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/* Copyright (c) 2008-2023, Nathan Sweet
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided with the distribution.
* - Neither the name of Esoteric Software nor the names of its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
* SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
package com.esotericsoftware.kryo.util;
import static com.esotericsoftware.kryo.util.ObjectMap.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.NoSuchElementException;
import com.esotericsoftware.kryo.KryoException;
/** An unordered map where the keys are unboxed ints and values are objects. No allocation is done except when growing the table
* size.
*
* This class performs fast contains and remove (typically O(1), worst case O(n) but that is rare in practice). Add may be
* slightly slower, depending on hash collisions. Hashcodes are rehashed to reduce collisions and the need to resize. Load factors
* greater than 0.91 greatly increase the chances to resize to the next higher POT size.
*
* Unordered sets and maps are not designed to provide especially fast iteration.
*
* This implementation uses linear probing with the backward shift algorithm for removal. Hashcodes are rehashed using Fibonacci
* hashing, instead of the more common power-of-two mask, to better distribute poor hashCodes (see Malte
* Skarupke's blog post). Linear probing continues to work even when all hashCodes collide, just more slowly.
* @author Nathan Sweet
* @author Tommy Ettinger */
public class IntMap implements Iterable> {
public int size;
int[] keyTable;
V[] valueTable;
V zeroValue;
boolean hasZeroValue;
private final float loadFactor;
private int threshold;
/** Used by {@link #place(int)} to bit shift the upper bits of a {@code long} into a usable range (>= 0 and <=
* {@link #mask}). The shift can be negative, which is convenient to match the number of bits in mask: if mask is a 7-bit
* number, a shift of -7 shifts the upper 7 bits into the lowest 7 positions. This class sets the shift > 32 and < 64,
* which if used with an int will still move the upper bits of an int to the lower bits due to Java's implicit modulus on
* shifts.
*
* {@link #mask} can also be used to mask the low bits of a number, which may be faster for some hashcodes, if
* {@link #place(int)} is overridden. */
protected int shift;
/** A bitmask used to confine hashcodes to the size of the table. Must be all 1 bits in its low positions, ie a power of two
* minus 1. If {@link #place(int)} is overriden, this can be used instead of {@link #shift} to isolate usable bits of a
* hash. */
protected int mask;
/** Creates a new map with an initial capacity of 51 and a load factor of 0.8. */
public IntMap () {
this(51, 0.8f);
}
/** Creates a new map with a load factor of 0.8.
*
* @param initialCapacity If not a power of two, it is increased to the next nearest power of two. */
public IntMap (int initialCapacity) {
this(initialCapacity, 0.8f);
}
/** Creates a new map with the specified initial capacity and load factor. This map will hold initialCapacity items before
* growing the backing table.
* @param initialCapacity If not a power of two, it is increased to the next nearest power of two. */
public IntMap (int initialCapacity, float loadFactor) {
if (loadFactor <= 0f || loadFactor >= 1f)
throw new IllegalArgumentException("loadFactor must be > 0 and < 1: " + loadFactor);
this.loadFactor = loadFactor;
int tableSize = tableSize(initialCapacity, loadFactor);
threshold = (int)(tableSize * loadFactor);
mask = tableSize - 1;
shift = Long.numberOfLeadingZeros(mask);
keyTable = new int[tableSize];
valueTable = (V[])new Object[tableSize];
}
/** Creates a new map identical to the specified map. */
public IntMap (IntMap map) {
this((int)(map.keyTable.length * map.loadFactor), map.loadFactor);
System.arraycopy(map.keyTable, 0, keyTable, 0, map.keyTable.length);
System.arraycopy(map.valueTable, 0, valueTable, 0, map.valueTable.length);
size = map.size;
zeroValue = map.zeroValue;
hasZeroValue = map.hasZeroValue;
}
/** Returns an index >= 0 and <= {@link #mask} for the specified {@code item}.
*
* The default implementation uses Fibonacci hashing on the item's {@link Object#hashCode()}: the hashcode is multiplied by a
* long constant (2 to the 64th, divided by the golden ratio) then the uppermost bits are shifted into the lowest positions to
* obtain an index in the desired range. Multiplication by a long may be slower than int (eg on GWT) but greatly improves
* rehashing, allowing even very poor hashcodes, such as those that only differ in their upper bits, to be used without high
* collision rates. Fibonacci hashing has increased collision rates when all or most hashcodes are multiples of larger
* Fibonacci numbers (see Malte
* Skarupke's blog post).
