TRef#getAndSet

durban · Jan 6, 2025 · 2d9fdca · 2d9fdca
1 parent d8481c5
commit 2d9fdca
Show file tree

Hide file tree

Showing 5 changed files with 16 additions and 0 deletions.
diff --git a/build.sbt b/build.sbt
@@ -419,6 +419,7 @@ lazy val stm = crossProject(JVMPlatform, JSPlatform)
       // there is no backward compat for `choam-stm`:
       ProblemFilters.exclude[ReversedMissingMethodProblem]("dev.tauri.choam.stm.TRef.update"),
       ProblemFilters.exclude[ReversedMissingMethodProblem]("dev.tauri.choam.stm.TRef.modify"),
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("dev.tauri.choam.stm.TRef.getAndSet"),
     ),
   )
 

diff --git a/stm/js/src/main/scala/dev/tauri/choam/stm/TRefImpl.scala b/stm/js/src/main/scala/dev/tauri/choam/stm/TRefImpl.scala
@@ -109,6 +109,9 @@ private final class TRefImpl[F[_], A](
   final override def modify[B](f: A => (A, B)): Txn[F, B] =
     core.Rxn.loc.upd[A, Any, B](this) { (ov, _) => f(ov) }.castF[F]
 
+  final override def getAndSet(a: A): Txn[F, A] =
+    this.modify { ov => (a, ov) }
+
   final override def hashCode: Int = {
     // `RefIdGen` generates IDs with
     // Fibonacci hashing, so no need

diff --git a/stm/jvm/src/main/scala/dev/tauri/choam/stm/TRefImpl.scala b/stm/jvm/src/main/scala/dev/tauri/choam/stm/TRefImpl.scala
@@ -98,6 +98,9 @@ private final class TRefImpl[F[_], A](
   final override def modify[B](f: A => (A, B)): Txn[F, B] =
     core.Rxn.loc.upd[A, Any, B](this) { (ov, _) => f(ov) }.castF[F]
 
+  final override def getAndSet(a: A): Txn[F, A] =
+    this.modify { ov => (a, ov) }
+
   final override def hashCode: Int = {
     // `RefIdGen` generates IDs with
     // Fibonacci hashing, so no need

diff --git a/stm/shared/src/main/scala/dev/tauri/choam/stm/TRef.scala b/stm/shared/src/main/scala/dev/tauri/choam/stm/TRef.scala
@@ -23,6 +23,7 @@ sealed trait TRef[F[_], A] {
   def set(a: A): Txn[F, Unit]
   def update(f: A => A): Txn[F, Unit]
   def modify[B](f: A => (A, B)): Txn[F, B]
+  def getAndSet(a: A): Txn[F, A]
 }
 
 object TRef {

diff --git a/stm/shared/src/test/scala/dev/tauri/choam/stm/TxnSpec.scala b/stm/shared/src/test/scala/dev/tauri/choam/stm/TxnSpec.scala
@@ -223,6 +223,14 @@ trait TxnSpec[F[_]] extends TxnBaseSpec[F] { this: McasImplSpec =>
       _ <- assertResultF(r.get.commit, 1)
     } yield ()
   }
+
+  test("TRef#getAndSet") {
+    for {
+      r <- TRef[F, Int](0).commit
+      _ <- assertResultF(r.getAndSet(42).commit, 0)
+      _ <- assertResultF(r.get.commit, 42)
+    } yield ()
+  }
 }
 
 trait TxnSpecTicked[F[_]] extends TxnBaseSpec[F] with TestContextSpec[F] { this: McasImplSpec =>