Issue #6566 - cleanups of ByteBufferCallbackAccumulator

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-io/src/main/java/org/eclipse/jetty/io/ByteBufferCallbackAccumulator.java

@@ -15,7 +15,6 @@ package org.eclipse.jetty.io;
 
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
-import java.util.Iterator;
 import java.util.List;
 
 import org.eclipse.jetty.util.BufferUtil;
@@ -74,19 +73,16 @@ public class ByteBufferCallbackAccumulator
 
     public void writeTo(ByteBuffer buffer)
     {
-        for (Iterator<Entry> iterator = _entries.iterator(); iterator.hasNext();)
+        if (BufferUtil.space(buffer) < _length)
+            throw new IllegalArgumentException("not enough buffer space remaining");
+
+        for (Entry entry : _entries)
         {
-            Entry entry = iterator.next();
-            _length -= entry.buffer.remaining();
             buffer.put(entry.buffer);
-            iterator.remove();
             entry.callback.succeeded();
         }
-
+        _entries.clear();
-        if (!_entries.isEmpty())
+        _length = 0;
-            throw new IllegalStateException("remaining entries: " + _entries.size());
-        if (_length != 0)
-            throw new IllegalStateException("non-zero length: " + _length);
     }
 
     public void fail(Throwable t)

jetty-websocket/websocket-core-common/src/main/java/org/eclipse/jetty/websocket/core/internal/messages/DispatchedMessageSink.java

@@ -156,8 +156,8 @@ public abstract class DispatchedMessageSink extends AbstractMessageSink
                 @Override
                 public void succeeded()
                 {
-                    session.demand(1);
                     super.succeeded();
+                    session.demand(1);
                 }
             };
         }

jetty-websocket/websocket-jetty-common/src/main/java/org/eclipse/jetty/websocket/common/JettyWebSocketFrameHandler.java

@@ -326,7 +326,7 @@ public class JettyWebSocketFrameHandler implements FrameHandler
         if (activeMessageSink == null)
         {
             callback.succeeded();
-            coreSession.demand(1);
+            demand();
             return;
         }