*
* This method can be overriden to customizing hashing. This may be useful eg in the unlikely event that most hashcodes are
* Fibonacci numbers, if keys provide poor or incorrect hashcodes, or to simplify hashing if keys provide high quality
* hashcodes and don't need Fibonacci hashing: {@code return item.hashCode() & mask;} */
protected int place (int item) {
return (int)(item * 0x9E3779B97F4A7C15L >>> shift);
}
/** Returns the index of the key if already present, else -(index + 1) for the next empty index. This can be overridden in this
* pacakge to compare for equality differently than {@link Object#equals(Object)}. */
private int locateKey (int key) {
int[] keyTable = this.keyTable;
for (int i = place(key);; i = i + 1 & mask) {
int other = keyTable[i];
if (other == 0) return -(i + 1); // Empty space is available.
if (other == key) return i; // Same key was found.
}
}
@Null
public V put (int key, @Null V value) {
if (key == 0) {
V oldValue = zeroValue;
zeroValue = value;
if (!hasZeroValue) {
hasZeroValue = true;
size++;
}
return oldValue;
}
int i = locateKey(key);
if (i >= 0) { // Existing key was found.
V oldValue = valueTable[i];
valueTable[i] = value;
return oldValue;
}
i = -(i + 1); // Empty space was found.
keyTable[i] = key;
valueTable[i] = value;
if (++size >= threshold) resize(keyTable.length << 1);
return null;
}
public void putAll (IntMap map) {
ensureCapacity(map.size);
if (map.hasZeroValue) put(0, map.zeroValue);
int[] keyTable = map.keyTable;
V[] valueTable = map.valueTable;
for (int i = 0, n = keyTable.length; i < n; i++) {
int key = keyTable[i];
if (key != 0) put(key, valueTable[i]);
}
}
/** Skips checks for existing keys, doesn't increment size, doesn't need to handle key 0. */
private void putResize (int key, @Null V value) {
int[] keyTable = this.keyTable;
for (int i = place(key);; i = (i + 1) & mask) {
if (keyTable[i] == 0) {
keyTable[i] = key;
valueTable[i] = value;
return;
}
}
}
public V get (int key) {
if (key == 0) return hasZeroValue ? zeroValue : null;
for (int i = place(key);; i = i + 1 & mask) {
int other = keyTable[i];
if (other == 0) return null;
if (other == key) return valueTable[i];
}
}
public V get (int key, @Null V defaultValue) {
if (key == 0) return hasZeroValue ? zeroValue : null;
for (int i = place(key);; i = i + 1 & mask) {
int other = keyTable[i];
if (other == 0) return defaultValue;
if (other == key) return valueTable[i];
}
}
@Null
public V remove (int key) {
if (key == 0) {
if (!hasZeroValue) return null;
hasZeroValue = false;
V oldValue = zeroValue;
zeroValue = null;
size--;
return oldValue;
}
int i = locateKey(key);
if (i < 0) return null;
int[] keyTable = this.keyTable;
V[] valueTable = this.valueTable;
V oldValue = valueTable[i];
int mask = this.mask, next = i + 1 & mask;
while ((key = keyTable[next]) != 0) {
int placement = place(key);
if ((next - placement & mask) > (i - placement & mask)) {
keyTable[i] = key;
valueTable[i] = valueTable[next];
i = next;
}
next = next + 1 & mask;
}
keyTable[i] = 0;
size--;
return oldValue;
}
/** Returns true if the map has one or more items. */
public boolean notEmpty () {
return size > 0;
}
/** Returns true if the map is empty. */
public boolean isEmpty () {
return size == 0;
}
/** Reduces the size of the backing arrays to be the specified capacity / loadFactor, or less. If the capacity is already less,
* nothing is done. If the map contains more items than the specified capacity, the next highest power of two capacity is used
* instead. */
public void shrink (int maximumCapacity) {
if (maximumCapacity < 0) throw new IllegalArgumentException("maximumCapacity must be >= 0: " + maximumCapacity);
int tableSize = tableSize(maximumCapacity, loadFactor);
if (keyTable.length > tableSize) resize(tableSize);
}
/** Clears the map and reduces the size of the backing arrays to be the specified capacity / loadFactor, if they are larger. */
public void clear (int maximumCapacity) {
int tableSize = tableSize(maximumCapacity, loadFactor);
if (keyTable.length <= tableSize) {
clear();
return;
}
size = 0;
hasZeroValue = false;
zeroValue = null;
resize(tableSize);
}
public void clear () {
if (size == 0) return;
size = 0;
Arrays.fill(keyTable, 0);
Arrays.fill(valueTable, null);
zeroValue = null;
hasZeroValue = false;
}
/** Returns true if the specified value is in the map. Note this traverses the entire map and compares every value, which may
* be an expensive operation.
