Package javajs.util

Class BS

java.lang.Object
javajs.util.BS
All Implemented Interfaces:
Cloneable, JSONEncodable
Direct Known Subclasses:
BondSet

public class BS extends Object implements Cloneable, JSONEncodable
a fast 32-bit BitSet optimized for Java2Script -- about 25 times faster than java.util.BitSet
Since:
JDK1.0
Author:
Bob Hanson hansonr@stolaf.edu Additions by Bob Hanson to allow for JavaScript mix of int/long Note that Firefox (Sept 2012) does not really treat "Int32Array" as such, because any element can be pushed into being a 64-bit number, which really isn't because the last 8 bits are not usable. This class implements a vector of bits that grows as needed. Each component of the bit set has a boolean value. The bits of a BitSet are indexed by nonnegative integers. Individual indexed bits can be examined, set, or cleared. One BitSet may be used to modify the contents of another BitSet through logical AND, logical inclusive OR, and logical exclusive OR operations.

By default, all bits in the set initially have the value false.

Every bit set has a current size, which is the number of bits of space currently in use by the bit set. Note that the size is related to the implementation of a bit set, so it may change with implementation. The length of a bit set relates to logical length of a bit set and is defined independently of implementation.

Unless otherwise noted, passing a null parameter to any of the methods in a BitSet will result in a NullPointerException.

A BitSet is not safe for multithreaded use without external synchronization., Arthur van Hoff, Michael McCloskey, Martin Buchholz

  • Constructor Summary

    Constructors
    Constructor
    Description
    BS()
    Creates a new bit set.
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    and(BS set)
    Performs a logical AND of this target bit set with the argument bit set.
    void
    andNot(BS set)
    Clears all of the bits in this BitSet whose corresponding bit is set in the specified BitSet.
    int
    Returns the number of bits set to true in this BitSet.
    int
    cardinalityN(int max)
     
    void
    clear(int bitIndex)
    Sets the bit specified by the index to false.
    void
    Sets all of the bits in this BitSet to false.
    void
    clearBits(int fromIndex, int toIndex)
    Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to false.
    Cloning this BitSet produces a new BitSet that is equal to it.
    static BS
    copy(BS bitsetToCopy)
    fast copy
    boolean
    Compares this object against the specified object.
    static String
    escape(BS bs, char chOpen, char chClose)
     
    boolean
    get(int bitIndex)
    Returns the value of the bit with the specified index.
    int
    Returns a hash code value for this bit set.
    boolean
    Returns true if the specified BitSet has any bits set to true that are also set to true in this BitSet.
    boolean
    Returns true if this BitSet contains no bits that are set to true.
    int
    Returns the "logical size" of this BitSet: the index of the highest set bit in the BitSet plus one.
    static BS
    newN(int nbits)
    Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range 0 through nbits-1.
    int
    nextClearBit(int fromIndex)
    Returns the index of the first bit that is set to false that occurs on or after the specified starting index.
    int
    nextSetBit(int fromIndex)
    Returns the index of the first bit that is set to true that occurs on or after the specified starting index.
    void
    or(BS set)
    Performs a logical OR of this bit set with the bit set argument.
    void
    set(int bitIndex)
    Sets the bit at the specified index to true.
    void
    setBits(int fromIndex, int toIndex)
    Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to true.
    void
    setBitTo(int bitIndex, boolean value)
    Sets the bit at the specified index to the specified value.
    int
    Returns the number of bits of space actually in use by this BitSet to represent bit values.
     
    Returns a string representation of this bit set.
    static BS
     
    void
    xor(BS set)
    Performs a logical XOR of this bit set with the bit set argument.

    Methods inherited from class java.lang.Object

    finalize, getClass, notify, notifyAll, wait, wait, wait
  • Constructor Details

    • BS

      public BS()
      Creates a new bit set. All bits are initially false.
  • Method Details

    • newN

      public static BS newN(int nbits)
      Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range 0 through nbits-1. All bits are initially false.
      Parameters:
      nbits - the initial size of the bit set
      Returns:
      bs
      Throws:
      NegativeArraySizeException - if the specified initial size is negative
    • set

      public void set(int bitIndex)
      Sets the bit at the specified index to true.
      Parameters:
      bitIndex - a bit index
      Throws:
      IndexOutOfBoundsException - if the specified index is negative
      Since:
      JDK1.0
    • setBitTo

      public void setBitTo(int bitIndex, boolean value)
      Sets the bit at the specified index to the specified value.
      Parameters:
      bitIndex - a bit index
      value - a boolean value to set
      Throws:
      IndexOutOfBoundsException - if the specified index is negative
      Since:
      1.4
    • setBits

      public void setBits(int fromIndex, int toIndex)
      Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to true.
      Parameters:
      fromIndex - index of the first bit to be set
      toIndex - index after the last bit to be set
      Throws:
      IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex
      Since:
      1.4
    • clear

      public void clear(int bitIndex)
      Sets the bit specified by the index to false.
      Parameters:
      bitIndex - the index of the bit to be cleared
      Throws:
      IndexOutOfBoundsException - if the specified index is negative
      Since:
      JDK1.0
    • clearBits

      public void clearBits(int fromIndex, int toIndex)
      Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to false.
      Parameters:
      fromIndex - index of the first bit to be cleared
      toIndex - index after the last bit to be cleared
      Throws:
      IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex
      Since:
      1.4
    • clearAll

      public void clearAll()
      Sets all of the bits in this BitSet to false.
      Since:
      1.4
    • get

      public boolean get(int bitIndex)
      Returns the value of the bit with the specified index. The value is true if the bit with the index bitIndex is currently set in this BitSet; otherwise, the result is false.
      Parameters:
      bitIndex - the bit index
      Returns:
      the value of the bit with the specified index
      Throws:
      IndexOutOfBoundsException - if the specified index is negative
    • nextSetBit

      public int nextSetBit(int fromIndex)
      Returns the index of the first bit that is set to true that occurs on or after the specified starting index. If no such bit exists then -1 is returned.

