Regina Calculation Engine
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regina::NBitmask2< T, U > Class Template Reference

A small but extremely fast bitmask class that can store up to 8 * sizeof(T) + 8 * sizeof(U) true-or-false bits. More...

#include <utilities/nbitmask.h>

Public Member Functions

 NBitmask2 ()
 Creates a new bitmask with all bits set to false. More...
 
 NBitmask2 (size_t)
 Creates a new bitmask with all bits set to false. More...
 
 NBitmask2 (const NBitmask2< T, U > &cloneMe)
 Creates a clone of the given bitmask. More...
 
void reset ()
 Sets all bits of this bitmask to false. More...
 
void reset (size_t)
 Sets all bits of this bitmask to false. More...
 
NBitmask2< T, U > & operator= (const NBitmask2< T, U > &other)
 Sets this bitmask to a copy of the given bitmask. More...
 
void truncate (size_t numBits)
 Leaves the first numBits bits of this bitmask intact, but sets all subsequent bits to false. More...
 
bool get (size_t index) const
 Returns the value of the given bit of this bitmask. More...
 
void set (size_t index, bool value)
 Sets the given bit of this bitmask to the given value. More...
 
template<typename ForwardIterator >
void set (ForwardIterator indexBegin, ForwardIterator indexEnd, bool value)
 Sets all bits in the given sorted list to the given value. More...
 
NBitmask2< T, U > & operator&= (const NBitmask2< T, U > &other)
 Sets this to the intersection of this and the given bitmask. More...
 
NBitmask2< T, U > & operator|= (const NBitmask2< T, U > &other)
 Sets this to the union of this and the given bitmask. More...
 
NBitmask2< T, U > & operator^= (const NBitmask2< T, U > &other)
 Sets this to the exclusive disjunction (XOR) of this and the given bitmask. More...
 
NBitmask2< T, U > & operator-= (const NBitmask2< T, U > &other)
 Sets this to the set difference of this and the given bitmask. More...
 
void flip ()
 Negates every bit in this bitmask. More...
 
bool operator== (const NBitmask2< T, U > &other) const
 Determines whether this and the given bitmask are identical. More...
 
bool lessThan (const NBitmask2< T, U > &other) const
 Determines whether this bitmask appears strictly before the given bitmask when bitmasks are sorted in lexicographical order. More...
 
bool operator<= (const NBitmask2< T, U > &other) const
 Determines whether this bitmask is entirely contained within the given bitmask. More...
 
bool inUnion (const NBitmask2< T, U > &x, const NBitmask2< T, U > &y) const
 Determines whether this bitmask is entirely contained within the union of the two given bitmasks. More...
 
bool containsIntn (const NBitmask2< T, U > &x, const NBitmask2< T, U > &y) const
 Determines whether this bitmask contains the intersection of the two given bitmasks. More...
 
size_t bits () const
 Returns the number of bits currently set to true in this bitmask. More...
 
long firstBit () const
 Returns the index of the first true bit in this bitmask, or -1 if there are no true bits. More...
 
long lastBit () const
 Returns the index of the last true bit in this bitmask, or -1 if there are no true bits. More...
 
bool atMostOneBit () const
 Determines whether at most one bit is set to true in this bitmask. More...
 

Friends

template<typename X , typename Y >
std::ostream & operator<< (std::ostream &out, const NBitmask2< X, Y > &mask)
 

Detailed Description

template<typename T, typename U = T>
class regina::NBitmask2< T, U >

A small but extremely fast bitmask class that can store up to 8 * sizeof(T) + 8 * sizeof(U) true-or-false bits.

This bitmask packs all of the bits together into a single variable of type T and a single variable of type U. This means that operations on entire bitmasks are extremely fast, because all of the bits can be processed in just two "native" operations.

The downside of course is that the number of bits that can be stored is limited to 8 * sizeof(T) + 8 * sizeof(U), where T and U must be native unsigned integer types (such as unsigned char, unsigned int, or unsigned long long).

For an even faster bitmask class that can only store half as many bits, see NBitmask1. For a bitmask class that can store arbitrarily many bits, see NBitmask.

Precondition
Types T and U are unsigned integral numeric types.
Python:
Not present.

Constructor & Destructor Documentation

template<typename T , typename U = T>
regina::NBitmask2< T, U >::NBitmask2 ( )
inline

Creates a new bitmask with all bits set to false.

template<typename T , typename U = T>
regina::NBitmask2< T, U >::NBitmask2 ( size_t  )
inline

Creates a new bitmask with all bits set to false.

