io.questdb.std.ByteCharSequenceObjHashMap Maven / Gradle / Ivy
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*
* Copyright (c) 2014-2019 Appsicle
* Copyright (c) 2019-2022 QuestDB
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
******************************************************************************/
package io.questdb.std;
import io.questdb.std.str.ByteCharSequence;
import io.questdb.std.str.DirectByteCharSequence;
import java.util.Arrays;
/**
* A copy implementation of CharSequenceObjHashMap. It is there to work with concrete classes
* and avoid incurring performance penalty of megamorphic virtual calls. These calls originate
* from calling charAt() on CharSequence interface. C2 compiler cannot inline these calls due to
* multiple implementations of charAt(). It resorts to a virtual method call via itable. ILP is the
* main victim of itable, suffering from non-deterministic performance loss. With this specific
* implementation of the map C2 compiler seems to be able to inline chatAt() calls and itables are
* no longer present in the async profiler.
*
* This map is optimized for ASCII and UTF8 DirectByteCharSequence lookups.
*/
public class ByteCharSequenceObjHashMap implements Mutable {
private static final int MIN_INITIAL_CAPACITY = 16;
private final ObjList list;
private final double loadFactor;
private int capacity;
private int free;
private int[] hashCodes;
private ByteCharSequence[] keys;
private int mask;
private V[] values;
public ByteCharSequenceObjHashMap() {
this(8);
}
public ByteCharSequenceObjHashMap(int initialCapacity) {
this(initialCapacity, 0.5);
}
@SuppressWarnings("unchecked")
private ByteCharSequenceObjHashMap(int initialCapacity, double loadFactor) {
if (loadFactor <= 0d || loadFactor >= 1d) {
throw new IllegalArgumentException("0 < loadFactor < 1");
}
free = capacity = initialCapacity < MIN_INITIAL_CAPACITY ? MIN_INITIAL_CAPACITY : Numbers.ceilPow2(initialCapacity);
this.loadFactor = loadFactor;
int len = Numbers.ceilPow2((int) (capacity / loadFactor));
keys = new ByteCharSequence[len];
hashCodes = new int[len];
mask = len - 1;
list = new ObjList<>(capacity);
values = (V[]) new Object[keys.length];
clear();
}
@Override
public void clear() {
Arrays.fill(keys, null);
Arrays.fill(hashCodes, 0);
free = capacity;
list.clear();
}
public boolean contains(DirectByteCharSequence key) {
return keyIndex(key) < 0;
}
public boolean excludes(DirectByteCharSequence key) {
return keyIndex(key) > -1;
}
public V get(DirectByteCharSequence key) {
return valueAt(keyIndex(key));
}
public V get(ByteCharSequence key) {
return valueAt(keyIndex(key));
}
public int keyIndex(DirectByteCharSequence key) {
int hashCode = Hash.hashMem32(key);
int index = Hash.spread(hashCode) & mask;
if (keys[index] == null) {
return index;
}
if (hashCode == hashCodes[index] && Chars.equals(key, keys[index])) {
return -index - 1;
}
return probe(key, hashCode, index);
}
public int keyIndex(ByteCharSequence key) {
int hashCode = Hash.hashMem32(key);
int index = Hash.spread(hashCode) & mask;
if (keys[index] == null) {
return index;
}
if (hashCode == hashCodes[index] && Chars.equals(key, keys[index])) {
return -index - 1;
}
return probe(key, hashCode, index);
}
public ObjList keys() {
return list;
}
public boolean put(ByteCharSequence key, V value) {
return putAt(keyIndex(key), key, value);
}
public boolean putAt(int index, ByteCharSequence key, V value) {
assert value != null;
if (putAt0(index, key, value)) {
list.add(key);
return true;
}
return false;
}
public int remove(ByteCharSequence key) {
int index = keyIndex(key);
if (index < 0) {
removeAt(index);
return -index - 1;
}
return -1;
}
public void removeAt(int index) {
if (index < 0) {
ByteCharSequence key = keys[-index - 1];
removeAt0(index);
list.remove(key);
}
}
public void removeAt0(int index) {
if (index < 0) {
int from = -index - 1;
erase(from);
free++;
// after we have freed up a slot
// consider non-empty keys directly below
// they may have been a direct hit but because
// directly hit slot wasn't empty these keys would
// have moved.
//
// After slot if freed these keys require re-hash
from = (from + 1) & mask;
for (
ByteCharSequence key = keys[from];
key != null;
from = (from + 1) & mask, key = keys[from]
) {
int hashCode = Hash.hashMem32(key);
int idealHit = Hash.spread(hashCode) & mask;
if (idealHit != from) {
int to;
if (keys[idealHit] != null) {
to = probe(key, hashCode, idealHit);
} else {
to = idealHit;
}
if (to > -1) {
move(from, to);
}
}
}
}
}
public int size() {
return capacity - free;
}
public V valueAt(int index) {
return index < 0 ? valueAtQuick(index) : null;
}
public V valueAtQuick(int index) {
return values[-index - 1];
}
public V valueQuick(int index) {
return get(list.getQuick(index));
}
private void erase(int index) {
keys[index] = null;
hashCodes[index] = 0;
values[index] = null;
}
private void move(int from, int to) {
keys[to] = keys[from];
hashCodes[to] = hashCodes[from];
values[to] = values[from];
erase(from);
}
private int probe(DirectByteCharSequence key, long hashCode, int index) {
do {
index = (index + 1) & mask;
if (keys[index] == null) {
return index;
}
if (hashCode == hashCodes[index] && Chars.equals(key, keys[index])) {
return -index - 1;
}
} while (true);
}
private int probe(ByteCharSequence key, long hashCode, int index) {
do {
index = (index + 1) & mask;
if (keys[index] == null) {
return index;
}
if (hashCode == hashCodes[index] && Chars.equals(key, keys[index])) {
return -index - 1;
}
} while (true);
}
private boolean putAt0(int index, ByteCharSequence key, V value) {
if (index < 0) {
values[-index - 1] = value;
return false;
} else {
keys[index] = key;
hashCodes[index] = Hash.hashMem32(key);
values[index] = value;
if (--free == 0) {
rehash();
}
return true;
}
}
@SuppressWarnings({"unchecked"})
private void rehash() {
int size = size();
int newCapacity = capacity * 2;
free = capacity = newCapacity;
int len = Numbers.ceilPow2((int) (newCapacity / loadFactor));
V[] oldValues = values;
ByteCharSequence[] oldKeys = keys;
int[] oldHashCodes = hashCodes;
keys = new ByteCharSequence[len];
hashCodes = new int[len];
values = (V[]) new Object[len];
Arrays.fill(keys, null);
mask = len - 1;
free -= size;
for (int i = oldKeys.length; i-- > 0; ) {
ByteCharSequence key = oldKeys[i];
if (key != null) {
final int index = keyIndex(key);
keys[index] = key;
hashCodes[index] = oldHashCodes[i];
values[index] = oldValues[i];
}
}
}
}