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/*
* Copyright (C) 2009, Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.util;
/**
* Simple Map<long, Object>.
*
* @param <V>
* type of the value instance.
* @since 4.9
*/
public class LongMap<V> {
private static final float LOAD_FACTOR = 0.75f;
private Node<V>[] table;
/** Number of entries currently in the map. */
private int size;
/** Next {@link #size} to trigger a {@link #grow()}. */
private int growAt;
/**
* Initialize an empty LongMap.
*/
public LongMap() {
table = createArray(64);
growAt = (int) (table.length * LOAD_FACTOR);
}
/**
* Whether {@code key} is present in the map.
*
* @param key
* the key to find.
* @return {@code true} if {@code key} is present in the map.
*/
public boolean containsKey(long key) {
return get(key) != null;
}
/**
* Get value for this {@code key}
*
* @param key
* the key to find.
* @return stored value for this key, or {@code null}.
*/
public V get(long key) {
for (Node<V> n = table[index(key)]; n != null; n = n.next) {
if (n.key == key)
return n.value;
}
return null;
}
/**
* Remove an entry from the map
*
* @param key
* key to remove from the map.
* @return old value of the key, or {@code null}.
*/
public V remove(long key) {
Node<V> n = table[index(key)];
Node<V> prior = null;
while (n != null) {
if (n.key == key) {
if (prior == null)
table[index(key)] = n.next;
else
prior.next = n.next;
size--;
return n.value;
}
prior = n;
n = n.next;
}
return null;
}
/**
* Put a new entry into the map
*
* @param key
* key to store {@code value} under.
* @param value
* new value.
* @return prior value, or null.
*/
public V put(long key, V value) {
for (Node<V> n = table[index(key)]; n != null; n = n.next) {
if (n.key == key) {
final V o = n.value;
n.value = value;
return o;
}
}
if (++size == growAt)
grow();
insert(new Node<>(key, value));
return null;
}
private void insert(Node<V> n) {
final int idx = index(n.key);
n.next = table[idx];
table[idx] = n;
}
private void grow() {
final Node<V>[] oldTable = table;
final int oldSize = table.length;
table = createArray(oldSize << 1);
growAt = (int) (table.length * LOAD_FACTOR);
for (int i = 0; i < oldSize; i++) {
Node<V> e = oldTable[i];
while (e != null) {
final Node<V> n = e.next;
insert(e);
e = n;
}
}
}
private final int index(long key) {
int h = ((int) key) >>> 1;
h ^= (h >>> 20) ^ (h >>> 12);
return h & (table.length - 1);
}
@SuppressWarnings("unchecked")
private static final <V> Node<V>[] createArray(int sz) {
return new Node[sz];
}
private static class Node<V> {
final long key;
V value;
Node<V> next;
Node(long k, V v) {
key = k;
value = v;
}
}
}
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