* @param identity If true, uses == to compare the specified value with values in the map. If false, uses
* {@link #equals(Object)}. */
public boolean containsValue (@Null Object value, boolean identity) {
V[] valueTable = this.valueTable;
if (value == null) {
if (hasZeroValue && zeroValue == null) return true;
int[] keyTable = this.keyTable;
for (int i = valueTable.length - 1; i >= 0; i--)
if (keyTable[i] != 0 && valueTable[i] == null) return true;
} else if (identity) {
if (value == zeroValue) return true;
for (int i = valueTable.length - 1; i >= 0; i--)
if (valueTable[i] == value) return true;
} else {
if (hasZeroValue && value.equals(zeroValue)) return true;
for (int i = valueTable.length - 1; i >= 0; i--)
if (value.equals(valueTable[i])) return true;
}
return false;
}
public boolean containsKey (int key) {
if (key == 0) return hasZeroValue;
return locateKey(key) >= 0;
}
/** Returns the key for the specified value, or notFound if it is not in the map. Note this traverses the entire map
* and compares every value, which may be an expensive operation.
* @param identity If true, uses == to compare the specified value with values in the map. If false, uses
* {@link #equals(Object)}. */
public int findKey (@Null Object value, boolean identity, int notFound) {
V[] valueTable = this.valueTable;
if (value == null) {
if (hasZeroValue && zeroValue == null) return 0;
int[] keyTable = this.keyTable;
for (int i = valueTable.length - 1; i >= 0; i--)
if (keyTable[i] != 0 && valueTable[i] == null) return keyTable[i];
} else if (identity) {
if (value == zeroValue) return 0;
for (int i = valueTable.length - 1; i >= 0; i--)
if (valueTable[i] == value) return keyTable[i];
} else {
if (hasZeroValue && value.equals(zeroValue)) return 0;
for (int i = valueTable.length - 1; i >= 0; i--)
if (value.equals(valueTable[i])) return keyTable[i];
}
return notFound;
}
/** Increases the size of the backing array to accommodate the specified number of additional items / loadFactor. Useful before
* adding many items to avoid multiple backing array resizes. */
public void ensureCapacity (int additionalCapacity) {
int tableSize = tableSize(size + additionalCapacity, loadFactor);
if (keyTable.length < tableSize) resize(tableSize);
}
private void resize (int newSize) {
int oldCapacity = keyTable.length;
threshold = (int)(newSize * loadFactor);
mask = newSize - 1;
shift = Long.numberOfLeadingZeros(mask);
int[] oldKeyTable = keyTable;
V[] oldValueTable = valueTable;
keyTable = new int[newSize];
valueTable = (V[])new Object[newSize];
if (size > 0) {
for (int i = 0; i < oldCapacity; i++) {
int key = oldKeyTable[i];
if (key != 0) putResize(key, oldValueTable[i]);
}
}
}
public int hashCode () {
int h = size;
if (hasZeroValue && zeroValue != null) h += zeroValue.hashCode();
int[] keyTable = this.keyTable;
V[] valueTable = this.valueTable;
for (int i = 0, n = keyTable.length; i < n; i++) {
int key = keyTable[i];
if (key != 0) {
h += key * 31;
V value = valueTable[i];
if (value != null) h += value.hashCode();
}
}
return h;
}
public boolean equals (Object obj) {
if (obj == this) return true;
if (!(obj instanceof IntMap)) return false;
IntMap other = (IntMap)obj;
if (other.size != size) return false;
if (other.hasZeroValue != hasZeroValue) return false;
if (hasZeroValue) {
if (other.zeroValue == null) {
if (zeroValue != null) return false;
} else {
if (!other.zeroValue.equals(zeroValue)) return false;
}
}
int[] keyTable = this.keyTable;
V[] valueTable = this.valueTable;
for (int i = 0, n = keyTable.length; i < n; i++) {
int key = keyTable[i];
if (key != 0) {
V value = valueTable[i];
if (value == null) {
if (other.get(key, ObjectMap.dummy) != null) return false;
} else {
if (!value.equals(other.get(key))) return false;
}
}
}
return true;
}
/** Uses == for comparison of each value. */
public boolean equalsIdentity (@Null Object obj) {
if (obj == this) return true;
if (!(obj instanceof IntMap)) return false;
IntMap other = (IntMap)obj;
if (other.size != size) return false;
if (other.hasZeroValue != hasZeroValue) return false;
if (hasZeroValue && zeroValue != other.zeroValue) return false;
int[] keyTable = this.keyTable;
V[] valueTable = this.valueTable;
for (int i = 0, n = keyTable.length; i < n; i++) {
int key = keyTable[i];
if (key != 0 && valueTable[i] != other.get(key, ObjectMap.dummy)) return false;
}
return true;
}
public String toString () {
if (size == 0) return "[]";
