Add name based UUIDv5 implementation

davenverse · Dec 9, 2019 · 8c1c4bf · 8c1c4bf
1 parent c8c44fb
commit 8c1c4bf
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diff --git a/modules/core/src/main/scala/io/chrisdavenport/fuuid/FUUID.scala b/modules/core/src/main/scala/io/chrisdavenport/fuuid/FUUID.scala
@@ -4,6 +4,7 @@ import cats._
 import cats.implicits._
 import cats.effect.Sync
 import java.util.UUID
+import java.security.MessageDigest
 
 import scala.reflect.macros.blackbox
 
@@ -74,6 +75,50 @@ object FUUID {
       }
   }
 
+  /**
+    * Creates a new name-based UUIDv5
+    **/ 
+  def nameBased[F[_]](namespace: FUUID, name: String)(implicit AE: ApplicativeError[F, Throwable]): F[FUUID] =
+    Either
+      .catchNonFatal(
+        MessageDigest
+          .getInstance("SHA-1")
+          .digest(
+            uuidBytes(namespace) ++
+              name.getBytes("UTF-8")
+          )
+      )
+      .map { bs =>
+        val cs = bs.take(16) // Truncate 160 bits (20 bytes) SHA-1 to fit into our 128 bits of space
+        cs(6) = (cs(6) & 0x0f).asInstanceOf[Byte] /* clear version                */
+        cs(6) = (cs(6) | 0x50).asInstanceOf[Byte] /* set to version 5, SHA1 UUID  */
+        cs(8) = (cs(8) & 0x3f).asInstanceOf[Byte] /* clear variant                */
+        cs(8) = (cs(8) | 0x80).asInstanceOf[Byte] /* set to IETF variant          */
+        cs
+      }
+      .flatMap(
+        bs =>
+          Either.catchNonFatal {
+            val bb = java.nio.ByteBuffer.allocate(java.lang.Long.BYTES)
+            bb.put(bs, 0, 8)
+            bb.flip
+            val most = bb.getLong
+            bb.flip
+            bb.put(bs, 8, 8)
+            bb.flip
+            val least = bb.getLong
+            new FUUID(new UUID(most, least))
+          }
+      )
+      .liftTo[F]
+
+  private def uuidBytes(fuuid: FUUID): Array[Byte] = {
+    val bb = java.nio.ByteBuffer.allocate(2 * java.lang.Long.BYTES)
+    bb.putLong(fuuid.uuid.getMostSignificantBits)
+    bb.putLong(fuuid.uuid.getLeastSignificantBits)
+    bb.array
+  }
+
   /**
     * A Home For functions we don't trust
     * Hopefully making it very clear that this code needs

diff --git a/modules/core/src/test/scala/io/chrisdavenport/fuuid/FUUIDSpec.scala b/modules/core/src/test/scala/io/chrisdavenport/fuuid/FUUIDSpec.scala
@@ -23,6 +23,28 @@ object FUUIDSpec extends mutable.Specification with ScalaCheck {
     }
   }
 
+  "FUUID.nameBased" should {
+    "produce a valid UUID" in {
+      (for {
+        namespace <- FUUID.randomFUUID[IO]
+        namebased <- FUUID.nameBased[IO](namespace, "What up yo!")
+        parsed <- FUUID.fromStringF[IO](namebased.toString)
+      } yield parsed)
+        .attempt
+        .unsafeRunSync
+        .isRight must_=== true
+    }
+
+    "conform to an example" in {
+      val namespace = FUUID.fromStringF[IO]("dc79a6bc-de3c-5bc7-a877-712bea708d8f").unsafeRunSync()
+      val name = "What up yo!"
+
+      val expected = FUUID.fromStringF[IO]("1cce4593-d217-5b33-be0d-2e81462e79d3").unsafeRunSync()
+
+      FUUID.nameBased[IO](namespace, name).unsafeRunSync must_=== expected
+    }
+  }
+
   "FUUID.hashCode" should {
     "have same hashcode as uuid" in {
       val baseString = "00000000-075b-cd15-0000-0000075bcd15"