/audiobox.fm-sync/src/main/java/com/twmacinta/util/MD5.java

package com.twmacinta.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

/**
 * Fast implementation of RSA's MD5 hash generator in Java JDK Beta-2 or higher.
 * <p>
 * Originally written by Santeri Paavolainen, Helsinki Finland 1996.<br>
 * (c) Santeri Paavolainen, Helsinki Finland 1996<br>
 * Many changes Copyright (c) 2002 - 2010 Timothy W Macinta<br>
 * <p>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * <p>
 * See http://www.twmacinta.com/myjava/fast_md5.php for more information
 * on this file and the related files.
 * <p>
 * This was originally a rather straight re-implementation of the
 * reference implementation given in RFC1321 by RSA.  It passes the MD5
 * test suite as defined in RFC1321.
 * <p>
 * Many optimizations made by Timothy W Macinta.  Reduced time to checksum a
 * test file in Java alone to roughly half the time taken compared with
 * java.security.MessageDigest (within an intepretter).  Also added an
 * optional native method to reduce the time even further.
 * See http://www.twmacinta.com/myjava/fast_md5.php for further information
 * on the time improvements achieved.
 * <p>
 * Some bug fixes also made by Timothy W Macinta.
 * <p>
 * Please note: I (Timothy Macinta) have put this code in the
 * com.twmacinta.util package only because it came without a package.  I
 * was not the the original author of the code, although I did
 * optimize it (substantially) and fix some bugs.
 * <p>
 * This Java class has been derived from the RSA Data Security, Inc. MD5 
 * Message-Digest Algorithm and its reference implementation.
 * <p>
 * This class will attempt to use a native method to quickly compute
 * checksums when the appropriate native library is available.  On Linux,
 * this library should be named "MD5.so" and on Windows it should be
 * named "MD5.dll".  The code will attempt to locate the library in the
 * following locations in the order given:
 *
 * <ol>
 *   <li>The path specified by the system property
 *       "com.twmacinta.util.MD5.NATIVE_LIB_FILE"
 *       (be sure to include "MD5.so", "MD5.dll",
 *       or "MD5.jnilib" as appropriate at the end
 *       of the path).
 *   <li>A platform specific directory beneath the "lib/arch/" directory.
 *       For example, On Windows for 32 bit x86 architectures, this is
 *       "lib/arch/win32_x86/".
 *   <li>Within the "lib/" directory.
 *   <li>Within the current directory.
 * </ol>
 *
 * <p>
 * If the library is not found, the code will fall back to the default
 * (slower) Java code.
 * <p>
 * As a side effect of having the code search for the native library,
 * SecurityExceptions might be thrown on JVMs that have a restrictive
 * SecurityManager.  The initialization code attempts to silently discard
 * these exceptions and continue, but many SecurityManagers will
 * attempt to notify the user directly of all SecurityExceptions thrown.
 * Consequently, the code has provisions for skipping the search for
 * the native library.  Any of these provisions may be used to skip the
 * search as long as they are performed <i>before</i> the first
 * instance of a com.twmacinta.util.MD5 object is constructed (note that
 * the convenience stream objects will implicitly create an MD5 object).
 * <p>
 * The first option is to set the system property
 * "com.twmacinta.util.MD5.NO_NATIVE_LIB" to "true" or "1".
 * Unfortunately, SecurityManagers may also choose to disallow system
 * property setting, so this won't be of use in all cases.
 * <p>
 * The second option is to call
 * com.twmacinta.util.MD5.initNativeLibrary(true) before any MD5 objects
 * are constructed.
 *
 * @author Santeri Paavolainen <sjpaavol@cc.helsinki.fi>
 * @author Timothy W Macinta (twm@alum.mit.edu) (optimizations and bug fixes)
 */

public class MD5 {
    
    /**
     * MD5 state
     **/
    MD5State state;
    
    /**
     * If Final() has been called, finals is set to the current finals
     * state. Any Update() causes this to be set to null.
     **/
    MD5State finals;
    
    /** 
     * Padding for Final()
     **/
    static byte padding[] = {
        (byte) 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
    };
    
    private static boolean native_lib_loaded = false;
    private static boolean native_lib_init_pending = true;
    
