CombinatoryUnitCache.java

// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
 
package org.wpilib.units;
 
import java.util.Objects;
import java.util.function.BiFunction;
import org.wpilib.units.collections.LongToObjectHashMap;

public final class CombinatoryUnitCache<A extends Unit, B extends Unit, Out extends Unit> {
  private final LongToObjectHashMap<Out> m_cache = new LongToObjectHashMap<>();
 
  private final BiFunction<? super A, ? super B, ? extends Out> m_constructor;

  public CombinatoryUnitCache(BiFunction<? super A, ? super B, ? extends Out> constructor) {
    this.m_constructor =
        Objects.requireNonNull(constructor, "Cache unit constructor must be provided");
  }

  public Out combine(A a, B b) {
    final long key = ((long) a.hashCode()) << 32L | (b.hashCode() & 0xFFFFFFFFL);
 
    var existing = m_cache.get(key);
    if (existing != null) {
      return existing;
    }
 
    var newUnit = m_constructor.apply(a, b);
    m_cache.put(key, newUnit);
    return newUnit;
  }
}