Java example source code file (SpdyHeaderBlockJZlibEncoder.java)

This example Java source code file (SpdyHeaderBlockJZlibEncoder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bytebuf, compressionexception, deflater, illegalargumentexception, override, spdy, spdyheaderblockjzlibencoder, spdyheaderblockrawencoder, spdyheadersframe, spdyversion

The SpdyHeaderBlockJZlibEncoder.java Java example source code

/*
 * 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 io.netty.handler.codec.spdy;

import com.jcraft.jzlib.Deflater;
import com.jcraft.jzlib.JZlib;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.buffer.Unpooled;
import io.netty.handler.codec.compression.CompressionException;

import static io.netty.handler.codec.spdy.SpdyCodecUtil.*;

class SpdyHeaderBlockJZlibEncoder extends SpdyHeaderBlockRawEncoder {

    private final Deflater z = new Deflater();

    private boolean finished;

    SpdyHeaderBlockJZlibEncoder(
            SpdyVersion version, int compressionLevel, int windowBits, int memLevel) {
        super(version);
        if (compressionLevel < 0 || compressionLevel > 9) {
            throw new IllegalArgumentException(
                    "compressionLevel: " + compressionLevel + " (expected: 0-9)");
        }
        if (windowBits < 9 || windowBits > 15) {
            throw new IllegalArgumentException(
                    "windowBits: " + windowBits + " (expected: 9-15)");
        }
        if (memLevel < 1 || memLevel > 9) {
            throw new IllegalArgumentException(
                    "memLevel: " + memLevel + " (expected: 1-9)");
        }

        int resultCode = z.deflateInit(
                compressionLevel, windowBits, memLevel, JZlib.W_ZLIB);
        if (resultCode != JZlib.Z_OK) {
            throw new CompressionException(
                    "failed to initialize an SPDY header block deflater: " + resultCode);
        } else {
            resultCode = z.deflateSetDictionary(SPDY_DICT, SPDY_DICT.length);
            if (resultCode != JZlib.Z_OK) {
                throw new CompressionException(
                        "failed to set the SPDY dictionary: " + resultCode);
            }
        }
    }

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

        byte[] in;
        int offset;
        if (decompressed.hasArray()) {
            in = decompressed.array();
            offset = decompressed.arrayOffset() + decompressed.readerIndex();
        } else {
            in = new byte[len];
            decompressed.getBytes(decompressed.readerIndex(), in);
            offset = 0;
        }
        z.next_in = in;
        z.next_in_index = offset;
        z.avail_in = len;
    }

    private ByteBuf encode(ByteBufAllocator alloc) {
        boolean release = true;
        ByteBuf out = null;
        try {
            int oldNextInIndex = z.next_in_index;
            int oldNextOutIndex = z.next_out_index;

            int maxOutputLength = (int) Math.ceil(z.next_in.length * 1.001) + 12;
            out = alloc.heapBuffer(maxOutputLength);
            z.next_out = out.array();
            z.next_out_index = out.arrayOffset() + out.writerIndex();
            z.avail_out = maxOutputLength;

            int resultCode;
            try {
                resultCode = z.deflate(JZlib.Z_SYNC_FLUSH);
            } finally {
                out.skipBytes(z.next_in_index - oldNextInIndex);
            }
            if (resultCode != JZlib.Z_OK) {
                throw new CompressionException("compression failure: " + resultCode);
            }

            int outputLength = z.next_out_index - oldNextOutIndex;
            if (outputLength > 0) {
                out.writerIndex(out.writerIndex() + outputLength);
            }
            release = false;
            return out;
        } finally {
            // Deference the external references explicitly to tell the VM that
            // the allocated byte arrays are temporary so that the call stack
            // can be utilized.
            // I'm not sure if the modern VMs do this optimization though.
            z.next_in = null;
            z.next_out = null;
            if (release && out != null) {
                out.release();
            }
        }
    }

    @Override
    public ByteBuf encode(ByteBufAllocator alloc, SpdyHeadersFrame frame) throws Exception {
        if (frame == null) {
            throw new IllegalArgumentException("frame");
        }

        if (finished) {
            return Unpooled.EMPTY_BUFFER;
        }

        ByteBuf decompressed = super.encode(alloc, frame);
        try {
            if (!decompressed.isReadable()) {
                return Unpooled.EMPTY_BUFFER;
            }

            setInput(decompressed);
            return encode(alloc);
        } finally {
            decompressed.release();
        }
    }

    @Override
    public void end() {
        if (finished) {
            return;
        }
        finished = true;
        z.deflateEnd();
        z.next_in = null;
        z.next_out = null;
    }
}