This class defines a bit field that is part of some larger array or that uses an allocated piece of memory. More...

#include <bitfield.h>

Public Member Functions
	BitField ()
	The constructor of an undefined bit field. More...

	~BitField ()
	The destructor which actually does nothing. More...

bool	defined () const
	Returns true if the bit field has already been defined, that is, it is bound with some memory piece, or its memory has been allocated. More...

void	define (unsigned char *buf, int_t length)
	Define the bit field as a piece of a larger memory buffer. More...

void	allocate (int_t length)
	Allocates memory for a bit field. More...

void	free ()
	Releases the memory allocated for the bit field. More...

void	set (int_t n)
	Sets the given bit to 1. More...

void	clear (int_t n)
	Clears the given bit (sets it to 0). More...

int	test (int_t n) const
	Tests the given bit. Returns 0 or 1. More...

void	takebits (const BitField &from, int_t length)
	Copies all the bits from the given bitfield. More...

void	clearall (int_t length)
	Clears all the bits in the entire bit field of specified length. More...

int	find (int_t first, int_t length) const
	Finds the first bit that is set to 1, beginning at the given one. More...

int_t	hashkey (int_t length) const
	Returns the first key for hashing. More...

int_t	hashadd (int_t length) const
	Returns the second key for hashing. More...

Private Attributes
unsigned char *	table
	The table of 8-bit cells which store the subsequent bits. More...

Friends
bool	thesame (const BitField &b1, const BitField &b2, int_t length)
	Compares two bit fields of the giben length. More...

void	int2bits (int bits, int_t length, BitField &field)
	Converts an integer into the bits of a bit field of the given length. More...

int	bits2int (const BitField &field, int_t length)
	Converts the bits of a bit field of the given length into an integer. More...

Detailed Description

This class defines a bit field that is part of some larger array or that uses an allocated piece of memory.

This class may be useful for efficient management of multiple bit fields, or just one bit field. Note the very specific behavior of memory management!

Definition at line 72 of file bitfield.h.

Constructor & Destructor Documentation

◆ BitField()

chomp::homology::BitField::BitField ( )

inline

The constructor of an undefined bit field.

Definition at line 161 of file bitfield.h.

{
        table = NULL;
        return;
} /* BitField::BitField */

References table.

◆ ~BitField()

chomp::homology::BitField::~BitField ( )

inline

The destructor which actually does nothing.

Definition at line 179 of file bitfield.h.

{
        return;
} /* BitField::~BitField */

Member Function Documentation

◆ allocate()

void chomp::homology::BitField::allocate ( int_t length )

Allocates memory for a bit field.

The memory enough to store the given number of bits (the length of the bit field) is allocated with the 'new' operator. The allocated memory is filled with zeros, which isequivalent to calling the clearall procedure.

◆ clear()

void chomp::homology::BitField::clear ( int_t n )

inline

Clears the given bit (sets it to 0).

Definition at line 190 of file bitfield.h.

{
        table [n >> 3] &= static_cast<unsigned char> (~(0x01 << (n & 0x07)));
        return;
} /* BitField::clear */

References table.

◆ clearall()

void chomp::homology::BitField::clearall ( int_t length )

Clears all the bits in the entire bit field of specified length.

Note that the bit field itself does not store its length.

◆ define()

void chomp::homology::BitField::define	(	unsigned char *	buf,
		int_t	length
	)

Define the bit field as a piece of a larger memory buffer.

The memory enough to store the given number of bits (the length of the bit field) will be used.

◆ defined()

bool chomp::homology::BitField::defined ( ) const

inline

Returns true if the bit field has already been defined, that is, it is bound with some memory piece, or its memory has been allocated.

Definition at line 167 of file bitfield.h.

{
        return !!table;
} /* BitField::defined */

References table.

◆ find()

int chomp::homology::BitField::find	(	int_t	first,
		int_t	length
	)		const

Finds the first bit that is set to 1, beginning at the given one.

