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BitSet.java

package antlr.collections.impl;

/* ANTLR Translator Generator
 * Project led by Terence Parr at http://www.jGuru.com
 * Software rights: http://www.antlr.org/RIGHTS.html
 *
 * $Id: //depot/code/org.antlr/release/antlr-2.7.2/antlr/collections/impl/BitSet.java#1 $
 */

import antlr.CharFormatter;

/**A BitSet to replace java.util.BitSet.
 * Primary differences are that most set operators return new sets
 * as opposed to oring and anding "in place".  Further, a number of
 * operations were added.  I cannot contain a BitSet because there
 * is no way to access the internal bits (which I need for speed)
 * and, because it is final, I cannot subclass to add functionality.
 * Consider defining set degree.  Without access to the bits, I must
 * call a method n times to test the ith bit...ack!
 *
 * Also seems like or() from util is wrong when size of incoming set is bigger
 * than this.bits.length.
 *
 * @author Terence Parr
 * @author <br><a href="mailto:pete@yamuna.demon.co.uk">Pete Wells</a>
 */
00027 public class BitSet implements Cloneable {
    protected final static int BITS = 64;    // number of bits / long
    protected final static int NIBBLE = 4;
    protected final static int LOG_BITS = 6; // 2^6 == 64

    /* We will often need to do a mod operator (i mod nbits).  Its
     * turns out that, for powers of two, this mod operation is
     * same as (i & (nbits-1)).  Since mod is slow, we use a
     * precomputed mod mask to do the mod instead.
     */
    protected final static int MOD_MASK = BITS - 1;

    /** The actual data bits */
00040     protected long bits[];

    /** Construct a bitset of size one word (64 bits) */
00043     public BitSet() {
        this(BITS);
    }

    /** Construction from a static array of longs */
00048     public BitSet(long[] bits_) {
        bits = bits_;
    }

    /** Construct a bitset given the size
     * @param nbits The size of the bitset in bits
     */
00055     public BitSet(int nbits) {
        bits = new long[((nbits - 1) >> LOG_BITS) + 1];
    }

    /** or this element into this set (grow as necessary to accommodate) */
00060     public void add(int el) {
        //System.out.println("add("+el+")");
        int n = wordNumber(el);
        //System.out.println("word number is "+n);
        //System.out.println("bits.length "+bits.length);
        if (n >= bits.length) {
            growToInclude(el);
        }
        bits[n] |= bitMask(el);
    }

    public BitSet and(BitSet a) {
        BitSet s = (BitSet)this.clone();
        s.andInPlace(a);
        return s;
    }

    public void andInPlace(BitSet a) {
        int min = Math.min(bits.length, a.bits.length);
        for (int i = min - 1; i >= 0; i--) {
            bits[i] &= a.bits[i];
        }
        // clear all bits in this not present in a (if this bigger than a).
        for (int i = min; i < bits.length; i++) {
            bits[i] = 0;
        }
    }

    private final static long bitMask(int bitNumber) {
        int bitPosition = bitNumber & MOD_MASK; // bitNumber mod BITS
        return 1L << bitPosition;
    }

    public void clear() {
        for (int i = bits.length - 1; i >= 0; i--) {
            bits[i] = 0;
        }
    }

    public void clear(int el) {
        int n = wordNumber(el);
        if (n >= bits.length) {     // grow as necessary to accommodate
            growToInclude(el);
        }
        bits[n] &= ~bitMask(el);
    }

    public Object clone() {
        BitSet s;
        try {
            s = (BitSet)super.clone();
            s.bits = new long[bits.length];
            System.arraycopy(bits, 0, s.bits, 0, bits.length);
        }
        catch (CloneNotSupportedException e) {
            throw new InternalError();
        }
        return s;
    }

    public int degree() {
        int deg = 0;
        for (int i = bits.length - 1; i >= 0; i--) {
            long word = bits[i];
            if (word != 0L) {
                for (int bit = BITS - 1; bit >= 0; bit--) {
                    if ((word & (1L << bit)) != 0) {
                        deg++;
                    }
                }
            }
        }
        return deg;
    }

    /** code "inherited" from java.util.BitSet */
00136     public boolean equals(Object obj) {
        if ((obj != null) && (obj instanceof BitSet)) {
            BitSet set = (BitSet)obj;

            int n = Math.min(bits.length, set.bits.length);
            for (int i = n; i-- > 0;) {
                if (bits[i] != set.bits[i]) {
                    return false;
                }
            }
            if (bits.length > n) {
                for (int i = bits.length; i-- > n;) {
                    if (bits[i] != 0) {
                        return false;
                    }
                }
            }
            else if (set.bits.length > n) {
                for (int i = set.bits.length; i-- > n;) {
                    if (set.bits[i] != 0) {
                        return false;
                    }
                }
            }
            return true;
        }
        return false;
    }

