Mandatory cancellation support, coverage tests

Author: akarnokd

README.md

@@ -9,7 +9,7 @@ Prototype Java 9 library based on the asynchronous enumerable concept (where mov
 ### Gradle
 
 ```groovy
-compile "com.github.akarnokd:async-enumerable:0.5.0"
+compile "com.github.akarnokd:async-enumerable:0.6.0"
 ```
 
 ### Getting started

gradle.properties

@@ -1,3 +1,3 @@
-version=0.5.0
+version=0.6.0
 org.gradle.jvmargs=-XX:+IgnoreUnrecognizedVMOptions --permit-illegal-access --show-version
 

src/main/java/hu/akarnokd/asyncenum/AsyncConcatArray.java

@@ -17,7 +17,7 @@
 package hu.akarnokd.asyncenum;
 
 import java.util.concurrent.*;
-import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.*;
 import java.util.function.BiConsumer;
 
 final class AsyncConcatArray<T> implements AsyncEnumerable<T> {
@@ -38,33 +38,36 @@ static final class ConcatArrayEnumerator<T> extends AtomicInteger
 
         final AsyncEnumerable<T>[] sources;
 
-        AsyncEnumerator<T> currentEnumerator;
+        final AtomicReference<AsyncEnumerator<T>> currentEnumerator;
 
         CompletableFuture<Boolean> currentStage;
 
         int index;
 
         ConcatArrayEnumerator(AsyncEnumerable<T>[] sources) {
             this.sources = sources;
+            this.currentEnumerator = new AtomicReference<>();
         }
 
         @Override
         public CompletionStage<Boolean> moveNext() {
-            if (currentEnumerator == null) {
+            if (currentEnumerator.get() == null) {
                 if (index == sources.length) {
                     return FALSE;
                 }
-                currentEnumerator = sources[index++].enumerator();
+                if (!AsyncEnumeratorHelper.replace(currentEnumerator, sources[index++].enumerator())) {
+                    return CANCELLED;
+                }
             }
 
             currentStage = new CompletableFuture<>();
-            currentEnumerator.moveNext().whenComplete(this);
+            currentEnumerator.getPlain().moveNext().whenComplete(this);
             return currentStage;
         }
 
         @Override
         public T current() {
-            return currentEnumerator.current();
+            return currentEnumerator.getPlain().current();
         }
 
         @Override
@@ -82,11 +85,20 @@ public void accept(Boolean aBoolean, Throwable throwable) {
                             currentStage.complete(false);
                             break;
                         }
-                        currentEnumerator = sources[index++].enumerator();
-                        currentEnumerator.moveNext().whenComplete(this);
+                        AsyncEnumerator<T> en = sources[index++].enumerator();
+                        if (AsyncEnumeratorHelper.replace(currentEnumerator, en)) {
+                            en.moveNext().whenComplete(this);
+                        } else {
+                            break;
+                        }
                     } while (decrementAndGet() != 0);
                 }
             }
         }
+
+        @Override
+        public void cancel() {
+            AsyncEnumeratorHelper.cancel(currentEnumerator);
+        }
     }
 }

src/main/java/hu/akarnokd/asyncenum/AsyncEmpty.java

@@ -40,4 +40,9 @@ public CompletionStage<Boolean> moveNext() {
     public Object current() {
         return null;
     }
+
+    @Override
+    public void cancel() {
+        // No action, consumer should stop calling moveNext().
+    }
 }

src/main/java/hu/akarnokd/asyncenum/AsyncEnumerator.java

@@ -51,8 +51,5 @@ public interface AsyncEnumerator<T> {
      * Instructs the AsyncEnumerator to cancel any outstanding async activity and
      * release resources associated with it.
      */
-    // FIXME make mandatory
-    default void cancel() {
-
-    }
+    void cancel();
 }

src/main/java/hu/akarnokd/asyncenum/AsyncEnumeratorHelper.java

@@ -33,6 +33,11 @@ public Object current() {
         return null;
     }
 
+    @Override
+    public void cancel() {
+        // No action, consumer should stop calling moveNext().
+    }
+
     @SuppressWarnings("unchecked")
     static <T> boolean cancel(AtomicReference<AsyncEnumerator<T>> target) {
         AsyncEnumerator<?> current = target.getAndSet((AsyncEnumerator<T>)CANCELLED);

src/main/java/hu/akarnokd/asyncenum/AsyncError.java

@@ -40,4 +40,9 @@ public CompletionStage<Boolean> moveNext() {
     public T current() {
         return null;
     }
+
+    @Override
+    public void cancel() {
+        // No action, consumer should stop calling moveNext().
+    }
 }

src/main/java/hu/akarnokd/asyncenum/AsyncFromArray.java

@@ -59,5 +59,10 @@ public CompletionStage<Boolean> moveNext() {
         public T current() {
             return current;
         }
+
+        @Override
+        public void cancel() {
+            // No action, consumer should stop calling moveNext().
+        }
     }
 }

src/main/java/hu/akarnokd/asyncenum/AsyncFromCallable.java

@@ -62,5 +62,10 @@ public CompletionStage<Boolean> moveNext() {
         public T current() {
             return result;
         }
+
+        @Override
+        public void cancel() {
+            // No action, consumer should stop calling moveNext().
+        }
     }
 }

src/main/java/hu/akarnokd/asyncenum/AsyncFromCharSequence.java

@@ -59,5 +59,10 @@ public CompletionStage<Boolean> moveNext() {
         public Integer current() {
             return current;
         }
+
+        @Override
+        public void cancel() {
+            // No action, consumer should stop calling moveNext().
+        }
     }
 }