Merge branch '5.2.x' into master

spring-core/src/main/java/org/springframework/core/io/buffer/DataBufferUtils.java

@@ -683,9 +683,7 @@ public abstract class DataBufferUtils {
 
 		private final AtomicLong position;
 
-		private final AtomicBoolean reading = new AtomicBoolean();
-
-		private final AtomicBoolean disposed = new AtomicBoolean();
+		private final AtomicReference<State> state = new AtomicReference<>(State.IDLE);
 
 		public ReadCompletionHandler(AsynchronousFileChannel channel,
 				FluxSink<DataBuffer> sink, long position, DataBufferFactory dataBufferFactory, int bufferSize) {
@@ -697,39 +695,68 @@ public abstract class DataBufferUtils {
 			this.bufferSize = bufferSize;
 		}
 
-		public void read() {
-			if (this.sink.requestedFromDownstream() > 0 &&
-					isNotDisposed() &&
-					this.reading.compareAndSet(false, true)) {
-				DataBuffer dataBuffer = this.dataBufferFactory.allocateBuffer(this.bufferSize);
-				ByteBuffer byteBuffer = dataBuffer.asByteBuffer(0, this.bufferSize);
-				this.channel.read(byteBuffer, this.position.get(), dataBuffer, this);
+		/**
+		 * Invoked when Reactive Streams consumer signals demand.
+		 */
+		public void request(long n) {
+			tryRead();
+		}
+
+		/**
+		 * Invoked when Reactive Streams consumer cancels.
+		 */
+		public void cancel() {
+			this.state.getAndSet(State.DISPOSED);
+
+			// According java.nio.channels.AsynchronousChannel "if an I/O operation is outstanding
+			// on the channel and the channel's close method is invoked, then the I/O operation
+			// fails with the exception AsynchronousCloseException". That should invoke the failed
+			// callback below and the current DataBuffer should be released.
+
+			closeChannel(this.channel);
+		}
+
+		private void tryRead() {
+			if (this.sink.requestedFromDownstream() > 0 && this.state.compareAndSet(State.IDLE, State.READING)) {
+				read();
 			}
 		}
 
+		private void read() {
+			DataBuffer dataBuffer = this.dataBufferFactory.allocateBuffer(this.bufferSize);
+			ByteBuffer byteBuffer = dataBuffer.asByteBuffer(0, this.bufferSize);
+			this.channel.read(byteBuffer, this.position.get(), dataBuffer, this);
+		}
+
 		@Override
 		public void completed(Integer read, DataBuffer dataBuffer) {
-			if (isNotDisposed()) {
-				if (read != -1) {
-					this.position.addAndGet(read);
-					dataBuffer.writePosition(read);
-					this.sink.next(dataBuffer);
-					this.reading.set(false);
-					read();
-				}
-				else {
-					release(dataBuffer);
-					closeChannel(this.channel);
-					if (this.disposed.compareAndSet(false, true)) {
-						this.sink.complete();
-					}
-					this.reading.set(false);
-				}
+			if (this.state.get().equals(State.DISPOSED)) {
+				release(dataBuffer);
+				closeChannel(this.channel);
+				return;
 			}
-			else {
+
+			if (read == -1) {
 				release(dataBuffer);
 				closeChannel(this.channel);
-				this.reading.set(false);
+				this.state.set(State.DISPOSED);
+				this.sink.complete();
+				return;
+			}
+
+			this.position.addAndGet(read);
+			dataBuffer.writePosition(read);
+			this.sink.next(dataBuffer);
+
+			// Stay in READING mode if there is demand
+			if (this.sink.requestedFromDownstream() > 0) {
+				read();
+				return;
+			}
+
+			// Release READING mode and then try again in case of concurrent "request"
+			if (this.state.compareAndSet(State.READING, State.IDLE)) {
+				tryRead();
 			}
 		}
 
@@ -737,26 +764,12 @@ public abstract class DataBufferUtils {
 		public void failed(Throwable exc, DataBuffer dataBuffer) {
 			release(dataBuffer);
 			closeChannel(this.channel);
-			if (this.disposed.compareAndSet(false, true)) {
-				this.sink.error(exc);
-			}
-			this.reading.set(false);
-		}
-
-		public void request(long n) {
-			read();
-		}
-
-		public void cancel() {
-			if (this.disposed.compareAndSet(false, true)) {
-				if (!this.reading.get()) {
-					closeChannel(this.channel);
-				}
-			}
+			this.state.set(State.DISPOSED);
+			this.sink.error(exc);
 		}
 
-		private boolean isNotDisposed() {
-			return !this.disposed.get();
+		private enum State {
+			IDLE, READING, DISPOSED
 		}
 	}