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1: /* BitString.java -- Java representation of the BIT STRING type. 2: Copyright (C) 2003 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.java.security.der; 40: 41: import java.math.BigInteger; 42: import java.util.Arrays; 43: 44: /** 45: * Immutable representation of a bit string, which is equivalent to a 46: * byte array except some number of the rightmost bits are ignored. For 47: * example, this could be the bit string: 48: * 49: * <pre> 00010101 11101101 11010xxx</pre> 50: * 51: * <p>Where the "xxx" represents three bits that should be ignored, and 52: * can have any value. 53: * 54: * @author Casey Marshall (csm@gnu.org) 55: */ 56: public class BitString implements Cloneable, Comparable 57: { 58: 59: // Fields. 60: // ------------------------------------------------------------------------ 61: 62: /** The bits themselves. */ 63: private final byte[] bytes; 64: 65: /** 66: * The exportable byte array. This array has the ignored bits 67: * removed. 68: */ 69: private transient byte[] externBytes; 70: 71: /** The number of bits ignored at the end of the byte array. */ 72: private final int ignoredBits; 73: 74: /** This bit string as a boolean array. */ 75: private transient boolean[] boolVal; 76: 77: // Constructors. 78: // ------------------------------------------------------------------------ 79: 80: /** 81: * Create a new bit string, shifting the given byte array if needed. 82: * 83: * @param bytes The byte array holding the bit string. 84: * @param ignoredBits The number of bits to ignore. 85: * @param doShift Pass true in this parameter if the byte array has 86: * not yet been shifted left by <i>ignoredBits</i>. 87: * @throws IllegalArgumentException If <i>ignoredBits</i> is negative 88: * or greater than 7. 89: * @throws NullPointerException If <i>bytes</i> is null. 90: */ 91: public BitString(byte[] bytes, int ignoredBits, boolean doShift) 92: { 93: this(bytes, 0, bytes.length, ignoredBits, doShift); 94: } 95: 96: /** 97: * Create a new bit string, shifting the given byte array if needed. 98: * 99: * @param bytes The byte array holding the bit string. 100: * @param offset The offset where the meaningful bytes begin. 101: * @param length The number of meaningful bytes. 102: * @param ignoredBits The number of bits to ignore. 103: * @param doShift Pass true in this parameter if the byte array has 104: * not yet been shifted left by <i>ignoredBits</i>. 105: * @throws IllegalArgumentException If <i>ignoredBits</i> is negative 106: * or greater than 7. 107: * @throws NullPointerException If <i>bytes</i> is null. 108: */ 109: public BitString(byte[] bytes, int offset, int length, 110: int ignoredBits, boolean doShift) 111: { 112: if (ignoredBits < 0 || ignoredBits > 7) 113: throw new IllegalArgumentException(); 114: if (bytes == null) 115: throw new NullPointerException(); 116: if (doShift && ignoredBits > 0) 117: { 118: this.externBytes = new byte[length]; 119: System.arraycopy(bytes, offset, externBytes, 0, length); 120: this.bytes = new BigInteger(externBytes).shiftLeft(ignoredBits) 121: .toByteArray(); 122: } 123: else 124: { 125: this.bytes = new byte[length]; 126: System.arraycopy(bytes, offset, this.bytes, 0, length); 127: } 128: this.ignoredBits = ignoredBits; 129: } 130: 131: /** 132: * Create a new bit string. 133: * 134: * @param bytes The byte array holding the bit string. 135: * @param offset The offset where the meaningful bytes begin. 136: * @param length The number of meaningful bytes. 137: * @param ignoredBits The number of bits to ignore. 138: * @throws IllegalArgumentException If <i>ignoredBits</i> is negative 139: * or greater than 7. 140: * @throws NullPointerException If <i>bytes</i> is null. 141: */ 142: public BitString(byte[] bytes, int offset, int length, int ignoredBits) 143: { 144: this(bytes, offset, length, ignoredBits, false); 145: } 146: 147: /** 148: * Create a new bit string. 149: * 150: * @param bytes The byte array holding the bit string. 151: * @param ignoredBits The number of bits to ignore. 152: * @throws IllegalArgumentException If <i>ignoredBits</i> is negative 153: * or greater than 7. 154: * @throws NullPointerException If <i>bytes</i> is null. 155: */ 156: public BitString(byte[] bytes, int ignoredBits) 157: { 158: this(bytes, 0, bytes.length, ignoredBits, false); 159: } 160: 161: /** 162: * Create a new bit string. 