Package com.googlecode.javaewah

Class EWAHCompressedBitmap

java.lang.Object
com.googlecode.javaewah.EWAHCompressedBitmap
All Implemented Interfaces:
BitmapStorage, LogicalElement<EWAHCompressedBitmap>, Externalizable, Serializable, Cloneable, Iterable<Integer>
public final class EWAHCompressedBitmap extends Object implements Cloneable, Externalizable, Iterable<Integer>, BitmapStorage, LogicalElement<EWAHCompressedBitmap>

This implements the patent-free(1) EWAH scheme. Roughly speaking, it is a 64-bit variant of the BBC compression scheme used by Oracle for its bitmap indexes.

The objective of this compression type is to provide some compression, while reducing as much as possible the CPU cycle usage.

Once constructed, the bitmap is essentially immutable (unless you call the "set" or "add" methods). Thus, it can be safely used in multi-threaded programs.

This implementation being 64-bit, it assumes a 64-bit CPU together with a 64-bit Java Virtual Machine. This same code on a 32-bit machine may not be as fast. There is also a 32-bit version of this code in the class javaewah32.EWAHCompressedBitmap32.

Here is a code sample to illustrate usage: 

 EWAHCompressedBitmap ewahBitmap1 = EWAHCompressedBitmap.bitmapOf(0, 2, 55, 64,
         1 << 30);
 EWAHCompressedBitmap ewahBitmap2 = EWAHCompressedBitmap.bitmapOf(1, 3, 64,
         1 << 30);
 EWAHCompressedBitmap ewahBitmap3 = EWAHCompressedBitmap
         .bitmapOf(5, 55, 1 << 30);
 EWAHCompressedBitmap ewahBitmap4 = EWAHCompressedBitmap
         .bitmapOf(4, 66, 1 << 30);
 EWAHCompressedBitmap orbitmap = ewahBitmap1.or(ewahBitmap2);
 EWAHCompressedBitmap andbitmap = ewahBitmap1.and(ewahBitmap2);
 EWAHCompressedBitmap xorbitmap = ewahBitmap1.xor(ewahBitmap2);
 andbitmap = EWAHCompressedBitmap.and(ewahBitmap1, ewahBitmap2, ewahBitmap3,
         ewahBitmap4);
 ByteArrayOutputStream bos = new ByteArrayOutputStream();
 ObjectOutputStream oo = new ObjectOutputStream(bos);
 ewahBitmap1.writeExternal(oo);
 oo.close();
 ewahBitmap1 = null;
 ewahBitmap1 = new EWAHCompressedBitmap();
 ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
 ewahBitmap1.readExternal(new ObjectInputStream(bis));
 EWAHCompressedBitmap threshold2 = EWAHCompressedBitmap.threshold(2,
         ewahBitmap1, ewahBitmap2, ewahBitmap3, ewahBitmap4);

For more details, see the following papers:

A 32-bit version of the compressed format was described by Wu et al. and named WBC:

  • K. Wu, E. J. Otoo, A. Shoshani, H. Nordberg, Notes on design and implementation of compressed bit vectors, Tech. Rep. LBNL/PUB-3161, Lawrence Berkeley National Laboratory, available from http://crd.lbl. gov/~kewu/ps/PUB-3161.html (2001).

Probably, the best prior art is the Oracle bitmap compression scheme (BBC):

  • G. Antoshenkov, Byte-Aligned Bitmap Compression, DCC'95, 1995.

1- The authors do not know of any patent infringed by the following implementation. However, similar schemes, like WAH are covered by patents.

Since:
0.1.0
See Also:
EWAHCompressedBitmap32, Serialized Form

  • Field Details

    • ADJUST_CONTAINER_SIZE_WHEN_AGGREGATING

      public static final boolean ADJUST_CONTAINER_SIZE_WHEN_AGGREGATING
      whether we adjust after some aggregation by adding in zeroes *
      See Also:
      Constant Field Values

    • WORD_IN_BITS

      public static final int WORD_IN_BITS
      The Constant WORD_IN_BITS represents the number of bits in a long.
      See Also:
      Constant Field Values

  • Constructor Details

    • EWAHCompressedBitmap

      public EWAHCompressedBitmap()
      Creates an empty bitmap (no bit set to true).

