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This nifi-utils module should be a general purpose place to store widely and generally useful functions that any component might want to leverage. NO DEPENDENCIES should be added. This module is likely to be leveraged by every extension and should not bring along any other dependencies. The only dependency intended is the nifi-api and even this is expected to be already provided in any case where it would be used. The typical place this util would be found is within a nar and all nars already have nifi-api as a parent dependency. The nifi-api can be thought of as a NiFi Application Container level dependency.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.nifi.remote.io;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.zip.DataFormatException;
import java.util.zip.Inflater;

public class CompressionInputStream extends InputStream {

    private final InputStream in;
    private final Inflater inflater;

    private byte[] compressedBuffer;
    private byte[] buffer;

    private int bufferIndex;
    private boolean eos = false;    // whether or not we've reached the end of stream
    private boolean allDataRead = false;    // different from eos b/c eos means allDataRead == true && buffer is empty

    private final byte[] fourByteBuffer = new byte[4];

    public CompressionInputStream(final InputStream in) {
        this.in = in;
        inflater = new Inflater();

        buffer = new byte[0];
        compressedBuffer = new byte[0];
        bufferIndex = 1;
    }

    private String toHex(final byte[] array) {
        final StringBuilder sb = new StringBuilder("0x");
        for (final byte b : array) {
            final String hex = Integer.toHexString(b).toUpperCase();
            if (hex.length() == 1) {
                sb.append("0");
            }
            sb.append(hex);
        }
        return sb.toString();
    }

    protected void readChunkHeader() throws IOException {
        // Ensure that we have a valid SYNC chunk
        fillBuffer(fourByteBuffer);
        if (!Arrays.equals(CompressionOutputStream.SYNC_BYTES, fourByteBuffer)) {
            throw new IOException("Invalid CompressionInputStream. Expected first 4 bytes to be 'SYNC' but were " + toHex(fourByteBuffer));
        }

        // determine the size of the decompressed buffer
        fillBuffer(fourByteBuffer);
        buffer = new byte[toInt(fourByteBuffer)];

        // determine the size of the compressed buffer
        fillBuffer(fourByteBuffer);
        compressedBuffer = new byte[toInt(fourByteBuffer)];

        bufferIndex = buffer.length;  // indicate that buffer is empty
    }

    private int toInt(final byte[] data) {
        return ((data[0] & 0xFF) << 24)
                | ((data[1] & 0xFF) << 16)
                | ((data[2] & 0xFF) << 8)
                | (data[3] & 0xFF);
    }

    protected void bufferAndDecompress() throws IOException {
        if (allDataRead) {
            eos = true;
            return;
        }

        readChunkHeader();
        fillBuffer(compressedBuffer);

        inflater.setInput(compressedBuffer);
        try {
            inflater.inflate(buffer);
        } catch (final DataFormatException e) {
            throw new IOException(e);
        }
        inflater.reset();

        bufferIndex = 0;
        final int moreDataByte = in.read();
        if (moreDataByte < 1) {
            allDataRead = true;
        } else if (moreDataByte > 1) {
            throw new IOException("Expected indicator of whether or not more data was to come (-1, 0, or 1) but got " + moreDataByte);
        }
    }

    private void fillBuffer(final byte[] buffer) throws IOException {
        int len;
        int bytesLeft = buffer.length;
        int bytesRead = 0;
        while (bytesLeft > 0 && (len = in.read(buffer, bytesRead, bytesLeft)) > 0) {
            bytesLeft -= len;
            bytesRead += len;
        }

        if (bytesRead < buffer.length) {
            throw new EOFException();
        }
    }

    private boolean isBufferEmpty() {
        return bufferIndex >= buffer.length;
    }

    @Override
    public int read() throws IOException {
        if (eos) {
            return -1;
        }

        if (isBufferEmpty()) {
            bufferAndDecompress();
        }

        if (isBufferEmpty()) {
            eos = true;
            return -1;
        }

        return buffer[bufferIndex++] & 0xFF;
    }

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

    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        if (eos) {
            return -1;
        }

        if (isBufferEmpty()) {
            bufferAndDecompress();
        }

        if (isBufferEmpty()) {
            eos = true;
            return -1;
        }

        final int free = buffer.length - bufferIndex;
        final int bytesToTransfer = Math.min(len, free);
        System.arraycopy(buffer, bufferIndex, b, off, bytesToTransfer);
        bufferIndex += bytesToTransfer;

        return bytesToTransfer;
    }

    /**
     * Calls {@link Inflater#end()} to free acquired memory to prevent OutOfMemory error.
     * However, does NOT close underlying InputStream.
     *
     * @throws java.io.IOException for any issues closing underlying stream
     */
    @Override
    public void close() throws IOException {
        inflater.end();
    }
}