Class FormatableBitSet

  • All Implemented Interfaces:
    java.io.Externalizable, java.io.Serializable, java.lang.Cloneable, Formatable, TypedFormat

    public final class FormatableBitSet
    extends java.lang.Object
    implements Formatable, java.lang.Cloneable
    FormatableBitSet is implemented as a packed array of bytes.
    See Also:
    Serialized Form
    • Field Summary

      Fields 
      Modifier and Type Field Description
      private byte bitsInLastByte  
      private int lengthAsBits  
      private byte[] value
      Bits are stored as an array of bytes.
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void and​(FormatableBitSet otherBit)
      Bitwise AND this FormatableBitSet with another FormatableBitSet.
      int anySetBit()
      If any bit is set, return the zero-based bit index of the first bit that is set.
      int anySetBit​(int beyondBit)
      Like anySetBit(), but return any set bit whose number is bigger than beyondBit.
      private int calculateLength​(int realByteLength)  
      private void checkPosition​(int p)  
      void clear()
      Clear all the bits in this FormatableBitSet
      void clear​(int position)
      Bit clear
      java.lang.Object clone()  
      int compare​(FormatableBitSet other)
      Bit comparison.
      void copyFrom​(FormatableBitSet that)
      Copy the bytes from another FormatableBitSet.
      boolean equals​(java.lang.Object other)
      Bit equivalence.
      private static byte firstSet​(byte v)
      A utility method which treats the byte argument as an 8-bit bitset and finds the first set bit in that byte.
      boolean get​(int position)
      Bit get -- alias for isSet()
      byte[] getByteArray()
      Get the value of the byte array
      int getLength()
      Get the length in bits
      int getLengthInBytes()
      Get the length in bytes of a Bit value
      int getNumBitsSet()
      Get a count of the number of bits that are set.
      int getTypeFormatId()
      Get the formatID which corresponds to this class.
      void grow​(int n)
      Grow (widen) a FormatableBitSet so that it contains at least N bits.
      int hashCode()
      Produce a hash code by putting the value bytes into an int, exclusive OR'ing if there are more than 4 bytes.
      private void initializeBits​(int numBits)  
      boolean invariantHolds()
      This method returns true if the following conditions hold: 1.
      boolean isSet​(int position)
      Bit isSet
      static int maxBitsForSpace​(int numBytes)
      Statically calculates how many bits can fit into the number of bytes if this Bit object is externalized.
      private static byte numBitsInLastByte​(int bits)
      Figure out how many bits are in the last byte from the total number of bits.
      private static int numBytesFromBits​(int bits)
      Figure out how many bytes are needed to store the input number of bits.
      void or​(FormatableBitSet otherBit)
      Bitwise OR this FormatableBitSet with another FormatableBitSet.
      void readExternal​(java.io.ObjectInput in)
      Note: gracefully handles zero length bits -- will create a zero length array with no bits being used.
      void set​(int position)
      Bit set
      void shrink​(int n)
      Shrink (narrow) a FormatableBitSet to N bits.
      int size()
      Get the length in bits -- alias for getLength()
      java.lang.String toString()
      Format the string into BitSet format: {0, 2, 4, 8} if bits 0, 2, 4, 8 are set.
      private static int udiv8​(int i)  
      private static byte umod8​(int i)  
      private static int umul8​(int i)  
      void writeExternal​(java.io.ObjectOutput out)
      Format: int length in bits byte[]
      void xor​(FormatableBitSet otherBit)
      Bitwise XOR this FormatableBitSet with another FormatableBitSet.
      • Methods inherited from class java.lang.Object

        finalize, getClass, notify, notifyAll, wait, wait, wait
    • Field Detail

      • value

        private byte[] value
        Bits are stored as an array of bytes. Bits are numbered starting at 0. Bits 0..7 go in byte[0], 8..15 in byte[1] and so on. The number of bytes is tracked as part of the byte array. The number of bits being used is derived by the number of bytes being used and the number of bits being used by the last byte. The partially unused byte is always byte[byte.length] with the lowest bits being unused. Zero length bits are stored using a zero length byte array, with all bits marked as unused.
      • bitsInLastByte

        private byte bitsInLastByte
      • lengthAsBits

        private transient int lengthAsBits
    • Constructor Detail

      • FormatableBitSet

        public FormatableBitSet()
        Niladic Constructor
      • FormatableBitSet

        public FormatableBitSet​(int numBits)
        Constructs a Bit with the initial number of bits
      • FormatableBitSet

        public FormatableBitSet​(byte[] newValue)
        Constructs a Bit from an array of bytes. Assume bytes are all being used.
        Parameters:
        newValue - The array of bytes to make up the new Bit
      • FormatableBitSet

        public FormatableBitSet​(FormatableBitSet original)
        Copy constructor
        Parameters:
        original - the FormatableBitSet to make a copy from
    • Method Detail