    • EWAHCompressedBitmap

      public EWAHCompressedBitmap​(int bufferSize)
      Sets explicitly the buffer size (in 64-bit words). The initial memory usage will be "bufferSize * 64". For large poorly compressible bitmaps, using large values may improve performance. If the requested bufferSize is less than 1, a value of 1 is used by default. In particular, negative values of bufferSize are effectively ignored.
      Parameters:
      bufferSize - number of 64-bit words reserved when the object is created)

    • EWAHCompressedBitmap

      public EWAHCompressedBitmap​(ByteBuffer buffer)
      Creates a bitmap with the specified ByteBuffer backend. It assumes that a bitmap was serialized at this location. It is effectively "deserialized" though the actual content is not copied. This might be useful for implementing memory-mapped bitmaps.
      Parameters:
      buffer - data source

    • EWAHCompressedBitmap

      public EWAHCompressedBitmap​(LongBuffer buffer)
      Creates a bitmap with the specified java.nio.LongBuffer backend. The content of the LongBuffer is discarded.
      Parameters:
      buffer - data source

  • Method Details

    • add

      @Deprecated public void add​(long newData)
      Deprecated.
      use addWord() instead.
      Parameters:
      newData - the word

    • add

      @Deprecated public void add​(long newData, int bitsThatMatter)
      Deprecated.
      use addWord() instead.
      Parameters:
      newData - the word
      bitsThatMatter - the number of significant bits (by default it should be 64)

    • addWord

      public void addWord​(long newData)
      Adding words directly to the bitmap (for expert use). This method adds bits in words of 4*8 bits. It is not to be confused with the set method which sets individual bits. Most users will want the set method. Example: if you add word 321 to an empty bitmap, you are have added (in binary notation) 0b101000001, so you have effectively called set(0), set(6), set(8) in sequence. Since this modifies the bitmap, this method is not thread-safe. API change: prior to version 0.8.3, this method was called add.
      Specified by:
      addWord in interface BitmapStorage
      Parameters:
      newData - the word

    • addWord

      public void addWord​(long newData, int bitsThatMatter)
      Adding words directly to the bitmap (for expert use). Since this modifies the bitmap, this method is not thread-safe. API change: prior to version 0.8.3, this method was called add.
      Parameters:
      newData - the word
      bitsThatMatter - the number of significant bits (by default it should be 64)

    • addLiteralWord

      public void addLiteralWord​(long newData)
      Adding literal word directly to the bitmap (for expert use). Since this modifies the bitmap, this method is not thread-safe.
      Specified by:
      addLiteralWord in interface BitmapStorage
      Parameters:
      newData - the word

    • addStreamOfLiteralWords

      public void addStreamOfLiteralWords​(com.googlecode.javaewah.Buffer buffer, int start, int number)
      if you have several literal words to copy over, this might be faster. Since this modifies the bitmap, this method is not thread-safe.
      Specified by:
      addStreamOfLiteralWords in interface BitmapStorage
      Parameters:
      buffer - the buffer wrapping the literal words
      start - the starting point in the array
      number - the number of literal words to add

    • addStreamOfEmptyWords

      public void addStreamOfEmptyWords​(boolean v, long number)
      For experts: You want to add many zeroes or ones? This is the method you use. Since this modifies the bitmap, this method is not thread-safe.
      Specified by:
      addStreamOfEmptyWords in interface BitmapStorage
      Parameters:
      v - the boolean value
      number - the number

    • addStreamOfNegatedLiteralWords

      public void addStreamOfNegatedLiteralWords​(com.googlecode.javaewah.Buffer buffer, int start, int number)
      Same as addStreamOfLiteralWords, but the words are negated. Since this modifies the bitmap, this method is not thread-safe.
      Specified by:
      addStreamOfNegatedLiteralWords in interface BitmapStorage
      Parameters:
      buffer - the buffer wrapping the literal words
      start - the starting point in the array
      number - the number of literal words to add

    • and

      public EWAHCompressedBitmap and​(EWAHCompressedBitmap a)
      Returns a new compressed bitmap containing the bitwise AND values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.
      Specified by:
      and in interface LogicalElement<EWAHCompressedBitmap>
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the EWAH compressed bitmap
      Since:
      0.4.3

    • andToContainer

      public void andToContainer​(EWAHCompressedBitmap a, BitmapStorage container)
      Computes new compressed bitmap containing the bitwise AND values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). The current bitmap is not modified. The content of the container is overwritten.
      Parameters:
      a - the other bitmap (it will not be modified)
      container - where we store the result
      Since:
      0.4.0

    • andCardinality

      public int andCardinality​(EWAHCompressedBitmap a)
      Returns the cardinality of the result of a bitwise AND of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the cardinality
      Since:
      0.4.0

