openbns.commons.net.codec.sts.HttpObjectEncoder.java Source code

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Here is the source code for openbns.commons.net.codec.sts.HttpObjectEncoder.java

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/*
 * 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.
 */
package openbns.commons.net.codec.sts;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.FileRegion;
import io.netty.handler.codec.MessageToMessageEncoder;
import io.netty.util.internal.StringUtil;

import java.util.List;

import static io.netty.buffer.Unpooled.*;
import static io.netty.handler.codec.http.HttpConstants.CR;
import static io.netty.handler.codec.http.HttpConstants.LF;

/**
 * Encodes an {@link StsMessage} or an {@link StsContent} into
 * a {@link io.netty.buffer.ByteBuf}.
 * <p/>
 * <h3>Extensibility</h3>
 * <p/>
 * Please note that this encoder is designed to be extended to implement
 * a protocol derived from HTTP, such as
 * <a href="sts://en.wikipedia.org/wiki/Real_Time_Streaming_Protocol">RTSP</a> and
 * <a href="sts://en.wikipedia.org/wiki/Internet_Content_Adaptation_Protocol">ICAP</a>.
 * To implement the encoder of such a derived protocol, extend this class and
 * implement all abstract methods properly.
 */
public abstract class HttpObjectEncoder<H extends StsMessage> extends MessageToMessageEncoder<Object> {
    private static final byte[] CRLF = { CR, LF };
    private static final byte[] ZERO_CRLF = { '0', CR, LF };
    private static final byte[] ZERO_CRLF_CRLF = { '0', CR, LF, CR, LF };
    private static final ByteBuf CRLF_BUF = unreleasableBuffer(directBuffer(CRLF.length).writeBytes(CRLF));
    private static final ByteBuf ZERO_CRLF_CRLF_BUF = unreleasableBuffer(
            directBuffer(ZERO_CRLF_CRLF.length).writeBytes(ZERO_CRLF_CRLF));

    private static final int ST_INIT = 0;
    private static final int ST_CONTENT_NON_CHUNK = 1;

    @SuppressWarnings("RedundantFieldInitialization")
    private int state = ST_INIT;

    @Override
    protected void encode(ChannelHandlerContext ctx, Object msg, List<Object> out) throws Exception {
        ByteBuf buf = null;

        if (msg instanceof StsMessage) {
            if (state != ST_INIT) {
                throw new IllegalStateException("unexpected message type: " + StringUtil.simpleClassName(msg));
            }

            @SuppressWarnings({ "unchecked", "CastConflictsWithInstanceof" })
            H m = (H) msg;

            buf = ctx.alloc().buffer();
            // Encode the message.
            encodeInitialLine(buf, m);
            StsHeaders.encode(m.headers(), buf);
            buf.writeBytes(CRLF);
            state = ST_CONTENT_NON_CHUNK;
        }
        if (msg instanceof StsContent || msg instanceof ByteBuf || msg instanceof FileRegion) {
            if (state == ST_INIT) {
                throw new IllegalStateException("unexpected message type: " + StringUtil.simpleClassName(msg));
            }

            int contentLength = contentLength(msg);
            if (state == ST_CONTENT_NON_CHUNK) {
                if (contentLength > 0) {
                    if (buf != null && buf.writableBytes() >= contentLength && msg instanceof StsContent) {
                        // merge into other buffer for performance reasons
                        buf.writeBytes(((StsContent) msg).content());
                        out.add(buf);
                    } else {
                        if (buf != null) {
                            out.add(buf);
                        }
                        out.add(encodeAndRetain(msg));
                    }
                } else {
                    if (buf != null) {
                        out.add(buf);
                    } else {
                        // Need to produce some output otherwise an
                        // IllegalStateException will be thrown
                        out.add(EMPTY_BUFFER);
                    }
                }

                if (msg instanceof LastStsContent) {
                    state = ST_INIT;
                }
            } else {
                throw new Error();
            }
        } else {
            if (buf != null) {
                out.add(buf);
            }
        }
    }

    @Override
    public boolean acceptOutboundMessage(Object msg) throws Exception {
        return msg instanceof StsObject || msg instanceof ByteBuf || msg instanceof FileRegion;
    }

    private static Object encodeAndRetain(Object msg) {
        if (msg instanceof ByteBuf) {
            return ((ByteBuf) msg).retain();
        }
        if (msg instanceof StsContent) {
            return ((StsContent) msg).content().retain();
        }
        if (msg instanceof FileRegion) {
            return ((FileRegion) msg).retain();
        }
        throw new IllegalStateException("unexpected message type: " + StringUtil.simpleClassName(msg));
    }

    private static int contentLength(Object msg) {
        if (msg instanceof StsContent) {
            return ((StsContent) msg).content().readableBytes();
        }
        if (msg instanceof ByteBuf) {
            return ((ByteBuf) msg).readableBytes();
        }
        if (msg instanceof FileRegion) {
            return (int) ((FileRegion) msg).count();
        }
        throw new IllegalStateException("unexpected message type: " + StringUtil.simpleClassName(msg));
    }

    @Deprecated
    protected static void encodeAscii(String s, ByteBuf buf) {
        StsHeaders.encodeAscii0(s, buf);
    }

    protected abstract void encodeInitialLine(ByteBuf buf, H message) throws Exception;
}