org.lanternpowered.server.network.pipeline.MessageFramingHandler.java Source code

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Here is the source code for org.lanternpowered.server.network.pipeline.MessageFramingHandler.java

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/*
 * This file is part of LanternServer, licensed under the MIT License (MIT).
 *
 * Copyright (c) LanternPowered <https://www.lanternpowered.org>
 * Copyright (c) SpongePowered <https://www.spongepowered.org>
 * Copyright (c) contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the Software), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
/*
 * Copyright (c) 2011-2014 Glowstone - Tad Hardesty
 * Copyright (c) 2010-2011 Lightstone - Graham Edgecombe
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.lanternpowered.server.network.pipeline;

import static org.lanternpowered.server.network.buffer.LanternByteBuffer.writeVarInt;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageCodec;
import io.netty.handler.codec.DecoderException;

import java.util.List;

public final class MessageFramingHandler extends ByteToMessageCodec<ByteBuf> {

    @Override
    protected void encode(ChannelHandlerContext ctx, ByteBuf buf, ByteBuf output) throws Exception {
        writeVarInt(output, buf.readableBytes());
        output.writeBytes(buf);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf buf, List<Object> output) throws Exception {
        int length;
        while ((length = readableMessage(buf)) != -1) {
            final ByteBuf msg = ctx.alloc().buffer(length);
            buf.readBytes(msg, length);
            output.add(msg);
        }
    }

    /**
     * Reads the length and checks if the message can be read in one call.
     *
     * @param buf The byte buffer
     * @return The message length, or -1 if it's not possible to read a message
     */
    private static int readableMessage(ByteBuf buf) {
        int idx = buf.readerIndex();
        int i = 0;
        int length = 0;

        byte b;
        do {
            // The variable integer is not complete, try again next time
            if (buf.readableBytes() < 1) {
                buf.readerIndex(idx);
                return -1;
            }
            b = buf.readByte();
            length |= (b & 0x7F) << i;
            i += 7;
            if (i > 35) {
                throw new DecoderException("Variable length is too long!");
            }
        } while ((b & 0x80) != 0);
        if (length < 0) {
            throw new DecoderException("Message length cannot be negative: " + length);
        }
        // Not all the message bytes are available yet, try again later
        if (buf.readableBytes() < length) {
            buf.readerIndex(idx);
            return -1;
        }
        return length;
    }
}