Decoder

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

//Alexander Linton
//I discussed this with Elisabeth Hutzel

/**
 * HW9
 *
 * This class takes in a file and decodes the file from a Huffman encoding and
 * makes an output file based on the input.
 */
public class Decoder
{

    /**
     * This method takes in a file from the command line and then decodes the
     * file from a Huffman encoding in the way specified in the homework
     * @param args the file
     */
    public static void main(String[] args) throws IOException
    {
        DataInputStream input = new DataInputStream(new FileInputStream(args[0]));
        String filename = args[0].substring(0, (args[0].length() - 3));
        DataOutputStream output = new DataOutputStream(new FileOutputStream(filename));
        int[] header = new int[772];
        int Iindex = 0;
        while ((input.available()>0) && (Iindex<772))
        {
            header[Iindex] = input.readUnsignedByte();
            Iindex++;
        }
        int size =  header[0]<<24 | header[1]<<16 | header[2]<<8 | header[3];
        int[] frequencies = new int[256];
        for(int i = 0; i < 256; i++)
        {
            frequencies[i] = header[3*i +4]<<16 | header[3*i + 5]<<8 | header[3*i + 6];
        }
        HuffmanNodeType node = HuffmanNode.buildHuffmanTree(frequencies);
        HuffmanNodeType copy = node;
        int current = input.readUnsignedByte();
        int bit = 7;
        while(output.size() < size && input.available() > 0)
        {
            while(node.getData() == null)
            {
                if(((current>>>bit)&1) == 1)
                    node = node.getRightChild();
                else if(((current>>>bit)&1) == 0)
                    node = node.getLeftChild();
                if(bit > 0)
                {
                    bit--;
                }
                else
                {
                    current = input.readUnsignedByte();
                    bit = 7;
                }
            }
            output.write(node.getData());
            node = copy;
        }
        input.close();
        output.close();
    }


}