| /* BitString.java -- Java representation of the BIT STRING type. |
| Copyright (C) 2003 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package gnu.java.security.der; |
| |
| import java.math.BigInteger; |
| import java.util.Arrays; |
| |
| /** |
| * Immutable representation of a bit string, which is equivalent to a |
| * byte array except some number of the rightmost bits are ignored. For |
| * example, this could be the bit string: |
| * |
| * <pre> 00010101 11101101 11010xxx</pre> |
| * |
| * <p>Where the "xxx" represents three bits that should be ignored, and |
| * can have any value. |
| * |
| * @author Casey Marshall (csm@gnu.org) |
| */ |
| public class BitString implements Cloneable, Comparable |
| { |
| |
| // Fields. |
| // ------------------------------------------------------------------------ |
| |
| /** The bits themselves. */ |
| private final byte[] bytes; |
| |
| /** |
| * The exportable byte array. This array has the ignored bits |
| * removed. |
| */ |
| private transient byte[] externBytes; |
| |
| /** The number of bits ignored at the end of the byte array. */ |
| private final int ignoredBits; |
| |
| /** This bit string as a boolean array. */ |
| private transient boolean[] boolVal; |
| |
| // Constructors. |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Create a new bit string, shifting the given byte array if needed. |
| * |
| * @param bytes The byte array holding the bit string. |
| * @param ignoredBits The number of bits to ignore. |
| * @param doShift Pass true in this parameter if the byte array has |
| * not yet been shifted left by <i>ignoredBits</i>. |
| * @throws IllegalArgumentException If <i>ignoredBits</i> is negative |
| * or greater than 7. |
| * @throws NullPointerException If <i>bytes</i> is null. |
| */ |
| public BitString(byte[] bytes, int ignoredBits, boolean doShift) |
| { |
| this(bytes, 0, bytes.length, ignoredBits, doShift); |
| } |
| |
| /** |
| * Create a new bit string, shifting the given byte array if needed. |
| * |
| * @param bytes The byte array holding the bit string. |
| * @param offset The offset where the meaningful bytes begin. |
| * @param length The number of meaningful bytes. |
| * @param ignoredBits The number of bits to ignore. |
| * @param doShift Pass true in this parameter if the byte array has |
| * not yet been shifted left by <i>ignoredBits</i>. |
| * @throws IllegalArgumentException If <i>ignoredBits</i> is negative |
| * or greater than 7. |
| * @throws NullPointerException If <i>bytes</i> is null. |
| */ |
| public BitString(byte[] bytes, int offset, int length, |
| int ignoredBits, boolean doShift) |
| { |
| if (ignoredBits < 0 || ignoredBits > 7) |
| throw new IllegalArgumentException(); |
| if (bytes == null) |
| throw new NullPointerException(); |
| if (doShift && ignoredBits > 0) |
| { |
| this.externBytes = new byte[length]; |
| System.arraycopy(bytes, offset, externBytes, 0, length); |
| this.bytes = new BigInteger(externBytes).shiftLeft(ignoredBits) |
| .toByteArray(); |
| } |
| else |
| { |
| this.bytes = new byte[length]; |
| System.arraycopy(bytes, offset, this.bytes, 0, length); |
| } |
| this.ignoredBits = ignoredBits; |
| } |
| |
| /** |
| * Create a new bit string. |
| * |
| * @param bytes The byte array holding the bit string. |
| * @param offset The offset where the meaningful bytes begin. |
| * @param length The number of meaningful bytes. |
| * @param ignoredBits The number of bits to ignore. |
| * @throws IllegalArgumentException If <i>ignoredBits</i> is negative |
| * or greater than 7. |
| * @throws NullPointerException If <i>bytes</i> is null. |
| */ |
| public BitString(byte[] bytes, int offset, int length, int ignoredBits) |
| { |
| this(bytes, offset, length, ignoredBits, false); |
| } |
| |
| /** |
| * Create a new bit string. |
| * |
| * @param bytes The byte array holding the bit string. |
| * @param ignoredBits The number of bits to ignore. |
| * @throws IllegalArgumentException If <i>ignoredBits</i> is negative |
| * or greater than 7. |
| * @throws NullPointerException If <i>bytes</i> is null. |