The integer argument is merely for compatibility with the NBitmask constructor, and will be ignored.

Warning
This is not a constructor that initialises the bitmask to a given pattern.
template<typename T , typename U = T>
regina::NBitmask2< T, U >::NBitmask2 ( const NBitmask2< T, U > &  cloneMe)
inline

Creates a clone of the given bitmask.

Parameters
cloneMethe bitmask to clone.

Member Function Documentation

template<typename T , typename U = T>
bool regina::NBitmask2< T, U >::atMostOneBit ( ) const
inline

Determines whether at most one bit is set to true in this bitmask.

If this bitmask is entirely false or if only one bit is set to true, then this routine will return true. Otherwise this routine will return false.

Returns
true if and only if at most one bit is set to true.
template<typename T , typename U = T>
size_t regina::NBitmask2< T, U >::bits ( ) const
inline

Returns the number of bits currently set to true in this bitmask.

Returns
the number of true bits.
template<typename T , typename U = T>
bool regina::NBitmask2< T, U >::containsIntn ( const NBitmask2< T, U > &  x,
const NBitmask2< T, U > &  y 
) const
inline

Determines whether this bitmask contains the intersection of the two given bitmasks.

For this routine to return true, every bit that is set in both x and y must be set in this bitmask also.

Parameters
xthe first bitmask used to form the intersection.
ythe first bitmask used to form the intersection.
Returns
true if and only if this bitmask entirely contains the intersection of x and y.
template<typename T , typename U = T>
long regina::NBitmask2< T, U >::firstBit ( ) const
inline

Returns the index of the first true bit in this bitmask, or -1 if there are no true bits.

Returns
the index of the first true bit.
template<typename T , typename U = T>
void regina::NBitmask2< T, U >::flip ( )
inline

Negates every bit in this bitmask.

All true bits will be set to false and vice versa.

Unlike the more generic NBitmask, this optimised bitmask class does not store a length. This means that all 8 * sizeof(T) + 8 * sizeof(U) possible bits will be negated.

template<typename T , typename U = T>
bool regina::NBitmask2< T, U >::get ( size_t  index) const
inline

Returns the value of the given bit of this bitmask.

Parameters
indexindicates which bit to query; this must be between 0 and (8 * sizeof(T) + 8 * sizeof(U) - 1) inclusive.
Returns
the value of the (index)th bit.
template<typename T , typename U = T>
bool regina::NBitmask2< T, U >::inUnion ( const NBitmask2< T, U > &  x,
const NBitmask2< T, U > &  y 
) const
inline

Determines whether this bitmask is entirely contained within the union of the two given bitmasks.

For this routine to return true, every bit that is set in this bitmask must also be set in either x or y.

Parameters
xthe first bitmask used to form the union.
ythe first bitmask used to form the union.
Returns
true if and only if this bitmask is entirely contained within the union of x and y.
template<typename T , typename U = T>
long regina::NBitmask2< T, U >::lastBit ( ) const
inline

Returns the index of the last true bit in this bitmask, or -1 if there are no true bits.

Returns
the index of the last true bit.
template<typename T , typename U = T>
bool regina::NBitmask2< T, U >::lessThan ( const NBitmask2< T, U > &  other) const
inline

Determines whether this bitmask appears strictly before the given bitmask when bitmasks are sorted in lexicographical order.

Here the bit at index 0 is least significant, and the bit at index length-1 is most significant.

Warning
We do not use < for this operation, since <= represents the subset operation.
Parameters
otherthe bitmask to compare against this.
Returns
true if and only if this is lexicographically strictly smaller than the given bitmask.
template<typename T , typename U = T>
NBitmask2<T, U>& regina::NBitmask2< T, U >::operator&= ( const NBitmask2< T, U > &  other)
inline

Sets this to the intersection of this and the given bitmask.

Every bit that is unset in other will be unset in this bitmask.

Parameters
otherthe bitmask to intersect with this.
Returns
a reference to this bitmask.
template<typename T , typename U = T>
NBitmask2<T, U>& regina::NBitmask2< T, U >::operator-= ( const NBitmask2< T, U > &  other)
inline

Sets this to the set difference of this and the given bitmask.

Every bit that is set in other will be cleared in this bitmask.

Parameters
otherthe bitmask to XOR with this.
Returns
a reference to this bitmask.
template<typename T , typename U = T>
bool regina::NBitmask2< T, U >::operator<= ( const NBitmask2< T, U > &  other) const
inline

Determines whether this bitmask is entirely contained within the given bitmask.

