com.twitter.bijection.ModDivInjection.scala Maven / Gradle / Ivy

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/*
Copyright 2012 Twitter, Inc.

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.twitter.bijection
import scala.util.Success

/**
  * A common injection on numbers: N -> (m = N mod K, (N-m)/K) The first element in result tuple is
  * always [0, modulus)
  */
class IntModDivInjection(val modulus: Int) extends Injection[Int, (Int, Int)] {
  require(modulus > 0, "Modulus must be positive: " + modulus)
  override def apply(n: Int) = {
    val cmod = n % modulus
    val mod = if (cmod < 0) cmod + modulus else cmod
    val div = n / modulus
    val toNegInf = if ((n < 0) && (mod != 0)) div - 1 else div
    (mod, toNegInf)
  }

  private val maxDiv = Int.MaxValue / modulus
  private val minDiv = (Int.MinValue / modulus) - 1

  override def invert(moddiv: (Int, Int)) = {
    val (mod, div) = moddiv
    val res = div * modulus + mod
    if (
      mod >= 0 && mod < modulus && div <= maxDiv && div >= minDiv &&
      // We could wrap around if we get bad input:
      ((res >= 0) == (div >= 0))
    ) Success(res)
    else InversionFailure.failedAttempt(moddiv)
  }
}

/**
  * A common injection on numbers: N -> (m = N mod K, (N-m)/K) The first element in result tuple is
  * always [0, modulus)
  */
class LongModDivInjection(val modulus: Long) extends Injection[Long, (Long, Long)] {
  require(modulus > 0, "Modulus must be positive: " + modulus)
  override def apply(n: Long) = {
    val cmod = n % modulus
    val mod = if (cmod < 0) cmod + modulus else cmod
    val div = n / modulus
    val toNegInf = if ((n < 0) && (mod != 0)) div - 1L else div
    (mod, toNegInf)
  }

  private val maxDiv = Long.MaxValue / modulus
  private val minDiv = (Long.MinValue / modulus) - 1L

  override def invert(moddiv: (Long, Long)) = {
    val (mod, div) = moddiv
    val res = div * modulus + mod
    if (
      mod >= 0 && mod < modulus && div <= maxDiv && div >= minDiv &&
      ((res >= 0) == (div >= 0))
    ) Success(res)
    else InversionFailure.failedAttempt(moddiv)
  }
}