src.it.unimi.dsi.bits.BitVector Maven / Gradle / Ivy
Show all versions of dsiutils Show documentation
package it.unimi.dsi.bits;
/*
* DSI utilities
*
* Copyright (C) 2007-2018 Sebastiano Vigna
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at your option)
* any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, see This interface define several operations on finite sequences of bits.
* Efficient implementations, such as {@link LongArrayBitVector},
* use approximately one bit of memory for each bit in the vector, but this is not enforced.
*
*
Operation of a bit vector are partially of boolean nature
* (e.g., logical operations between vectors),
* partially of language-theoretical nature (e.g., concatenation), and
* partially of set-theoretical nature (e.g., asking which bits are set to one).
* To accomodate all these points of view, this interface extends
* {@link it.unimi.dsi.fastutil.booleans.BooleanBigList}, but also provides an
* {@link #asLongSet()} method that exposes a {@link java.util.BitSet}-like view
* and a {@link #asLongBigList(int)} method that provides integer-like access to
* blocks of bits of given width.
*
*
Most, if not all, classical operations on bit vectors can be seen as standard
* operations on these two views: for instance, the number of bits set to one is just
* the number of elements of the set returned by {@link #asLongSet()} (albeit a direct {@link #count()} method
* is provided, too). The standard {@link java.util.Collection#addAll(java.util.Collection)} method
* can be used to concatenate bit vectors, and {@linkplain it.unimi.dsi.fastutil.booleans.BooleanBigList#subList(long, long) sublist views}
* make it easy performing any kind of logical operation on subvectors.
*
*
The only caveat is that sometimes the standard interface naming clashes slightly
* with standard usage: for instance, {@link #clear()} will not set to zero
* all bits (use {@link #fill(int) fill(0)} for that purpose), but rather will set the
* vector length to zero. Also, {@link #add(long, int)} will not add logically a value at
* the specified index, but rather will insert a new bit with the specified value at the specified
* position.
*
*
To increase clarity, this interface provides methods {@link #length()} and {@link #length(long)}
* which have a semantics similar to {@link #size64()} and {@link #size(long)}.
*
*
The {@link AbstractBitVector} class provides a fairly complete
* abstract implementation that provides all methods except for the most
* basic operations. Of course, the methods of {@link AbstractBitVector} are
* sometimes very inefficient, but implementations such as {@link LongArrayBitVector}
* have their own optimised implementations.
*/
public interface BitVector extends RandomAccess, BooleanBigList {
/** Sets a bit in this bit vector (optional operation).
* @param index the index of a bit.
*/
void set(long index);
/** Clears a bit in this bit vector (optional operation).
* @param index the index of a bit.
*/
void clear(long index);
/** Flips a bit in this bit vector (optional operation).
* @param index the index of a bit.
*/
void flip(long index);
/** Fills a range of bits in this bit vector (optional operation).
* @param from the first index (inclusive).
* @param to the last index (not inclusive).
* @param value the value (true or false).
*/
void fill(long from, long to, boolean value);
/** Clears a range of bits in this bit vector (optional operation).
* @param from the first index (inclusive).
* @param to the last index (not inclusive).
* @param value the value (zero or nonzero).
*/
void fill(long from, long to, int value);
/** Sets all bits this bit vector to the given boolean value (optional operation).
* @param value the value (true or false).
*/
void fill(boolean value);
/** Sets all bits this bit vector to the given integer value (optional operation).
* @param value the value (zero or nonzero).
*/
void fill(int value);
/** Flips a range of bits in this bit vector (optional operation).
* @param from the first index (inclusive).
* @param to the last index (not inclusive).
*/
void flip(long from, long to);
/** Flips all bits in this bit vector (optional operation). */
void flip();
/** Replaces the content of this bit vector with another bit vector.
*
* @param bitVector a bit vector.
* @return this bit vector.
*/
BitVector replace(BitVector bitVector);
/** Returns a subvector view specified by initial and final index.
*
*
The object returned by this method is a bit vector representing a view of this
* bit vector restricted to the given indices. Changes to the subvector
* will be reflected in the main vector.
*
* @param from the first index (inclusive).
* @param to the last index (not inclusive).
*/
BitVector subVector(long from, long to);
/** Returns a subvector view specified by initial index and running up to the end of this vector.
*
* @param from the first index (inclusive).
* @see #subVector(long, long)
*/
BitVector subVector(long from);
/** Returns a view of this bit vector as a sorted set of long integers.
