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 *
 * Copyright (C) 2014-2016 Appsicle
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
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 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 *
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package com.questdb.net;

import com.questdb.misc.ByteBuffers;
import com.questdb.misc.Unsafe;
import com.questdb.misc.Zip;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.WritableByteChannel;

public class GZipWritableChannel implements WritableByteChannel {
    private final ByteBuffer out;
    private final long outAddr;
    private final int outAvail;
    private T channel;
    private long z_streamp;
    private boolean flushed = false;
    private int crc = 0;
    private long total = 0;

    public GZipWritableChannel(int bufferSize) {
        this.out = ByteBuffer.allocateDirect(bufferSize);
        this.outAvail = bufferSize;
        this.outAddr = ByteBuffers.getAddress(out);
        this.z_streamp = Zip.deflateInit();
        if (z_streamp <= 0) {
            throw new OutOfMemoryError();
        }
    }

    public void flush() throws IOException {
        if (flushed) {
            return;
        }

        deflate(true);
        Unsafe.getUnsafe().putInt(outAddr, crc);
        Unsafe.getUnsafe().putInt(outAddr + 4, (int) total);
        out.limit(8).position(0);
        channel.write(out);

        flushed = true;
    }

    @Override
    public boolean isOpen() {
        return z_streamp != 0;
    }

    @Override
    public void close() throws IOException {

        flush();

        if (channel.isOpen()) {
            channel.close();
        }

        if (z_streamp != 0) {
            Zip.deflateEnd(z_streamp);
            z_streamp = 0;
        }
        ByteBuffers.release(out);
    }

    public GZipWritableChannel of(T channel) throws IOException {
        reset();
        this.channel = channel;
        Unsafe.getUnsafe().copyMemory(Zip.gzipHeader, outAddr, Zip.gzipHeaderLen);
        out.limit(Zip.gzipHeaderLen).position(0);
        channel.write(out);
        return this;
    }

    @Override
    public int write(ByteBuffer src) throws IOException {
        if (!ByteBuffers.isDirect(src)) {
            throw new IllegalArgumentException("Heap buffers are not supported");
        }

        int result = src.remaining();
        int pos = src.position();
        Zip.setInput(z_streamp, ByteBuffers.getAddress(src) + pos, result);
        crc = Zip.crc32(crc, ByteBuffers.getAddress(src) + pos, result);
        deflate(false);
        src.position(pos + result);
        total += result;
        return result;
    }

    private void deflate(boolean flush) throws IOException {
        int ret;
        do {
            ret = Zip.deflate(z_streamp, outAddr, outAvail, flush);
            if (ret < 0) {
                throw new IOException("Deflater error: " + ret);
            }

            int len = outAvail - Zip.availOut(z_streamp);
            if (len > 0) {
                out.limit(len).position(0);
                channel.write(out);
            }
        } while (Zip.availIn(z_streamp) > 0 || (flush && ret != 1));
    }

    private void reset() {
        Zip.deflateReset(z_streamp);
        crc = 0;
        total = 0;
        flushed = false;
    }
}