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Diffstat (limited to 'base/util/src/netscape/security/util/BitArray.java')
| -rw-r--r-- | base/util/src/netscape/security/util/BitArray.java | 257 |
1 files changed, 257 insertions, 0 deletions
diff --git a/base/util/src/netscape/security/util/BitArray.java b/base/util/src/netscape/security/util/BitArray.java new file mode 100644 index 000000000..ab77c226e --- /dev/null +++ b/base/util/src/netscape/security/util/BitArray.java @@ -0,0 +1,257 @@ +// --- BEGIN COPYRIGHT BLOCK --- +// This program 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; version 2 of the License. +// +// This program 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 this program; if not, write to the Free Software Foundation, Inc., +// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. +// +// (C) 2007 Red Hat, Inc. +// All rights reserved. +// --- END COPYRIGHT BLOCK --- +package netscape.security.util; + +import java.io.ByteArrayOutputStream; + +/** + * A packed array of booleans. + * + * @author Joshua Bloch + * @author Douglas Hoover + * @version 1.2 97/12/10 + */ + +public class BitArray { + + private byte[] repn; + private int length; + + private static final int BITS_PER_UNIT = 8; + + private static int subscript(int idx) { + return idx / BITS_PER_UNIT; + } + + private static int position(int idx) { // bits big-endian in each unit + return 1 << (BITS_PER_UNIT - 1 - (idx % BITS_PER_UNIT)); + } + + /** + * Creates a BitArray of the specified size, initialized to zeros. + */ + public BitArray(int length) throws IllegalArgumentException { + if (length < 0) { + throw new IllegalArgumentException("Negative length for BitArray"); + } + + this.length = length; + + repn = new byte[(length + BITS_PER_UNIT - 1) / BITS_PER_UNIT]; + } + + /** + * Creates a BitArray of the specified size, initialized from the + * specified byte array. The most significant bit of a[0] gets + * index zero in the BitArray. The array a must be large enough + * to specify a value for every bit in the BitArray. In other words, + * 8*a.length >= length. + */ + public BitArray(int length, byte[] a) throws IllegalArgumentException { + + if (length < 0) { + throw new IllegalArgumentException("Negative length for BitArray"); + } + if (a.length * BITS_PER_UNIT < length) { + throw new IllegalArgumentException("Byte array too short to represent " + + "bit array of given length"); + } + + this.length = length; + + int repLength = ((length + BITS_PER_UNIT - 1) / BITS_PER_UNIT); + int unusedBits = repLength * BITS_PER_UNIT - length; + byte bitMask = (byte) (0xFF << unusedBits); + + /* + normalize the representation: + 1. discard extra bytes + 2. zero out extra bits in the last byte + */ + repn = new byte[repLength]; + System.arraycopy(a, 0, repn, 0, repLength); + if (repn.length > 0) + repn[repn.length - 1] = (byte) (repn[repn.length - 1] & bitMask); + } + + /** + * Create a BitArray whose bits are those of the given array + * of Booleans. + */ + public BitArray(boolean[] bits) { + length = bits.length; + repn = new byte[(length + 7) / 8]; + + for (int i = 0; i < length; i++) { + set(i, bits[i]); + } + } + + /** + * Copy constructor (for cloning). + */ + private BitArray(BitArray ba) { + length = ba.length; + repn = (byte[]) ba.repn.clone(); + } + + /** + * Returns the indexed bit in this BitArray. + */ + public boolean get(int index) throws ArrayIndexOutOfBoundsException { + if (index < 0 || index >= length) { + throw new ArrayIndexOutOfBoundsException(Integer.toString(index)); + } + + return (repn[subscript(index)] & position(index)) != 0; + } + + /** + * Sets the indexed bit in this BitArray. + */ + public void set(int index, boolean value) + throws ArrayIndexOutOfBoundsException { + if (index < 0 || index >= length) { + throw new ArrayIndexOutOfBoundsException(Integer.toString(index)); + } + int idx = subscript(index); + int bit = position(index); + + if (value) { + repn[idx] |= bit; + } else { + repn[idx] &= ~bit; + } + } + + /** + * Returns the length of this BitArray. + */ + public int length() { + return length; + } + + /** + * Returns a Byte array containing the contents of this BitArray. + * The bit stored at index zero in this BitArray will be copied + * into the most significant bit of the zeroth element of the + * returned byte array. The last byte of the returned byte array + * will be contain zeros in any bits that do not have corresponding + * bits in the BitArray. (This matters only if the BitArray's size + * is not a multiple of 8.) + */ + public byte[] toByteArray() { + return (byte[]) repn.clone(); + } + + public boolean equals(Object obj) { + if (obj == this) + return true; + if (obj == null || !(obj instanceof BitArray)) + return false; + + BitArray ba = (BitArray) obj; + + if (ba.length != length) + return false; + + for (int i = 0; i < repn.length; i += 1) { + if (repn[i] != ba.repn[i]) + return false; + } + return true; + } + + /** + * Return a boolean array with the same bit values a this BitArray. + */ + public boolean[] toBooleanArray() { + boolean[] bits = new boolean[length]; + + for (int i = 0; i < length; i++) { + bits[i] = get(i); + } + return bits; + } + + /** + * Returns a hash code value for this bit array. + * + * @return a hash code value for this bit array. + */ + public int hashCode() { + int hashCode = 0; + + for (int i = 0; i < repn.length; i++) + hashCode = 31 * hashCode + repn[i]; + + return hashCode ^ length; + } + + public Object clone() { + return new BitArray(this); + } + + private static final byte[][] NYBBLE = { + { (byte) '0', (byte) '0', (byte) '0', (byte) '0' }, + { (byte) '0', (byte) '0', (byte) '0', (byte) '1' }, + { (byte) '0', (byte) '0', (byte) '1', (byte) '0' }, + { (byte) '0', (byte) '0', (byte) '1', (byte) '1' }, + { (byte) '0', (byte) '1', (byte) '0', (byte) '0' }, + { (byte) '0', (byte) '1', (byte) '0', (byte) '1' }, + { (byte) '0', (byte) '1', (byte) '1', (byte) '0' }, + { (byte) '0', (byte) '1', (byte) '1', (byte) '1' }, + { (byte) '1', (byte) '0', (byte) '0', (byte) '0' }, + { (byte) '1', (byte) '0', (byte) '0', (byte) '1' }, + { (byte) '1', (byte) '0', (byte) '1', (byte) '0' }, + { (byte) '1', (byte) '0', (byte) '1', (byte) '1' }, + { (byte) '1', (byte) '1', (byte) '0', (byte) '0' }, + { (byte) '1', (byte) '1', (byte) '0', (byte) '1' }, + { (byte) '1', (byte) '1', (byte) '1', (byte) '0' }, + { (byte) '1', (byte) '1', (byte) '1', (byte) '1' } + }; + + private static final int BYTES_PER_LINE = 8; + + /** + * Returns a string representation of this BitArray. + */ + public String toString() { + ByteArrayOutputStream out = new ByteArrayOutputStream(); + + for (int i = 0; i < repn.length - 1; i++) { + out.write(NYBBLE[(repn[i] >> 4) & 0x0F], 0, 4); + out.write(NYBBLE[repn[i] & 0x0F], 0, 4); + + if (i % BYTES_PER_LINE == BYTES_PER_LINE - 1) { + out.write('\n'); + } else { + out.write(' '); + } + } + + // in last byte of repn, use only the valid bits + for (int i = BITS_PER_UNIT * (repn.length - 1); i < length; i++) { + out.write(get(i) ? '1' : '0'); + } + + return new String(out.toByteArray()); + + } + +} |