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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) -> bool;
type hashmap[K, V] = obj {
fn insert(&K key, &V val);
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 = uint(32); // 2^5
let util.rational load_factor = rec(num=3, den=4);
type bucket[V] = tag(nil(), deleted(), some(V));
// 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]() * uint(8) / uint(2)))
% nbkts;
}
fn hashr[K](hashfn[K] hasher, uint nbkts, &K key) -> uint {
ret ((((~ uint(0)) >>> (sys.rustrt.size_of[uint]() * uint(8) / uint(2)))
& hasher(key)) * uint(2) + uint(1))
% 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);
}
fn find_common[K, V](hashfn[K] hasher,
vec[mutable bucket[V]] bkts,
uint nbkts,
&K key)
-> util.option[V]
{
let uint i = uint(0);
while (i < nbkts) {
// Pending fix to issue #94, remove uint coercion.
let int j = int(hash[K](hasher, nbkts, key, i));
alt (bkts.(j)) {
case (some[V](val)) {
ret util.some[V](val);
}
case (nil[V]()) {
ret util.none[V]();
}
case (deleted[V]()) {
i += uint(1);
}
}
}
ret util.none[V]();
}
obj hashmap[K, V](hashfn[K] hasher,
eqfn[K] eqer,
mutable vec[mutable bucket[V]] bkts,
mutable uint nbkts,
mutable uint nelts,
util.rational lf)
{
fn insert(&K key, &V val) {
// FIXME grow the table and rehash if we ought to.
let uint i = uint(0);
while (i < nbkts) {
// Issue #94, as in find_common()
let int j = int(hash[K](hasher, nbkts, key, i));
alt (bkts.(j)) {
case (some[V](_)) {
i += uint(1);
}
case (_) {
bkts.(j) = some[V](val);
nelts += uint(1);
ret;
}
}
}
// full table, impossible unless growth is broken. remove after testing.
fail;
}
fn contains_key(&K key) -> bool {
alt (find_common[K, V](hasher, bkts, nbkts, key)) {
case (util.some[V](_)) { ret true; }
case (_) { ret false; }
}
}
fn get(&K key) -> V {
alt (find_common[K, V](hasher, 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, bkts, nbkts, key);
}
fn remove(&K key) -> util.option[V] {
let uint i = uint(0);
while (i < nbkts) {
// Issue #94, as in find_common()
let int j = int(hash[K](hasher, nbkts, key, i));
alt (bkts.(j)) {
case (some[V](val)) {
bkts.(j) = deleted[V]();
ret util.some[V](val);
}
case (deleted[V]()) {
nelts += uint(1);
}
case (nil[V]()) {
ret util.none[V]();
}
}
}
ret util.none[V]();
}
fn rehash() {}
}
let vec[mutable bucket[V]] bkts =
_vec.init_elt[mutable bucket[V]](nil[V](),
uint(initial_capacity));
ret hashmap[K, V](hasher, eqer, bkts, uint(0), uint(0), load_factor);
}
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