    /**
     * Initialize MD5 internal state (object can be reused just by
     * calling Init() after every Final()
     **/
    public synchronized void Init () {
        state = new MD5State();
        finals = null;
    }
    
    /**
     * Class constructor
     **/
    public MD5 () {
        if (native_lib_init_pending) _initNativeLibrary();
        this.Init();
    }
    
    /**
     * Initialize class, and update hash with ob.toString()
     *
     * @param ob Object, ob.toString() is used to update hash
     *           after initialization
     **/
    public MD5 (Object ob) {
        this();
        Update(ob.toString());
    }
    
    private void Decode (byte buffer[], int shift, int[] out) {
        /*len += shift;
        for (int i = 0; shift < len; i++, shift += 4) {
            out[i] = ((int) (buffer[shift] & 0xff)) |
                (((int) (buffer[shift + 1] & 0xff)) << 8) |
                (((int) (buffer[shift + 2] & 0xff)) << 16) |
                (((int)  buffer[shift + 3]) << 24);
        }*/
        
        // unrolled loop (original loop shown above)
        
    out[0] = (buffer[shift] & 0xff) |
        ((buffer[shift + 1] & 0xff) << 8) |
        ((buffer[shift + 2] & 0xff) << 16) |
        ((buffer[shift + 3]) << 24);
    out[1] = (buffer[shift + 4] & 0xff) |
        ((buffer[shift + 5] & 0xff) << 8) |
        ((buffer[shift + 6] & 0xff) << 16) |
        ((buffer[shift + 7]) << 24);
    out[2] = (buffer[shift + 8] & 0xff) |
        ((buffer[shift + 9] & 0xff) << 8) |
        ((buffer[shift + 10] & 0xff) << 16) |
        ((buffer[shift + 11]) << 24);
    out[3] = (buffer[shift + 12] & 0xff) |
        ((buffer[shift + 13] & 0xff) << 8) |
        ((buffer[shift + 14] & 0xff) << 16) |
        ((buffer[shift + 15]) << 24);
    out[4] = (buffer[shift + 16] & 0xff) |
        ((buffer[shift + 17] & 0xff) << 8) |
        ((buffer[shift + 18] & 0xff) << 16) |
        ((buffer[shift + 19]) << 24);
    out[5] = (buffer[shift + 20] & 0xff) |
        ((buffer[shift + 21] & 0xff) << 8) |
        ((buffer[shift + 22] & 0xff) << 16) |
        ((buffer[shift + 23]) << 24);
    out[6] = (buffer[shift + 24] & 0xff) |
        ((buffer[shift + 25] & 0xff) << 8) |
        ((buffer[shift + 26] & 0xff) << 16) |
        ((buffer[shift + 27]) << 24);
    out[7] = (buffer[shift + 28] & 0xff) |
        ((buffer[shift + 29] & 0xff) << 8) |
        ((buffer[shift + 30] & 0xff) << 16) |
        ((buffer[shift + 31]) << 24);
    out[8] = (buffer[shift + 32] & 0xff) |
        ((buffer[shift + 33] & 0xff) << 8) |
        ((buffer[shift + 34] & 0xff) << 16) |
        ((buffer[shift + 35]) << 24);
    out[9] = (buffer[shift + 36] & 0xff) |
        ((buffer[shift + 37] & 0xff) << 8) |
        ((buffer[shift + 38] & 0xff) << 16) |
        ((buffer[shift + 39]) << 24);
    out[10] = (buffer[shift + 40] & 0xff) |
        ((buffer[shift + 41] & 0xff) << 8) |
        ((buffer[shift + 42] & 0xff) << 16) |
        ((buffer[shift + 43]) << 24);
    out[11] = (buffer[shift + 44] & 0xff) |
        ((buffer[shift + 45] & 0xff) << 8) |
        ((buffer[shift + 46] & 0xff) << 16) |
        ((buffer[shift + 47]) << 24);
    out[12] = (buffer[shift + 48] & 0xff) |
        ((buffer[shift + 49] & 0xff) << 8) |
        ((buffer[shift + 50] & 0xff) << 16) |
        ((buffer[shift + 51]) << 24);
    out[13] = (buffer[shift + 52] & 0xff) |
        ((buffer[shift + 53] & 0xff) << 8) |
        ((buffer[shift + 54] & 0xff) << 16) |
        ((buffer[shift + 55]) << 24);
    out[14] = (buffer[shift + 56] & 0xff) |
        ((buffer[shift + 57] & 0xff) << 8) |
        ((buffer[shift + 58] & 0xff) << 16) |
        ((buffer[shift + 59]) << 24);
    out[15] = (buffer[shift + 60] & 0xff) |
        ((buffer[shift + 61] & 0xff) << 8) |
        ((buffer[shift + 62] & 0xff) << 16) |
        ((buffer[shift + 63]) << 24);
    }
    