      To iterate over the true bits in a BitSet, use the following loop:

    • nextClearBit

      public int nextClearBit(int fromIndex)
      Returns the index of the first bit that is set to false that occurs on or after the specified starting index.
      Parameters:
      fromIndex - the index to start checking from (inclusive)
      Returns:
      the index of the next clear bit
      Throws:
      IndexOutOfBoundsException - if the specified index is negative
      Since:
      1.4
    • length

      public int length()
      Returns the "logical size" of this BitSet: the index of the highest set bit in the BitSet plus one. Returns zero if the BitSet contains no set bits.
      Returns:
      the logical size of this BitSet
      Since:
      1.2
    • isEmpty

      public boolean isEmpty()
      Returns true if this BitSet contains no bits that are set to true.
      Returns:
      boolean indicating whether this BitSet is empty
      Since:
      1.4
    • intersects

      public boolean intersects(BS set)
      Returns true if the specified BitSet has any bits set to true that are also set to true in this BitSet.
      Parameters:
      set - BitSet to intersect with
      Returns:
      boolean indicating whether this BitSet intersects the specified BitSet
      Since:
      1.4
    • cardinality

      public int cardinality()
      Returns the number of bits set to true in this BitSet.
      Returns:
      the number of bits set to true in this BitSet
      Since:
      1.4
    • and

      public void and(BS set)
      Performs a logical AND of this target bit set with the argument bit set. This bit set is modified so that each bit in it has the value true if and only if it both initially had the value true and the corresponding bit in the bit set argument also had the value true.
      Parameters:
      set - a bit set
    • or

      public void or(BS set)
      Performs a logical OR of this bit set with the bit set argument. This bit set is modified so that a bit in it has the value true if and only if it either already had the value true or the corresponding bit in the bit set argument has the value true.
      Parameters:
      set - a bit set
    • xor

      public void xor(BS set)
      Performs a logical XOR of this bit set with the bit set argument. This bit set is modified so that a bit in it has the value true if and only if one of the following statements holds:
      • The bit initially has the value true, and the corresponding bit in the argument has the value false.
      • The bit initially has the value false, and the corresponding bit in the argument has the value true.
      Parameters:
      set - a bit set
    • andNot

      public void andNot(BS set)
      Clears all of the bits in this BitSet whose corresponding bit is set in the specified BitSet.
      Parameters:
      set - the BitSet with which to mask this BitSet
      Since:
      1.2
    • hashCode

      public int hashCode()
      Returns a hash code value for this bit set. The hash code depends only on which bits have been set within this BitSet. The algorithm used to compute it may be described as follows.

      Suppose the bits in the BitSet were to be stored in an array of long integers called, say, words, in such a manner that bit k is set in the BitSet (for nonnegative values of k) if and only if the expression

       ((k >> 6) < words.length) && ((words[k >> 6] & (1 << (bit & 0x3F))) != 0)
       
      is true. Then the following definition of the hashCode method would be a correct implementation of the actual algorithm:
       public int hashCode() {
        long h = 1234;
        for (int i = words.length; --i >= 0;) {
          h ˆ= words[i] * (i + 1);
        }
        return (int) ((h >> 32) ˆ h);
       }
       
      Note that the hash code values change if the set of bits is altered.

      Overrides the hashCode method of Object.

      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this bit set.
    • size

      public int size()
      Returns the number of bits of space actually in use by this BitSet to represent bit values. The maximum element in the set is the size - 1st element.
      Returns:
      the number of bits currently in this bit set
    • equals

      public boolean equals(Object obj)
      Compares this object against the specified object. The result is true if and only if the argument is not null and is a Bitset object that has exactly the same set of bits set to true as this bit set. That is, for every nonnegative int index k,
       ((BitSet) obj).get(k) == this.get(k)
       
      must be true. The current sizes of the two bit sets are not compared.
      Overrides:
      equals in class Object
      Parameters:
      obj - the object to compare with
      Returns:
      true if the objects are the same; false otherwise
      See Also:
    • clone

      public Object clone()
      Cloning this BitSet produces a new BitSet that is equal to it. The clone of the bit set is another bit set that has exactly the same bits set to true as this bit set.
      Overrides:
      clone in class Object
      Returns:
      a clone of this bit set
      See Also:
    • toString

      public String toString()
      Returns a string representation of this bit set. For every index for which this BitSet contains a bit in the set state, the decimal representation of that index is included in the result. Such indices are listed in order from lowest to highest, separated by ", " (a comma and a space) and surrounded by braces, resulting in the usual mathematical notation for a set of integers.

      Example:

       BitSet drPepper = new BitSet();
       
      Now drPepper.toString() returns "{}".

       drPepper.set(2);
       
      Now drPepper.toString() returns "{2}".

       drPepper.set(4);
       drPepper.set(10);
       
      Now drPepper.toString() returns "{2, 4, 10}".
      Overrides:
      toString in class Object
      Returns:
      a string representation of this bit set
    • copy

      public static BS copy(BS bitsetToCopy)
      fast copy
      Parameters:
      bitsetToCopy -
      Returns:
      bs
    • cardinalityN

      public int cardinalityN(int max)
      Parameters:
      max -
      Returns:
      n bits below max
    • toJSON

      public String toJSON()
      Specified by:
      toJSON in interface JSONEncodable
    • escape

      public static String escape(BS bs, char chOpen, char chClose)
    • unescape

      public static BS unescape(String str)