feat(common): Add compatibility with Kotlin coroutines

This change adds support for converting a `Dispatcher` implementation
into a `CoroutineDispatcher` instance.

2 files changed, 106 insertions, 0 deletions

diff --git a/opendc-common/src/main/kotlin/org/opendc/common/DispatcherCoroutineDispatcher.kt b/opendc-common/src/main/kotlin/org/opendc/common/DispatcherCoroutineDispatcher.kt
new file mode 100644
index 00000000..63744ef9
--- /dev/null
+++ b/opendc-common/src/main/kotlin/org/opendc/common/DispatcherCoroutineDispatcher.kt
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2022 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.common
+
+import kotlinx.coroutines.CancellableContinuation
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Delay
+import kotlinx.coroutines.DisposableHandle
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.InternalCoroutinesApi
+import kotlin.coroutines.CoroutineContext
+
+/**
+ * A [CoroutineDispatcher] that uses a [Dispatcher] to dispatch pending co-routines.
+ *
+ * @param dispatcher The [Dispatcher] used to manage the execution of future tasks.
+ */
+@OptIn(InternalCoroutinesApi::class)
+internal class DispatcherCoroutineDispatcher(private val dispatcher: Dispatcher) : CoroutineDispatcher(), Delay, DispatcherProvider {
+    override fun dispatch(context: CoroutineContext, block: Runnable) {
+        block.run()
+    }
+
+    override fun dispatchYield(context: CoroutineContext, block: Runnable) {
+        dispatcher.schedule(block)
+    }
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    override fun scheduleResumeAfterDelay(timeMillis: Long, continuation: CancellableContinuation<Unit>) {
+        dispatcher.schedule(timeMillis, CancellableContinuationRunnable(continuation) { resumeUndispatched(Unit) })
+    }
+
+    override fun invokeOnTimeout(timeMillis: Long, block: Runnable, context: CoroutineContext): DisposableHandle {
+        val handle = dispatcher.scheduleCancellable(timeMillis, block)
+        return DisposableHandle { handle.cancel() }
+    }
+
+    override fun getDispatcher(): Dispatcher = dispatcher
+
+    override fun toString(): String {
+        return "DispatcherCoroutineDispatcher[dispatcher=$dispatcher]"
+    }
+
+    /**
+     * This class exists to allow cleanup code to avoid throwing for cancelled continuations scheduled
+     * in the future.
+     */
+    private class CancellableContinuationRunnable<T>(
+        @JvmField val continuation: CancellableContinuation<T>,
+        private val block: CancellableContinuation<T>.() -> Unit
+    ) : Runnable {
+        override fun run() = continuation.block()
+    }
+}
diff --git a/opendc-common/src/main/kotlin/org/opendc/common/Dispatchers.kt b/opendc-common/src/main/kotlin/org/opendc/common/Dispatchers.kt
new file mode 100644
index 00000000..6dcd17af
--- /dev/null
+++ b/opendc-common/src/main/kotlin/org/opendc/common/Dispatchers.kt
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2022 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.common
+
+import kotlinx.coroutines.CoroutineDispatcher
+
+/**
+ * Convert a [Dispatcher] to a [CoroutineDispatcher].
+ */
+public fun Dispatcher.asCoroutineDispatcher(): CoroutineDispatcher {
+    return DispatcherCoroutineDispatcher(this)
+}