    • andNot

      public EWAHCompressedBitmap andNot​(EWAHCompressedBitmap a)
      Returns a new compressed bitmap containing the bitwise AND NOT values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.
      Specified by:
      andNot in interface LogicalElement<EWAHCompressedBitmap>
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the EWAH compressed bitmap

    • andNotToContainer

      public void andNotToContainer​(EWAHCompressedBitmap a, BitmapStorage container)
      Returns a new compressed bitmap containing the bitwise AND NOT values of the current bitmap with some other bitmap. This method is expected to be faster than doing A.and(B.clone().not()). The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). The current bitmap is not modified. The content of the container is overwritten.
      Parameters:
      a - the other bitmap (it will not be modified)
      container - where to store the result
      Since:
      0.4.0

    • andNotCardinality

      public int andNotCardinality​(EWAHCompressedBitmap a)
      Returns the cardinality of the result of a bitwise AND NOT of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the cardinality
      Since:
      0.4.0

    • cardinality

      public int cardinality()
      reports the number of bits set to true. Running time is proportional to compressed size (as reported by sizeInBytes).
      Returns:
      the number of bits set to true

    • clear

      public void clear()
      Clear any set bits and set size in bits back to 0
      Specified by:
      clear in interface BitmapStorage

    • clone

      public EWAHCompressedBitmap clone() throws CloneNotSupportedException
      Overrides:
      clone in class Object
      Throws:
      CloneNotSupportedException

    • serialize

      public void serialize​(DataOutput out) throws IOException
      Serialize. The current bitmap is not modified.
      Parameters:
      out - the DataOutput stream
      Throws:
      IOException - Signals that an I/O exception has occurred.

    • deserialize

      public void deserialize​(DataInput in) throws IOException
      Deserialize.
      Parameters:
      in - the DataInput stream
      Throws:
      IOException - Signals that an I/O exception has occurred.

    • equals

      public boolean equals​(Object o)
      Check to see whether the two compressed bitmaps contain the same set bits.
      Overrides:
      equals in class Object
      See Also:
      Object.equals(java.lang.Object)

    • getEWAHIterator

      public EWAHIterator getEWAHIterator()
      Gets an EWAHIterator over the data. This is a customized iterator which iterates over run length words. For experts only. The current bitmap is not modified.
      Returns:
      the EWAHIterator

    • getIteratingRLW

      public IteratingRLW getIteratingRLW()
      Gets an IteratingRLW to iterate over the data. For experts only. Note that iterator does not know about the size in bits of the bitmap: the size in bits is effectively rounded up to the nearest multiple of 64. However, if you materialize a bitmap from an iterator, you can set the desired size in bits using the setSizeInBitsWithinLastWord methods: EWAHCompressedBitmap n = IteratorUtil.materialize(bitmap.getIteratingRLW())); n.setSizeInBitsWithinLastWord(bitmap.sizeInBits()); The current bitmap is not modified.
      Returns:
      the IteratingRLW iterator corresponding to this bitmap

    • getPositions

      @Deprecated public List<Integer> getPositions()
      Deprecated.
      use toList() instead.
      Returns:
      a list

    • toList

      public List<Integer> toList()
      Gets the locations of the true values as one list. (May use more memory than iterator().) The current bitmap is not modified. API change: prior to version 0.8.3, this method was called getPositions.
      Returns:
      the positions in a list

    • hashCode

      public int hashCode()
      Returns a customized hash code (based on Karp-Rabin). Naturally, if the bitmaps are equal, they will hash to the same value. The current bitmap is not modified.
      Overrides:
      hashCode in class Object

    • intersects

      public boolean intersects​(EWAHCompressedBitmap a)
      Return true if the two EWAHCompressedBitmap have both at least one true bit in the same position. Equivalently, you could call "and" and check whether there is a set bit, but intersects will run faster if you don't need the result of the "and" operation. The current bitmap is not modified.
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      whether they intersect
      Since:
      0.3.2

    • intIterator

      public IntIterator intIterator()
      Iterator over the set bits (this is what most people will want to use to browse the content if they want an iterator). The location of the set bits is returned, in increasing order. The current bitmap is not modified.
      Returns:
      the int iterator

    • reverseIntIterator

      public IntIterator reverseIntIterator()
      Iterator over the set bits in reverse order. The current bitmap is not modified.
      Returns:
      the int iterator

    • isEmpty

      public boolean isEmpty()
      Checks whether this bitmap is empty (has a cardinality of zero).
      Returns:
      true if no bit is set

