Add ByteBuffer Utils Class (#65)

src/main/java/software/amazon/awssdk/crt/utils/ByteBufferUtils.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file 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 software.amazon.awssdk.crt.utils;
+
+import java.nio.ByteBuffer;
+
+/**
+ * Utility Class with Helper functions for working with ByteBuffers
+ */
+public class ByteBufferUtils {
+    private ByteBufferUtils() {}
+
+    /**
+     * Allocates a new backing byte[] with a new ByteBuffer, and copies the contents of the input buffer to the copy.
+     *
+     * @param input The ByteBuffer to copy
+     * @return A new ByteBuffer containing a deep copy of the input ByteBuffer.
+     */
+    public static ByteBuffer deepCopy(ByteBuffer input) {
+        // Allocate a new ByteBuffer that's large enough to store a copy
+        ByteBuffer deepCopy = ByteBuffer.allocate(input.remaining());
+
+        // Copy contents of input buffer to new Buffer
+        deepCopy.put(input);
+
+        // Flip deepCopy from Write mode to Read Mode
+        deepCopy.flip();
+
+        return deepCopy;
+    }
+
+    /**
+     * Transfers as much data as possible from an input ByteBuffer to an output ByteBuffer
+     * @param in The input ByteBuffer
+     * @param out The output ByteBuffer
+     * @return The number of bytes transferred
+     */
+    public static int transferData(ByteBuffer in, ByteBuffer out) {
+        int amtToTransfer = Math.min(in.remaining(), out.remaining());
+
+        // Make a new ByteBuffer that shares the same underlying buffer as the input ByteBuffer
+        ByteBuffer shallowCopy = in.duplicate();
+
+        // Modify the shallow copy's read limit so that it matches the write space remaining in the output Buffer so
+        // we don't throw an OutOfBounds exception
+        shallowCopy.limit(shallowCopy.position() + amtToTransfer);
+
+        // Transfer the data
+        out.put(shallowCopy);
+
+        // Increment the read position of the original input buffer by the number of bytes transferred
+        in.position(in.position() + amtToTransfer);
+        return amtToTransfer;
+    }
+}

src/test/java/software/amazon/awssdk/crt/test/HttpRequestResponseTest.java

@@ -15,6 +15,8 @@
 
 package software.amazon.awssdk.crt.test;
 
+import static software.amazon.awssdk.crt.utils.ByteBufferUtils.transferData;
+
 import org.junit.Assert;
 import org.junit.Test;
 import software.amazon.awssdk.crt.CRT;
@@ -75,19 +77,11 @@ public String toString() {
         }
     }
 
-    private void transferData(ByteBuffer in, ByteBuffer out) {
-        int amtToTransfer = Math.min(in.remaining(), out.remaining());
-
-        if (amtToTransfer > 0) {
-            out.put(in.array(), in.arrayOffset() + in.position(), amtToTransfer);
-            in.position(in.position() + amtToTransfer);
-        }
-    }
-
     public static String byteArrayToHex(byte[] input) {
         StringBuilder output = new StringBuilder(input.length * 2);
-        for(byte b: input)
+        for (byte b: input) {
             output.append(String.format("%02X", b));
+        }
         return output.toString();
     }