,V>(
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initial_capacity: uint) -> LinearMap<K,V> {
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let r = rand::Rng();
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linear_map_with_capacity_and_keys(r.gen_u64(), r.gen_u64(),
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initial_capacity)
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}
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fn linear_map_with_capacity_and_keys<K:Eq Hash,V> (
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k0: u64, k1: u64,
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initial_capacity: uint) -> LinearMap<K,V> {
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LinearMap {
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k0: k0, k1: k1,
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resize_at: resize_at(initial_capacity),
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size: 0,
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buckets: vec::from_fn(initial_capacity, |_i| None)
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}
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}
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priv impl<K:Hash IterBytes Eq, V> LinearMap<K,V> {
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#[inline(always)]
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pure fn to_bucket(&const self,
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h: uint) -> uint {
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// FIXME(#3041) borrow a more sophisticated technique here from
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// Gecko, for example borrowing from Knuth, as Eich so
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// colorfully argues for here:
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// https://bugzilla.mozilla.org/show_bug.cgi?id=743107#c22
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h % self.buckets.len()
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}
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#[inline(always)]
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pure fn next_bucket(&const self,
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idx: uint,
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len_buckets: uint) -> uint {
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let n = (idx + 1) % len_buckets;
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unsafe{ // argh. log not considered pure.
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debug!("next_bucket(%?, %?) = %?", idx, len_buckets, n);
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}
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return n;
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}
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#[inline(always)]
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pure fn bucket_sequence(&const self,
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hash: uint,
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op: fn(uint) -> bool) -> uint {
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let start_idx = self.to_bucket(hash);
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let len_buckets = self.buckets.len();
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let mut idx = start_idx;
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loop {
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if !op(idx) {
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return idx;
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}
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idx = self.next_bucket(idx, len_buckets);
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if idx == start_idx {
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return start_idx;
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}
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}
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}
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#[inline(always)]
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pure fn bucket_for_key(&const self,
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buckets: &[Option<Bucket<K,V>>],
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k: &K) -> SearchResult {
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let hash = k.hash_keyed(self.k0, self.k1) as uint;
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self.bucket_for_key_with_hash(buckets, hash, k)
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}
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#[inline(always)]
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pure fn bucket_for_key_with_hash(&const self,
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buckets: &[Option<Bucket<K,V>>],
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hash: uint,
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k: &K) -> SearchResult {
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let _ = for self.bucket_sequence(hash) |i| {
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match buckets[i] {
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Some(bkt) => if bkt.hash == hash && *k == bkt.key {
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return FoundEntry(i);
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},
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None => return FoundHole(i)
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}
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};
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return TableFull;
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}
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/// Expands the capacity of the array and re-inserts each
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/// of the existing buckets.
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fn expand(&mut self) {
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let old_capacity = self.buckets.len();
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let new_capacity = old_capacity * 2;
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self.resize_at = ((new_capacity as float) * 3.0 / 4.0) as uint;
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let mut old_buckets = vec::from_fn(new_capacity, |_i| None);
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self.buckets <-> old_buckets;
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for uint::range(0, old_capacity) |i| {
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let mut bucket = None;
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bucket <-> old_buckets[i];
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self.insert_opt_bucket(move bucket);
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}
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}
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fn insert_opt_bucket(&mut self, +bucket: Option<Bucket<K,V>>) {
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match move bucket {
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Some(Bucket {hash: move hash,
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key: move key,
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value: move value}) => {
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self.insert_internal(hash, move key, move value);
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}
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None => {}
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}
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}
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/// Inserts the key value pair into the buckets.
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/// Assumes that there will be a bucket.
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/// True if there was no previous entry with that key
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fn insert_internal(&mut self, hash: uint, +k: K, +v: V) -> bool {
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match self.bucket_for_key_with_hash(self.buckets, hash, &k) {
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TableFull => {fail ~"Internal logic error";}
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FoundHole(idx) => {
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debug!("insert fresh (%?->%?) at idx %?, hash %?",
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k, v, idx, hash);
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self.buckets[idx] = Some(Bucket {hash: hash,
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key: k,
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value: v});
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self.size += 1;
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return true;
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}
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FoundEntry(idx) => {
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debug!("insert overwrite (%?->%?) at idx %?, hash %?",
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k, v, idx, hash);
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self.buckets[idx] = Some(Bucket {hash: hash,
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key: k,
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value: v});
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return false;
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}
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}
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}
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fn search(&self,
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hash: uint,
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op: fn(x: &Option<Bucket<K,V>>) -> bool) {
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let _ = self.bucket_sequence(hash, |i| op(&self.buckets[i]));
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}
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}
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impl<K:Hash IterBytes Eq,V> LinearMap<K,V> {
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fn insert(&mut self, +k: K, +v: V) -> bool {
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if self.size >= self.resize_at {
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// n.b.: We could also do this after searching, so
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// that we do not resize if this call to insert is
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// simply going to update a key in place. My sense
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// though is that it's worse to have to search through
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// buckets to find the right spot twice than to just
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// resize in this corner case.
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self.expand();
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}
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let hash = k.hash_keyed(self.k0, self.k1) as uint;
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self.insert_internal(hash, move k, move v)
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}
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fn remove(&mut self, k: &K) -> bool {
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// Removing from an open-addressed hashtable
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// is, well, painful. The problem is that
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// the entry may lie on the probe path for other
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// entries, so removing it would make you think that
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// those probe paths are empty.
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//
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// To address this we basically have to keep walking,
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// re-inserting entries we find until we reach an empty
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// bucket. We know we will eventually reach one because
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// we insert one ourselves at the beginning (the removed
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// entry).