    • clearIntIterator

      public IntIterator clearIntIterator()
      Iterator over the clear bits. The location of the clear bits is returned, in increasing order. The current bitmap is not modified.
      Returns:
      the int iterator

    • chunkIterator

      public ChunkIterator chunkIterator()
      Iterator over the chunk of bits. The current bitmap is not modified.
      Returns:
      the chunk iterator

    • iterator

      public Iterator<Integer> iterator()
      Iterates over the positions of the true values. This is similar to intIterator(), but it uses Java generics. The current bitmap is not modified.
      Specified by:
      iterator in interface Iterable<Integer>
      Returns:
      the iterator

    • not

      public void not()
      Negate (bitwise) the current bitmap. To get a negated copy, do EWAHCompressedBitmap x= ((EWAHCompressedBitmap) mybitmap.clone()); x.not(); The running time is proportional to the compressed size (as reported by sizeInBytes()). Because this modifies the bitmap, this method is not thread-safe.
      Specified by:
      not in interface LogicalElement<EWAHCompressedBitmap>

    • or

      public EWAHCompressedBitmap or​(EWAHCompressedBitmap a)
      Returns a new compressed bitmap containing the bitwise OR values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.
      Specified by:
      or in interface LogicalElement<EWAHCompressedBitmap>
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the EWAH compressed bitmap

    • orToContainer

      public void orToContainer​(EWAHCompressedBitmap a, BitmapStorage container)
      Computes the bitwise or between the current bitmap and the bitmap "a". Stores the result in the container. The current bitmap is not modified. The content of the container is overwritten.
      Parameters:
      a - the other bitmap (it will not be modified)
      container - where we store the result
      Since:
      0.4.0

    • orCardinality

      public int orCardinality​(EWAHCompressedBitmap a)
      Returns the cardinality of the result of a bitwise OR of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the cardinality
      Since:
      0.4.0

    • readExternal

      public void readExternal​(ObjectInput in) throws IOException, ClassNotFoundException
      Specified by:
      readExternal in interface Externalizable
      Throws:
      IOException
      ClassNotFoundException

    • writeExternal

      public void writeExternal​(ObjectOutput out) throws IOException
      Specified by:
      writeExternal in interface Externalizable
      Throws:
      IOException

    • serializedSizeInBytes

      public int serializedSizeInBytes()
      Report the number of bytes required to serialize this bitmap The current bitmap is not modified.
      Returns:
      the size in bytes

    • get

      public boolean get​(int i)
      Query the value of a single bit. Relying on this method when speed is needed is discouraged. The complexity is linear with the size of the bitmap. (This implementation is based on zhenjl's Go version of JavaEWAH.) The current bitmap is not modified.
      Parameters:
      i - the bit we are interested in
      Returns:
      whether the bit is set to true

    • getFirstSetBit

      public int getFirstSetBit()
      getFirstSetBit is a light-weight method that returns the location of the set bit (=1) or -1 if there is none.
      Returns:
      location of the first set bit or -1

    • clear

      public boolean clear​(int i)
      Set the bit at position i to false. Though you can clear the bits in any order (e.g., clear(100), clear(10), clear(1), you will typically get better performance if you clear the bits in increasing order (e.g., clear(1), clear(10), clear(100)). Clearing a bit that is larger than the biggest bit is a constant time operation. Clearing a bit that is smaller than the biggest bit can require time proportional to the compressed size of the bitmap, as the bitmap may need to be rewritten. Since this modifies the bitmap, this method is not thread-safe.
      Parameters:
      i - the index
      Returns:
      true if the value was unset
      Throws:
      IndexOutOfBoundsException - if i is negative or greater than Integer.MAX_VALUE - 64

    • set

      public boolean set​(int i)
      Set the bit at position i to true. Though you can set the bits in any order (e.g., set(100), set(10), set(1), you will typically get better performance if you set the bits in increasing order (e.g., set(1), set(10), set(100)). Setting a bit that is larger than any of the current set bit is a constant time operation. Setting a bit that is smaller than an already set bit can require time proportional to the compressed size of the bitmap, as the bitmap may need to be rewritten. Since this modifies the bitmap, this method is not thread-safe.
      Parameters:
      i - the index
      Returns:
      true if the value was set
      Throws:
      IndexOutOfBoundsException - if i is negative or greater than Integer.MAX_VALUE - 64

