Files
file	AlgBits.c
	Provides bit fiddling functions.

file	AlgGrayCode.c
	Provides functions for computing Gray codes and their inverse. See Christopher H. Hamilton. "Range Searching Data Structures with Cache Locality" PhD Thesis, Dalhousie University, March 20011. The code within this file is derived from this thesis and the software it refers to.

file	AlgHilbertIndex.c
	Provides functions for Hilbert indices and their inverse. See J. K. Lawder "Calculation of Mappings Between One an n-dimensional Values Using the Hilbert Space-filling Curve", Birkbeck, University of London Research Report BBKCS-00-01, 2000. The code in this technical report has been modifiied to support n-dimensions and variable bit orders without recompilation.

Functions
unsigned int	AlgBitSetCount (unsigned long gMsk)
	Counts the number of bits set in the given mask. More...

int	AlgBitMostSigSet (unsigned long gMsk)
	Finds the most significant bit set in the given mask. The value returned will be zero if the mask was zero one if the mask had the value 1 or higher integer if the most significant bit set in the mask is greater. More...

int	AlgBitMostSigSetLL (unsigned long long gMsk)
	Finds the most significant bit set in the given mask. The value returned will be zero if the mask was zero one if the mask had the value 1 or higher integer if the most significant bit set in the mask is greater. More...

unsigned int	AlgBitSetPositions (unsigned int *posA, unsigned long gMsk)
	Counts the number of bits set in the given mask and sets the first elements of the given bit position array. More...

unsigned int	AlgBitRotateRight (unsigned int g, unsigned int n, unsigned int d)
	Rotates the given bit mask d places to the right (towards less significant bits) where there are n valid bits in the given bit mask. More...

unsigned long	AlgBitNextNOfM (unsigned long curMsk, int n, int m)
	Computes a bit mask which has n bits set and is <= maxMsk, the new bit mask is the next after the given current mask. The maximum number of bits that can be stored in an unsigned long is assumed to be 32. If the actual number is less than this then this code won't work, if it's higher everything should be fine. This function can be used together with AlgBitSetPositions() to select all ordered combinations of N of M. Eg to select all ordered combinations of 3 out of 5 this function would return 00111, 01011, 01101, 01110, 10110, 11010, 11100. More...

int	AlgBitNextSet (unsigned long msk, int idC)
	Computes the index of the next bit set in the given mask using the index to the current bit as the start index. maxMsk, the new bit mask is the next after the given current mask. More...

int	AlgBitNextPowerOfTwo (unsigned int *dstP2I, unsigned int gI)
	Computes the next integer that is >= the given integer and has only a single bit set. More...

int	AlgBitIsPowerOfTwo (unsigned int gI)
	Checks that the given integer is an integral power of two. More...

unsigned int	AlgGrayCode (unsigned int g)
	Computes the Gray code of the given value. More...

unsigned long long	AlgGrayCodeLL (unsigned long long g)
	Computes the Gray code of the given value. More...

unsigned int	AlgGrayCodeInv (unsigned int g)
	Computes the inverse Gray code, ie the value corresponding to the given Gray code. More...

unsigned long long	AlgGrayCodeInvLL (unsigned long long g)
	Computes the inverse Gray code, ie the value corresponding to the given Gray code. More...

void	AlgHilbertIndex (unsigned int h, unsigned int p, int n, int o)
	Computes the Hilbert index of a point in n dimensions. More...

void	AlgHilbertIndexInv (unsigned int h, unsigned int p, int n, int o)
	Computes the coordinates of the point in n dimensions corresponding to the given Hilbert index. More...

Detailed Description

Function Documentation

◆ AlgBitSetCount()

unsigned int AlgBitSetCount ( unsigned long gMsk )

Counts the number of bits set in the given mask.

Returns: Number of bits set.

Parameters

gMsk	Given bit mask.

◆ AlgBitMostSigSet()

int AlgBitMostSigSet ( unsigned long gMsk )

Finds the most significant bit set in the given mask. The value returned will be zero if the mask was zero one if the mask had the value 1 or higher integer if the most significant bit set in the mask is greater.

Returns: Most significant bit set in the given mask.

Parameters

gMsk	Given bit mask.

◆ AlgBitMostSigSetLL()

int AlgBitMostSigSetLL ( unsigned long long gMsk )

Finds the most significant bit set in the given mask. The value returned will be zero if the mask was zero one if the mask had the value 1 or higher integer if the most significant bit set in the mask is greater.

Returns: Most significant bit set in the given mask.

Parameters

gMsk	Given bit mask.

◆ AlgBitSetPositions()

unsigned int AlgBitSetPositions	(	unsigned int *	posA,
		unsigned long	gMsk
	)

Counts the number of bits set in the given mask and sets the first elements of the given bit position array.

Returns: Number of bits set.

Parameters

posA	Bit set position array, MUST have a length >= the number of bits in the unsigned long bit mask.
gMsk	Given bit mask.