java.lang.StringBuilder buffer = new java.lang.StringBuilder(32);
buffer.append('[');
int[] keyTable = this.keyTable;
V[] valueTable = this.valueTable;
int i = keyTable.length;
if (hasZeroValue) {
buffer.append("0=");
buffer.append(zeroValue);
} else {
while (i-- > 0) {
int key = keyTable[i];
if (key == 0) continue;
buffer.append(key);
buffer.append('=');
buffer.append(valueTable[i]);
break;
}
}
while (i-- > 0) {
int key = keyTable[i];
if (key == 0) continue;
buffer.append(", ");
buffer.append(key);
buffer.append('=');
buffer.append(valueTable[i]);
}
buffer.append(']');
return buffer.toString();
}
public Iterator> iterator () {
return entries();
}
/** Returns an iterator for the entries in the map. Remove is supported. */
public Entries entries () {
return new Entries(this);
}
/** Returns an iterator for the values in the map. Remove is supported. */
public Values values () {
return new Values(this);
}
/** Returns an iterator for the keys in the map. Remove is supported. */
public Keys keys () {
return new Keys(this);
}
public static class Entry {
public int key;
public @Null V value;
public String toString () {
return key + "=" + value;
}
}
private static class MapIterator {
private static final int INDEX_ILLEGAL = -2;
static final int INDEX_ZERO = -1;
public boolean hasNext;
final IntMap map;
int nextIndex, currentIndex;
boolean valid = true;
public MapIterator (IntMap map) {
this.map = map;
reset();
}
public void reset () {
currentIndex = INDEX_ILLEGAL;
nextIndex = INDEX_ZERO;
if (map.hasZeroValue)
hasNext = true;
else
findNextIndex();
}
void findNextIndex () {
int[] keyTable = map.keyTable;
for (int n = keyTable.length; ++nextIndex < n;) {
if (keyTable[nextIndex] != 0) {
hasNext = true;
return;
}
}
hasNext = false;
}
public void remove () {
int i = currentIndex;
if (i == INDEX_ZERO && map.hasZeroValue) {
map.hasZeroValue = false;
} else if (i < 0) {
throw new IllegalStateException("next must be called before remove.");
} else {
int[] keyTable = map.keyTable;
V[] valueTable = map.valueTable;
int mask = map.mask, next = i + 1 & mask, key;
while ((key = keyTable[next]) != 0) {
int placement = map.place(key);
if ((next - placement & mask) > (i - placement & mask)) {
keyTable[i] = key;
valueTable[i] = valueTable[next];
i = next;
}
next = next + 1 & mask;
}
keyTable[i] = 0;
if (i != currentIndex) --nextIndex;
}
currentIndex = INDEX_ILLEGAL;
map.size--;
}
}
public static class Entries extends MapIterator implements Iterable>, Iterator> {
private final Entry entry = new Entry();
public Entries (IntMap map) {
super(map);
}
/** Note the same entry instance is returned each time this method is called. */
public Entry next () {
if (!hasNext) throw new NoSuchElementException();
if (!valid) throw new KryoException("#iterator() cannot be used nested.");
int[] keyTable = map.keyTable;
if (nextIndex == INDEX_ZERO) {
entry.key = 0;
entry.value = map.zeroValue;
} else {
entry.key = keyTable[nextIndex];
entry.value = map.valueTable[nextIndex];
}
currentIndex = nextIndex;
findNextIndex();
return entry;
}
public boolean hasNext () {
if (!valid) throw new KryoException("#iterator() cannot be used nested.");
return hasNext;
}
public Iterator> iterator () {
return this;
}
}
public static class Values extends MapIterator implements Iterable, Iterator {
public Values (IntMap map) {
super(map);
}
public boolean hasNext () {
return hasNext;
}
@Null
public V next () {
if (!hasNext) throw new NoSuchElementException();
V value;
if (nextIndex == INDEX_ZERO)
value = map.zeroValue;
else
value = map.valueTable[nextIndex];
currentIndex = nextIndex;
findNextIndex();
return value;
}
public Iterator iterator () {
return this;
}
/** Returns a new list containing the remaining values. */
public ArrayList toList () {
ArrayList array = new ArrayList(map.size);
while (hasNext)
array.add(next());
return array;
}
}
public static class Keys extends MapIterator {
public Keys (IntMap map) {
super(map);
}
public int next () {
if (!hasNext) throw new NoSuchElementException();
int key = nextIndex == INDEX_ZERO ? 0 : map.keyTable[nextIndex];
currentIndex = nextIndex;
findNextIndex();
return key;
}
/** Returns a new array containing the remaining keys. */
public IntArray toArray () {
IntArray array = new IntArray(true, map.size);
while (hasNext)
array.add(next());
return array;
}
/** Adds the remaining values to the specified array. */
public IntArray toArray (IntArray array) {
while (hasNext)
array.add(next());
return array;
}
}
}