      • checkPosition

        private final void checkPosition​(int p)
      • udiv8

        private static int udiv8​(int i)
      • umod8

        private static byte umod8​(int i)
      • umul8

        private static int umul8​(int i)
      • initializeBits

        private void initializeBits​(int numBits)
      • clone

        public java.lang.Object clone()
        Overrides:
        clone in class java.lang.Object
      • invariantHolds

        public boolean invariantHolds()
        This method returns true if the following conditions hold: 1. The number of bits in the bitset will fit into the allocated byte array. 2. 'lengthAsBits' and 'bitsInLastByte' are consistent. 3. All unused bits in the byte array are unset. This represents an invariant for the class, so this method should always return true. The method is public, but is primarily intended for testing and ASSERTS.
        Returns:
        true if invariant holds, false otherwise
      • getLengthInBytes

        public int getLengthInBytes()
        Get the length in bytes of a Bit value
        Returns:
        The length in bytes of this value
      • getLength

        public int getLength()
        Get the length in bits
        Returns:
        The length in bits for this value NOTE: could possibly be changed to a long. As is we are restricted to 2^(31-3) -> 256meg instead of 2^31 (Integer.MAX_VALUE) like other datatypes (or 2 gig). If it is ever changed to a long be sure to change read/writeExternal which write out the length in bits.
      • calculateLength

        private int calculateLength​(int realByteLength)
      • size

        public int size()
        Get the length in bits -- alias for getLength()
        Returns:
        The length in bits for this value
      • getByteArray

        public byte[] getByteArray()
        Get the value of the byte array
        Returns:
        The value of the byte array
      • grow

        public void grow​(int n)
        Grow (widen) a FormatableBitSet so that it contains at least N bits. If the bitset already has more than n bits, this is a noop. Negative values of n are not allowed. ASSUMPTIONS: that all extra bits in the last byte are zero.
        Parameters:
        n - The number of bits you want. The bits are always added as 0 and are appended to the least significant end of the bit array.
      • shrink

        public void shrink​(int n)
        Shrink (narrow) a FormatableBitSet to N bits. N may not be larger than the current bitset size, or negative.
        Parameters:
        n - The number of bits the caller wants. The bits are always removed from the least significant end of the bit array.
      • equals

        public boolean equals​(java.lang.Object other)
        Bit equivalence. Compare this with other. If the length is different, then cannot be equal so short circuit. Otherwise, rely on compare(). Note that two zero length bits are considered equal.
        Overrides:
        equals in class java.lang.Object
        Parameters:
        other - the other bit to compare to
        Returns:
        TRUE|FALSE
      • compare

        public int compare​(FormatableBitSet other)
        Bit comparison. Compare this with other. Will always do a byte by byte compare. Given 2 similar bits of unequal lengths (x and y), where x.getLength() < y.getLength() but where: x[0..x.getLength()] == y[0..x.getLength()] then x < y.
        Parameters:
        other - the other bit to compare to
        Returns:
        -1 - if other < this 0 - if other == this 1 - if other > this
      • hashCode

        public int hashCode()
        Produce a hash code by putting the value bytes into an int, exclusive OR'ing if there are more than 4 bytes.
        Overrides:
        hashCode in class java.lang.Object
        Returns:
        the hash code
      • isSet

        public final boolean isSet​(int position)
        Bit isSet
        Parameters:
        position - the bit to check
      • get

        public final boolean get​(int position)
        Bit get -- alias for isSet()
        Parameters:
        position - the bit to check
      • set

        public void set​(int position)
        Bit set
        Parameters:
        position - the bit to set
      • clear

        public void clear​(int position)
        Bit clear
        Parameters:
        position - the bit to clear
      • clear

        public void clear()
        Clear all the bits in this FormatableBitSet
      • numBytesFromBits

        private static int numBytesFromBits​(int bits)
        Figure out how many bytes are needed to store the input number of bits.
        Parameters:
        bits - bits
        Returns:
        the number of bytes
      • numBitsInLastByte

