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Swirlds is a software platform designed to build fully-distributed applications that harness the power of the cloud without servers. Now you can develop applications with fairness in decision making, speed, trust and reliability, at a fraction of the cost of traditional server-based platforms.
/*
* Copyright (C) 2021-2024 Hedera Hashgraph, LLC
*
* 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 com.swirlds.merkledb.collections;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Provides auto-expanding storage for triples of longs, up to some maximum capacity. The triples
* are stored in "chunks" of configurable size, and retrieved by using an integer index.
*
* Allocated chunks are never released; but the existing chunks may be re-used by calling
* {@link ThreeLongsList#clear()} and then storing more triples starting again at index 0.
*
* Important: This class is not thread-safe, and by default has a capacity of only 4k triples (12k total longs).
*/
public class ThreeLongsList {
private static final int LONGS_PER_TRIPLE = 3;
private static final int SECOND_LONG_OFFSET = 1;
private static final int THIRD_LONG_OFFSET = 2;
public static final int SMALL_MAX_TRIPLES = 4_000;
public static final int SMALL_TRIPLES_PER_CHUNK = 1_000;
private final int maxTriples;
private final int triplesPerChunk;
private final List data = new ArrayList<>();
private int numChunks = 0;
private int nextIndex = 0;
/**
* Construct a new ThreeLongsList with the default max and initial capacities.
*/
public ThreeLongsList() {
this(SMALL_MAX_TRIPLES, SMALL_TRIPLES_PER_CHUNK);
}
/**
* Construct a new ThreeLongsList with the given max capacity and default
* initial triples per chunk.
*
* @param maxTriples
* the maximum number of triplets that can be stored
*/
public ThreeLongsList(final int maxTriples) {
this(maxTriples, Math.min(maxTriples, SMALL_TRIPLES_PER_CHUNK));
}
/**
* Construct a new ThreeLongsList with the given max capacity and triples per chunk.
*
* @param maxTriples
* the maximum number of triplets that can be stored
* @throws IllegalArgumentException
* if triplesPerChunk is non-positive or greater than maxTriples
*/
public ThreeLongsList(final int maxTriples, final int triplesPerChunk) {
if (triplesPerChunk < 1 || maxTriples < triplesPerChunk) {
throw new IllegalArgumentException("Cannot construct ThreeLongsList with " + maxTriples
+ " max triples and " + triplesPerChunk + " triples per chunk");
}
this.maxTriples = maxTriples;
this.triplesPerChunk = triplesPerChunk;
}
/**
* Adds a triple of longs.
*
* @param l1
* first long to add
* @param l2
* second long to add
* @param l3
* third long to add
* @throws IllegalStateException
* if the list size would exceed its max capacity
*/
public void add(final long l1, final long l2, final long l3) {
if (nextIndex == maxTriples) {
throw new IllegalStateException("Cannot store any more triples, reached max capacity of " + maxTriples);
}
final int chunkIndex = nextIndex / triplesPerChunk;
int subIndex = nextIndex % triplesPerChunk;
if (subIndex == 0 && numChunks == chunkIndex) {
final long[] nextChunk = new long[LONGS_PER_TRIPLE * triplesPerChunk];
data.add(nextChunk);
numChunks++;
}
final long[] chunk = data.get(chunkIndex);
subIndex *= LONGS_PER_TRIPLE;
chunk[subIndex] = l1;
chunk[subIndex + SECOND_LONG_OFFSET] = l2;
chunk[subIndex + THIRD_LONG_OFFSET] = l3;
nextIndex++;
}
/**
* Get long triplet at given index
*
* @param index
* the index to get
* @return array of the three longs in triplet
* @throws IndexOutOfBoundsException
* if index is negative or not less than nextIndex
*/
public long[] get(final int index) {
if (index < 0 || index >= nextIndex) {
throw new IndexOutOfBoundsException("Index " + index + " unusable with " + nextIndex + " triples stored");
}
final int chunkIndex = index / triplesPerChunk;
final long[] chunk = data.get(chunkIndex);
final int subIndex = (index % triplesPerChunk) * LONGS_PER_TRIPLE;
return Arrays.copyOfRange(chunk, subIndex, subIndex + LONGS_PER_TRIPLE);
}
/**
* Clear contents leaving capacity the same.
*/
public void clear() {
nextIndex = 0;
}
/**
* For each to iterate over all triples stored.
*
* @param handler
* callback to receieve each triple.
*/
public void forEach(final ThreeLongFunction handler) throws T {
int index = 0;
for (final long[] chunk : data) {
for (int j = 0, k = 0; j < triplesPerChunk; j++, k += LONGS_PER_TRIPLE) {
if (index == nextIndex) {
return;
}
handler.process(chunk[k], chunk[k + SECOND_LONG_OFFSET], chunk[k + THIRD_LONG_OFFSET]);
index++;
}
}
}
/**
* Gets the number of long triplets actually stored in this list (that is, the number
* of times that {@link ThreeLongsList#add(long, long, long)} has been called since
* the last call to {@link ThreeLongsList#clear()}.
*
* @return the number of triplets in the list
*/
public int size() {
return nextIndex;
}
/**
* Gets the maximum number of triples that can be stored in this list.
*
* @return the max capacity of the list
*/
public int capacity() {
return maxTriples;
}
/**
* Simple functional interface to process three longs. A Throwable of the given
* type may be thrown.
*
* @param
* Type of Throwable that may be thrown
*/
@FunctionalInterface
public interface ThreeLongFunction {
void process(long l1, long l2, long l3) throws T;
}
int getTriplesPerChunk() {
return triplesPerChunk;
}
}