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package org.mariadb.jdbc.internal.common.packet;

import org.mariadb.jdbc.internal.common.packet.buffer.ReadUtil;

import java.io.ByteArrayInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.security.InvalidParameterException;
import java.util.zip.Inflater;
import java.util.zip.DataFormatException;

public class DecompressInputStream extends InputStream{
    InputStream baseStream;
    int remainingBytes;
    byte header[];
    boolean doDecompress;
    ByteArrayInputStream decompressedByteStream;

    public DecompressInputStream(InputStream baseStream) {
        this.baseStream = baseStream;
        header = new byte[7];
    }

    @Override
    public int read(byte[] bytes, int off, int len) throws IOException {
        if (len == 0 || off < 0 || bytes == null)
            throw new InvalidParameterException();

        if (remainingBytes == 0) {
            nextPacket();
        }

        int ret;
        int bytesToRead = Math.min(remainingBytes, len);
        if (doDecompress) {
            ret = decompressedByteStream.read(bytes, off, bytesToRead);
        }  else {
            ret = baseStream.read(bytes, off, bytesToRead);
        }
        if (ret <= 0)  {
            throw new EOFException("got "+ ret +"bytes, bytesToRead = " + bytesToRead);
        }

        remainingBytes -= ret;
        return ret;
    }

    @Override
    public int read(byte[] bytes) throws  IOException{
       return read(bytes, 0, bytes.length);
    }

    @Override
    public int read() throws IOException {
        byte[] b = new byte[1];
        if (read(b) == 0)
            return -1;
        return (b[0] & 0xff);
    }


    /**
     * Read packet header. If required, decompress compressed packet.
     * @throws IOException
     */
    private  void nextPacket() throws IOException {
            ReadUtil.readFully(baseStream, header);
            int compressedLength = (header[0] & 0xff) + ((header[1] & 0xff) << 8) + ((header[2] & 0xff) << 16);
            int decompressedLength = (header[4] & 0xff) + ((header[5] & 0xff) << 8) + ((header[6] & 0xff) << 16);
            if (decompressedLength != 0) {
                doDecompress = true;
                remainingBytes += decompressedLength;
                byte[] compressedBuffer = new byte[compressedLength];
                byte[] decompressedBuffer = new byte[decompressedLength];
                ReadUtil.readFully(baseStream, compressedBuffer);
                Inflater inflater = new Inflater();
                inflater.setInput(compressedBuffer);
                try {
                   int n = inflater.inflate(decompressedBuffer);
                   if (n != decompressedLength)
                       throw new IOException("Invalid packet length after decompression "+n + ",expected "
                               + decompressedLength);
                }
                catch(DataFormatException dfe) {
                    throw new IOException(dfe);
                }
                inflater.end();
                decompressedByteStream = new ByteArrayInputStream(decompressedBuffer);

            }  else {
                doDecompress = false;
                remainingBytes += compressedLength;
                decompressedByteStream = null;
            }
    }

}