/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.handler.codec.http.websocketx.extensions.compression;
import io.netty.handler.codec.compression.ZlibCodecFactory;
import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionData;
import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionDecoder;
import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionEncoder;
import io.netty.handler.codec.http.websocketx.extensions.WebSocketServerExtension;
import io.netty.handler.codec.http.websocketx.extensions.WebSocketServerExtensionHandshaker;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map.Entry;
/**
* <a href="http://tools.ietf.org/html/draft-ietf-hybi-permessage-compression-18">permessage-deflate</a>
* handshake implementation.
*/
public final class PerMessageDeflateServerExtensionHandshaker implements WebSocketServerExtensionHandshaker {
public static final int MIN_WINDOW_SIZE = 8;
public static final int MAX_WINDOW_SIZE = 15;
static final String PERMESSAGE_DEFLATE_EXTENSION = "permessage-deflate";
static final String CLIENT_MAX_WINDOW = "client_max_window_bits";
static final String SERVER_MAX_WINDOW = "server_max_window_bits";
static final String CLIENT_NO_CONTEXT = "client_no_context_takeover";
static final String SERVER_NO_CONTEXT = "server_no_context_takeover";
private final int compressionLevel;
private final boolean allowServerWindowSize;
private final int preferredClientWindowSize;
private final boolean allowServerNoContext;
private final boolean preferredClientNoContext;
/**
* Constructor with default configuration.
*/
public PerMessageDeflateServerExtensionHandshaker() {
this(6, ZlibCodecFactory.isSupportingWindowSizeAndMemLevel(), MAX_WINDOW_SIZE, false, false);
}
/**
* Constructor with custom configuration.
*
* @param compressionLevel
* Compression level between 0 and 9 (default is 6).
* @param allowServerWindowSize
* allows WebSocket client to customize the server inflater window size
* (default is false).
* @param preferredClientWindowSize
* indicates the preferred client window size to use if client inflater is customizable.
* @param allowServerNoContext
* allows WebSocket client to activate server_no_context_takeover
* (default is false).
* @param preferredClientNoContext
* indicates if server prefers to activate client_no_context_takeover
* if client is compatible with (default is false).
*/
public PerMessageDeflateServerExtensionHandshaker(int compressionLevel,
boolean allowServerWindowSize, int preferredClientWindowSize,
boolean allowServerNoContext, boolean preferredClientNoContext) {
if (preferredClientWindowSize > MAX_WINDOW_SIZE || preferredClientWindowSize < MIN_WINDOW_SIZE) {
throw new IllegalArgumentException(
"preferredServerWindowSize: " + preferredClientWindowSize + " (expected: 8-15)");
}
if (compressionLevel < 0 || compressionLevel > 9) {
throw new IllegalArgumentException(
"compressionLevel: " + compressionLevel + " (expected: 0-9)");
}
this.compressionLevel = compressionLevel;
this.allowServerWindowSize = allowServerWindowSize;
this.preferredClientWindowSize = preferredClientWindowSize;
this.allowServerNoContext = allowServerNoContext;
this.preferredClientNoContext = preferredClientNoContext;
}
@Override
public WebSocketServerExtension handshakeExtension(WebSocketExtensionData extensionData) {
if (!PERMESSAGE_DEFLATE_EXTENSION.equals(extensionData.name())) {
return null;
}
boolean deflateEnabled = true;
int clientWindowSize = MAX_WINDOW_SIZE;
int serverWindowSize = MAX_WINDOW_SIZE;
boolean serverNoContext = false;
boolean clientNoContext = false;
Iterator<Entry<String, String>> parametersIterator =
extensionData.parameters().entrySet().iterator();
while (deflateEnabled && parametersIterator.hasNext()) {
Entry<String, String> parameter = parametersIterator.next();
if (CLIENT_MAX_WINDOW.equalsIgnoreCase(parameter.getKey())) {
// use preferred clientWindowSize because client is compatible with customization
clientWindowSize = preferredClientWindowSize;
} else if (SERVER_MAX_WINDOW.equalsIgnoreCase(parameter.getKey())) {
// use provided windowSize if it is allowed
if (allowServerWindowSize) {
serverWindowSize = Integer.parseInt(parameter.getValue());
if (serverWindowSize > MAX_WINDOW_SIZE || serverWindowSize < MIN_WINDOW_SIZE) {
deflateEnabled = false;
}
} else {
deflateEnabled = false;
}
} else if (CLIENT_NO_CONTEXT.equalsIgnoreCase(parameter.getKey())) {
// use preferred clientNoContext because client is compatible with customization
clientNoContext = preferredClientNoContext;
} else if (SERVER_NO_CONTEXT.equalsIgnoreCase(parameter.getKey())) {
// use server no context if allowed
if (allowServerNoContext) {
serverNoContext = true;
} else {
deflateEnabled = false;
}
} else {
// unknown parameter
deflateEnabled = false;
}
}
if (deflateEnabled) {
return new PermessageDeflateExtension(compressionLevel, serverNoContext,
serverWindowSize, clientNoContext, clientWindowSize);
} else {
return null;
}
}
private static class PermessageDeflateExtension implements WebSocketServerExtension {
private final int compressionLevel;
private final boolean serverNoContext;
private final int serverWindowSize;
private final boolean clientNoContext;
private final int clientWindowSize;
public PermessageDeflateExtension(int compressionLevel, boolean serverNoContext,
int serverWindowSize, boolean clientNoContext, int clientWindowSize) {
this.compressionLevel = compressionLevel;
this.serverNoContext = serverNoContext;
this.serverWindowSize = serverWindowSize;
this.clientNoContext = clientNoContext;
this.clientWindowSize = clientWindowSize;
}
@Override
public int rsv() {
return RSV1;
}
@Override
public WebSocketExtensionEncoder newExtensionEncoder() {
return new PerMessageDeflateEncoder(compressionLevel, clientWindowSize, clientNoContext);
}
@Override
public WebSocketExtensionDecoder newExtensionDecoder() {
return new PerMessageDeflateDecoder(serverNoContext);
}
@Override
public WebSocketExtensionData newReponseData() {
HashMap<String, String> parameters = new HashMap<String, String>(4);
if (serverNoContext) {
parameters.put(SERVER_NO_CONTEXT, null);
}
if (clientNoContext) {
parameters.put(CLIENT_NO_CONTEXT, null);
}
if (serverWindowSize != MAX_WINDOW_SIZE) {
parameters.put(SERVER_MAX_WINDOW, Integer.toString(serverWindowSize));
}
if (clientWindowSize != MAX_WINDOW_SIZE) {
parameters.put(CLIENT_MAX_WINDOW, Integer.toString(clientWindowSize));
}
return new WebSocketExtensionData(PERMESSAGE_DEFLATE_EXTENSION, parameters);
}
}
}