Make WebSocket compression actually work

Add a new implementation of RFC 7962 WebSocket Compression, with tests
verifying the examples from RFC 7962, full extension parameter handling,
compression ratio statistics and maximum decompressed frame size limit.

Adapt MultiProtocolJSONClient and MultiProtocolJSONServer to use this
new implementation.

Author: robert-s-ubi

ocpp-v2/src/main/java/eu/chargetime/ocpp/MultiProtocolJSONClient.java

@@ -44,7 +44,6 @@
 import org.java_websocket.drafts.Draft;
 import org.java_websocket.drafts.Draft_6455;
 import org.java_websocket.extensions.IExtension;
-import org.java_websocket.extensions.permessage_deflate.PerMessageDeflateExtension;
 import org.java_websocket.protocols.IProtocol;
 import org.java_websocket.protocols.Protocol;
 import org.slf4j.Logger;
@@ -58,6 +57,7 @@ public class MultiProtocolJSONClient implements IMultiProtocolClientAPI {
   private final String identity;
   private final MultiProtocolFeatureRepository featureRepository;
   private final MultiProtocolWebSocketTransmitter transmitter;
+  private final WebSocketPerMessageDeflateExtension compressionExtension;
   private final Client client;
 
   /**
@@ -92,12 +92,13 @@ public MultiProtocolJSONClient(
     featureRepository = new MultiProtocolFeatureRepository(protocolVersions);
     List<IExtension> inputExtensions = new ArrayList<>();
     if (configuration.getParameter(JSONConfiguration.WEBSOCKET_COMPRESSION_SUPPORT, false)) {
-      PerMessageDeflateExtension perMessageDeflateExtension =
-          new PerMessageDeflateExtension(Deflater.BEST_COMPRESSION);
-      perMessageDeflateExtension.setThreshold(0);
-      perMessageDeflateExtension.setServerNoContextTakeover(false);
-      perMessageDeflateExtension.setClientNoContextTakeover(false);
-      inputExtensions.add(perMessageDeflateExtension);
+      compressionExtension = new WebSocketPerMessageDeflateExtension(Deflater.BEST_COMPRESSION);
+      compressionExtension.setThreshold(64);
+      compressionExtension.setServerNoContextTakeover(false);
+      compressionExtension.setClientNoContextTakeover(false);
+      inputExtensions.add(compressionExtension);
+    } else {
+      compressionExtension = null;
     }
     List<IProtocol> inputProtocols = new ArrayList<>(protocolVersions.size());
     for (ProtocolVersion protocolVersion : protocolVersions) {
@@ -221,6 +222,10 @@ public Exception getLastError() {
     return transmitter.getLastError();
   }
 
+  public double getCompressionRatio() {
+    return compressionExtension != null ? compressionExtension.getCompressionRatio() : 1;
+  }
+
   @Override
   public boolean isClosed() {
     return transmitter.isClosed();

ocpp-v2/src/main/java/eu/chargetime/ocpp/MultiProtocolJSONServer.java

@@ -43,7 +43,6 @@ of this software and associated documentation files (the "Software"), to deal
 import org.java_websocket.drafts.Draft;
 import org.java_websocket.drafts.Draft_6455;
 import org.java_websocket.extensions.IExtension;
-import org.java_websocket.extensions.permessage_deflate.PerMessageDeflateExtension;
 import org.java_websocket.protocols.IProtocol;
 import org.java_websocket.protocols.Protocol;
 import org.slf4j.Logger;
@@ -71,12 +70,12 @@ public MultiProtocolJSONServer(
 
     List<IExtension> extensions = new ArrayList<>();
     if (configuration.getParameter(JSONConfiguration.WEBSOCKET_COMPRESSION_SUPPORT, true)) {
-      PerMessageDeflateExtension perMessageDeflateExtension =
-          new PerMessageDeflateExtension(Deflater.BEST_COMPRESSION);
-      perMessageDeflateExtension.setThreshold(0);
-      perMessageDeflateExtension.setServerNoContextTakeover(false);
-      perMessageDeflateExtension.setClientNoContextTakeover(false);
-      extensions.add(perMessageDeflateExtension);
+      WebSocketPerMessageDeflateExtension compressionExtension =
+          new WebSocketPerMessageDeflateExtension(Deflater.BEST_COMPRESSION);
+      compressionExtension.setThreshold(64);
+      compressionExtension.setServerNoContextTakeover(false);
+      compressionExtension.setClientNoContextTakeover(false);
+      extensions.add(compressionExtension);
     }
     List<IProtocol> protocols = new ArrayList<>(protocolVersions.size());
     for (ProtocolVersion protocolVersion : protocolVersions) {