/*******************************************************************************
* Copyright (c) 2002 - 2006 IBM Corporation.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package com.ibm.wala.util.intset;
public final class FixedSizeBitVector implements Cloneable, java.io.Serializable {
public static final long serialVersionUID = 33181877746462822L;
private final static int LOG_BITS_PER_UNIT = 5;
private final static int MASK = 0xffffffff;
private final static int LOW_MASK = 0x1f;
private int bits[];
final private int nbits;
/**
* Convert bitIndex to a subscript into the bits[] array.
*/
private static int subscript(int bitIndex) {
return bitIndex >> LOG_BITS_PER_UNIT;
}
/**
* Creates an empty string with the specified size.
*
* @param nbits the size of the string
*/
public FixedSizeBitVector(int nbits) {
// subscript(nbits) is the length of the array needed to
// hold nbits
if (nbits < 0) {
throw new IllegalArgumentException("illegal nbits: " + nbits);
}
bits = new int[subscript(nbits) + 1];
this.nbits = nbits;
}
/**
* Creates a copy of a Bit String
*
* @param s the string to copy
* @throws IllegalArgumentException if s is null
*/
public FixedSizeBitVector(FixedSizeBitVector s) {
if (s == null) {
throw new IllegalArgumentException("s is null");
}
bits = new int[s.bits.length];
this.nbits = s.nbits;
copyBits(s);
}
/**
* Sets all bits.
*/
public void setAll() {
for (int i = 0; i < bits.length; i++) {
bits[i] = MASK;
}
}
/**
* Sets a bit.
*
* @param bit the bit to be set
*/
public void set(int bit) {
try {
int shiftBits = bit & LOW_MASK;
bits[subscript(bit)] |= (1 << shiftBits);
} catch (ArrayIndexOutOfBoundsException e) {
throw new IllegalArgumentException("invalid bit " + bit);
}
}
/**
* Clears all bits.
*/
public void clearAll() {
for (int i = 0; i < bits.length; i++) {
bits[i] = 0;
}
}
/**
* Clears a bit.
*
* @param bit the bit to be cleared
*/
public void clear(int bit) {
try {
int shiftBits = bit & LOW_MASK;
bits[subscript(bit)] &= ~(1 << shiftBits);
} catch (ArrayIndexOutOfBoundsException e) {
throw new IllegalArgumentException("invalid bit: " + bit);
}
}
/**
* Gets a bit.
*
* @param bit the bit to be gotten
*/
public boolean get(int bit) {
if (bit < 0) {
throw new IllegalArgumentException("illegal bit: " + bit);
}
int shiftBits = bit & LOW_MASK;
int n = subscript(bit);
try {
return ((bits[n] & (1 << shiftBits)) != 0);
} catch (ArrayIndexOutOfBoundsException e) {
return false;
}
}
/**
* Logically NOT this bit string
*/
public void not() {
for (int i = 0; i < bits.length; i++) {
bits[i] ^= MASK;
}
}
/**
* Return the NOT of a bit string
*/
public static FixedSizeBitVector not(FixedSizeBitVector s) {
FixedSizeBitVector b = new FixedSizeBitVector(s);
b.not();
return b;
}
/**
* Logically ANDs this bit set with the specified set of bits.
*
* @param set the bit set to be ANDed with
*/
public void and(FixedSizeBitVector set) {
if (set == null) {
throw new IllegalArgumentException("null set");
}
if (this == set) {
return;
}
int n = bits.length;
for (int i = n; i-- > 0;) {
bits[i] &= set.bits[i];
}
}
/**
* Return a new bit string as the AND of two others.
*/
public static FixedSizeBitVector and(FixedSizeBitVector b1, FixedSizeBitVector b2) {
FixedSizeBitVector b = new FixedSizeBitVector(b1);
b.and(b2);
return b;
}
/**
* Logically ORs this bit set with the specified set of bits.
