From c40beae1ff9418372711db818365cb7c21d0bc22 Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Sun, 24 May 2026 04:27:37 -0400
Subject: [PATCH] Add benchmark

---
 build.sbt                                     | 11 ++++
 .../sbt/internal/util/HashBenchmark.scala     | 60 +++++++++++++++++++
 project/plugins.sbt                           |  1 +
 .../src/main/scala/sbt/util/Digest.scala      |  3 +
 4 files changed, 75 insertions(+)
 create mode 100644 internal/hash-benchmark/src/main/scala/sbt/internal/util/HashBenchmark.scala

diff --git a/build.sbt b/build.sbt
index 67ad2ae0c..c78323fcf 100644
--- a/build.sbt
+++ b/build.sbt
@@ -396,6 +396,17 @@ lazy val utilCache = project
     addSbtCompilerInterface,
   )
 
+lazy val hashBenchmark = (project in file("internal") / "hash-benchmark")
+  .dependsOn(utilControl, utilCache)
+  .enablePlugins(JmhPlugin)
+  .settings(
+    utilCommonSettings,
+    name := "Hash Benchmark",
+    Jmh / run / javaOptions ++= Seq("-Xmx1G", "-Dfile.encoding=UTF8"),
+    mimaSettings,
+    publish / skip := true,
+  )
+
 // Builds on cache to provide caching for filesystem-related operations
 lazy val utilTracking = (project in file("util-tracking"))
   .dependsOn(utilCache)
diff --git a/internal/hash-benchmark/src/main/scala/sbt/internal/util/HashBenchmark.scala b/internal/hash-benchmark/src/main/scala/sbt/internal/util/HashBenchmark.scala
new file mode 100644
index 000000000..ef0d522c0
--- /dev/null
+++ b/internal/hash-benchmark/src/main/scala/sbt/internal/util/HashBenchmark.scala
@@ -0,0 +1,60 @@
+package sbt.internal.util
+
+import java.util.concurrent.{ ThreadLocalRandom, TimeUnit }
+import net.openhft.hashing.LongHashFunction
+import org.openjdk.jmh.annotations.*
+import sbt.util.Digest
+import sbt.internal.util.hashing.Hashing
+import scala.util.hashing.MurmurHash3
+
+@State(Scope.Benchmark)
+abstract class AbstractHashBenchmark:
+  def hash(buf: Array[Byte]): String
+
+  val buf: Array[Byte] = new Array[Byte](2048)
+  ThreadLocalRandom.current().nextBytes(buf)
+
+  @Benchmark
+  @BenchmarkMode(Array(Mode.AverageTime))
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  def hashByteArray: Unit =
+    hash(buf)
+end AbstractHashBenchmark
+
+class XXHash64HashBenchmark extends AbstractHashBenchmark:
+  override def hash(buf: Array[Byte]): String =
+    val h = Hashing.xxhash64
+    val hash = h.hash(buf, 0, buf.size, 0)
+    java.lang.Long.toHexString(hash)
+
+class WyHash64HashBenchmark extends AbstractHashBenchmark:
+  override def hash(buf: Array[Byte]): String =
+    val h = Hashing.wyhash64
+    val hash = h.hash(buf, 0, buf.size, 0)
+    java.lang.Long.toHexString(hash)
+
+class FarmHashHashBenchmark extends AbstractHashBenchmark:
+  override def hash(buf: Array[Byte]): String =
+    val hash = LongHashFunction.farmNa().hashBytes(buf)
+    java.lang.Long.toHexString(hash)
+
+class MurmurHash32HashBenchmark extends AbstractHashBenchmark:
+  override def hash(buf: Array[Byte]): String =
+    val lo = MurmurHash3.bytesHash(buf, 0x85ebca6b)
+    val hash = lo.toLong & 0xffffffffL
+    java.lang.Long.toHexString(hash)
+
+class MurmurHash64HashBenchmark extends AbstractHashBenchmark:
+  override def hash(buf: Array[Byte]): String =
+    val hi = MurmurHash3.bytesHash(buf, 0x9747b28c)
+    val lo = MurmurHash3.bytesHash(buf, 0x85ebca6b)
+    val hash = (hi.toLong << 32) | (lo.toLong & 0xffffffffL)
+    java.lang.Long.toHexString(hash)
+
+class Md5HashBenchmark extends AbstractHashBenchmark:
+  override def hash(buf: Array[Byte]): String =
+    Digest.md5Hash(buf).toString
+
+class Sha256HashBenchmark extends AbstractHashBenchmark:
+  override def hash(buf: Array[Byte]): String =
+    Digest.sha256Hash(buf).toString
diff --git a/project/plugins.sbt b/project/plugins.sbt
index a6a70315a..43bfde102 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -13,5 +13,6 @@ addSbtPlugin("org.scalameta" % "sbt-native-image" % "0.4.0")
 addDependencyTreePlugin
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.14.5")
 addSbtPlugin("com.github.sbt" % "sbt-native-packager" % "1.11.7")
+addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.4.8")
 
 // libraryDependencies += "org.scala-sbt" %% "scripted-plugin" % sbtVersion.value
diff --git a/util-cache/src/main/scala/sbt/util/Digest.scala b/util-cache/src/main/scala/sbt/util/Digest.scala
index 2e95324f1..8e059b8ea 100644
--- a/util-cache/src/main/scala/sbt/util/Digest.scala
+++ b/util-cache/src/main/scala/sbt/util/Digest.scala
@@ -67,6 +67,9 @@ object Digest:
   def sha256Hash(digests: Digest*): Digest =
     sha256Hash(digests.toSeq.map(_.toBytes).flatten.toArray[Byte])
 
+  private[sbt] def md5Hash(bytes: Array[Byte]): Digest =
+    apply(Md5, hashBytes(Md5, bytes), bytes.length)
+
   // first check the file size, then the hash
   def sameDigest(path: Path, digest: Digest): Boolean =
     if Files.size(path) != digest.sizeBytes then false