alexandru commented on code in PR #371: URL: https://github.com/apache/incubator-pekko/pull/371#discussion_r1226284401
########## actor/src/main/scala/org/apache/pekko/util/UniqueRandomShortProvider.scala: ########## @@ -0,0 +1,106 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * license agreements; and to You under the Apache License, version 2.0: + * + * https://www.apache.org/licenses/LICENSE-2.0 + * + * This file is part of the Apache Pekko project, derived from Akka. + */ + +package org.apache.pekko.util + +import org.apache.pekko.annotation.InternalApi + +import java.security.SecureRandom + +/** + * An efficient collision free threadsafe generator of pseudo random + * shorts based on https://en.wikipedia.org/wiki/Double_hashing#Enhanced_double_hashing + * using SecureRandom as a seed. + * + * The avoidance of collisions is achieved by using a Short Array buffer + * that is prefilled with a dimension of 65536 (~ 131072 bytes in size per + * instance of [[UniqueRandomShortProvider]]). This means it will loop + * through all possible 65536 values before starting to re-generating + * the same numbers again. + */ + +@InternalApi +private[pekko] class UniqueRandomShortProvider { + import UniqueRandomShortProvider._ + + @volatile private var index = 0L + @volatile private var increment = 0L + @volatile private var count = 0L + @volatile private var limit = 0 + private val buffer: Array[Short] = new Array[Short](UniqueRandomShortProvider.MaxLimit) + val r = new SecureRandom() + + resetBuffer() + resetSeed() + + count = 1 + + private def resetSeed(): Unit = { + index = r.nextLong + increment = r.nextLong + } + + private def resetBuffer(): Unit = { + System.arraycopy(Filler, 0, buffer, 0, UniqueRandomShortProvider.MaxLimit) + limit = UniqueRandomShortProvider.MaxLimit + } + def nextId(): Short = { Review Comment: Formatting is important, but PR comments on formatting (in large projects) don't scale. Scalafmt is enabled on the project. I think it's Scalafmt's job to reformat and complain. Its configuration is never perfect, but it avoids the bike shedding in PRs. Does Scalafmt not add/require these new lines? If not, then maybe a configuration change would be needed. I see there's also a `verifyCodeStyle` command in `build.sbt`, it would be a good idea to include this in CI to have the build fail if the code style fails. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