*
*
More formally, this bit vector is infinitely extended to the
* left with zeros (e.g., all bits beyond {@link #length(long)} are
* considered zeroes). The resulting infinite string is interpreted as the
* characteristic function of a set of integers.
*
*
Note that, in particular, the resulting string representation is
* exactly that of a {@link java.util.BitSet}.
*
*/
LongSortedSet asLongSet();
/** Returns a view of this bit vector as a list of nonnegative integers of specified width.
*
*
More formally, {@link LongBigList#getLong(long) getLong(p)} will return
* the nonnegative integer defined by the bits starting at p * width (bit 0, inclusive)
* and ending at (p + 1) * width (bit width − 1, exclusive).
*/
LongBigList asLongBigList(int width);
/** Returns the value of the specified bit as an integer.
*
*
This method is a useful synonym for {@link #getBoolean(long)}.
*
* @param index the index of a bit.
* @return the value of the specified bit as an integer (0 or 1).
*/
int getInt(long index);
/** Returns the specified bit range as a long.
*
*
Note that bit 0 of the returned long will be bit from
* of this bit vector.
*
*
Implementations are invited to provide high-speed implementations for
* the case in which from is a multiple of {@link Long#SIZE}
* and to is from + {@link Long#SIZE} (or less,
* in case the vector length is exceeded). This behaviour make it possible to
* implement high-speed hashing, copies, etc.
*
* @param from the starting bit (inclusive).
* @param to the ending bit (exclusive).
* @return the long value contained in the specified bits.
*/
long getLong(long from, long to);
/** Sets the value of the specified bit as an integer (optional operation).
*
*
This method is a useful synonym for {@link #set(long, boolean)}.
*
* @param index the index of a bit.
* @param value the new value (any nonzero integer for setting the bit, zero for clearing the bit).
*/
void set(long index, int value);
/** Adds a bit with specified integer value at the specified index (optional operation).
*
*
This method is a useful synonym for {@link #add(long, boolean)}.
*
* @param index the index of a bit.
* @param value the value that will be inserted at position index (any nonzero integer for a true bit, zero for a false bit).
*/
void add(long index, int value);
/** Adds a bit with specified value at the end of this bit vector.
*
*
This method is a useful synonym for {@link BooleanList#add(boolean)}.
*
* @param value the new value (any nonzero integer for a true bit, zero for a false bit).
*/
void add(int value);
/** Appends the less significant bits of a long integer to this bit vector.
*
* @param value a value to be appended
* @param k the number of less significant bits to be added to this bit vector.
* @return this bit vector.
*/
BitVector append(long value, int k);
/** Appends another bit vector to this bit vector.
*
* @param bitVector a bit vector to be appended.
* @return this bit vector.
*/
BitVector append(BitVector bitVector);
/** Returns the number of bits in this bit vector.
*
*
If the number of bits in this vector is smaller than or equal to {@link Integer#MAX_VALUE}, this
* method is semantically equivalent to {@link List#size()}. In any case, this method is semantically
* equivalent to {@link BooleanBigList#size64()}, but it is prefererred.
*
* @return the number of bits in this bit vector.
*/
long length();
/** Sets the number of bits in this bit vector.
*
*
It is expected that this method will try to allocate exactly
* the necessary space.
*
*
If the argument fits an integer, this
* method has the same side effects of {@link BooleanList#size(int)}.
* In any case, this method has the same side effects of
* {@link BooleanBigList#size(long)}, but it is preferred,
* as it has the advantage of returning this bit vector,
* thus making it possible to chain methods.
*
* @return this bit vector.
*/
BitVector length(long newLength);
/** Counts the number of bits set to true in this bit vector.
*
* @return the number of bits set to true in this bit vector.
*/
long count();
/** Performs a logical and between this bit vector and another one, leaving the result in this vector.
*
* @param v a bit vector.
* @return this bit vector.
*/
BitVector and(BitVector v);
/** Performs a logical or between this bit vector and another one, leaving the result in this vector.
*
* @param v a bit vector.
* @return this bit vector.
*/
BitVector or(BitVector v);
/** Performs a logical xor between this bit vector and another one, leaving the result in this vector.
*
* @param v a bit vector.
* @return this bit vector.
*/
BitVector xor(BitVector v);
/** Returns the position of the first bit set in this vector.
*
* @return the first bit set, or -1 for a vector of zeroes.
*/
long firstOne();
/** Returns the position of the last bit set in this vector.
*
* @return the last bit set, or -1 for a vector of zeroes.
