WebSocket13FrameEncoder.java

/*
 * 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:
 *
 *   https://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: https://www.opensource.org/licenses/bsd-license)
//
// Copyright (c) 2011, Joe Walnes and contributors
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package io.netty5.handler.codec.http.websocketx;

import io.netty5.buffer.Buffer;
import io.netty5.channel.ChannelHandlerContext;
import io.netty5.handler.codec.MessageToMessageEncoder;
import io.netty5.handler.codec.TooLongFrameException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

/**
 * <p>
 * Encodes a web socket frame into wire protocol version 13 format. V13 is essentially the same as V8.
 * </p>
 */
public class WebSocket13FrameEncoder extends MessageToMessageEncoder<WebSocketFrame> implements WebSocketFrameEncoder {

    private static final Logger logger = LoggerFactory.getLogger(WebSocket13FrameEncoder.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 threshold for gathering writes. Non-Masked messages bigger than this size will be be sent fragmented as
     * a header and a content Buffer 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_THRESHOLD = 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 WebSocket13FrameEncoder(boolean maskPayload) {
        this.maskPayload = maskPayload;
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
        final Buffer data = msg.binaryData();

        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());
        }

        int length = data.readableBytes();

        if (logger.isTraceEnabled()) {
            logger.trace("Encoding WebSocket Frame opCode={} length={}", opcode, length);
        }

        int b0 = 0;
        if (msg.isFinalFragment()) {
            b0 |= 1 << 7;
        }
        b0 |= msg.rsv() % 8 << 4;
        b0 |= opcode % 128;

        if (opcode == OPCODE_PING && length > 125) {
            throw new TooLongFrameException("invalid payload for PING (payload length must be <= 125, was "
                    + length);
        }

        Buffer buf = null;
        try {
            int maskLength = maskPayload ? 4 : 0;
            if (length <= 125) {
                int size = 2 + maskLength;
                if (maskPayload || length <= GATHERING_WRITE_THRESHOLD) {
                    size += length;
                }
                buf = ctx.bufferAllocator().allocate(size);
                buf.writeByte((byte) b0);
                byte b = (byte) (maskPayload ? 0x80 | (byte) length : (byte) length);
                buf.writeByte(b);
            } else if (length <= 0xFFFF) {
                int size = 4 + maskLength;
                if (maskPayload || length <= GATHERING_WRITE_THRESHOLD) {
                    size += length;
                }
                buf = ctx.bufferAllocator().allocate(size);
                buf.writeByte((byte) b0);
                buf.writeByte((byte) (maskPayload ? 0xFE : 126));
                buf.writeByte((byte) (length >>> 8 & 0xFF));
                buf.writeByte((byte) (length & 0xFF));
            } else {
                int size = 10 + maskLength;
                if (maskPayload || length <= GATHERING_WRITE_THRESHOLD) {
                    size += length;
                }
                buf = ctx.bufferAllocator().allocate(size);
                buf.writeByte((byte) b0);
                buf.writeByte((byte) (maskPayload ? 0xFF : 127));
                buf.writeLong(length);
            }

            // Write payload
            if (maskPayload) {
                int mask = ThreadLocalRandom.current().nextInt(Integer.MAX_VALUE);
                buf.writeInt(mask);

                int i = data.readerOffset();
                int end = data.writerOffset();

                int maskOffset = 0;
                for (; i < end; i++) {
                    byte byteData = data.getByte(i);
                    buf.writeByte((byte) (byteData ^ WebSocketUtil.byteAtIndex(mask, maskOffset++ & 3)));
                }
                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.split());
                }
            }
        } catch (Throwable t) {
            if (buf != null) {
                buf.close();
            }
            throw t;
        }
    }
}