io.finch.internal.ParseNumber.scala Maven / Gradle / Ivy

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package io.finch.internal

abstract class ParseNumber[@specialized(Int, Long) A] {

  protected def max: Long
  protected def min: Long
  protected def prepare(a: Long): A

  // adopted from Java's Long.parseLong
  // scalastyle:off return
  final def apply(s: String): Option[A] = {
    var negative = false
    var limit = -max
    var result = 0L

    var i = 0
    if (s.length > 0) {
      val firstChar = s.charAt(0)
      if (firstChar < '0') {
        if (firstChar == '-') {
          negative = true
          limit = min
        } else if (firstChar != '+') return None

        if (s.length == 1) return None

        i += 1
      }

      // skip zeros
      while (i < s.length && s.charAt(i) == '0') i += 1

      val mulMin = limit / 10L

      while (i < s.length) {
        val c = s.charAt(i)
        if ('0' <= c && c <= '9') {
          if (result < mulMin) return None
          result = result * 10L
          val digit = c - '0'
          if (result < limit + digit) return None
          result = result - digit
        } else return None

        i += 1
      }
    } else return None

    Some(prepare(if (negative) result else -result))
  }
  // scalastyle:on return
}

object parseInt extends ParseNumber[Int] {
  protected def min: Long = Int.MinValue
  protected def max: Long = Int.MaxValue
  protected def prepare(a: Long): Int = a.toInt
}

object parseLong extends ParseNumber[Long] {
  protected def min: Long = Long.MinValue
  protected def max: Long = Long.MaxValue
  protected def prepare(a: Long): Long = a
}