    • setSizeInBitsWithinLastWord

      public void setSizeInBitsWithinLastWord​(int size)
      Description copied from interface: BitmapStorage
      Sets the size in bits of the bitmap as an *uncompressed* bitmap. Normally, this is used to reduce the size of the bitmaps within the scope of the last word. Specifically, this means that (sizeInBits()+63)/64 must be equal to (size +63)/64. If needed, the bitmap can be further padded with zeroes.
      Specified by:
      setSizeInBitsWithinLastWord in interface BitmapStorage
      Parameters:
      size - the size in bits

    • setSizeInBits

      public boolean setSizeInBits​(int size, boolean defaultValue)
      Change the reported size in bits of the *uncompressed* bitmap represented by this compressed bitmap. It may change the underlying compressed bitmap. It is not possible to reduce the sizeInBits, but it can be extended. The new bits are set to false or true depending on the value of defaultValue. This method is not thread-safe.
      Parameters:
      size - the size in bits
      defaultValue - the default boolean value
      Returns:
      true if the update was possible

    • sizeInBits

      public int sizeInBits()
      Returns the size in bits of the *uncompressed* bitmap represented by this compressed bitmap. Initially, the sizeInBits is zero. It is extended automatically when you set bits to true. The current bitmap is not modified.
      Specified by:
      sizeInBits in interface LogicalElement<EWAHCompressedBitmap>
      Returns:
      the size in bits

    • sizeInBytes

      public int sizeInBytes()
      Report the *compressed* size of the bitmap (equivalent to memory usage, after accounting for some overhead).
      Specified by:
      sizeInBytes in interface LogicalElement<EWAHCompressedBitmap>
      Returns:
      the size in bytes

    • threshold

      public static EWAHCompressedBitmap threshold​(int t, EWAHCompressedBitmap... bitmaps)
      Compute a Boolean threshold function: bits are true where at least t bitmaps have a true bit.
      Parameters:
      t - the threshold
      bitmaps - input data
      Returns:
      the aggregated bitmap
      Since:
      0.8.1

    • thresholdWithContainer

      public static void thresholdWithContainer​(BitmapStorage container, int t, EWAHCompressedBitmap... bitmaps)
      Compute a Boolean threshold function: bits are true where at least T bitmaps have a true bit. The content of the container is overwritten.
      Parameters:
      t - the threshold
      bitmaps - input data
      container - where we write the aggregated bitmap
      Since:
      0.8.1

    • toArray

      public int[] toArray()
      Populate an array of (sorted integers) corresponding to the location of the set bits.
      Returns:
      the array containing the location of the set bits

    • toDebugString

      public String toDebugString()
      A more detailed string describing the bitmap (useful for debugging). A JSON output is produced.
      Returns:
      the string

    • toString

      public String toString()
      A string describing the bitmap.
      Overrides:
      toString in class Object
      Returns:
      the string

    • swap

      public void swap​(EWAHCompressedBitmap other)
      Swap the content of the bitmap with another.
      Parameters:
      other - bitmap to swap with

    • trim

      public void trim()
      Reduce the internal buffer to its minimal allowable size. This can free memory.

    • xor

      public EWAHCompressedBitmap xor​(EWAHCompressedBitmap a)
      Returns a new compressed bitmap containing the bitwise XOR values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.
      Specified by:
      xor in interface LogicalElement<EWAHCompressedBitmap>
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the EWAH compressed bitmap

    • xorToContainer

      public void xorToContainer​(EWAHCompressedBitmap a, BitmapStorage container)
      Computes a new compressed bitmap containing the bitwise XOR values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). The current bitmap is not modified. The content of the container is overwritten.
      Parameters:
      a - the other bitmap (it will not be modified)
      container - where we store the result
      Since:
      0.4.0

    • xorCardinality

      public int xorCardinality​(EWAHCompressedBitmap a)
      Returns the cardinality of the result of a bitwise XOR of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the cardinality
      Since:
      0.4.0

    • compose

      public EWAHCompressedBitmap compose​(EWAHCompressedBitmap a)
      Returns a new compressed bitmap containing the composition of the current bitmap with some other bitmap. The composition A.compose(B) is defined as follows: we retain the ith set bit of A only if the ith bit of B is set. For example, if you have the following bitmap A = { 0, 1, 0, 1, 1, 0 } and want to keep only the second and third ones, you can call A.compose(B) with B = { 0, 1, 1 } and you will get C = { 0, 0, 0, 1, 1, 0 }. If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.
      Specified by:
      compose in interface LogicalElement<EWAHCompressedBitmap>
      Parameters:
      a - the other bitmap (it will not be modified)
      Returns:
      the EWAH compressed bitmap

