cern.colt.bitvector
Class BitMatrix

java.lang.Object
  cern.colt.PersistentObject
      cern.colt.bitvector.BitMatrix

All Implemented Interfaces:

Cloneable, Serializable

public class BitMatrix

extends PersistentObject

Fixed sized (non resizable) n*m bit matrix. A bit matrix has a number of columns and rows, which are assigned upon instance construction - The matrix's size is then columns()*rows(). Bits are accessed via (column,row) coordinates.

Individual bits can be examined, set, or cleared. Rectangular parts (boxes) can quickly be extracted, copied and replaced. Quick iteration over boxes is provided by optimized internal iterators (forEach() methods). One BitMatrix may be used to modify the contents of another BitMatrix through logical AND, OR, XOR and other similar operations.

Legal coordinates range from [0,0] to [columns()-1,rows()-1]. Any attempt to access a bit at a coordinate column<0 || column>=columns() || row<0 || row>=rows() will throw an IndexOutOfBoundsException. Operations involving two bit matrices (like AND, OR, XOR, etc.) will throw an IllegalArgumentException if both bit matrices do not have the same number of columns and rows.

If you need extremely quick access to individual bits: Although getting and setting individual bits with methods get(...) and put(...) is quick, it is even quicker (but not safe) to use getQuick(...) and putQuick(...).

Note that this implementation is not synchronized.

Version:

1.0, 09/24/99

See Also:

BitVector, QuickBitVector, BitSet, Serialized Form

BitMatrix

public BitMatrix(int columns,
                 int rows)

Constructs a bit matrix with a given number of columns and rows. All bits are initially false.

Parameters:

columns - the number of columns the matrix shall have.

rows - the number of rows the matrix shall have.

Throws:

IllegalArgumentException - if columns < 0 || rows < 0.

and

public void and(BitMatrix other)

Performs a logical AND of the receiver with another bit matrix. The receiver is modified so that a bit in it has the value true if and only if it already had the value true and the corresponding bit in the other bit matrix argument has the value true.

Parameters:

other - a bit matrix.

Throws:

IllegalArgumentException - if columns() != other.columns() || rows() != other.rows().

andNot

public void andNot(BitMatrix other)

Clears all of the bits in receiver whose corresponding bit is set in the other bit matrix. In other words, determines the difference (A\B) between two bit matrices.

Parameters:

other - a bit matrix with which to mask the receiver.

Throws:

IllegalArgumentException - if columns() != other.columns() || rows() != other.rows().

cardinality

public int cardinality()

Returns the number of bits currently in the true state. Optimized for speed. Particularly quick if the receiver is either sparse or dense.

clear

public void clear()

Clears all bits of the receiver.

clone

public Object clone()

Cloning this BitMatrix produces a new BitMatrix that is equal to it. The clone of the bit matrix is another bit matrix that has exactly the same bits set to true as this bit matrix and the same number of columns and rows.

Overrides:

clone in class PersistentObject

Returns:

a clone of this bit matrix.

columns

public int columns()

Returns the number of columns of the receiver.

copy

public BitMatrix copy()

Returns a shallow clone of the receiver; calls clone() and casts the result.

Returns:

a shallow clone of the receiver.

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 BitMatrix object that has the same number of columns and rows as the receiver and that has exactly the same bits set to true as the receiver.

Parameters:

obj - the object to compare with.

Returns:

true if the objects are the same; false otherwise.

forEachCoordinateInState

public boolean forEachCoordinateInState(boolean state,
                                        IntIntProcedure procedure)

Applies a procedure to each coordinate that holds a bit in the given state. Iterates rowwise downwards from [columns()-1,rows()-1] to [0,0]. Useful, for example, if you want to copy bits into an image or somewhere else. Optimized for speed. Particularly quick if one of the following conditions holds

• state==true and the receiver is sparse (cardinality() is small compared to size()).
• state==false and the receiver is dense (cardinality() is large compared to size()).

Parameters:

state - element to search for.

procedure - a procedure object taking as first argument the current column and as second argument the current row. Stops iteration if the procedure returns false, otherwise continues.

Returns:

false if the procedure stopped before all elements where iterated over, true otherwise.

get

public boolean get(int column,
                   int row)

Returns from the receiver the value of the bit at the specified coordinate. The value is true if this bit is currently set; otherwise, returns false.

Parameters:

column - the index of the column-coordinate.

row - the index of the row-coordinate.

Returns:

the value of the bit at the specified coordinate.

Throws:

IndexOutOfBoundsException - if column<0 || column>=columns() || row<0 || row>=rows()

getQuick

public boolean getQuick(int column,
                        int row)

Returns from the receiver the value of the bit at the specified coordinate; WARNING: Does not check preconditions. The value is true if this bit is currently set; otherwise, returns false.