| */ |
| public BitString(byte[] bytes, int ignoredBits) |
| { |
| this(bytes, 0, bytes.length, ignoredBits, false); |
| } |
| |
| /** |
| * Create a new bit string. |
| * |
| * @param bytes The byte array holding the bit string. |
| * @param offset The offset where the meaningful bytes begin. |
| * @param length The number of meaningful bytes. |
| * @throws NullPointerException If <i>bytes</i> is null. |
| */ |
| public BitString(byte[] bytes, int offset, int length) |
| { |
| this(bytes, offset, length, 0, false); |
| } |
| |
| /** |
| * Create a new bit string. |
| * |
| * @param bytes The byte array holding the bit string. |
| * @throws NullPointerException If <i>bytes</i> is null. |
| */ |
| public BitString(byte[] bytes) |
| { |
| this(bytes, 0, bytes.length, 0, false); |
| } |
| |
| // Instance methods. |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Return this bit string as a byte array, with the ignored bits |
| * trimmed off. The byte array is cloned every time this method is |
| * called to prevent modification. |
| * |
| * @return The trimmed byte array. |
| */ |
| public byte[] toByteArray() |
| { |
| if (ignoredBits == 0) |
| return (byte[]) bytes.clone(); |
| if (externBytes == null) |
| externBytes = new BigInteger(bytes).shiftRight(ignoredBits).toByteArray(); |
| return (byte[]) externBytes.clone(); |
| } |
| |
| /** |
| * Returns this bit string as a byte array, with the ignored bits |
| * present. The byte array is cloned every time this method is |
| * called to prevent modification. |
| * |
| * @return The byte array. |
| */ |
| public byte[] getShiftedByteArray() |
| { |
| return (byte[]) bytes.clone(); |
| } |
| |
| /** |
| * Returns the number of ignored bits. |
| * |
| * @return The number of ignored bits. |
| */ |
| public int getIgnoredBits() |
| { |
| return ignoredBits; |
| } |
| |
| /** |
| * Returns the size, in bits, of this bit string. |
| * |
| * @return The size of this bit string. |
| */ |
| public int size() |
| { |
| return (bytes.length << 3) - ignoredBits; |
| } |
| |
| /** |
| * Return this bit string as a boolean array. The value returned is of |
| * size {@link #size()}, and each <code>true</code> value |
| * corresponding to each "1" in this bit string. The boolean array is |
| * cloned before it is returned. |
| * |
| * @return The boolean array. |
| */ |
| public boolean[] toBooleanArray() |
| { |
| if (boolVal == null) |
| { |
| boolVal = new boolean[size()]; |
| for (int i = 0, j = 7, k = 0; i < boolVal.length; i++) |
| { |
| boolVal[i] = (bytes[k] & 1 << j--) != 0; |
| if (j < 0) |
| { |
| j = 7; |
| k++; |
| } |
| } |
| } |
| return (boolean[]) boolVal.clone(); |
| } |
| |
| public Object clone() |
| { |
| try |
| { |
| return super.clone(); |
| } |
| catch (CloneNotSupportedException cce) |
| { |
| throw new InternalError(cce.getMessage()); |
| } |
| } |
| |
| public int compareTo(Object o) |
| { |
| BitString that = (BitString) o; |
| if (this.equals(that)) |
| return 0; |
| if (this.bytes.length != that.bytes.length) |
| return (this.bytes.length < that.bytes.length) ? -1 : 1; |
| if (this.ignoredBits != that.ignoredBits) |
| return (this.ignoredBits < that.ignoredBits) ? -1 : 1; |
| for (int i = 0; i < this.bytes.length; i++) |
| if (this.bytes[i] != that.bytes[i]) |
| return (this.bytes[i] < that.bytes[i]) ? -1 : 1; |
| return 0; // not reached. |
| } |
| |
| public boolean equals(Object o) |
| { |
| if (!(o instanceof BitString)) |
| return false; |
| BitString that = (BitString) o; |
| // True for cloned instances. |
| if (this.bytes == that.bytes && this.ignoredBits == that.ignoredBits) |
| return true; |
| if (this.ignoredBits == that.ignoredBits) |
| return Arrays.equals(this.bytes, that.bytes); |
| return false; |
| } |
| |
| public String toString() |
| { |
| StringBuffer sb = new StringBuffer(); |
| for (int i = 0, j = 7, k = 0; i < size(); i++) |
| { |
| sb.append((bytes[k] & 1 << j) != 0 ? "1" : "0"); |
| j--; |
| if (j < 0) |
| { |
| j = 7; |
| k++; |
| } |
| } |
| return sb.toString(); |
| } |
| } |