Data.java

// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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.twitter.common.quantity;

/**
 * Provides a unit to allow conversions and unambiguous passing around of data {@link Amount}s.
 * The kilo/mega/giga/... hierarchy is built on base 2 so that the hierarchy increases by a factor
 * of 1024 instead of 1000 as typical in metric units.  Additionally, units are divided in 2
 * hierarchies one based on bits and the other on bytes.  Thus {@link #Kb} represents kilobits; so
 * 1 Kb = 1024 bits, and {@link #KB} represents kilobytes so 1 KB = 1024 bytes or 8192 bits.
 *
 * @author John Sirois
 */
public enum Data implements Unit<Data> {
  BITS(1),
  Kb(1024, BITS),
  Mb(1024, Kb),
  Gb(1024, Mb),
  BYTES(8, BITS),
  KB(1024, BYTES),
  MB(1024, KB),
  GB(1024, MB),
  TB(1024, GB),
  PB(1024, TB);

  private final double multiplier;

  private Data(double multiplier) {
    this.multiplier = multiplier;
  }

  private Data(double multiplier, Data base) {
    this(multiplier * base.multiplier);
  }

  @Override
  public double multiplier() {
    return multiplier;
  }
}