org.glowroot.agent.model.QueryDataMap Maven / Gradle / Ivy
/*
* Copyright 2016-2018 the original author or authors.
*
* 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 org.glowroot.agent.model;
import org.glowroot.agent.shaded.org.checkerframework.checker.nullness.qual.Nullable;
import static org.glowroot.agent.shaded.com.google.common.base.Preconditions.checkNotNull;
// micro-optimized map for query data
public class QueryDataMap {
private static final Object CHAINED_KEY = new Object();
private final String type;
// capacity must always be a power of 2, see comments in get() and put()
private int capacity = 4;
private @Nullable Object[] table = new Object[capacity << 1];
private int size = 0;
private int threshold = 3; // 0.75 * capacity
public QueryDataMap(String type) {
this.type = type;
}
public String getType() {
return type;
}
public @Nullable SyncQueryData get(String key) {
// this mask requires capacity to be a power of 2
int bucket = (key.hashCode() & (capacity - 1)) << 1;
Object keyAtBucket = table[bucket];
Object value = table[bucket + 1];
if (key.equals(keyAtBucket)) {
return (SyncQueryData) value;
}
if (keyAtBucket == CHAINED_KEY) {
return getChained(key, checkNotNull(value));
}
return null;
}
// IMPORTANT put assumes get was already called and key is not present in this map
public void put(String key, SyncQueryData value) {
if (size++ > threshold) {
rehash();
}
putWithoutRehashCheck(key, value);
}
private void putWithoutRehashCheck(Object key, @Nullable Object value) {
// this mask requires capacity to be a power of 2
int bucket = (key.hashCode() & (capacity - 1)) << 1;
Object keyAtBucket = table[bucket];
if (keyAtBucket == null) {
table[bucket] = key;
table[bucket + 1] = value;
return;
}
putChained(key, value, bucket, keyAtBucket);
}
private void putChained(Object key, @Nullable Object value, int bucket, Object keyAtBucket) {
if (keyAtBucket == CHAINED_KEY) {
@Nullable
Object[] chain = (/*@Nullable*/ Object[]) checkNotNull(table[bucket + 1]);
int chainLength = chain.length;
for (int i = 0; i < chainLength; i += 2) {
if (chain[i] == null) {
chain[i] = key;
chain[i + 1] = value;
return;
}
}
@Nullable
Object[] newChain = new Object[chainLength << 1];
System.arraycopy(chain, 0, newChain, 0, chainLength);
newChain[chainLength] = key;
newChain[chainLength + 1] = value;
table[bucket + 1] = newChain;
return;
}
@Nullable
Object[] chain = new Object[4];
chain[0] = keyAtBucket;
chain[1] = table[bucket + 1];
chain[2] = key;
chain[3] = value;
table[bucket] = CHAINED_KEY;
table[bucket + 1] = chain;
}
private void rehash() {
@Nullable
Object[] existingTable = table;
capacity <<= 1;
threshold <<= 1;
table = new Object[capacity << 1];
for (int i = 0; i < existingTable.length; i += 2) {
Object key = existingTable[i];
if (key == null) {
continue;
}
if (key == CHAINED_KEY) {
@Nullable
Object[] values = (/*@Nullable*/ Object[]) checkNotNull(existingTable[i + 1]);
putChainedValues(values);
} else {
putWithoutRehashCheck(key, existingTable[i + 1]);
}
}
}
private void putChainedValues(/*@Nullable*/ Object[] values) {
for (int j = 0; j < values.length; j += 2) {
Object chainedKey = values[j];
if (chainedKey == null) {
break;
}
putWithoutRehashCheck(chainedKey, values[j + 1]);
}
}
private static @Nullable SyncQueryData getChained(String key, Object value) {
@Nullable
Object[] chainedTable = (/*@Nullable*/ Object[]) value;
for (int i = 0; i < chainedTable.length; i += 2) {
if (key.equals(chainedTable[i])) {
return (SyncQueryData) chainedTable[i + 1];
}
}
return null;
}
}