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/**
* At the moment, this is a partial hashmap implementation, not yet fit for
* use, but useful as a stress test for rustboot.
*/
import std._int;
import std.sys;
import std.util;
import std._vec;
type hashfn[K] = fn(&K) -> uint;
type eqfn[K] = fn(&K, &K) -> bool;
type hashmap[K, V] = obj {
fn insert(&K key, &V val) -> bool;
fn contains_key(&K key) -> bool;
fn get(&K key) -> V;
fn find(&K key) -> util.option[V];
fn remove(&K key) -> util.option[V];
fn rehash();
};
fn mk_hashmap[K, V](&hashfn[K] hasher, &eqfn[K] eqer) -> hashmap[K, V] {
let uint initial_capacity = 32u; // 2^5
let util.rational load_factor = rec(num=3, den=4);
type bucket[K, V] = tag(nil(), deleted(), some(K, V));
fn make_buckets[K, V](uint nbkts) -> vec[mutable bucket[K, V]] {
ret _vec.init_elt[mutable bucket[K, V]](nil[K, V](), nbkts);
}
// Derive two hash functions from the one given by taking the upper
// half and lower half of the uint bits. Our bucket probing
// sequence is then defined by
//
// hash(key, i) := hashl(key) + i * hashr(key) for i = 0, 1, 2, ...
//
// Tearing the hash function apart this way is kosher in practice
// as, assuming 32-bit uints, the table would have to be at 2^32
// buckets before the resulting pair of hash functions no longer
// probes all buckets for a fixed key. Note that hashr is made to
// output odd numbers (hence coprime to the number of nbkts, which
// is always a power of 2), so that all buckets are probed for a
// fixed key.
fn hashl[K](&hashfn[K] hasher, uint nbkts, &K key) -> uint {
ret (hasher(key) >>> (sys.rustrt.size_of[uint]() * 8u / 2u))
% nbkts;
}
fn hashr[K](&hashfn[K] hasher, uint nbkts, &K key) -> uint {
ret ((((~ 0u) >>> (sys.rustrt.size_of[uint]() * 8u / 2u))
& hasher(key)) * 2u + 1u)
% nbkts;
}
fn hash[K](&hashfn[K] hasher, uint nbkts, &K key, uint i) -> uint {
ret hashl[K](hasher, nbkts, key) + i * hashr[K](hasher, nbkts, key);
}
/**
* We attempt to never call this with a full table. If we do, it
* will fail.
*/
fn insert_common[K, V](&hashfn[K] hasher,
&eqfn[K] eqer,
vec[mutable bucket[K, V]] bkts,
uint nbkts,
&K key,
&V val)
-> bool
{
let uint i = 0u;
while (i < nbkts) {
// FIXME (issue #94): as in find_common()
let int j = (hash[K](hasher, nbkts, key, i)) as int;
alt (bkts.(j)) {
case (some[K, V](k, _)) {
if (eqer(key, k)) {
bkts.(j) = some[K, V](k, val);
ret false;
}
i += 1u;
}
case (_) {
bkts.(j) = some[K, V](key, val);
ret true;
}
}
}
fail; // full table
}
fn find_common[K, V](&hashfn[K] hasher,
&eqfn[K] eqer,
vec[mutable bucket[K, V]] bkts,
uint nbkts,
&K key)
-> util.option[V]
{
let uint i = 0u;
while (i < nbkts) {
// FIXME (issue #94): Pending bugfix, remove uint coercion.
let int j = (hash[K](hasher, nbkts, key, i)) as int;
alt (bkts.(j)) {
case (some[K, V](k, v)) {
if (eqer(key, k)) {
ret util.some[V](v);
}
}
case (nil[K, V]()) {
ret util.none[V]();
}
case (deleted[K, V]()) { }
}
i += 1u;
}
ret util.none[V]();
}
fn rehash[K, V](&hashfn[K] hasher,
&eqfn[K] eqer,
vec[mutable bucket[K, V]] oldbkts, uint noldbkts,
vec[mutable bucket[K, V]] newbkts, uint nnewbkts)
{
for (bucket[K, V] b in oldbkts) {
alt (b) {
case (some[K, V](k, v)) {
insert_common[K, V](hasher, eqer, newbkts, nnewbkts, k, v);
}
case (_) { }
}
}
}
obj hashmap[K, V](hashfn[K] hasher,
eqfn[K] eqer,
mutable vec[mutable bucket[K, V]] bkts,
mutable uint nbkts,
mutable uint nelts,
util.rational lf)
{
fn insert(&K key, &V val) -> bool {
let util.rational load = rec(num=(nelts + 1u) as int, den=nbkts as int);
if (!util.rational_leq(load, lf)) {
let uint nnewbkts = _int.next_power_of_two(nbkts + 1u);
// FIXME (issue #94): Enforce our workaround to issue #94.
check ((nnewbkts as int) > 0);
let vec[mutable bucket[K, V]] newbkts = make_buckets[K, V](nnewbkts);
rehash[K, V](hasher, eqer, bkts, nbkts, newbkts, nnewbkts);
}
if (insert_common[K, V](hasher, eqer, bkts, nbkts, key, val)) {
nelts += 1u;
ret true;
}
ret false;
}
fn contains_key(&K key) -> bool {
alt (find_common[K, V](hasher, eqer, bkts, nbkts, key)) {
case (util.some[V](_)) { ret true; }
case (_) { ret false; }
}
}
fn get(&K key) -> V {
alt (find_common[K, V](hasher, eqer, bkts, nbkts, key)) {
case (util.some[V](val)) { ret val; }
case (_) { fail; }
}
}
fn find(&K key) -> util.option[V] {
be find_common[K, V](hasher, eqer, bkts, nbkts, key);
}
fn remove(&K key) -> util.option[V] {
let uint i = 0u;
while (i < nbkts) {
// FIXME (issue #94): as in find_common()
let int j = (hash[K](hasher, nbkts, key, i)) as int;
alt (bkts.(j)) {
case (some[K, V](_, val)) {
bkts.(j) = deleted[K, V]();
ret util.some[V](val);
}
case (deleted[K, V]()) {
nelts += 1u;
}
case (nil[K, V]()) {
ret util.none[V]();
}
}
}
ret util.none[V]();
}
fn rehash() {
let vec[mutable bucket[K, V]] newbkts = make_buckets[K, V](nbkts);
rehash[K, V](hasher, eqer, bkts, nbkts, newbkts, nbkts);
bkts = newbkts;
}
}
let vec[mutable bucket[K, V]] bkts = make_buckets[K, V](initial_capacity);
ret hashmap[K, V](hasher, eqer, bkts, initial_capacity, 0u, load_factor);
}
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