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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* Hash table.
*
* Copyright: Eugene Wissner 2017.
* License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
* Mozilla Public License, v. 2.0).
* Authors: $(LINK2 mailto:info@caraus.de, Eugene Wissner)
*/
module tanya.container.hashtable;
import std.algorithm.comparison;
import std.traits;
import tanya.container.entry;
import tanya.memory;
private int compare(const(char)[] key1, const(char)[] key2)
{
return cmp(key1, key2);
}
private int compare(K)(K key1, K key2)
if (isIntegral!K)
{
return cast(int) (key1 - key2);
}
struct Range(K, V)
{
private HashEntry!(K, V)*[] table;
private size_t begin, end;
invariant
{
assert(this.begin <= this.end);
}
private this(HashEntry!(K, V)*[] table)
{
this.table = table;
}
@property bool empty() const
{
for (size_t i = this.begin; i < this.begin; ++i)
{
if (this.table[i] !is null)
{
return false;
}
}
return true;
}
}
struct HashTable(K, V)
{
/**
* Create a new hashtable.
*
* Params:
* size = Minimum number of initial buckets.
* allocator = Allocator.
*/
this(const size_t size, shared Allocator allocator = defaultAllocator)
in
{
assert(size >= 1);
}
body
{
this(allocator);
this.table = new HashEntry!(K, V)*[size];
}
/// Ditto.
this(shared Allocator allocator)
in
{
assert(allocator !is null);
}
body
{
this.allocator_ = allocator;
}
private size_t calculateHash(const(char)[] key)
{
size_t hashval;
for (int i; hashval < size_t.max && i < key.length; ++i)
{
hashval = hashval << 8;
hashval += key[i];
}
return hashval % this.table.length;
}
private size_t calculateHash()(K key)
if (isIntegral!K)
{
return key % this.table.length;
}
/**
* Retrieve a key-value pair from a hash table.
*/
V opIndex(K key)
{
auto bin = calculateHash(key);
auto pair = this.table[bin];
while (pair !is null && compare(key, pair.pair[0]) > 0)
{
pair = pair.next;
}
// Did we actually find anything?
if (pair is null || compare(key, pair.pair[0]) != 0)
{
return null;
}
else
{
return pair.pair[1];
}
}
/**
* Insert a key-value pair into a hash table.
*/
bool insert(K key, V value)
{
HashEntry!(K, V)* last;
auto bin = calculateHash(key);
auto next = this.table[bin];
while (next !is null && compare(key, next.pair[0]) > 0)
{
last = next;
next = next.next;
}
// There's already a pair.
if (next !is null && compare(key, next.pair[0]) == 0)
{
next.pair[1] = value;
return false;
}
else // Nope, could't find it. Time to grow a pair.
{
auto newpair = new HashEntry!(K, V)(key, value);
// We're at the start of the linked list in this bin.
if (next == this.table[bin])
{
newpair.next = next;
this.table[bin] = newpair;
}
else if (next is null)
{
// We're at the end of the linked list in this bin.
last.next = newpair;
}
else
{
// We're in the middle of the list.
newpair.next = next;
last.next = newpair;
}
return true;
}
}
void opIndexAssign(V value, K key)
{
insert(key, value);
}
Range!(K, V) opIndex()
{
return typeof(return)(this.table);
}
@property bool empty() const
{
foreach (entry; this.table)
{
if (entry !is null)
{
return false;
}
}
return true;
}
private HashEntry!(K, V)*[] table;
mixin DefaultAllocator;
}
unittest
{
auto ht = HashTable!(string, string)(65536);
assert(ht.empty);
ht["key1"] = "inky";
ht["key2"] = "pinky";
ht["key3"] = "blinky";
ht["key4"] = "floyd";
assert(!ht.empty);
assert("inky" == ht["key1"]);
assert("pinky" == ht["key2"]);
assert("blinky" == ht["key3"]);
assert("floyd" == ht["key4"]);
}
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