Fix immutableCopyOf bug (#4266)

* Set limit when cloning ByteBuffer

* Add changelog

Author: davidh44

.changes/next-release/bugfix-AWSSDKforJavav2-5ae7899.json

@@ -0,0 +1,6 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "contributor": "", 
+    "type": "bugfix", 
+    "description": "Fixed bug where limit was not copied over when cloning ByteBuffer using immutableCopyOf()"
+}

utils/src/main/java/software/amazon/awssdk/utils/BinaryUtils.java

@@ -133,12 +133,12 @@ public static ByteBuffer immutableCopyOf(ByteBuffer bb) {
         if (bb == null) {
             return null;
         }
-        int sourceBufferPosition = bb.position();
         ByteBuffer readOnlyCopy = bb.asReadOnlyBuffer();
         readOnlyCopy.rewind();
         ByteBuffer cloned = ByteBuffer.allocate(readOnlyCopy.capacity())
                                       .put(readOnlyCopy);
-        cloned.position(sourceBufferPosition);
+        cloned.position(bb.position());
+        cloned.limit(bb.limit());
         return cloned.asReadOnlyBuffer();
     }
 

utils/src/test/java/software/amazon/awssdk/utils/BinaryUtilsTest.java

@@ -226,6 +226,17 @@ public void testImmutableCopyOfByteBuffer() {
         assertArrayEquals(bytesInSourceAfterCopy, fromSource);
     }
 
+    @Test
+    public void immutableCopyOf_retainsOriginalLimit() {
+        ByteBuffer sourceBuffer = ByteBuffer.allocate(10);
+        byte[] bytes = {1, 2, 3, 4};
+        sourceBuffer.put(bytes);
+        sourceBuffer.rewind();
+        sourceBuffer.limit(bytes.length);
+        ByteBuffer copy = BinaryUtils.immutableCopyOf(sourceBuffer);
+        assertThat(copy.limit()).isEqualTo(sourceBuffer.limit());
+    }
+
     @Test
     public void testImmutableCopyOfByteBuffer_nullBuffer() {
         assertNull(BinaryUtils.immutableCopyOf(null));