Various DataBuffer utility enhancements

- Javadoc for DataBufferUtils
 - Introduction of DataBufferTestUtils, containing methods for dumping
   the entire contents of a buffer

spring-web-reactive/src/main/java/org/springframework/core/io/buffer/DefaultDataBuffer.java

@@ -244,7 +244,7 @@ public class DefaultDataBuffer implements DataBuffer {
 
 		@Override
 		public int available() throws IOException {
-			return byteBuffer.limit() - readPosition;
+			return readableByteCount();
 		}
 
 		@Override

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

@@ -25,23 +25,42 @@ import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.util.Assert;
 
 /**
+ * Utility class for working with {@link DataBuffer}s.
+ *
  * @author Arjen Poutsma
  */
 public abstract class DataBufferUtils {
 
+	/**
+	 * Returns the given {@link DataBuffer} as a {@link Flux} of bytes.
+	 * @param buffer the buffer to return the bytes of
+	 * @return the bytes as a flux
+	 */
 	public static Flux<Byte> toPublisher(DataBuffer buffer) {
 		Assert.notNull(buffer, "'buffer' must not be null");
 
-		byte[] bytes1 = new byte[buffer.readableByteCount()];
-		buffer.read(bytes1);
+		byte[] bytes = new byte[buffer.readableByteCount()];
+		buffer.read(bytes);
+
+		Byte[] bytesObjects = box(bytes);
+
+		return Flux.fromArray(bytesObjects);
+	}
 
-		Byte[] bytes2 = new Byte[bytes1.length];
-		for (int i = 0; i < bytes1.length; i++) {
-			bytes2[i] = bytes1[i];
+	private static Byte[] box(byte[] bytes) {
+		Byte[] bytesObjects = new Byte[bytes.length];
+		for (int i = 0; i < bytes.length; i++) {
+			bytesObjects[i] = bytes[i];
 		}
-		return Flux.fromArray(bytes2);
+		return bytesObjects;
 	}
 
+	/**
+	 * Returns the given data buffer publisher as an input stream, streaming over all
+	 * underlying buffers when available.
+	 * @param publisher the publisher to create the input stream for
+	 * @return the input stream
+	 */
 	public static InputStream toInputStream(Publisher<DataBuffer> publisher) {
 		return new DataBufferPublisherInputStream(publisher);
 	}

spring-web-reactive/src/test/java/org/springframework/core/io/buffer/support/DataBufferTestUtils.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2002-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.io.buffer.support;
+
+import java.nio.charset.Charset;
+
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.util.Assert;
+
+/**
+ * Utility class for working with {@link DataBuffer}s in tests.
+ *
+ * <p>Note that this class is in the {@code test} tree of the project: the methods
+ * contained herein are not suitable for production code bases.
+ *
+ * @author Arjen Poutsma
+ */
+public abstract class DataBufferTestUtils {
+
+	/**
+	 * Dumps all the bytes in the given data buffer, and returns them as a byte array.
+	 *
+	 * <p>Note that this method reads the entire buffer into the heap,  which might
+	 * consume a lot of memory.
+	 * @param buffer the data buffer to dump the bytes of
+	 * @return the bytes in the given data buffer
+	 */
+	public static byte[] dumpBytes(DataBuffer buffer) {
+		Assert.notNull(buffer, "'buffer' must not be null");
+
+		byte[] bytes = new byte[buffer.readableByteCount()];
+		buffer.read(bytes);
+		return bytes;
+	}
+
+	/**
+	 * Dumps all the bytes in the given data buffer, and returns them as a string.
+	 *
+	 * <p>Note that this method reads the entire buffer into the heap,  which might
+	 * consume a lot of memory.
+	 * @param buffer the data buffer to dump the string contents of
+	 * @param charset the charset of the data
+	 * @return the string representation of the given data buffer
+	 */
+	public static String dumpString(DataBuffer buffer, Charset charset) {
+		Assert.notNull(charset, "'charset' must not be null");
+
+		byte[] bytes = dumpBytes(buffer);
+		return new String(bytes, charset);
+	}
+}

spring-web-reactive/src/test/java/org/springframework/core/io/buffer/support/DataBufferTestUtilsTests.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2002-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.io.buffer.support;
+
+import java.nio.charset.StandardCharsets;
+
+import io.netty.buffer.PooledByteBufAllocator;
+import io.netty.buffer.UnpooledByteBufAllocator;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferAllocator;
+import org.springframework.core.io.buffer.DefaultDataBufferAllocator;
+import org.springframework.core.io.buffer.NettyDataBufferAllocator;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author Arjen Poutsma
+ */
+@RunWith(Parameterized.class)
+public class DataBufferTestUtilsTests {
+
+	@Parameterized.Parameter
+	public DataBufferAllocator allocator;
+
+	@Parameterized.Parameters(name = "{0}")
+	public static Object[][] buffers() {
+
+		return new Object[][]{
+				{new NettyDataBufferAllocator(new UnpooledByteBufAllocator(true))},
+				{new NettyDataBufferAllocator(new UnpooledByteBufAllocator(false))},
+				{new NettyDataBufferAllocator(new PooledByteBufAllocator(true))},
+				{new NettyDataBufferAllocator(new PooledByteBufAllocator(false))},
+				{new DefaultDataBufferAllocator(true)},
+				{new DefaultDataBufferAllocator(false)}};
+	}
+
+	@Test
+	public void dumpBytes() {
+		DataBuffer buffer = allocator.allocateBuffer(4);
+		byte[] source = {'a', 'b', 'c', 'd'};
+		buffer.write(source);
+
+		byte[] result = DataBufferTestUtils.dumpBytes(buffer);
+
+		assertArrayEquals(source, result);
+	}
+
+	@Test
+	public void dumpString() {
+		DataBuffer buffer = allocator.allocateBuffer(4);
+		String source = "abcd";
+		buffer.write(source.getBytes(StandardCharsets.UTF_8));
+
+		String result = DataBufferTestUtils.dumpString(buffer, StandardCharsets.UTF_8);
+
+
+		assertEquals(source, result);
+	}
+
+}