Provided with invalid parameters this method may return invalid values without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): column>=0 && column<columns() && row>=0 && row<rows().

Parameters:

column - the index of the column-coordinate.

row - the index of the row-coordinate.

Returns:

the value of the bit at the specified coordinate.

hashCode

public int hashCode()

Returns a hash code value for the receiver.

not

public void not()

Performs a logical NOT on the bits of the receiver.

or

public void or(BitMatrix other)

Performs a logical OR of the receiver with another bit matrix. The receiver 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 other bit matrix argument has the value true.

Parameters:

other - a bit matrix.

Throws:

IllegalArgumentException - if columns() != other.columns() || rows() != other.rows().

part

public BitMatrix part(int column,
                      int row,
                      int width,
                      int height)

Constructs and returns a new matrix with width columns and height rows which is a copy of the contents of the given box. The box ranges from [column,row] to [column+width-1,row+height-1], all inclusive.

Parameters:

column - the index of the column-coordinate.

row - the index of the row-coordinate.

width - the width of the box.

height - the height of the box.

Throws:

IndexOutOfBoundsException - if column<0 || column+width>columns() || row<0 || row+height>rows()

put

public void put(int column,
                int row,
                boolean value)

Sets the bit at the specified coordinate to the state specified by value.

Parameters:

column - the index of the column-coordinate.

row - the index of the row-coordinate.

value - the value of the bit to be copied into the specified coordinate.

Throws:

IndexOutOfBoundsException - if column<0 || column>=columns() || row<0 || row>=rows()

putQuick

public void putQuick(int column,
                     int row,
                     boolean value)

Sets the bit at the specified coordinate to the state specified by value; WARNING: Does not check preconditions.

Provided with invalid parameters this method may return invalid values without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): column>=0 && column<columns() && row>=0 && row<rows().

Parameters:

column - the index of the column-coordinate.

row - the index of the row-coordinate.

value - the value of the bit to be copied into the specified coordinate.

replaceBoxWith

public void replaceBoxWith(int column,
                           int row,
                           int width,
                           int height,
                           BitMatrix source,
                           int sourceColumn,
                           int sourceRow)

Replaces a box of the receiver with the contents of another matrix's box. The source box ranges from [sourceColumn,sourceRow] to [sourceColumn+width-1,sourceRow+height-1], all inclusive. The destination box ranges from [column,row] to [column+width-1,row+height-1], all inclusive. Does nothing if width <= 0 || height <= 0. If source==this and the source and destination box intersect in an ambiguous way, then replaces as if using an intermediate auxiliary copy of the receiver.

Parameters:

column - the index of the column-coordinate.

row - the index of the row-coordinate.

width - the width of the box.

height - the height of the box.

source - the source matrix to copy from(may be identical to the receiver).

sourceColumn - the index of the source column-coordinate.

sourceRow - the index of the source row-coordinate.

Throws:

IndexOutOfBoundsException - if column<0 || column+width>columns() || row<0 || row+height>rows()

IndexOutOfBoundsException - if sourceColumn<0 || sourceColumn+width>source.columns() || sourceRow<0 || sourceRow+height>source.rows()

replaceBoxWith

public void replaceBoxWith(int column,
                           int row,
                           int width,
                           int height,
                           boolean value)

Sets the bits in the given box to the state specified by value. The box ranges from [column,row] to [column+width-1,row+height-1], all inclusive. (Does nothing if width <= 0 || height <= 0).

Parameters:

column - the index of the column-coordinate.

row - the index of the row-coordinate.

width - the width of the box.

height - the height of the box.

value - the value of the bit to be copied into the bits of the specified box.

Throws:

IndexOutOfBoundsException - if column<0 || column+width>columns() || row<0 || row+height>rows()

rows

public int rows()

Returns the number of rows of the receiver.

size

public int size()

Returns the size of the receiver which is columns()*rows().

toBitVector

public BitVector toBitVector()

Converts the receiver to a bitvector. In many cases this method only makes sense on one-dimensional matrices. WARNING: The returned bitvector and the receiver share the same backing bits. Modifying either of them will affect the other. If this behaviour is not what you want, you should first use copy() to make sure both objects use separate internal storage.

toString

public String toString()

Returns a (very crude) string representation of the receiver.

xor

public void xor(BitMatrix other)

Performs a logical XOR of the receiver with another bit matrix. The receiver 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:

other - a bit matrix.

Throws:

IllegalArgumentException - if columns() != other.columns() || rows() != other.rows().