org.nustaq.serialization.FSTClazzLineageInfo Maven / Gradle / Ivy

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A fast java serialization drop in-replacement and some serialization based utils such as Structs and OffHeap Memory.
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package org.nustaq.serialization;

import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * Represents a ordered class lineage based on the specificity of classes, where specificity is defined as follows:
 * 
 * null has specificity 0
 * java.lang.Object has specificity 0
 * an interface without any extends clause has specificity 1
 * a class or interface has a specificity of 1 + the specificity of the superclass + the sum of the specificity of the implemented interfaces.
 * 
 * @author Odd Moeller 2017-03-08.
 */
public final class FSTClazzLineageInfo {
  private static final Class[] EMPTY_CLASS_ARRAY = new Class[0];
  private static final LineageInfo OBJECT_LINEAGE_INFO = new LineageInfo(new LinkedHashSet>(Collections.singletonList(Object.class)), 0);
  private static final ConcurrentMap, LineageInfo> lineageInfos = new ConcurrentHashMap, LineageInfo>();
  public static final Comparator SPECIFICITY_CLASS_COMPARATOR = new Comparator() {
    @Override
    public int compare(final Class c1, final Class c2) {
      return getLineageInfo(c2).specificity - getLineageInfo(c1).specificity;
    }
  };

  private FSTClazzLineageInfo() {}

  /**
   * Returns the specificity of the specified class as defined above.
   */
  public static int getSpecificity(final Class clazz) {
    if (clazz == null) return 0;
    final LineageInfo lineageInfo = FSTClazzLineageInfo.getLineageInfo(clazz);
    return lineageInfo == null ? 0 : lineageInfo.specificity;
  }

  /**
   * Returns the lineage of the specified class ordered by specificity (the class itself is at position 0 since it is most specific in its lineage).
   */
  public static Class[] getLineage(final Class clazz) {
    final LineageInfo lineageInfo = getLineageInfo(clazz);
    return lineageInfo == null ? EMPTY_CLASS_ARRAY : lineageInfo.lineage.toArray(new Class[lineageInfo.lineage.size()]);
  }

  private static LineageInfo getLineageInfo(final Class clazz) {
    if (clazz == null) return null;
    else if (clazz.equals(Object.class)) return OBJECT_LINEAGE_INFO;
    final LineageInfo lineageInfo = lineageInfos.get(clazz);
    if (lineageInfo != null) {
      return lineageInfo;
    }

    int specificity = 1;
    final LinkedHashSet> ancestors = new LinkedHashSet>();
    final Class sc = getSuperclass(clazz);
    final LineageInfo sl = getLineageInfo(sc);
    if (sl != null) {
      ancestors.addAll(sl.lineage);
      specificity += sl.specificity;
    }
    for (final Class i : getInterfaces(clazz)) {
      final LineageInfo il = getLineageInfo(i);
      if (il != null) {
        ancestors.removeAll(il.lineage);
        ancestors.addAll(il.lineage);
        specificity += il.specificity;
      }
    }
    final Class[] array = ancestors.toArray(new Class[ancestors.size()]);
    Arrays.sort(array, SPECIFICITY_CLASS_COMPARATOR);
    final LinkedHashSet> lineage = new LinkedHashSet>(array.length + 1);
    lineage.add(clazz);
    Collections.addAll(lineage, array);
    final LineageInfo result = new LineageInfo(lineage, specificity);
    lineageInfos.putIfAbsent(clazz, result);
    return result;
  }

  private static Class getSuperclass(final Class c) {
    if (c == null) return null;
    return c.getSuperclass();
  }

  private static Class[] getInterfaces(final Class c) {
    if (c == null) return null;
    return c.getInterfaces();
  }

  private static final class LineageInfo {
    private final LinkedHashSet> lineage;
    private final int specificity;
    private LineageInfo(final LinkedHashSet> lineage, final int specificity) {
      this.lineage = lineage;
      this.specificity = specificity;
    }
  }
}