163: * 164: * @param bytes The byte array holding the bit string. 165: * @param offset The offset where the meaningful bytes begin. 166: * @param length The number of meaningful bytes. 167: * @throws NullPointerException If <i>bytes</i> is null. 168: */ 169: public BitString(byte[] bytes, int offset, int length) 170: { 171: this(bytes, offset, length, 0, false); 172: } 173: 174: /** 175: * Create a new bit string. 176: * 177: * @param bytes The byte array holding the bit string. 178: * @throws NullPointerException If <i>bytes</i> is null. 179: */ 180: public BitString(byte[] bytes) 181: { 182: this(bytes, 0, bytes.length, 0, false); 183: } 184: 185: // Instance methods. 186: // ------------------------------------------------------------------------ 187: 188: /** 189: * Return this bit string as a byte array, with the ignored bits 190: * trimmed off. The byte array is cloned every time this method is 191: * called to prevent modification. 192: * 193: * @return The trimmed byte array. 194: */ 195: public byte[] toByteArray() 196: { 197: if (ignoredBits == 0) 198: return (byte[]) bytes.clone(); 199: if (externBytes == null) 200: externBytes = new BigInteger(bytes).shiftRight(ignoredBits).toByteArray(); 201: return (byte[]) externBytes.clone(); 202: } 203: 204: /** 205: * Returns this bit string as a byte array, with the ignored bits 206: * present. The byte array is cloned every time this method is 207: * called to prevent modification. 208: * 209: * @return The byte array. 210: */ 211: public byte[] getShiftedByteArray() 212: { 213: return (byte[]) bytes.clone(); 214: } 215: 216: /** 217: * Returns the number of ignored bits. 218: * 219: * @return The number of ignored bits. 220: */ 221: public int getIgnoredBits() 222: { 223: return ignoredBits; 224: } 225: 226: /** 227: * Returns the size, in bits, of this bit string. 228: * 229: * @return The size of this bit string. 230: */ 231: public int size() 232: { 233: return (bytes.length << 3) - ignoredBits; 234: } 235: 236: /** 237: * Return this bit string as a boolean array. The value returned is of 238: * size {@link #size()}, and each <code>true</code> value 239: * corresponding to each "1" in this bit string. The boolean array is 240: * cloned before it is returned. 241: * 242: * @return The boolean array. 243: */ 244: public boolean[] toBooleanArray() 245: { 246: if (boolVal == null) 247: { 248: boolVal = new boolean[size()]; 249: for (int i = 0, j = 7, k = 0; i < boolVal.length; i++) 250: { 251: boolVal[i] = (bytes[k] & 1 << j--) != 0; 252: if (j < 0) 253: { 254: j = 7; 255: k++; 256: } 257: } 258: } 259: return (boolean[]) boolVal.clone(); 260: } 261: 262: public Object clone() 263: { 264: try 265: { 266: return super.clone(); 267: } 268: catch (CloneNotSupportedException cce) 269: { 270: throw new InternalError(cce.getMessage()); 271: } 272: } 273: 274: public int compareTo(Object o) 275: { 276: BitString that = (BitString) o; 277: if (this.equals(that)) 278: return 0; 279: if (this.bytes.length != that.bytes.length) 280: return (this.bytes.length < that.bytes.length) ? -1 : 1; 281: if (this.ignoredBits != that.ignoredBits) 282: return (this.ignoredBits < that.ignoredBits) ? -1 : 1; 283: for (int i = 0; i < this.bytes.length; i++) 284: if (this.bytes[i] != that.bytes[i]) 285: return (this.bytes[i] < that.bytes[i]) ? -1 : 1; 286: return 0; // not reached. 287: } 288: 289: public int hashCode() 290: { 291: int result = 0; 292: for (int i = 0; i < bytes.length - 1; ++i) 293: result = result * 31 + bytes[i]; 294: if (bytes.length > 0) 295: { 296: int lastByte = bytes[bytes.length - 1] & ~ ((1 << ignoredBits) - 1); 297: result = result * 31 + lastByte; 298: } 299: return result; 300: } 301: 302: public boolean equals(Object o) 303: { 304: if (!(o instanceof BitString)) 305: return false; 306: BitString that = (BitString) o; 307: // True for cloned instances. 308: if (this.bytes == that.bytes && this.ignoredBits == that.ignoredBits) 309: return true; 310: if (this.ignoredBits == that.ignoredBits) 311: return Arrays.equals(this.bytes, that.bytes); 312: return false; 313: } 314: 315: public String toString() 316: { 317: StringBuffer sb = new StringBuffer(); 318: for (int i = 0, j = 7, k = 0; i < size(); i++) 319: { 320: sb.append((bytes[k] & 1 << j) != 0 ? "1" : "0"); 321: j--; 322: if (j < 0) 323: { 324: j = 7; 325: k++; 326: } 327: } 328: return sb.toString(); 329: } 330: }