--- old/src/jdk.internal.vm.compiler/share/classes/org.graalvm.graphio/src/org/graalvm/graphio/GraphOutput.java	2019-03-12 08:10:24.767891891 +0100
+++ new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.graphio/src/org/graalvm/graphio/GraphOutput.java	2019-03-12 08:10:24.407889561 +0100
@@ -28,6 +28,7 @@
 import java.io.IOException;
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.nio.ByteBuffer;
 import java.nio.channels.WritableByteChannel;
 import java.util.Collections;
 import java.util.Map;
@@ -37,8 +38,9 @@
  *
  * @param <G> the type of graph this instance handles
  * @param <M> the type of methods this instance handles
+ * @since 1.0 a {@link WritableByteChannel} is implemented
  */
-public final class GraphOutput<G, M> implements Closeable {
+public final class GraphOutput<G, M> implements Closeable, WritableByteChannel {
     private final GraphProtocol<G, ?, ?, ?, ?, M, ?, ?, ?, ?> printer;
 
     private GraphOutput(GraphProtocol<G, ?, ?, ?, ?, M, ?, ?, ?, ?> p) {
@@ -107,6 +109,30 @@
     }
 
     /**
+     * Checks if the {@link GraphOutput} is open.
+     *
+     * @return true if the {@link GraphOutput} is open.
+     * @since 1.0
+     */
+    @Override
+    public boolean isOpen() {
+        return printer.isOpen();
+    }
+
+    /**
+     * Writes raw bytes into {@link GraphOutput}.
+     *
+     * @param src the bytes to write
+     * @return the number of bytes written, possibly zero
+     * @throws IOException in case of IO error
+     * @since 1.0
+     */
+    @Override
+    public int write(ByteBuffer src) throws IOException {
+        return printer.write(src);
+    }
+
+    /**
      * Builder to configure and create an instance of {@link GraphOutput}.
      *
      * @param <G> the type of the (root element of) graph
@@ -121,6 +147,7 @@
         private GraphBlocks<G, ?, N> blocks = DefaultGraphBlocks.empty();
         private int major = 4;
         private int minor = 0;
+        private boolean embeddedGraphOutput;
 
         Builder(GraphStructure<G, N, ?, ?> structure) {
             this.structure = structure;
@@ -143,6 +170,22 @@
         }
 
         /**
+         * Sets {@link GraphOutput} as embedded. The embedded {@link GraphOutput} shares
+         * {@link WritableByteChannel channel} with another already open non parent
+         * {@link GraphOutput}. The embedded {@link GraphOutput} flushes data after each
+         * {@link GraphOutput#print print}, {@link GraphOutput#beginGroup beginGroup} and
+         * {@link GraphOutput#endGroup endGroup} call.
+         *
+         * @param embedded if {@code true} the builder creates an embedded {@link GraphOutput}
+         * @return this builder
+         * @since 1.0
+         */
+        public Builder<G, N, M> embedded(boolean embedded) {
+            this.embeddedGraphOutput = embedded;
+            return this;
+        }
+
+        /**
          * Associates different implementation of types.
          *
          * @param graphTypes implementation of types and enum recognition
@@ -226,7 +269,7 @@
         private <L, P> GraphOutput<G, M> buildImpl(ElementsAndLocations<M, L, P> e, WritableByteChannel channel) throws IOException {
             // @formatter:off
             ProtocolImpl<G, N, ?, ?, ?, M, ?, ?, ?, ?> p = new ProtocolImpl<>(
-                major, minor, structure, types, blocks,
+                major, minor, embeddedGraphOutput, structure, types, blocks,
                 e == null ? null : e.elements,
                 e == null ? null : e.locations, channel
             );