Refine NamedMutex

app/src/main/kotlin/moe/tarsin/coroutines/NamedMutex.kt

@@ -5,18 +5,17 @@ import io.ktor.utils.io.pool.DefaultPool
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
 
-class MutexTracker(val mutex: Mutex = Mutex(), var count: Int = 0) {
+class MutexTracker(mutex: Mutex = Mutex(), private var count: Int = 0) : Mutex by mutex {
     operator fun inc() = apply { count++ }
     operator fun dec() = apply { count-- }
+    val isFree
+        get() = count == 0
 }
 
-val MutexTracker.isFree
-    get() = count == 0
-
 class MutexPool(capacity: Int) : DefaultPool<MutexTracker>(capacity) {
     override fun produceInstance() = MutexTracker()
     override fun validateInstance(mutex: MutexTracker) {
-        check(!mutex.mutex.isLocked)
+        check(!mutex.isLocked)
         check(mutex.isFree)
     }
 }
@@ -24,15 +23,14 @@ class MutexPool(capacity: Int) : DefaultPool<MutexTracker>(capacity) {
 class NamedMutex<K>(capacity: Int) {
     val pool = MutexPool(capacity)
     val active = mutableScatterMapOf<K, MutexTracker>()
-    val lock = Any()
 }
 
 suspend inline fun <K, R> NamedMutex<K>.withLock(key: K, owner: Any? = null, action: () -> R): R {
-    val mutex = synchronized(lock) { active.getOrPut(key) { pool.borrow() }.inc() }
+    val mutex = synchronized(active) { active.getOrPut(key) { pool.borrow() }.inc() }
     return try {
-        mutex.mutex.withLock(owner, action)
+        mutex.withLock(owner, action)
     } finally {
-        synchronized(lock) {
+        synchronized(active) {
             mutex.dec()
             if (mutex.isFree) {
                 active.remove(key)