◆ AlgBitRotateRight()

unsigned int AlgBitRotateRight	(	unsigned int	g,
		unsigned int	n,
		unsigned int	d
	)

Rotates the given bit mask d places to the right (towards less significant bits) where there are n valid bits in the given bit mask.

Returns: Bitmask rotated right.

Parameters

g	Given bit mask.
n	Number of valid bits in the bit mask.
d	Number of places to rotate right.

◆ AlgBitNextNOfM()

unsigned long AlgBitNextNOfM	(	unsigned long	curMsk,
		int	n,
		int	m
	)

Computes a bit mask which has n bits set and is <= maxMsk, the new bit mask is the next after the given current mask. The maximum number of bits that can be stored in an unsigned long is assumed to be 32. If the actual number is less than this then this code won't work, if it's higher everything should be fine. This function can be used together with AlgBitSetPositions() to select all ordered combinations of N of M. Eg to select all ordered combinations of 3 out of 5 this function would return 00111, 01011, 01101, 01110, 10110, 11010, 11100.

Returns: Next bit mask for n bits, or zero on error.

Parameters

curMsk	Current mask value. If the current value is zero then the first valid mask will be computed, otherwise the current mask is assumed to be valid.
n	Number of bits to be set.
m	Maximum number of bits to use.

◆ AlgBitNextSet()

int AlgBitNextSet	(	unsigned long	msk,
		int	idC
	)

Computes the index of the next bit set in the given mask using the index to the current bit as the start index. maxMsk, the new bit mask is the next after the given current mask.

Returns: Index of the next bit set in the given mask, will be -ve if no next bit set.

Parameters

msk	Given bit mask.
idC	Current bit index, -ve to find first bit set.

◆ AlgBitNextPowerOfTwo()

int AlgBitNextPowerOfTwo	(	unsigned int *	dstP2I,
		unsigned int	gI
	)

Computes the next integer that is >= the given integer and has only a single bit set.

Returns: Index of the single bit that should be set for an unsigned integer that's >= the given int.

Parameters

dstP2I	Destination ptr for integer that's >= the given integer and is a power of two.
gI	Given integer.

Referenced by AlgAutoCorrelate2D(), AlgBitIsPowerOfTwo(), AlgCrossCorrelate2D(), WlzLBTBalanceDomain2D(), WlzLBTBalanceDomain3D(), WlzMakeLBTDomain2D(), WlzMakeLBTDomain3D(), WlzMakeTiledValuesObj2D(), and WlzMakeTiledValuesObj3D().

◆ AlgBitIsPowerOfTwo()

int AlgBitIsPowerOfTwo ( unsigned int gI )

Checks that the given integer is an integral power of two.

Returns: Non zero if the given integer is an integral power of two.

Parameters

gI	Given integer.

References AlgBitNextPowerOfTwo().

◆ AlgGrayCode()

unsigned int AlgGrayCode ( unsigned int g )

Computes the Gray code of the given value.

Returns: Gray code of the given integer.

Parameters

g	Given integer.

◆ AlgGrayCodeLL()

unsigned long long AlgGrayCodeLL ( unsigned long long g )

Computes the Gray code of the given value.

Returns: Gray code of the given integer.

Parameters

g	Given long integer.

◆ AlgGrayCodeInv()

unsigned int AlgGrayCodeInv ( unsigned int g )

Computes the inverse Gray code, ie the value corresponding to the given Gray code.

Returns: Integer corresponding to the given Gray code.

Parameters

g	Given Gray code.

◆ AlgGrayCodeInvLL()

unsigned long long AlgGrayCodeInvLL ( unsigned long long g )

Computes the inverse Gray code, ie the value corresponding to the given Gray code.

Returns: Integer corresponding to the given Gray code.

Parameters

g	Given Gray code.

◆ AlgHilbertIndex()

void AlgHilbertIndex	(	unsigned int *	h,
		unsigned int *	p,
		int	n,
		int	o
	)

Computes the Hilbert index of a point in n dimensions.

Parameters

h	Hilbert index (set on return).
p	Position of the n dimensional point.
n	Number of dimensions.
o	Order (number of bits for coordinate).

◆ AlgHilbertIndexInv()

void AlgHilbertIndexInv	(	unsigned int *	h,
		unsigned int *	p,
		int	n,
		int	o
	)

Computes the coordinates of the point in n dimensions corresponding to the given Hilbert index.

Parameters

h	The given Hilbert index.
p	Decoded point coordinates (set on return).
n	Number of dimensions.
o	Order (number of bits for coordinate).

Files

Functions

Detailed Description

Function Documentation

◆ AlgBitSetCount()

◆ AlgBitMostSigSet()

◆ AlgBitMostSigSetLL()

◆ AlgBitSetPositions()

◆ AlgBitRotateRight()

◆ AlgBitNextNOfM()

◆ AlgBitNextSet()

◆ AlgBitNextPowerOfTwo()

◆ AlgBitIsPowerOfTwo()

◆ AlgGrayCode()

◆ AlgGrayCodeLL()

◆ AlgGrayCodeInv()

◆ AlgGrayCodeInvLL()

◆ AlgHilbertIndex()

◆ AlgHilbertIndexInv()