    • composeToContainer

      public void composeToContainer​(EWAHCompressedBitmap a, EWAHCompressedBitmap container)
      Computes a new compressed bitmap containing the composition of the current bitmap with some other bitmap. The composition A.compose(B) is defined as follows: we retain the ith set bit of A only if the ith bit of B is set. For example, if you have the following bitmap A = { 0, 1, 0, 1, 1, 0 } and want to keep only the second and third ones, you can call A.compose(B) with B = { 0, 1, 1 } and you will get C = { 0, 0, 0, 1, 1, 0 }. The current bitmap is not modified. The content of the container is overwritten.
      Parameters:
      a - the other bitmap (it will not be modified)
      container - where we store the result

    • andWithContainer

      public static void andWithContainer​(BitmapStorage container, EWAHCompressedBitmap... bitmaps)
      For internal use. Computes the bitwise and of the provided bitmaps and stores the result in the container. The content of the container is overwritten.
      Parameters:
      container - where the result is stored
      bitmaps - bitmaps to AND
      Since:
      0.4.3

    • and

      public static EWAHCompressedBitmap and​(EWAHCompressedBitmap... bitmaps)
      Returns a new compressed bitmap containing the bitwise AND values of the provided bitmaps. It may or may not be faster than doing the aggregation two-by-two (A.and(B).and(C)). If only one bitmap is provided, it is returned as is. If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage.
      Parameters:
      bitmaps - bitmaps to AND together
      Returns:
      result of the AND
      Since:
      0.4.3

    • andCardinality

      public static int andCardinality​(EWAHCompressedBitmap... bitmaps)
      Returns the cardinality of the result of a bitwise AND of the values of the provided bitmaps. Avoids allocating an intermediate bitmap to hold the result of the AND.
      Parameters:
      bitmaps - bitmaps to AND
      Returns:
      the cardinality
      Since:
      0.4.3

    • bitmapOf

      public static EWAHCompressedBitmap bitmapOf​(int... setBits)
      Return a bitmap with the bit set to true at the given positions. The positions should be given in sorted order. (This is a convenience method.)
      Parameters:
      setBits - list of set bit positions
      Returns:
      the bitmap
      Since:
      0.4.5

    • orWithContainer

      public static void orWithContainer​(BitmapStorage container, EWAHCompressedBitmap... bitmaps)
      Uses an adaptive technique to compute the logical OR. Mostly for internal use. The content of the container is overwritten.
      Parameters:
      container - where the aggregate is written.
      bitmaps - to be aggregated

    • xorWithContainer

      public static void xorWithContainer​(BitmapStorage container, EWAHCompressedBitmap... bitmaps)
      Uses an adaptive technique to compute the logical XOR. Mostly for internal use. The content of the container is overwritten.
      Parameters:
      container - where the aggregate is written.
      bitmaps - to be aggregated

    • or

      public static EWAHCompressedBitmap or​(EWAHCompressedBitmap... bitmaps)
      Returns a new compressed bitmap containing the bitwise OR values of the provided bitmaps. This is typically faster than doing the aggregation two-by-two (A.or(B).or(C).or(D)). If only one bitmap is provided, it is returned as is. If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage.
      Parameters:
      bitmaps - bitmaps to OR together
      Returns:
      result of the OR
      Since:
      0.4.0

    • xor

      public static EWAHCompressedBitmap xor​(EWAHCompressedBitmap... bitmaps)
      Returns a new compressed bitmap containing the bitwise XOR values of the provided bitmaps. This is typically faster than doing the aggregation two-by-two (A.xor(B).xor(C).xor(D)). If only one bitmap is provided, it is returned as is. If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage.
      Parameters:
      bitmaps - bitmaps to XOR together
      Returns:
      result of the XOR

    • orCardinality

      public static int orCardinality​(EWAHCompressedBitmap... bitmaps)
      Returns the cardinality of the result of a bitwise OR of the values of the provided bitmaps. Avoids allocating an intermediate bitmap to hold the result of the OR.
      Parameters:
      bitmaps - bitmaps to OR
      Returns:
      the cardinality
      Since:
      0.4.0

    • shift

      public EWAHCompressedBitmap shift​(int b)
      Generates a new bitmap shifted by "b" bits. If b is positive, the position of all set bits is increased by b. The negative case is not supported.
      Parameters:
      b - number of bits
      Returns:
      new shifted bitmap