*
* @param set the bit set to be ORed with
* @throws IllegalArgumentException if set == null
*/
public void or(FixedSizeBitVector set) throws IllegalArgumentException {
if (set == null) {
throw new IllegalArgumentException("set == null");
}
if (this == set) { // should help alias analysis
return;
}
int setLength = set.bits.length;
for (int i = setLength; i-- > 0;) {
bits[i] |= set.bits[i];
}
}
/**
* Return a new FixedSizeBitVector as the OR of two others
*
* @throws IllegalArgumentException if b2 == null
*/
public static FixedSizeBitVector or(FixedSizeBitVector b1, FixedSizeBitVector b2) throws IllegalArgumentException {
if (b2 == null) {
throw new IllegalArgumentException("b2 == null");
}
FixedSizeBitVector b = new FixedSizeBitVector(b1);
b.or(b2);
return b;
}
/**
* Logically XORs this bit set with the specified set of bits.
*
* @param set the bit set to be XORed with
* @throws IllegalArgumentException if set is null
*/
public void xor(FixedSizeBitVector set) {
if (set == null) {
throw new IllegalArgumentException("set is null");
}
int setLength = set.bits.length;
for (int i = setLength; i-- > 0;) {
bits[i] ^= set.bits[i];
}
}
/**
* Check if the intersection of the two sets is empty
*
* @param other the set to check intersection with
*/
public boolean intersectionEmpty(FixedSizeBitVector other) {
if (other == null) {
throw new IllegalArgumentException("other is null");
}
int n = bits.length;
for (int i = n; i-- > 0;) {
if ((bits[i] & other.bits[i]) != 0)
return false;
}
return true;
}
/**
* Copies the values of the bits in the specified set into this set.
*
* @param set the bit set to copy the bits from
* @throws IllegalArgumentException if set is null
*/
public void copyBits(FixedSizeBitVector set) {
if (set == null) {
throw new IllegalArgumentException("set is null");
}
int setLength = set.bits.length;
for (int i = setLength; i-- > 0;) {
bits[i] = set.bits[i];
}
}
/**
* Gets the hashcode.
*/
@Override
public int hashCode() {
int h = 1234;
for (int i = bits.length; --i >= 0;) {
h ^= bits[i] * (i + 1);
}
return h;
}
/**
* How many bits are set?
*/
public int populationCount() {
int count = 0;
for (int i = 0; i < bits.length; i++) {
count += Bits.populationCount(bits[i]);
}
return count;
}
/**
* Calculates and returns the set's size in bits. The maximum element in the set is the size - 1st element.
*/
public int length() {
return bits.length << LOG_BITS_PER_UNIT;
}
/**
* Compares this object against the specified object.
*
* @param obj the object to compare with
* @return true if the objects are the same; false otherwise.
*/
@Override
public boolean equals(Object obj) {
if ((obj != null) && (obj instanceof FixedSizeBitVector)) {
if (this == obj) { // should help alias analysis
return true;
}
FixedSizeBitVector set = (FixedSizeBitVector) obj;
int n = bits.length;
if (n != set.bits.length)
return false;
for (int i = n; i-- > 0;) {
if (bits[i] != set.bits[i]) {
return false;
}
}
return true;
}
return false;
}
public boolean isZero() {
int setLength = bits.length;
for (int i = setLength; i-- > 0;) {
if (bits[i] != 0)
return false;
}
return true;
}
/**
* Clones the FixedSizeBitVector.
*/
@Override
public Object clone() {
FixedSizeBitVector result = null;
try {
result = (FixedSizeBitVector) super.clone();
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
result.bits = new int[bits.length];
System.arraycopy(bits, 0, result.bits, 0, result.bits.length);
return result;
}
/**
* Converts the FixedSizeBitVector to a String.
*/
@Override
public String toString() {
StringBuffer buffer = new StringBuffer();
boolean needSeparator = false;
buffer.append('{');
// int limit = length();
int limit = this.nbits;
for (int i = 0; i < limit; i++) {
if (get(i)) {
if (needSeparator) {
buffer.append(", ");
} else {
needSeparator = true;
}
buffer.append(i);
}
}
buffer.append('}');
return buffer.toString();
}
}