    private native void Transform_native (int[] state, byte buffer[], int shift, int length);
    
    private void Transform (MD5State state, byte buffer[], int shift, int[] decode_buf) {
        int
            a = state.state[0],
            b = state.state[1],
            c = state.state[2],
            d = state.state[3],
            x[] = decode_buf;
        
        Decode(buffer, shift, decode_buf);
        
        /* Round 1 */
        a += ((b & c) | (~b & d)) + x[ 0] + 0xd76aa478; /* 1 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[ 1] + 0xe8c7b756; /* 2 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[ 2] + 0x242070db; /* 3 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[ 3] + 0xc1bdceee; /* 4 */
        b = ((b << 22) | (b >>> 10)) + c;
        
        a += ((b & c) | (~b & d)) + x[ 4] + 0xf57c0faf; /* 5 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[ 5] + 0x4787c62a; /* 6 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[ 6] + 0xa8304613; /* 7 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[ 7] + 0xfd469501; /* 8 */
        b = ((b << 22) | (b >>> 10)) + c;
        
        a += ((b & c) | (~b & d)) + x[ 8] + 0x698098d8; /* 9 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[ 9] + 0x8b44f7af; /* 10 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[10] + 0xffff5bb1; /* 11 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[11] + 0x895cd7be; /* 12 */
        b = ((b << 22) | (b >>> 10)) + c;
        
        a += ((b & c) | (~b & d)) + x[12] + 0x6b901122; /* 13 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[13] + 0xfd987193; /* 14 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[14] + 0xa679438e; /* 15 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[15] + 0x49b40821; /* 16 */
        b = ((b << 22) | (b >>> 10)) + c;
        
        
        /* Round 2 */
        a += ((b & d) | (c & ~d)) + x[ 1] + 0xf61e2562; /* 17 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[ 6] + 0xc040b340; /* 18 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[11] + 0x265e5a51; /* 19 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[ 0] + 0xe9b6c7aa; /* 20 */
        b = ((b << 20) | (b >>> 12)) + c;
        
        a += ((b & d) | (c & ~d)) + x[ 5] + 0xd62f105d; /* 21 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[10] + 0x02441453; /* 22 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[15] + 0xd8a1e681; /* 23 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[ 4] + 0xe7d3fbc8; /* 24 */
        b = ((b << 20) | (b >>> 12)) + c;
        
        a += ((b & d) | (c & ~d)) + x[ 9] + 0x21e1cde6; /* 25 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[14] + 0xc33707d6; /* 26 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[ 3] + 0xf4d50d87; /* 27 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[ 8] + 0x455a14ed; /* 28 */
        b = ((b << 20) | (b >>> 12)) + c;
        
        a += ((b & d) | (c & ~d)) + x[13] + 0xa9e3e905; /* 29 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[ 2] + 0xfcefa3f8; /* 30 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[ 7] + 0x676f02d9; /* 31 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[12] + 0x8d2a4c8a; /* 32 */
        b = ((b << 20) | (b >>> 12)) + c;
        