    /** Find ranges in a set element array.  @param elems The array of
     * elements representing the set, usually from Bit Set.toArray().
     * @return Vector of ranges.
     */
00169     public static Vector getRanges(int[] elems) {
        if (elems.length == 0) {
            return null;
        }
        int begin = elems[0];
        int end = elems[elems.length - 1];
        if (elems.length <= 2) {
            // Not enough elements for a range expression
            return null;
        }

        Vector ranges = new Vector(5);
        // look for ranges
        for (int i = 0; i < elems.length - 2; i++) {
            int lastInRange;
            lastInRange = elems.length - 1;
            for (int j = i + 1; j < elems.length; j++) {
                if (elems[j] != elems[j - 1] + 1) {
                    lastInRange = j - 1;
                    break;
                }
            }
            // found a range
            if (lastInRange - i > 2) {
                ranges.appendElement(new IntRange(elems[i], elems[lastInRange]));
            }
        }
        return ranges;
    }

    /**
     * Grows the set to a larger number of bits.
     * @param bit element that must fit in set
     */
00203     public void growToInclude(int bit) {
        int newSize = Math.max(bits.length << 1, numWordsToHold(bit));
        long newbits[] = new long[newSize];
        System.arraycopy(bits, 0, newbits, 0, bits.length);
        bits = newbits;
    }

    public boolean member(int el) {
        int n = wordNumber(el);
        if (n >= bits.length) return false;
        return (bits[n] & bitMask(el)) != 0;
    }

    public boolean nil() {
        for (int i = bits.length - 1; i >= 0; i--) {
            if (bits[i] != 0) return false;
        }
        return true;
    }

    public BitSet not() {
        BitSet s = (BitSet)this.clone();
        s.notInPlace();
        return s;
    }

    public void notInPlace() {
        for (int i = bits.length - 1; i >= 0; i--) {
            bits[i] = ~bits[i];
        }
    }

    /** complement bits in the range 0..maxBit. */
00236     public void notInPlace(int maxBit) {
        notInPlace(0, maxBit);
    }

    /** complement bits in the range minBit..maxBit.*/
00241     public void notInPlace(int minBit, int maxBit) {
        // make sure that we have room for maxBit
        growToInclude(maxBit);
        for (int i = minBit; i <= maxBit; i++) {
            int n = wordNumber(i);
            bits[n] ^= bitMask(i);
        }
    }

    private final int numWordsToHold(int el) {
        return (el >> LOG_BITS) + 1;
    }

    public static BitSet of(int el) {
        BitSet s = new BitSet(el + 1);
        s.add(el);
        return s;
    }

    /** return this | a in a new set */
00261     public BitSet or(BitSet a) {
        BitSet s = (BitSet)this.clone();
        s.orInPlace(a);
        return s;
    }

    public void orInPlace(BitSet a) {
        // If this is smaller than a, grow this first
        if (a.bits.length > bits.length) {
            setSize(a.bits.length);
        }
        int min = Math.min(bits.length, a.bits.length);
        for (int i = min - 1; i >= 0; i--) {
            bits[i] |= a.bits[i];
        }
    }

    // remove this element from this set
    public void remove(int el) {
        int n = wordNumber(el);
        if (n >= bits.length) {
            growToInclude(el);
        }
        bits[n] &= ~bitMask(el);
    }

    /**
     * Sets the size of a set.
     * @param nwords how many words the new set should be
     */
00291     private void setSize(int nwords) {
        long newbits[] = new long[nwords];
        int n = Math.min(nwords, bits.length);
        System.arraycopy(bits, 0, newbits, 0, n);
        bits = newbits;
    }

    public int size() {
        return bits.length << LOG_BITS; // num words * bits per word
    }

    /** return how much space is being used by the bits array not
     *  how many actually have member bits on.
     */
00305     public int lengthInLongWords() {
        return bits.length;
    }

    /**Is this contained within a? */
00310     public boolean subset(BitSet a) {
        if (a == null || !(a instanceof BitSet)) return false;
        return this.and(a).equals(this);
    }

