org.forstdb.util.IntComparator Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of forstjni Show documentation

ForSt fat jar with modifications specific for Apache Flink that contains .so files for linux32 and linux64 (glibc and musl-libc), jnilib files for Mac OSX, and a .dll for Windows x64.

The newest version!

// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

package org.forstdb.util;

import org.forstdb.AbstractComparator;
import org.forstdb.ComparatorOptions;

import java.nio.ByteBuffer;

/**
 * This is a Java implementation of a Comparator for Java int
 * keys.
 *
 * This comparator assumes keys are (at least) four bytes, so
 * the caller must guarantee that in accessing other APIs in
 * combination with this comparator.
 *
 * The performance of Comparators implemented in Java is always
 * less than their C++ counterparts due to the bridging overhead,
 * as such you likely don't want to use this apart from benchmarking
 * or testing.
 */
public final class IntComparator extends AbstractComparator {

  public IntComparator(final ComparatorOptions copt) {
    super(copt);
  }

  @Override
  public String name() {
    return "rocksdb.java.IntComparator";
  }

  @Override
  public int compare(final ByteBuffer a, final ByteBuffer b) {
    return compareIntKeys(a, b);
  }

  /**
   * Compares integer keys
   * so that they are in ascending order
   *
   * @param a 4-bytes representing an integer key
   * @param b 4-bytes representing an integer key
   *
   * @return negative if a < b, 0 if a == b, positive otherwise
   */
  private int compareIntKeys(final ByteBuffer a, final ByteBuffer b) {
    final int iA = a.getInt();
    final int iB = b.getInt();

    // protect against int key calculation overflow
    final long diff = (long)iA - iB;
    final int result;
    if (diff < Integer.MIN_VALUE) {
      result = Integer.MIN_VALUE;
    } else if(diff > Integer.MAX_VALUE) {
      result = Integer.MAX_VALUE;
    } else {
      result = (int)diff;
    }
    return result;
  }
}