        
        /* Round 3 */
        a += (b ^ c ^ d) + x[ 5] + 0xfffa3942;      /* 33 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[ 8] + 0x8771f681;      /* 34 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[11] + 0x6d9d6122;      /* 35 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[14] + 0xfde5380c;      /* 36 */
        b = ((b << 23) | (b >>> 9)) + c;
        
        a += (b ^ c ^ d) + x[ 1] + 0xa4beea44;      /* 37 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[ 4] + 0x4bdecfa9;      /* 38 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[ 7] + 0xf6bb4b60;      /* 39 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[10] + 0xbebfbc70;      /* 40 */
        b = ((b << 23) | (b >>> 9)) + c;
        
        a += (b ^ c ^ d) + x[13] + 0x289b7ec6;      /* 41 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[ 0] + 0xeaa127fa;      /* 42 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[ 3] + 0xd4ef3085;      /* 43 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[ 6] + 0x04881d05;      /* 44 */
        b = ((b << 23) | (b >>> 9)) + c;
        
        a += (b ^ c ^ d) + x[ 9] + 0xd9d4d039;      /* 33 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[12] + 0xe6db99e5;      /* 34 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[15] + 0x1fa27cf8;      /* 35 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[ 2] + 0xc4ac5665;      /* 36 */
        b = ((b << 23) | (b >>> 9)) + c;
        
        
        /* Round 4 */
        a += (c ^ (b | ~d)) + x[ 0] + 0xf4292244; /* 49 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[ 7] + 0x432aff97; /* 50 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[14] + 0xab9423a7; /* 51 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[ 5] + 0xfc93a039; /* 52 */
        b = ((b << 21) | (b >>> 11)) + c;
        
        a += (c ^ (b | ~d)) + x[12] + 0x655b59c3; /* 53 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[ 3] + 0x8f0ccc92; /* 54 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[10] + 0xffeff47d; /* 55 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[ 1] + 0x85845dd1; /* 56 */
        b = ((b << 21) | (b >>> 11)) + c;
        
        a += (c ^ (b | ~d)) + x[ 8] + 0x6fa87e4f; /* 57 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[15] + 0xfe2ce6e0; /* 58 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[ 6] + 0xa3014314; /* 59 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[13] + 0x4e0811a1; /* 60 */
        b = ((b << 21) | (b >>> 11)) + c;
        
        a += (c ^ (b | ~d)) + x[ 4] + 0xf7537e82; /* 61 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[11] + 0xbd3af235; /* 62 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[ 2] + 0x2ad7d2bb; /* 63 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[ 9] + 0xeb86d391; /* 64 */
        b = ((b << 21) | (b >>> 11)) + c;
        
        state.state[0] += a;
        state.state[1] += b;
        state.state[2] += c;
        state.state[3] += d;
    }
    
    /**
     * Updates hash with the bytebuffer given (using at maximum length bytes from
     * that buffer)
     *
     * @param stat   Which state is updated
     * @param buffer Array of bytes to be hashed
     * @param offset Offset to buffer array
     * @param length Use at maximum `length' bytes (absolute
     *               maximum is buffer.length)
     */
    public void Update (MD5State stat, byte buffer[], int offset, int length) {
        int index, partlen, i, start;
        finals = null;
        
        /* Length can be told to be shorter, but not inter */
        if ((length - offset)> buffer.length)
            length = buffer.length - offset;
        
        /* compute number of bytes mod 64 */
        
        index = (int) (stat.count & 0x3f);
        stat.count += length;
        
        partlen = 64 - index;
        
        if (length >= partlen) {
            
            // update state (using native method) to reflect input
            
            if (native_lib_loaded) {
                if (partlen == 64) {
                    partlen = 0;
                } else {
                    for (i = 0; i < partlen; i++)
                        stat.buffer[i + index] = buffer[i + offset];
                    Transform_native(stat.state, stat.buffer, 0, 64);
                }
                i = partlen + ((length - partlen) / 64) * 64;
                
                // break into chunks to guard against stack overflow in JNI
                
                int transformLength = length - partlen;
                int transformOffset = partlen + offset;
                final int MAX_LENGTH = 65536; // prevent stack overflow in JNI
                while (true) {
                    if (transformLength > MAX_LENGTH) {
                        Transform_native(stat.state, buffer, transformOffset, MAX_LENGTH);
                        transformLength -= MAX_LENGTH;
                        transformOffset += MAX_LENGTH;
                    } else {
                        Transform_native(stat.state, buffer, transformOffset, transformLength);
                        break;
                    }
                }
            }
            
