Coverage Summary for Class: QosClass (dev.suresh.qos)

 package dev.suresh.qos
 
 import dev.suresh.downcallHandle
 import java.lang.foreign.FunctionDescriptor
 import java.lang.foreign.ValueLayout.JAVA_INT
 import java.util.concurrent.Executors
 import java.util.concurrent.SynchronousQueue
 import java.util.concurrent.ThreadFactory
 import java.util.concurrent.ThreadPoolExecutor
 import java.util.concurrent.TimeUnit
 import kotlinx.coroutines.asCoroutineDispatcher
 
 /** Constrain JVM threads and coroutines to the efficiency cores available on M-series Macs */
 object FFMQosSetter {
   fun setQosClass(qosClass: QosClass, relativePriority: Int = 0): Int {
     val result =
         downcallHandle(
                 "pthread_set_qos_class_self_np",
                 FunctionDescriptor.of(JAVA_INT, JAVA_INT, JAVA_INT))
             ?.invokeExact(qosClass.raw, relativePriority) as Int
 
     when (result != 0) {
       true -> System.err.println("Failed to set QoS class, error code: $result")
       else -> println("QoS class set successfully.")
     }
     return result
   }
 }
 
 /**
  * Refer to the
  * [Energy Efficiency Guide for Mac Apps](https://developer.apple.com/library/archive/documentation/Performance/Conceptual/power_efficiency_guidelines_osx/PrioritizeWorkAtTheTaskLevel.html#//apple_ref/doc/uid/TP40013929-CH35-SW5)
  */
 enum class QosClass(val raw: Int) {
   QOS_CLASS_USER_INTERACTIVE(0x21),
   QOS_CLASS_USER_INITIATED(0x19),
   QOS_CLASS_DEFAULT(0x15),
   QOS_CLASS_UTILITY(0x11),
   QOS_CLASS_BACKGROUND(0x09),
   QOS_CLASS_UNSPECIFIED(0x00),
 }
 
 val BackgroundQosCoroutineDispatcher by lazy {
   ThreadPoolExecutor(
           /* corePoolSize = */ 0,
           /* maximumPoolSize = */ Runtime.getRuntime().availableProcessors(),
           /* keepAliveTime = */ 60L,
           /* unit = */ TimeUnit.SECONDS,
           /* workQueue = */ SynchronousQueue(),
           /* threadFactory = */ object : ThreadFactory {
 
             override fun newThread(r: Runnable): Thread {
               val fact = Executors.defaultThreadFactory()
               return fact.newThread(r).apply {
                 FFMQosSetter.setQosClass(QosClass.QOS_CLASS_BACKGROUND)
                 name = "QosThreadPool-${threadId()}"
               }
             }
           })
       .asCoroutineDispatcher()
 }