Rename InputStreamSubscriber to SubscriberInputStream

It is both, but InputStream is what's exposed for public use,
in effect an InputStream backed by a Subscriber source.

See gh-31677

spring-web/src/main/java/org/springframework/http/client/SubscriberInputStream.java

@@ -42,16 +42,16 @@ import org.springframework.util.Assert;
  * Bridges between {@link Flow.Publisher Flow.Publisher<T>} and {@link InputStream}.
  *
  * <p>Note that this class has a near duplicate in
- * {@link org.springframework.core.io.buffer.InputStreamSubscriber}.
+ * {@link org.springframework.core.io.buffer.SubscriberInputStream}.
  *
  * @author Oleh Dokuka
  * @author Rossen Stoyanchev
  * @since 6.2
  * @param <T> the publisher byte buffer type
  */
-final class InputStreamSubscriber<T> extends InputStream implements Flow.Subscriber<T> {
+final class SubscriberInputStream<T> extends InputStream implements Flow.Subscriber<T> {
 
-	private static final Log logger = LogFactory.getLog(InputStreamSubscriber.class);
+	private static final Log logger = LogFactory.getLog(SubscriberInputStream.class);
 
 	private static final Object READY = new Object();
 
@@ -94,12 +94,12 @@ final class InputStreamSubscriber<T> extends InputStream implements Flow.Subscri
 	private Throwable error;
 
 
-	private InputStreamSubscriber(Function<T, byte[]> mapper, Consumer<T> onDiscardHandler, int prefetch) {
+	private SubscriberInputStream(Function<T, byte[]> mapper, Consumer<T> onDiscardHandler, int demand) {
 		this.mapper = mapper;
 		this.onDiscardHandler = onDiscardHandler;
-		this.prefetch = prefetch;
-		this.limit = (prefetch == Integer.MAX_VALUE ? Integer.MAX_VALUE : prefetch - (prefetch >> 2));
-		this.queue = new ArrayBlockingQueue<>(prefetch);
+		this.prefetch = demand;
+		this.limit = (demand == Integer.MAX_VALUE ? Integer.MAX_VALUE : demand - (demand >> 2));
+		this.queue = new ArrayBlockingQueue<>(demand);
 		this.lock = new ReentrantLock(false);
 	}
 
@@ -122,17 +122,16 @@ final class InputStreamSubscriber<T> extends InputStream implements Flow.Subscri
 	 * @param publisher the source of {@link DataBuffer} which should be represented as an {@link InputStream}
 	 * @param mapper function to transform &lt;T&gt; element to {@code byte[]}. Note, &lt;T&gt; should be released during the mapping if needed.
 	 * @param onDiscardHandler &lt;T&gt; element consumer if returned {@link InputStream} is closed prematurely.
-	 * @param bufferSize the maximum amount of &lt;T&gt; elements prefetched in advance and stored inside {@link InputStream}
+	 * @param demand the maximum number of buffers to request from the Publisher and buffer on an ongoing basis
 	 * @return an {@link InputStream} instance representing given {@link Flow.Publisher} messages
 	 */
-	public static <T> InputStream subscribeTo(Flow.Publisher<T> publisher, Function<T, byte[]> mapper, Consumer<T> onDiscardHandler, int bufferSize) {
-
+	public static <T> InputStream subscribeTo(Flow.Publisher<T> publisher, Function<T, byte[]> mapper, Consumer<T> onDiscardHandler, int demand) {
 		Assert.notNull(publisher, "Flow.Publisher must not be null");
 		Assert.notNull(mapper, "mapper must not be null");
 		Assert.notNull(onDiscardHandler, "onDiscardHandler must not be null");
-		Assert.isTrue(bufferSize > 0, "bufferSize must be greater than 0");
+		Assert.isTrue(demand > 0, "demand must be greater than 0");
 
-		InputStreamSubscriber<T> iss = new InputStreamSubscriber<>(mapper, onDiscardHandler, bufferSize);
+		SubscriberInputStream<T> iss = new SubscriberInputStream<>(mapper, onDiscardHandler, demand);
 		publisher.subscribe(iss);
 		return iss;
 	}