Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
//License from project: Open Source License 

import java.io.ByteArrayOutputStream;
import java.io.File;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.zip.DataFormatException;

import java.util.zip.Inflater;

public class Main {
    private static final int BUFSIZ = 4096;

    /**
     * <p>Decompresses a the content of a file from {@code startPosition} of {@code compressedSize}
     * and return the bytes of it.</p>
     *
     * @param file           the file
     * @param startPosition  the start position
     * @param compressedSize the compresse
     * @return the decompressed bytes
     * @throws IOException         if there was any io issues
     * @throws DataFormatException if there was an issue decompressing content
     */
    public static byte[] decompress(File file, int startPosition, int compressedSize)
            throws IOException, DataFormatException {

        try (FileChannel fileChannel = FileChannel.open(file.toPath())) {
            ByteBuffer buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, startPosition, compressedSize);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            Inflater inflater = new Inflater();
            byte[] compressedBytes = new byte[compressedSize];
            byte[] inflated = new byte[BUFSIZ];
            int read;

            buffer.get(compressedBytes);
            inflater.setInput(compressedBytes);

            // unzip contents
            while ((read = inflater.inflate(inflated)) != 0) {
                baos.write(inflated, 0, read);
            }

            inflater.end();

            return baos.toByteArray();
        }
    }

    /**
     * <p>Decompresses a the content of a file from {@code startPosition} of {@code compressedSize}
     * and return the bytes of it. If a {@code compressedSize} can be provided if it is known
     * how large the decompressed content will be.</p>
     *
     * @param file             the file
     * @param startPosition    the start position
     * @param compressedSize   the compresse
     * @param decompressedSize the decompressed size
     * @return the decompressed bytes
     * @throws IOException         if there was any io issues
     * @throws DataFormatException if there was an issue decompressing content
     */
    public static byte[] decompress(File file, int startPosition, int compressedSize, int decompressedSize)
            throws IOException, DataFormatException {

        if (decompressedSize == 0) {
            return decompress(file, startPosition, compressedSize);
        }

        try (FileChannel fileChannel = FileChannel.open(file.toPath())) {
            ByteBuffer buffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, startPosition, compressedSize);
            Inflater inflater = new Inflater();
            byte[] compressedBytes = new byte[compressedSize];
            byte[] bytes = new byte[decompressedSize];

            buffer.get(compressedBytes);
            inflater.setInput(compressedBytes, 0, compressedSize);
            inflater.inflate(bytes);
            inflater.end();

            return bytes;
        }
    }
}