        private static byte numBitsInLastByte​(int bits)
        Figure out how many bits are in the last byte from the total number of bits.
        Parameters:
        bits - bits
        Returns:
        the number of bits
      • toString

        public java.lang.String toString()
        Format the string into BitSet format: {0, 2, 4, 8} if bits 0, 2, 4, 8 are set.
        Overrides:
        toString in class java.lang.Object
        Returns:
        A new String containing the formatted Bit value
      • maxBitsForSpace

        public static int maxBitsForSpace​(int numBytes)
        Statically calculates how many bits can fit into the number of bytes if this Bit object is externalized. Only valid for this implementation of Bit.
      • firstSet

        private static byte firstSet​(byte v)
        A utility method which treats the byte argument as an 8-bit bitset and finds the first set bit in that byte. Assumes that at least one bit in v is set (v!=0).
        Parameters:
        v - a non-zero byte to check for set bits
        Returns:
        the zero-based index of the first set bit in the argument byte
      • anySetBit

        public int anySetBit()
        If any bit is set, return the zero-based bit index of the first bit that is set. If no bit is set, return -1. By using anySetBit() and anySetBit(beyondBit), one can quickly go thru the entire bit array to return all set bit.
        Returns:
        the zero-based index of the first bit that is set, or -1 if no bit is set
      • anySetBit

        public int anySetBit​(int beyondBit)
        Like anySetBit(), but return any set bit whose number is bigger than beyondBit. If no bit is set after beyondBit, -1 is returned. By using anySetBit() and anySetBit(beyondBit), one can quickly go thru the entire bit array to return all set bit.
        Parameters:
        beyondBit - Only look at bit that is greater than this bit number. Supplying a value of -1 makes the call equivalent to anySetBit().
        Returns:
        the bit number of a bit that is set, or -1 if no bit after beyondBit is set
      • or

        public void or​(FormatableBitSet otherBit)
        Bitwise OR this FormatableBitSet with another FormatableBitSet. The result is stored in this bitset. The operand is unaffected. A null operand is treated as an empty bitset (i.e. a noop). A bitset that is smaller than its operand is expanded to the same size.
        Parameters:
        otherBit - bitset operand
      • copyFrom

        public void copyFrom​(FormatableBitSet that)
        Copy the bytes from another FormatableBitSet. Assumes that this bit set is at least as large as the argument's bit set.
      • and

        public void and​(FormatableBitSet otherBit)
        Bitwise AND this FormatableBitSet with another FormatableBitSet. The result is stored in this bitset. The operand is unaffected. A null operand is treated as an empty bitset (i.e. clearing this bitset). A bitset that is smaller than its operand is expanded to the same size.
        Parameters:
        otherBit - bitset operand
      • xor

        public void xor​(FormatableBitSet otherBit)
        Bitwise XOR this FormatableBitSet with another FormatableBitSet. The result is stored in this bitset. The operand is unaffected. A null operand is treated as an empty bitset (i.e. a noop). A bitset that is smaller than its operand is expanded to the same size.
        Parameters:
        otherBit - bitset operand
      • getNumBitsSet

        public int getNumBitsSet()
        Get a count of the number of bits that are set.
        Returns:
        The number of bits that are set.
      • writeExternal

        public void writeExternal​(java.io.ObjectOutput out)
                           throws java.io.IOException
        Format:
        • int length in bits
        • byte[]
        Specified by:
        writeExternal in interface java.io.Externalizable
        Throws:
        java.io.IOException
        See Also:
        Externalizable.writeExternal(java.io.ObjectOutput)
      • readExternal

        public void readExternal​(java.io.ObjectInput in)
                          throws java.io.IOException
        Note: gracefully handles zero length bits -- will create a zero length array with no bits being used. Fortunately in.read() is ok with a zero length array so no special code.

        WARNING: this method cannot be changed w/o changing SQLBit because SQLBit calls this directly w/o calling read/writeObject(), so the format id is not stored in that case.

        Specified by:
        readExternal in interface java.io.Externalizable
        Throws:
        java.io.IOException
        See Also:
        Externalizable.readExternal(java.io.ObjectInput)
      • getTypeFormatId

        public int getTypeFormatId()
        Get the formatID which corresponds to this class.
        Specified by:
        getTypeFormatId in interface TypedFormat
        Returns:
        the formatID of this class