            // update state (using only Java) to reflect input
            
            else {
                int[] decode_buf = new int[16];
                if (partlen == 64) {
                    partlen = 0;
                } else {
                    for (i = 0; i < partlen; i++)
                        stat.buffer[i + index] = buffer[i + offset];
                    Transform(stat, stat.buffer, 0, decode_buf);
                }
                for (i = partlen; (i + 63) < length; i+= 64) {
                    Transform(stat, buffer, i + offset, decode_buf);
                }
            }
            index = 0;
        } else {
            i = 0;
        }
        
        /* buffer remaining input */
        if (i < length) {
            start = i;
            for (; i < length; i++) {
                stat.buffer[index + i - start] = buffer[i + offset];
            }
        }
    }
    
    /* 
     * Update()s for other datatypes than byte[] also. Update(byte[], int)
     * is only the main driver.
     */
    
    /**
     * Plain update, updates this object
     **/
    public void Update (byte buffer[], int offset, int length) {
        Update(this.state, buffer, offset, length);
    }
    
    public void Update (byte buffer[], int length) {
        Update(this.state, buffer, 0, length);
    }
    
    /**
     * Updates hash with given array of bytes
     *
     * @param buffer Array of bytes to use for updating the hash
     **/
    public void Update (byte buffer[]) {
        Update(buffer, 0, buffer.length);
    }
    
    /**
     * Updates hash with a single byte
     *
     * @param b Single byte to update the hash
     **/
    public void Update (byte b) {
        byte buffer[] = new byte[1];
        buffer[0] = b;
        
        Update(buffer, 1);
    }
    
    /**
     * Update buffer with given string.  Note that because the version of
     * the s.getBytes() method without parameters is used to convert the
     * string to a byte array, the results of this method may be different
     * on different platforms.  The s.getBytes() method converts the string
     * into a byte array using the current platform's default character set
     * and may therefore have different results on platforms with different
     * default character sets.  If a version that works consistently
     * across platforms with different default character sets is desired,
     * use the overloaded version of the Update() method which takes a
     * string and a character encoding.
     *
     * @param s String to be update to hash (is used as s.getBytes())
     **/
    public void Update (String s) {
        byte chars[] = s.getBytes();
        Update(chars, chars.length);
    }
    
    /**
     * Update buffer with given string using the given encoding.  If the
     * given encoding is null, the encoding "ISO8859_1" is used.
     *
     * @param s            String to be update to hash (is used as
     *                     s.getBytes(charset_name))
     * @param charset_name The character set to use to convert s to a
     *                     byte array, or null if the "ISO8859_1"
     *                     character set is desired.
     * @exception          java.io.UnsupportedEncodingException If the named
     *                     charset is not supported.
     **/
    public void Update (String s, String charset_name) throws java.io.UnsupportedEncodingException {
        if (charset_name == null) charset_name = "ISO8859_1";
        byte chars[] = s.getBytes(charset_name);
        Update(chars, chars.length);
    }
    
    /**
     * Update buffer with a single integer (only & 0xff part is used,
     * as a byte)
     *
     * @param i Integer value, which is then converted to byte as i & 0xff
     **/
    public void Update (int i) {
        Update((byte) (i & 0xff));
    }
    
    private byte[] Encode (int input[], int len) {
        int i, j;
        byte out[];
        
        out = new byte[len];
        
        for (i = j = 0; j  < len; i++, j += 4) {
            out[j] = (byte) (input[i] & 0xff);
            out[j + 1] = (byte) ((input[i] >>> 8) & 0xff);
            out[j + 2] = (byte) ((input[i] >>> 16) & 0xff);
            out[j + 3] = (byte) ((input[i] >>> 24) & 0xff);
        }
        
        return out;
    }
    
    /**
     * Returns array of bytes (16 bytes) representing hash as of the
     * current state of this object. Note: getting a hash does not
     * invalidate the hash object, it only creates a copy of the real
     * state which is finalized. 
     *
     * @return Array of 16 bytes, the hash of all updated bytes
     **/
    public synchronized byte[] Final () {
        byte bits[];
        int index, padlen;
        MD5State fin;
        
        if (finals == null) {
            fin = new MD5State(state);
            
            int[] count_ints = {(int) (fin.count << 3), (int) (fin.count >> 29)};
            bits = Encode(count_ints, 8);
            
            index = (int) (fin.count & 0x3f);
            padlen = (index < 56) ? (56 - index) : (120 - index);
            