*/
long lastOne();
/** Returns the position of the first bit set after the given position.
*
* @return the first bit set after position index (inclusive), or -1 if no such bit exists.
*/
long nextOne(long index);
/** Returns the position of the first bit set before or at the given position.
*
* @return the first bit set before or at the given position, or -1 if no such bit exists.
*/
long previousOne(long index);
/** Returns the position of the first bit unset in this vector.
*
* @return the first bit unset, or -1 for a vector of ones.
*/
long firstZero();
/** Returns the position of the last bit unset in this vector.
*
* @return the last bit unset, or -1 for a vector of ones.
*/
long lastZero();
/** Returns the position of the first bit unset after the given position.
*
* @return the first bit unset after position index (inclusive), or -1 if no such bit exists.
*/
long nextZero(long index);
/** Returns the position of the first bit unset before or at the given position.
*
* @return the first bit unset before or at the given position, or -1 if no such bit exists.
*/
long previousZero(long index);
/** Returns the length of the greatest common prefix between this and the specified vector.
*
* @param v a bit vector.
* @return the length of the greatest common prefix.
*/
long longestCommonPrefixLength(BitVector v);
/** Returns true if this vector is a prefix of the specified vector.
*
* @param v a bit vector.
* @return true if this vector is a prefix of v.
*/
boolean isPrefix(BitVector v);
/** Returns true if this vector is a proper prefix of the specified vector.
*
* @param v a bit vector.
* @return true if this vector is a proper prefix of v (i.e., it is a prefix but not equal).
*/
boolean isProperPrefix(BitVector v);
/** Checks for equality with a segment of another vector.
*
* @param v a bit vector.
* @param from the starting bit, inclusive.
* @param to the ending bit, not inclusive.
* @return true if this vector and v are equal in the range of positions [from..to).
*/
boolean equals(final BitVector v, final long from, final long to);
/** Returns a copy of a part of this bit vector.
*
* @param from the starting bit, inclusive.
* @param to the ending bit, not inclusive.
* @return a copy of the part of this bit vector going from bit from (inclusive) to bit to
* (not inclusive)
*/
BitVector copy(long from, long to);
/** Returns a copy of this bit vector.
*
* @return a copy of this bit vector.
*/
BitVector copy();
/** Returns the bits in this bit vector as an array of longs, not to be modified.
*
* @return an array of longs whose first {@link #length()} bits contain the bits of
* this bit vector. The array cannot be modified.
*/
long[] bits();
/** Returns a hash code for this bit vector.
*
*
Hash codes for bit vectors are defined as follows:
*
*
* final long length = length();
* long fullLength = length - length % Long.SIZE;
* long h = 0x9e3779b97f4a7c13L ^ length;
* for(long i = 0; i < fullLength; i += Long.SIZE) h ^= (h << 5) + getLong(i, i + Long.SIZE) + (h >>> 2);
* if (length != fullLength) h ^= (h << 5) + getLong(fullLength, length) + (h >>> 2);
* (int)((h >>> 32) ^ h);
*
*
* The last value is the hash code of the bit vector. This hashing is based on shift-add-xor hashing
* (M.V. Ramakrishna and Justin Zobel, “Performance in practice of string hashing functions”,
* Proc. of the Fifth International Conference on Database Systems for Advanced Applications, 1997, pages 215−223).
*
*
The returned value is not a high-quality hash such as
* Jenkins's,
* but it can be computed very quickly; in any case, 32 bits are too few for a high-quality hash to be used in large-scale applications.
*
*
Important: all bit vector implementations are required to return the value defined here.
* The simplest way to obtain this result is to subclass {@link AbstractBitVector}.
*
* @return a hash code for this bit vector.
*/
@Override
int hashCode();
/** Returns a fast version of this bit vector.
*
*
Different implementations of this interface might provide different level of efficiency.
* For instance, views on other data structures (e.g., strings) might implement
* {@link #getLong(long, long)} efficiently on multiples of {@link Long#SIZE}, but might
* fail to provide a generic, truly efficient random access.
*
*
This method returns a (possibly immutable) bit vector with the same content as
* that of this bit vector. However, the returned bit vector is guaranteed to provide fast random access.
*
* @return a fast version of this bit vector.
*/
BitVector fast();
/** {@inheritDoc}
* @deprecated Please use {@link #size64()} instead. */
@Deprecated
@Override
default int size() {
return (int) Math.min(Integer.MAX_VALUE, size64());
}
}