/*
* Copyright 2012 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.
*/
// (BSD License: http://www.opensource.org/licenses/bsd-license)
//
// Copyright (c) 2011, Joe Walnes and contributors
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or
// without modification, are permitted provided that the
// following conditions are met:
//
// * Redistributions of source code must retain the above
// copyright notice, this list of conditions and the
// following disclaimer.
//
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the
// following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// * Neither the name of the Webbit nor the names of
// its contributors may be used to endorse or promote products
// derived from this software without specific prior written
// permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
// CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
package io.netty.handler.codec.http.websocketx;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageEncoder;
import io.netty.handler.codec.TooLongFrameException;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.List;
/**
* <p>
* Encodes a web socket frame into wire protocol version 8 format. This code was forked from <a
* href="https://github.com/joewalnes/webbit">webbit</a> and modified.
* </p>
*/
public class WebSocket08FrameEncoder extends MessageToMessageEncoder<WebSocketFrame> implements WebSocketFrameEncoder {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(WebSocket08FrameEncoder.class);
private static final byte OPCODE_CONT = 0x0;
private static final byte OPCODE_TEXT = 0x1;
private static final byte OPCODE_BINARY = 0x2;
private static final byte OPCODE_CLOSE = 0x8;
private static final byte OPCODE_PING = 0x9;
private static final byte OPCODE_PONG = 0xA;
/**
* The size treshold for gathering writes. Non-Masked messages bigger than this size will be be sent fragmented as
* a header and a content ByteBuf whereas messages smaller than the size will be merged into a single buffer and
* sent at once.<br>
* Masked messages will always be sent at once.
*/
private static final int GATHERING_WRITE_TRESHOLD = 1024;
private final boolean maskPayload;
/**
* Constructor
*
* @param maskPayload
* Web socket clients must set this to true to mask payload. Server implementations must set this to
* false.
*/
public WebSocket08FrameEncoder(boolean maskPayload) {
this.maskPayload = maskPayload;
}
/**
* 将websocket frame 片段编码成满足websocket13协议的
* <br>
* 其执行过程是将msg 按照要求处理之后，变成ByteBuffere 然后放到List中。
*/
@Override
protected void encode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
final ByteBuf data = msg.content();
byte[] mask;
// 判断msg 类型，如文本，二进制等等，其中要特别注意的是ContinuationWebSocketFrame
byte opcode;
if (msg instanceof TextWebSocketFrame) {
opcode = OPCODE_TEXT;
} else if (msg instanceof PingWebSocketFrame) {
opcode = OPCODE_PING;
} else if (msg instanceof PongWebSocketFrame) {
opcode = OPCODE_PONG;
} else if (msg instanceof CloseWebSocketFrame) {
opcode = OPCODE_CLOSE;
} else if (msg instanceof BinaryWebSocketFrame) {
opcode = OPCODE_BINARY;
} else if (msg instanceof ContinuationWebSocketFrame) {
opcode = OPCODE_CONT;
} else {
throw new UnsupportedOperationException("Cannot encode frame of type: " + msg.getClass().getName());
}
// frame 实际内容长度
int length = data.readableBytes();
if (logger.isDebugEnabled()) {
logger.debug("Encoding WebSocket Frame opCode=" + opcode + " length=" + length);
}
// b0 是第一个byte,如果不是Continuation,则FIN 至1
int b0 = 0;
if (msg.isFinalFragment()) {
b0 |= 1 << 7;
}
// 判断是不是用到协议扩展
b0 |= msg.rsv() % 8 << 4;
// 添加opcode 来自WebsocketFrame
b0 |= opcode % 128;
// ping 没有内容，或者内容不允许长度大于125
if (opcode == OPCODE_PING && length > 125) {
throw new TooLongFrameException("invalid payload for PING (payload length must be <= 125, was "
+ length);
}
boolean release = true;
ByteBuf buf = null;
try {
// 如果掩码处理，添加4个byte 的掩码
int maskLength = maskPayload ? 4 : 0;
if (length <= 125) {
// 长度小于125 ,该处写入2个 byte---
// 两个字节的头部（FIN+opcode#mask+loadLen）加四个字节的掩码
int size = 2 + maskLength;
// 如果有掩码或者是frame 真实内容长度小于1k，加上真实内容长度
if (maskPayload || length <= GATHERING_WRITE_TRESHOLD) {
size += length;
}
buf = ctx.alloc().buffer(size);
buf.writeByte(b0);
// b 是第二个byte,负责 mask +load Len
byte b = (byte) (maskPayload ? 0x80 | (byte) length : (byte) length);
buf.writeByte(b);
} else if (length <= 0xFFFF) {
// 长度小于2^16 ，该处写入4个byte---
int size = 4 + maskLength;
if (maskPayload || length <= GATHERING_WRITE_TRESHOLD) {
size += length;
}
buf = ctx.alloc().buffer(size);
buf.writeByte(b0);
buf.writeByte(maskPayload ? 0xFE : 126);
buf.writeByte(length >>> 8 & 0xFF);
buf.writeByte(length & 0xFF);
} else {
// 长度小于2^64 ，该处写入10个byte---
int size = 10 + maskLength;
if (maskPayload || length <= GATHERING_WRITE_TRESHOLD) {
size += length;
}
buf = ctx.alloc().buffer(size);
buf.writeByte(b0);
buf.writeByte(maskPayload ? 0xFF : 127);
buf.writeLong(length);
}
// Write payload
if (maskPayload) {
int random = (int) (Math.random() * Integer.MAX_VALUE);
// 掩码四个byte ,写入
mask = ByteBuffer.allocate(4).putInt(random).array();
buf.writeBytes(mask);
ByteOrder srcOrder = data.order();
ByteOrder dstOrder = buf.order();
int counter = 0;
int i = data.readerIndex();
int end = data.writerIndex();
if (srcOrder == dstOrder) {
// Use the optimized path only when byte orders match
// Remark: & 0xFF is necessary because Java will do signed expansion from
// byte to int which we don't want.
int intMask = ((mask[0] & 0xFF) << 24)
| ((mask[1] & 0xFF) << 16)
| ((mask[2] & 0xFF) << 8)
| (mask[3] & 0xFF);
// If the byte order of our buffers it little endian we have to bring our mask
// into the same format, because getInt() and writeInt() will use a reversed byte order
if (srcOrder == ByteOrder.LITTLE_ENDIAN) {
intMask = Integer.reverseBytes(intMask);
}
for (; i + 3 < end; i += 4) {
int intData = data.getInt(i);
buf.writeInt(intData ^ intMask);
}
}
for (; i < end; i++) {
byte byteData = data.getByte(i);
// 掩码处理之后，写入frame 真实内容
buf.writeByte(byteData ^ mask[counter++ % 4]);
}
out.add(buf);
} else {
if (buf.writableBytes() >= data.readableBytes()) {
// merge buffers as this is cheaper then a gathering write if the payload is small enough
buf.writeBytes(data);
out.add(buf);
} else {
out.add(buf);
out.add(data.retain());
}
}
release = false;
} finally {
if (release && buf != null) {
buf.release();
}
}
}
}