Return the number of the bit, or -1 if not found. Note that the bit field itself does not store its length, so this length must be provided as an argument of this function.

◆ free()

void chomp::homology::BitField::free ( )

inline

Releases the memory allocated for the bit field.

This must be used if the memory was allocated, because the destructor does not deallocte the memory.

Definition at line 172 of file bitfield.h.

{
        delete [] table;
        table = NULL;
        return;
} /* BitField::free */

References table.

◆ hashadd()

int_t chomp::homology::BitField::hashadd ( int_t length ) const

Returns the second key for hashing.

Note that the bit field itself does not store its length, so this length must be provided as an argument of this function.

◆ hashkey()

int_t chomp::homology::BitField::hashkey ( int_t length ) const

Returns the first key for hashing.

Note that the bit field itself does not store its length, so this length must be provided as an argument of this function.

◆ set()

void chomp::homology::BitField::set ( int_t n )

inline

Sets the given bit to 1.

Definition at line 184 of file bitfield.h.

{
        table [n >> 3] |= static_cast<unsigned char> (0x01 << (n & 0x07));
        return;
} /* BitField::set */

References table.

◆ takebits()

void chomp::homology::BitField::takebits	(	const BitField &	from,
		int_t	length
	)

Copies all the bits from the given bitfield.

Assumes that both bit fields have the specified length. Note that the bit field itself does not store its length.

◆ test()

int chomp::homology::BitField::test ( int_t n ) const

inline

Tests the given bit. Returns 0 or 1.

Definition at line 196 of file bitfield.h.

{
        return !!(table [n >> 3] & (0x01 << (n & 0x07)));
} /* BitField::test */

References table.

Friends And Related Function Documentation

◆ bits2int

int bits2int	(	const BitField &	field,
		int_t	length
	)

friend

Converts the bits of a bit field of the given length into an integer.

The length must not exceed the size of the integer.

Definition at line 215 of file bitfield.h.

{
        const unsigned char *tab = field. table;
        if (!tab)
                throw "Trying to set values to an undefined bitfield.";
        int n = 0;
        int shiftvalue = 0;
        while (length >= 8)
        {
                n |= (*(tab ++)) << shiftvalue;
                length -= 8;
                shiftvalue += 8;
        }
        const int bitmasks [] = {0x00, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF};
        if (length > 0)
                n |= ((*(tab ++)) & bitmasks [length]) << shiftvalue;
        return n;
} /* bits2int */

◆ int2bits

void int2bits	(	int	bits,
		int_t	length,
		BitField &	field
	)

friend

Converts an integer into the bits of a bit field of the given length.

The length must not exceed the size of the integer.

Definition at line 201 of file bitfield.h.

{
        unsigned char *tab = field. table;
        if (!tab)
                throw "Trying to set values to an undefined bitfield.";
        while (length >= 0)
        {
                *(tab ++) = static_cast<unsigned char> (bits & 0xFF);
                bits >>= 8;
                length -= 8;
        }
        return;
} /* int2bits */

◆ thesame

bool thesame	(	const BitField &	b1,
		const BitField &	b2,
		int_t	length
	)

friend

Compares two bit fields of the giben length.

Returns true if they are the same, false otherwise.

Member Data Documentation

◆ table

unsigned char* chomp::homology::BitField::table

private

The table of 8-bit cells which store the subsequent bits.

It is either an address of some allocated memory, or an address of portion of some other memory, for example, allocated collectively for a large number of bit fields.

Definition at line 155 of file bitfield.h.

Referenced by BitField(), clear(), defined(), free(), set(), and test().

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

chomp/struct/bitfield.h

Public Member Functions

Private Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

◆ BitField()

◆ ~BitField()

Member Function Documentation

◆ allocate()

◆ clear()

◆ clearall()

◆ define()

◆ defined()

◆ find()

◆ free()

◆ hashadd()

◆ hashkey()

◆ set()

◆ takebits()

◆ test()

Friends And Related Function Documentation

◆ bits2int

◆ int2bits

◆ thesame

Member Data Documentation

◆ table