Issue #5198 - revert usage of deflater ByteBuffer API for GzipHandler

The CRC32 checksum may need to convert the ByteBuffer to an array anyway so
we are better off not setting the deflater input with ByteBuffer directly.

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

jetty-server/src/main/java/org/eclipse/jetty/server/handler/gzip/GzipHttpOutputInterceptor.java

@@ -263,6 +263,7 @@ public boolean mightCompress()
 
     private class GzipBufferCB extends IteratingNestedCallback
     {
+        private ByteBuffer _copy;
         private final ByteBuffer _content;
         private final boolean _last;
 
@@ -271,10 +272,6 @@ public GzipBufferCB(ByteBuffer content, boolean complete, Callback callback)
             super(callback);
             _content = content;
             _last = complete;
-            _crc.update(_content.slice());
-            _deflater.setInput(_content);
-            if (_last)
-                _deflater.finish();
         }
 
         @Override
@@ -299,6 +296,11 @@ protected Action process() throws Exception
                     _channel.getByteBufferPool().release(_buffer);
                     _buffer = null;
                 }
+                if (_copy != null)
+                {
+                    _channel.getByteBufferPool().release(_copy);
+                    _copy = null;
+                }
                 return Action.SUCCEEDED;
             }
 
@@ -318,13 +320,52 @@ protected Action process() throws Exception
             // If the deflator is not finished, then compress more data
             if (!_deflater.finished())
             {
-                if (_deflater.needsInput() && !_last)
-                    return Action.SUCCEEDED;
+                if (_deflater.needsInput())
+                {
+                    // if there is no more content available to compress
+                    // then we are either finished all content or just the current write.
+                    if (BufferUtil.isEmpty(_content))
+                    {
+                        if (_last)
+                            _deflater.finish();
+                        else
+                            return Action.SUCCEEDED;
+                    }
+                    else
+                    {
+                        // If there is more content available to compress, we have to make sure
+                        // it is available in an array for the current deflator API, maybe slicing
+                        // of content.
+                        ByteBuffer slice;
+                        if (_content.hasArray())
+                            slice = _content;
+                        else
+                        {
+                            if (_copy == null)
+                                _copy = _channel.getByteBufferPool().acquire(_bufferSize, false);
+                            else
+                                BufferUtil.clear(_copy);
+                            slice = _copy;
+                            BufferUtil.append(_copy, _content);
+                        }
+
+                        // transfer the data from the slice to the the deflator
+                        byte[] array = slice.array();
+                        int off = slice.arrayOffset() + slice.position();
+                        int len = slice.remaining();
+                        _crc.update(array, off, len);
+                        _deflater.setInput(array, off, len);
+                        slice.position(slice.position() + len);
+                        if (_last && BufferUtil.isEmpty(_content))
+                            _deflater.finish();
+                    }
+                }
 
                 // deflate the content into the available space in the buffer
-                int pos = BufferUtil.flipToFill(_buffer);
-                _deflater.deflate(_buffer, _syncFlush ? Deflater.SYNC_FLUSH : Deflater.NO_FLUSH);
-                BufferUtil.flipToFlush(_buffer, pos);
+                int off = _buffer.arrayOffset() + _buffer.limit();
+                int len = BufferUtil.space(_buffer);
+                int produced = _deflater.deflate(_buffer.array(), off, len, _syncFlush ? Deflater.SYNC_FLUSH : Deflater.NO_FLUSH);
+                _buffer.limit(_buffer.limit() + produced);
             }
 
             // If we have finished deflation and there is room for the trailer.
@@ -345,10 +386,11 @@ protected Action process() throws Exception
         @Override
         public String toString()
         {
-            return String.format("%s[content=%s last=%b buffer=%s deflate=%s %s]",
+            return String.format("%s[content=%s last=%b copy=%s buffer=%s deflate=%s %s]",
                 super.toString(),
                 BufferUtil.toDetailString(_content),
                 _last,
+                BufferUtil.toDetailString(_copy),
                 BufferUtil.toDetailString(_buffer),
                 _deflater,
                 _deflater != null && _deflater.finished() ? "(finished)" : "");