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//
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// I found this explanation elucidating:
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// http://www.maths.lse.ac.uk/Courses/MA407/del-hash.pdf
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let mut idx = match self.bucket_for_key(self.buckets, k) {
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TableFull | FoundHole(_) => {
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return false;
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}
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FoundEntry(idx) => {
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idx
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}
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};
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let len_buckets = self.buckets.len();
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self.buckets[idx] = None;
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idx = self.next_bucket(idx, len_buckets);
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while self.buckets[idx].is_some() {
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let mut bucket = None;
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bucket <-> self.buckets[idx];
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self.insert_opt_bucket(move bucket);
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idx = self.next_bucket(idx, len_buckets);
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}
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self.size -= 1;
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return true;
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}
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fn clear(&mut self) {
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for uint::range(0, self.buckets.len()) |idx| {
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self.buckets[idx] = None;
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}
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self.size = 0;
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}
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pure fn len(&const self) -> uint {
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self.size
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}
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pure fn is_empty(&const self) -> bool {
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self.len() == 0
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}
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fn contains_key(&const self,
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k: &K) -> bool {
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match self.bucket_for_key(self.buckets, k) {
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FoundEntry(_) => {true}
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TableFull | FoundHole(_) => {false}
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}
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}
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/*
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FIXME(#3148)--region inference fails to capture needed deps
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fn find_ref(&self, k: &K) -> option<&self/V> {
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match self.bucket_for_key(self.buckets, k) {
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FoundEntry(idx) => {
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match check self.buckets[idx] {
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some(ref bkt) => some(&bkt.value)
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}
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}
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TableFull | FoundHole(_) => {
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none
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}
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}
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}
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*/
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fn each_ref(&self, blk: fn(k: &K, v: &V) -> bool) {
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for vec::each(self.buckets) |slot| {
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let mut broke = false;
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do slot.iter |bucket| {
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if !blk(&bucket.key, &bucket.value) {
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broke = true; // FIXME(#3064) just write "break;"
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}
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}
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if broke { break; }
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}
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}
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fn each_key_ref(&self, blk: fn(k: &K) -> bool) {
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self.each_ref(|k, _v| blk(k))
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}
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fn each_value_ref(&self, blk: fn(v: &V) -> bool) {
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self.each_ref(|_k, v| blk(v))
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}
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}
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impl<K:Hash IterBytes Eq, V: Copy> LinearMap<K,V> {
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fn find(&const self, k: &K) -> Option<V> {
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match self.bucket_for_key(self.buckets, k) {
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FoundEntry(idx) => {
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// FIXME (#3148): Once we rewrite found_entry, this
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// failure case won't be necessary
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match self.buckets[idx] {
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Some(bkt) => {Some(copy bkt.value)}
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None => fail ~"LinearMap::find: internal logic error"
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}
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}
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TableFull | FoundHole(_) => {
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None
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}
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}
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}
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fn get(&const self, k: &K) -> V {
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let value = self.find(k);
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if value.is_none() {
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fail fmt!("No entry found for key: %?", k);
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}
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option::unwrap(value)
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}
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}
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impl<K: Hash IterBytes Eq Copy, V: Copy> LinearMap<K,V> {
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fn each(&self, blk: fn(+K,+V) -> bool) {
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self.each_ref(|k,v| blk(copy *k, copy *v));
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}
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}
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impl<K: Hash IterBytes Eq Copy, V> LinearMap<K,V> {
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fn each_key(&self, blk: fn(+K) -> bool) {
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self.each_key_ref(|k| blk(copy *k));
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}
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}
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impl<K: Hash IterBytes Eq, V: Copy> LinearMap<K,V> {
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fn each_value(&self, blk: fn(+V) -> bool) {
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self.each_value_ref(|v| blk(copy *v));
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}
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}
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}
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#[test]
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mod test {
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use linear::LinearMap;
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fn int_linear_map<V>() -> LinearMap<uint,V> {
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return LinearMap();
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}
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#[test]
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fn inserts() {
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let mut m = ~int_linear_map();
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assert m.insert(1, 2);
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assert m.insert(2, 4);
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assert m.get(&1) == 2;
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assert m.get(&2) == 4;
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}
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#[test]
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fn overwrite() {
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let mut m = ~int_linear_map();
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assert m.insert(1, 2);
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assert m.get(&1) == 2;
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assert !m.insert(1, 3);
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assert m.get(&1) == 3;
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}
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#[test]
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fn conflicts() {
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let mut m = ~linear::linear_map_with_capacity(4);
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assert m.insert(1, 2);
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assert m.insert(5, 3);
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assert m.insert(9, 4);
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assert m.get(&9) == 4;
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assert m.get(&5) == 3;
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assert m.get(&1) == 2;
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}
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#[test]
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fn conflict_remove() {
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let mut m = ~linear::linear_map_with_capacity(4);
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assert m.insert(1, 2);
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assert m.insert(5, 3);
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assert m.insert(9, 4);
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assert m.remove(&1);
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assert m.get(&9) == 4;
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assert m.get(&5) == 3;
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}
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#[test]
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fn empty() {
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let mut m = ~linear::linear_map_with_capacity(4);
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assert m.insert(1, 2);
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assert !m.is_empty();
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assert m.remove(&1);
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assert m.is_empty();
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}
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#[test]
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fn iterate() {
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let mut m = linear::linear_map_with_capacity(4);
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for uint::range(0, 32) |i| {
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assert (&mut m).insert(i, i*2);
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}
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let mut observed = 0;
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for (&m).each |k, v| {
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assert v == k*2;
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observed |= (1 << k);
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}
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assert observed == 0xFFFF_FFFF;
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}
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}
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