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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2013 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 org.jboss.netty.handler.codec.spdy;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;

import java.util.zip.Deflater;

import static org.jboss.netty.handler.codec.spdy.SpdyCodecUtil.*;

class SpdyHeaderBlockZlibEncoder extends SpdyHeaderBlockRawEncoder {

    private final Deflater compressor;

    private boolean finished;

    SpdyHeaderBlockZlibEncoder(SpdyVersion spdyVersion, int compressionLevel) {
        super(spdyVersion);
        if (compressionLevel < 0 || compressionLevel > 9) {
            throw new IllegalArgumentException(
                    "compressionLevel: " + compressionLevel + " (expected: 0-9)");
        }
        compressor = new Deflater(compressionLevel);
        compressor.setDictionary(SPDY_DICT);
    }

    private int setInput(ChannelBuffer decompressed) {
        int len = decompressed.readableBytes();

        if (decompressed.hasArray()) {
            compressor.setInput(decompressed.array(), decompressed.arrayOffset() + decompressed.readerIndex(), len);
        } else {
            byte[] in = new byte[len];
            decompressed.getBytes(decompressed.readerIndex(), in);
            compressor.setInput(in, 0, in.length);
        }

        return len;
    }

    private void encode(ChannelBuffer compressed) {
        while (compressInto(compressed)) {
            // Although unlikely, it's possible that the compressed size is larger than the decompressed size
            compressed.ensureWritableBytes(compressed.capacity() << 1);
        }
    }

    private boolean compressInto(ChannelBuffer compressed) {
        byte[] out = compressed.array();
        int off = compressed.arrayOffset() + compressed.writerIndex();
        int toWrite = compressed.writableBytes();
        int numBytes = compressor.deflate(out, off, toWrite, Deflater.SYNC_FLUSH);
        compressed.writerIndex(compressed.writerIndex() + numBytes);
        return numBytes == toWrite;
    }

    @Override
    public synchronized ChannelBuffer encode(SpdyHeadersFrame frame) throws Exception {
        if (frame == null) {
            throw new IllegalArgumentException("frame");
        }

        if (finished) {
            return ChannelBuffers.EMPTY_BUFFER;
        }

        ChannelBuffer decompressed = super.encode(frame);
        if (decompressed.readableBytes() == 0) {
            return ChannelBuffers.EMPTY_BUFFER;
        }

        ChannelBuffer compressed = ChannelBuffers.dynamicBuffer(decompressed.readableBytes());
        int len = setInput(decompressed);
        encode(compressed);
        decompressed.skipBytes(len);

        return compressed;
    }

    @Override
    public synchronized void end() {
        if (finished) {
            return;
        }
        finished = true;
        compressor.end();
        super.end();
    }
}