    /**Subtract the elements of 'a' from 'this' in-place.
     * Basically, just turn off all bits of 'this' that are in 'a'.
     */
00318     public void subtractInPlace(BitSet a) {
        if (a == null) return;
        // for all words of 'a', turn off corresponding bits of 'this'
        for (int i = 0; i < bits.length && i < a.bits.length; i++) {
            bits[i] &= ~a.bits[i];
        }
    }

    public int[] toArray() {
        int[] elems = new int[degree()];
        int en = 0;
        for (int i = 0; i < (bits.length << LOG_BITS); i++) {
            if (member(i)) {
                elems[en++] = i;
            }
        }
        return elems;
    }

    public long[] toPackedArray() {
        return bits;
    }

    public String toString() {
        return toString(",");
    }

    /** Transform a bit set into a string by formatting each element as an integer
     * @separator The string to put in between elements
     * @return A commma-separated list of values
     */
00349     public String toString(String separator) {
        String str = "";
        for (int i = 0; i < (bits.length << LOG_BITS); i++) {
            if (member(i)) {
                if (str.length() > 0) {
                    str += separator;
                }
                str = str + i;
            }
        }
        return str;
    }

    /** Transform a bit set into a string of characters.
     * @separator The string to put in between elements
     * @param formatter An object implementing the CharFormatter interface.
     * @return A commma-separated list of character constants.
     */
00367     public String toString(String separator, CharFormatter formatter) {
        String str = "";

        for (int i = 0; i < (bits.length << LOG_BITS); i++) {
            if (member(i)) {
                if (str.length() > 0) {
                    str += separator;
                }
                str = str + formatter.literalChar(i);
            }
        }
        return str;
    }

    /**Create a string representation where instead of integer elements, the
     * ith element of vocabulary is displayed instead.  Vocabulary is a Vector
     * of Strings.
     * @separator The string to put in between elements
     * @return A commma-separated list of character constants.
     */
00387     public String toString(String separator, Vector vocabulary) {
        if (vocabulary == null) {
            return toString(separator);
        }
        String str = "";
        for (int i = 0; i < (bits.length << LOG_BITS); i++) {
            if (member(i)) {
                if (str.length() > 0) {
                    str += separator;
                }
                if (i >= vocabulary.size()) {
                    str += "<bad element " + i + ">";
                }
                else if (vocabulary.elementAt(i) == null) {
                    str += "<" + i + ">";
                }
                else {
                    str += (String)vocabulary.elementAt(i);
                }
            }
        }
        return str;
    }

    /**
     * Dump a comma-separated list of the words making up the bit set.
     * Split each 64 bit number into two more manageable 32 bit numbers.
     * This generates a comma-separated list of C++-like unsigned long constants.
     */
00416     public String toStringOfHalfWords() {
        String s = new String();
        for (int i = 0; i < bits.length; i++) {
            if (i != 0) s += ", ";
            long tmp = bits[i];
            tmp &= 0xFFFFFFFFL;
            s += (tmp + "UL");
            s += ", ";
            tmp = bits[i] >>> 32;
            tmp &= 0xFFFFFFFFL;
            s += (tmp + "UL");
        }
        return s;
    }

    /**
     * Dump a comma-separated list of the words making up the bit set.
     * This generates a comma-separated list of Java-like long int constants.
     */
00435     public String toStringOfWords() {
        String s = new String();
        for (int i = 0; i < bits.length; i++) {
            if (i != 0) s += ", ";
            s += (bits[i] + "L");
        }
        return s;
    }

    /** Print out the bit set but collapse char ranges. */
00445     public String toStringWithRanges(String separator, CharFormatter formatter) {
        String str = "";
        int[] elems = this.toArray();
        if (elems.length == 0) {
            return "";
        }
        // look for ranges
        int i = 0;
        while (i < elems.length) {
            int lastInRange;
            lastInRange = 0;
            for (int j = i + 1; j < elems.length; j++) {
                if (elems[j] != elems[j - 1] + 1) {
                    break;
                }
                lastInRange = j;
            }
            // found a range
            if (str.length() > 0) {
                str += separator;
            }
            if (lastInRange - i >= 2) {
                str += formatter.literalChar(elems[i]);
                str += "..";
                str += formatter.literalChar(elems[lastInRange]);
                i = lastInRange;    // skip past end of range for next range
            }
            else {      // no range, just print current char and move on
                str += formatter.literalChar(elems[i]);
            }
            i++;
        }
        return str;
    }

    private final static int wordNumber(int bit) {
        return bit >> LOG_BITS; // bit / BITS
    }
}

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