Fix issue jetty#5499

this PR let the ByteAccumulator recyclable. after invoke ByteAccumulator.transferTo method
we can invoke ByteAccumulator.recycle method to reuse byte[] via ByteAccumulator.newByteArray method

Signed-off-by: Baoyi Chen <chen.bao.yi@qq.com>

jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulator.java

@@ -28,10 +28,10 @@
 
 public class ByteAccumulator
 {
-    private List<ByteBuffer> chunks = new ArrayList<>();
+    private final List<ByteBuffer> chunks = new ArrayList<>();
     private final int maxSize;
     private int length = 0;
-    private ByteBufferPool bufferPool;
+    private final ByteBufferPool bufferPool;
 
     public ByteAccumulator(int maxOverallBufferSize)
     {
@@ -44,17 +44,18 @@ public ByteAccumulator(int maxOverallBufferSize, ByteBufferPool bufferPool)
         this.bufferPool = bufferPool;
     }
 
-    public void copyChunk(ByteBuffer buffer, int length)
+    public void copyChunk(ByteBuffer buffer)
     {
+        int length = buffer.position();
         if (this.length + length > maxSize)
         {
             String err = String.format("Resulting message size [%,d] is too large for configured max of [%,d]", this.length + length, maxSize);
             throw new MessageTooLargeException(err);
         }
-        if (length > 0) 
+
+        if (length > 0)
         {
-            buffer.limit(length);
-            chunks.add(buffer);
+            chunks.add((ByteBuffer) buffer.flip());
             this.length += length;
         }
         else
@@ -124,6 +125,6 @@ void recycle()
             bufferPool.release(chunk);
         }
 
-        chunks = new ArrayList<>();
+        chunks.clear();
     }
 }

jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/extensions/compress/CompressExtension.java

@@ -193,12 +193,12 @@ int copyChunk(Inflater inflater, ByteAccumulator accumulator, ByteBuffer buf) th
             int read = inflater.inflate(buf.array(), position, capacity - position);
             if (read <= 0)
             {
-                accumulator.copyChunk(buf, position);
+                accumulator.copyChunk((ByteBuffer)buf.position(position));
                 return read;
             }
             position += read;
         }
-        accumulator.copyChunk(buf, position);
+        accumulator.copyChunk((ByteBuffer) buf.position(position));
         return position;
     }
 

jetty-websocket/websocket-common/src/test/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulatorTest.java

@@ -103,20 +103,20 @@ public void testRecycle()
             // 1
             ByteBuffer buf = accumulator.newByteBuffer(10);
             byte[] hello = "Hello".getBytes(UTF_8);
-            System.arraycopy(hello, 0, buf.array(), 0, hello.length);
-            accumulator.copyChunk(buf, hello.length);
+            buf.put(hello);
+            accumulator.copyChunk(buf);
 
             // 2
             buf = accumulator.newByteBuffer(10);
             byte[] space = " ".getBytes(UTF_8);
-            System.arraycopy(space, 0, buf.array(), 0, space.length);
-            accumulator.copyChunk(buf, space.length);
+            buf.put(space);
+            accumulator.copyChunk(buf);
 
             // 3
             buf = accumulator.newByteBuffer(10);
             byte[] world = "World".getBytes(UTF_8);
-            System.arraycopy(world, 0, buf.array(), 0, world.length);
-            accumulator.copyChunk(buf, world.length);
+            buf.put(world);
+            accumulator.copyChunk(buf);
 
             assertThat("Length", accumulator.getLength(), is(hello.length + space.length + world.length));
 
@@ -130,26 +130,26 @@ public void testRecycle()
             // 1
             ByteBuffer buf = accumulator.newByteBuffer(10);
             byte[] olleh = "olleH".getBytes(UTF_8);
-            System.arraycopy(olleh, 0, buf.array(), 0, olleh.length);
-            accumulator.copyChunk(buf, olleh.length);
+            buf.put(olleh);
+            accumulator.copyChunk(buf);
 
             // 2
             buf = accumulator.newByteBuffer(10);
             byte[] space = " ".getBytes(UTF_8);
-            System.arraycopy(space, 0, buf.array(), 0, space.length);
-            accumulator.copyChunk(buf, space.length);
+            buf.put(space);
+            accumulator.copyChunk(buf);
 
             // 3
             buf = accumulator.newByteBuffer(10);
             byte[] dlrow = "dlroW".getBytes(UTF_8);
-            System.arraycopy(dlrow, 0, buf.array(), 0, dlrow.length);
-            accumulator.copyChunk(buf, dlrow.length);
+            buf.put(dlrow);
+            accumulator.copyChunk(buf);
 
             // 4
             buf = accumulator.newByteBuffer(10);
             byte[] done = " enoD".getBytes(UTF_8);
-            System.arraycopy(done, 0, buf.array(), 0, done.length);
-            accumulator.copyChunk(buf, done.length);
+            buf.put(done);
+            accumulator.copyChunk(buf);
 
             assertThat("Length", accumulator.getLength(), is(olleh.length + space.length + dlrow.length + done.length));