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package prerna.security;
/*
 * Compression routines for SNOW.
 * Uses simple Huffman coding.
 *
 * Written by Matthew Kwan - April 1997
 */

class SnowCompress extends BitFilter {
	private boolean		encode_flag = false;
	private boolean		quiet_flag = false;
	private BitFilter	next_filter = null;

	private int		bit_count;
	private int		value;
	private int		bits_in;
	private int		bits_out;
	private boolean		bit_array[];

	SnowCompress (boolean encode, boolean quiet, BitFilter output) {
	    encode_flag = encode;
	    quiet_flag = quiet;
	    next_filter = output;

	    bit_count = 0;
	    value = 0;
	    bits_in = 0;
	    bits_out = 0;

	    if (!encode_flag)
		bit_array = new boolean[256];
	}

	public boolean		receive_bit (boolean bit) {
	    if (encode_flag) {
		bits_in++;
		value = (value << 1) | (bit ? 1 : 0);

		if (++bit_count == 8) {
		    boolean	s[] = huffcodes[value];

		    for (int i = 0; i < s.length; i++) {
			if (!next_filter.receive_bit (s[i]))
			    return (false);
			bits_out++;
		    }

		    value = 0;
		    bit_count = 0;
		}
	    } else {
		int	code;

		bit_array[bit_count++] = bit;

		if ((code = huffcode_find (bit_array, bit_count)) >= 0) {
		    for (int i=0; i<8; i++) {
			boolean		b = ((code & (128 >> i)) != 0);

			if (!next_filter.receive_bit (b))
			    return (true);
		    }

		    bit_count = 0;
		}

		if (bit_count >= 255) {
		    System.err.println (
				"Error: Huffman uncompress buffer overflow.");
		    return (false);
		}
	    }

	    return (true);
	}

	public boolean		flush () {
	    if (encode_flag) {
		if (bit_count != 0 && !quiet_flag)
		    System.err.println ("Warning: residual of " + bit_count
						+ " bits not compressed.");

		if (bits_out > 0 && !quiet_flag) {
		    double	cpc = (double) (bits_in - bits_out)
						/ (double) bits_in * 100.0;

		    cpc = Math.rint (cpc * 100.0) / 100.0;	// Rounding
		    if (cpc < 0.0)
			System.err.println ("Compression enlarged data by "
				+ -cpc + "% recommend not using compression.");
		    else
			System.err.println ("Compressed by " + cpc + "%.");
		}
	    } else {
		if (bit_count > 2 && !quiet_flag)
		    System.err.println ("Warning: residual of " + bit_count
						+ " bits not uncompressed.");
	    }

	    return (next_filter.flush ());
	}

		// Find a huffman code that matches the array of bits.
		// If no match, return -1
	private int	huffcode_find (boolean bits[], int len) {
	    for (int i=0; i<256; i++) {
		boolean		found = true;

		if (huffcodes[i].length != len)
		    continue;

		for (int j=0; j