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import org.scalacheck._
import Prop._
import Gen._
import Arbitrary._
import math._
import concurrent.duration.Duration.fromNanos
object Test extends Properties("Division of Duration by Long") {
val weightedLong =
frequency(
1 -> choose(-128L, 127L),
1 -> (arbitrary[Byte] map (_.toLong << 8)),
1 -> (arbitrary[Byte] map (_.toLong << 16)),
1 -> (arbitrary[Byte] map (_.toLong << 24)),
1 -> (arbitrary[Byte] map (_.toLong << 32)),
1 -> (arbitrary[Byte] map (_.toLong << 40)),
1 -> (arbitrary[Byte] map (_.toLong << 48)),
1 -> (choose(-127L, 127L) map (_ << 56))
)
val genTwoSmall = for {
a <- weightedLong
b <- choose(-(Long.MaxValue / max(1, abs(a))), Long.MaxValue / max(1, abs(a)))
} yield (a, b)
val genTwoLarge = for {
a <- weightedLong
b <- arbitrary[Long] suchThat (b => (abs(b) > Long.MaxValue / max(1, abs(a))))
} yield (a, b)
val genClose = for {
a <- weightedLong
if a != 0
b <- choose(Long.MaxValue / a - 10, Long.MaxValue / a + 10)
} yield (a, b)
val genBorderline =
frequency(
1 -> (Long.MinValue, 0L),
1 -> (Long.MinValue, 1L),
1 -> (Long.MinValue, -1L),
1 -> (0L, Long.MinValue),
1 -> (1L, Long.MinValue),
1 -> (-1L, Long.MinValue),
90 -> genClose
)
def mul(a: Long, b: Long): Long = {
(fromNanos(a) * b).toNanos
}
property("without overflow") = forAll(genTwoSmall) { case (a, b) =>
a * b == mul(a, b)
}
property("with overflow") = forAll(genTwoLarge) { case (a, b) =>
try { mul(a, b); false } catch { case _: IllegalArgumentException => true }
}
property("on overflow edge cases") = forAll(genBorderline) { case (a, b) =>
val shouldFit =
a != Long.MinValue && // must fail due to illegal duration length
(b != Long.MinValue || a == 0) && // Long factor may only be MinValue if the duration is zero, otherwise the result will be illegal
(abs(b) <= Long.MaxValue / max(1, abs(a))) // check the rest against the “safe” division method
try { mul(a, b); shouldFit }
catch { case _: IllegalArgumentException => !shouldFit }
}
}
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