1 /*

     2  * Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package sun.security.util;

    27 

    28 import java.math.BigInteger;

    29 

    30 

    31 /**

    32  * A low-overhead arbitrary-precision <em>unsigned</em> integer.

    33  * This is intended for use with ASN.1 parsing, and printing of

    34  * such parsed values.  Convert to "BigInteger" if you need to do

    35  * arbitrary precision arithmetic, rather than just represent

    36  * the number as a wrapped array of bytes.

    37  *

    38  * <P><em><b>NOTE:</b>  This class may eventually disappear, to

    39  * be supplanted by big-endian byte arrays which hold both signed

    40  * and unsigned arbitrary-precision integers.</em>

    41  *

    42  * @author David Brownell

    43  */

    44 public final class BigInt {

    45 

    46     // Big endian -- MSB first.

    47     private byte[]      places;

    48 

    49     /**

    50      * Constructs a "Big" integer from a set of (big-endian) bytes.

    51      * Leading zeroes should be stripped off.

    52      *

    53      * @param data a sequence of bytes, most significant bytes/digits

    54      *          first.  CONSUMED.

    55      */

    56     public BigInt(byte[] data) { places = data.clone(); }

    57 

    58     /**

    59      * Constructs a "Big" integer from a "BigInteger", which must be

    60      * positive (or zero) in value.

    61      */

    62     public BigInt(BigInteger i) {

    63         byte[]  temp = i.toByteArray();

    64 

    65         if ((temp[0] & 0x80) != 0)

    66             throw new IllegalArgumentException("negative BigInteger");

    67 

    68         // XXX we assume exactly _one_ sign byte is used...

    69 

    70         if (temp[0] != 0)

    71             places = temp;

    72         else {

    73             places = new byte[temp.length - 1];

    74             for (int j = 1; j < temp.length; j++)

    75                 places[j - 1] = temp[j];

    76         }

    77     }

    78 

    79     /**

    80      * Constructs a "Big" integer from a normal Java integer.

    81      *

    82      * @param i the java primitive integer

    83      */

    84     public BigInt(int i) {

    85         if (i < (1 << 8)) {

    86             places = new byte[1];

    87             places[0] = (byte) i;

    88         } else if (i < (1 << 16)) {

    89             places = new byte[2];

    90             places[0] = (byte) (i >> 8);

    91             places[1] = (byte) i;

    92         } else if (i < (1 << 24)) {

    93             places = new byte[3];

    94             places[0] = (byte) (i >> 16);

    95             places[1] = (byte) (i >> 8);

    96             places[2] = (byte) i;

    97         } else {

    98             places = new byte[4];

    99             places[0] = (byte) (i >> 24);

   100             places[1] = (byte) (i >> 16);

   101             places[2] = (byte) (i >> 8);

   102             places[3] = (byte) i;

   103         }

   104     }

   105 

   106     /**

   107      * Converts the "big" integer to a java primitive integer.

   108      *

   109      * @excpet NumberFormatException if 32 bits is insufficient.

   110      */

   111     public int toInt() {

   112         if (places.length > 4)

   113             throw new NumberFormatException("BigInt.toLong, too big");

   114         int retval = 0, i = 0;

   115         for (; i < places.length; i++)

   116             retval = (retval << 8) + ((int)places[i] & 0xff);

   117         return retval;

   118     }

   119 

   120     /**

   121      * Returns a hexadecimal printed representation.  The value is

   122      * formatted to fit on lines of at least 75 characters, with

   123      * embedded newlines.  Words are separated for readability,

   124      * with eight words (32 bytes) per line.

   125      */

   126     public String toString() { return hexify(); }

   127 

   128     /**

   129      * Returns a BigInteger value which supports many arithmetic

   130      * operations. Assumes negative values will never occur.

   131      */

   132     public BigInteger toBigInteger()

   133         { return new BigInteger(1, places); }

   134 

   135     /**

   136      * Returns the data as a byte array.  The most significant bit

   137      * of the array is bit zero (as in <code>java.math.BigInteger</code>).

   138      */

   139     public byte[] toByteArray() { return places.clone(); }

   140 

   141     private static final String digits = "0123456789abcdef";

   142     private String hexify() {

   143         if (places.length == 0)

   144             return "  0  ";

   145 

   146         StringBuffer buf = new StringBuffer(places.length * 2);

   147         buf.append("    ");     // four spaces

   148         for (int i = 0; i < places.length; i++) {

   149             buf.append(digits.charAt((places[i] >> 4) & 0x0f));

   150             buf.append(digits.charAt(places[i] & 0x0f));

   151             if (((i + 1) % 32) == 0) {

   152                 if ((i +  1) != places.length)

   153                     buf.append("\n    ");       // line after four words

   154             } else if (((i + 1) % 4) == 0)

   155                 buf.append(' ');                // space between words

   156         }

   157         return buf.toString();

   158     }

   159 

   160     /**

   161      * Returns true iff the parameter is a numerically equivalent

   162      * BigInt.

   163      *

   164      * @param other the object being compared with this one.

   165      */

   166     public boolean equals(Object other) {

   167         if (other instanceof BigInt)

   168             return equals((BigInt) other);

   169         return false;

   170     }

   171 

   172     /**

   173      * Returns true iff the parameter is numerically equivalent.

   174      *

   175      * @param other the BigInt being compared with this one.

   176      */

   177     public boolean equals(BigInt other) {

   178         if (this == other)

   179             return true;

   180 

   181         byte[] otherPlaces = other.toByteArray();

   182         if (places.length != otherPlaces.length)

   183             return false;

   184         for (int i = 0; i < places.length; i++)

   185             if (places[i] != otherPlaces[i])

   186                 return false;

   187         return true;

   188     }

   189 

   190     /**

   191      * Returns a hashcode for this BigInt.

   192      *

   193      * @return a hashcode for this BigInt.

   194      */

   195     public int hashCode() {

   196         return hexify().hashCode();

   197     }

   198 }