For this routine to return true, every bit that is set in this bitmask must also be set in the given bitmask.

Warning
This operation does not compare bitmasks lexicographically; moreover, it only describes a partial order, not a total order. To compare bitmasks lexicographically, use lessThan() instead.
Parameters
otherthe bitmask to compare against this.
Returns
true if and only if this bitmask is entirely contained within the given bitmask.
template<typename T , typename U = T>
NBitmask2<T, U>& regina::NBitmask2< T, U >::operator= ( const NBitmask2< T, U > &  other)
inline

Sets this bitmask to a copy of the given bitmask.

Parameters
otherthe bitmask to clone.
Returns
a reference to this bitmask.
template<typename T , typename U = T>
bool regina::NBitmask2< T, U >::operator== ( const NBitmask2< T, U > &  other) const
inline

Determines whether this and the given bitmask are identical.

Parameters
otherthe bitmask to compare against this.
Returns
true if and only if this and the given bitmask are identical.
template<typename T , typename U = T>
NBitmask2<T, U>& regina::NBitmask2< T, U >::operator^= ( const NBitmask2< T, U > &  other)
inline

Sets this to the exclusive disjunction (XOR) of this and the given bitmask.

Every bit that is set in other will be flipped in this bitmask.

Parameters
otherthe bitmask to XOR with this.
Returns
a reference to this bitmask.
template<typename T , typename U = T>
NBitmask2<T, U>& regina::NBitmask2< T, U >::operator|= ( const NBitmask2< T, U > &  other)
inline

Sets this to the union of this and the given bitmask.

Every bit that is set in other will be set in this bitmask.

Parameters
otherthe bitmask to union with this.
Returns
a reference to this bitmask.
template<typename T , typename U = T>
void regina::NBitmask2< T, U >::reset ( )
inline

Sets all bits of this bitmask to false.

template<typename T , typename U = T>
void regina::NBitmask2< T, U >::reset ( size_t  )
inline

Sets all bits of this bitmask to false.

The integer argument is merely for compatibility with NBitmask::reset(size_t), and will be ignored.

template<typename T , typename U = T>
void regina::NBitmask2< T, U >::set ( size_t  index,
bool  value 
)
inline

Sets the given bit of this bitmask to the given value.

Parameters
indexindicates which bit to set; this must be between 0 and (8 * sizeof(T) + 8 * sizeof(U) - 1) inclusive.
valuethe value that will be assigned to the (index)th bit.
template<typename T , typename U = T>
template<typename ForwardIterator >
void regina::NBitmask2< T, U >::set ( ForwardIterator  indexBegin,
ForwardIterator  indexEnd,
bool  value 
)
inline

Sets all bits in the given sorted list to the given value.

This is a convenience routine for setting many bits at once. The indices of the bits to set should be sorted and stored in some container, such as a std::set or a C-style array. This routine takes iterators over this container, and sets the bits at the corresponding indices to the given value.

For example, the following code would set bits 3, 5 and 6 to true:

std::vector<unsigned> indices;
indices.push(3); indices.push(5); indices.push(6);
bitmask.set(indices.begin(), indices.end(), true);

Likewise, the following code would set bits 1, 4 and 7 to false:

unsigned indices[3] = { 1, 4, 7 };
bitmask.set(indices, indices + 3, false);

All other bits of this bitmask are unaffected by this routine.

Precondition
ForwardIterator is a forward iterator type that iterates over integer values.
The list of indices described by these iterators is in sorted order. This is to allow optimisations for larger bitmask types.
All indices in the given list are between 0 and (8 * sizeof(T) + 8 * sizeof(U) - 1) inclusive.
Parameters
indexBeginthe beginning of the iterator range containing the sorted indices of the bits to set.
indexEndthe end of the iterator range containing the sorted indices of the bits to set.
valuethe value that will be assigned to each of the corresponding bits.
template<typename T , typename U = T>
void regina::NBitmask2< T, U >::truncate ( size_t  numBits)
inline

Leaves the first numBits bits of this bitmask intact, but sets all subsequent bits to false.

In other words, this routine "truncates" this bitmask to the given number of bits.

This routine does not change the length of this bitmask (as passed to the contructor or to reset()).

Parameters
numBitsthe number of bits that will not be cleared.

The documentation for this class was generated from the following file:

Copyright © 1999-2014, The Regina development team
This software is released under the GNU General Public License, with some additional permissions; see the source code for details.
For further information, or to submit a bug or other problem, please contact Ben Burton (bab@debian.org).