            Update(fin, padding, 0, padlen);
            Update(fin, bits, 0, 8);
            
            /* Update() sets finals to null */
            finals = fin;
        } 
        
        return Encode(finals.state, 16);
    }
    
    private static final char[] HEX_CHARS = {'0', '1', '2', '3',
                                             '4', '5', '6', '7',
                                             '8', '9', 'a', 'b',
                                             'c', 'd', 'e', 'f',};
    
    /**
     * Turns array of bytes into string representing each byte as
     * unsigned hex number.
     * 
     * @param hash Array of bytes to convert to hex-string
     * @return Generated hex string
     */
    public static String asHex (byte hash[]) {
        char buf[] = new char[hash.length * 2];
        for (int i = 0, x = 0; i < hash.length; i++) {
            buf[x++] = HEX_CHARS[(hash[i] >>> 4) & 0xf];
            buf[x++] = HEX_CHARS[hash[i] & 0xf];
        }
        return new String(buf);
    }
    
    /**
     * Returns 32-character hex representation of this objects hash
     *
     * @return String of this object's hash
     */
    public String asHex () {
        return asHex(this.Final());
    }
    
    /**
     * Convenience method for initNativeLibrary(false).
     **/
    public static synchronized final boolean initNativeLibrary () {
        return initNativeLibrary(false);
    }
    
    /**
     * Attempts to initialize native library support.  If
     * 'disallow_lib_loading' is true, will indicate that the native
     * library should not be loaded now or in the future.  If native
     * library support has been previously loaded or disabled, this
     * method has no effect.
     *
     * @return true iff native library support has been loaded
     **/
    public static synchronized final boolean initNativeLibrary (boolean disallow_lib_loading) {
        if (disallow_lib_loading) {
            native_lib_init_pending = false;
        } else {
            _initNativeLibrary();
        }
        return native_lib_loaded;
    }
    
    private static synchronized final void  _initNativeLibrary () {
        if (!native_lib_init_pending) return;
        native_lib_loaded = _loadNativeLibrary();
        native_lib_init_pending = false;
    }
    
    private static synchronized final boolean _loadNativeLibrary () {
        try {
            
            // don't try to load if the right property is set
            
            String prop = System.getProperty("com.twmacinta.util.MD5.NO_NATIVE_LIB");
            if (prop != null) {
                prop = prop.trim();
                if (prop.equalsIgnoreCase("true") || prop.equals("1")) return false;
            }
            
            // the library to load can be specified as a property
            
            File f;
            prop = System.getProperty("com.twmacinta.util.MD5.NATIVE_LIB_FILE");
            if (prop != null) {
                f = new File(prop);
                if (f.canRead()) {
                    System.load(f.getAbsolutePath());
                    return true;
                }
            }
            
            // determine the operating system and architecture
            
            String os_name = System.getProperty("os.name");
            String os_arch = System.getProperty("os.arch");
            if (os_name == null || os_arch == null) return false;
            os_name = os_name.toLowerCase();
            os_arch = os_arch.toLowerCase();
            
            // define settings which are OS arch architecture independent
            
            File arch_lib_path = null;
            String arch_libfile_suffix = null;
            
            // fill in settings for Linux on x86
            
            if (os_name.equals("linux") &&
                (os_arch.equals("x86") ||
                 os_arch.equals("i386") ||
                 os_arch.equals("i486") ||
                 os_arch.equals("i586") ||
                 os_arch.equals("i686"))) {
                arch_lib_path = new File(new File(new File("lib"), "arch"), "linux_x86");
                arch_libfile_suffix = ".so"; 
            }
            
            // fill in settings for Linux on amd64
            
            else if (os_name.equals("linux") &&
                     os_arch.equals("amd64")) {
                arch_lib_path = new File(new File(new File("lib"), "arch"), "linux_amd64");
                arch_libfile_suffix = ".so"; 
            }
            
            // fill in settings for Windows on x86
            
            else if (os_name.startsWith("windows ") &&
                     (os_arch.equals("x86") ||
                      os_arch.equals("i386") ||
                      os_arch.equals("i486") ||
                      os_arch.equals("i586") ||
                      os_arch.equals("i686"))) {
                arch_lib_path = new File(new File(new File("lib"), "arch"), "win32_x86");
                arch_libfile_suffix = ".dll"; 
            }
            
            // fill in settings for Windows on amd64
            
            else if (os_name.startsWith("windows ") &&
                     os_arch.equals("amd64")) {
                arch_lib_path = new File(new File(new File("lib"), "arch"), "win_amd64");
                arch_libfile_suffix = ".dll"; 
            }
            
            // fill in settings for Mac OS X on PPC
            
            else if (os_name.startsWith("mac os x") &&
                     (os_arch.equals("ppc"))) {
                arch_lib_path = new File(new File(new File("lib"), "arch"), "darwin_ppc");
                arch_libfile_suffix = ".jnilib";
            }
            
            // fill in settings for Mac OS X on x86
            
            else if (os_name.startsWith("mac os x") &&
                     (os_arch.equals("x86") ||
                      os_arch.equals("i386") ||
                      os_arch.equals("i486") ||
                      os_arch.equals("i586") ||
                      os_arch.equals("i686"))) {
                arch_lib_path = new File(new File(new File("lib"), "arch"), "darwin_x86");
                arch_libfile_suffix = ".jnilib";
            }
            
            // fill in settings for Mac OS X on x86_64
            
            else if (os_name.startsWith("mac os x") &&
                     os_arch.equals("x86_64")) {
                arch_lib_path = new File(new File(new File("lib"), "arch"), "darwin_x86_64");
                arch_libfile_suffix = ".jnilib";
            }
            
            // default to .so files with no architecture specific subdirectory
            
            else {
                arch_libfile_suffix = ".so"; 
            }
            
            // build the required filename
            
            String fname = "MD5" + arch_libfile_suffix;
            
            // try the architecture specific directory
            
            if (arch_lib_path != null) {
                f = new File(arch_lib_path, fname);
                if (f.canRead()) {
                    System.load(f.getAbsolutePath());
                    return true;
                }
            }
            
            // try the "lib" subdirectory
            
            f = new File(new File("lib"), fname);
            if (f.canRead()) {
                System.load(f.getAbsolutePath());
                return true;
            }
            
            // try the working directory
            
            f = new File(fname);
            if (f.canRead()) {
                System.load(f.getAbsolutePath());
                return true;
            }
        }
        
        // discard SecurityExceptions
        
        catch (SecurityException e) {}
        
        // Intercept UnsatisfiedLinkError since the code will still
        // work without the native method, but report it because it
        // indicates that the architecture detection and/or support
        // should be updated.
        
        catch (UnsatisfiedLinkError e) {
            e.printStackTrace();
        }
        
        // unable to load
        
        return false;
    }
    
    /**
     * Calculates and returns the hash of the contents of the given file.
     **/
    public static byte[] getHash (File f) throws IOException {
        if (!f.exists()) throw new FileNotFoundException(f.toString());
        InputStream close_me = null;
        try {
            long buf_size = f.length();
            if (buf_size < 512) buf_size = 512;
            if (buf_size > 65536) buf_size = 65536;
            byte[] buf = new byte[(int) buf_size];
            MD5InputStream in = new MD5InputStream(new FileInputStream(f));
            close_me = in;
            while (in.read(buf) != -1);
            in.close();
            return in.hash();
        } catch (IOException e) {
            if (close_me != null) try { close_me.close(); } catch (Exception e2) {}
            throw e;
        }
    }
    
    /**
     * @return true iff the first 16 bytes of both hash1 and hash2 are
     *         equal;  both hash1 and hash2 are null; or either hash
     *         array is less than 16 bytes in length and their lengths and
     *         all of their bytes are equal.
     **/
    public static boolean hashesEqual (byte[] hash1, byte[] hash2) {
        if (hash1 == null) return hash2 == null;
        if (hash2 == null) return false;
        int targ = 16;
        if (hash1.length < 16) {
            if (hash2.length != hash1.length) return false;
            targ = hash1.length;
        } else if (hash2.length < 16) {
            return false;
        }
        for (int i = 0; i < targ; i++) {
            if (hash1[i] != hash2[i]) return false;
        }
        return true;
    }
    
}