Bit String Functions

Macros
#define	OSRTBYTEARRAYSIZE(numbits)   ((numbits+7)/8)

Functions
OSUINT32	rtxGetBitCount (OSUINT32 value)
int	rtxSetBit (OSOCTET *pBits, OSSIZE numbits, OSSIZE bitIndex)
OSUINT32	rtxSetBitFlags (OSUINT32 flags, OSUINT32 mask, OSBOOL action)
int	rtxClearBit (OSOCTET *pBits, OSSIZE numbits, OSSIZE bitIndex)
OSBOOL	rtxTestBit (const OSOCTET *pBits, OSSIZE numbits, OSSIZE bitIndex)
OSSIZE	rtxLastBitSet (const OSOCTET *pBits, OSSIZE numbits)
int	rtxCheckBitBounds (OSCTXT *pctxt, OSOCTET **ppBits, OSSIZE *pNumocts, OSSIZE minRequiredBits, OSSIZE preferredLimitBits)
int	rtxZeroUnusedBits (OSOCTET *pBits, OSSIZE numbits)
int	rtxCheckUnusedBitsZero (const OSOCTET *pBits, OSSIZE numbits)

Detailed Description

Bit string functions allow bits to be set, cleared, or tested in arbitrarily sized byte arrays.

Macro Definition Documentation

OSRTBYTEARRAYSIZE

#define OSRTBYTEARRAYSIZE

(

numbits

)

((numbits+7)/8)

This macro is used to calculate the byte array size required to hold the given number of bits.

Function Documentation

rtxCheckBitBounds()

int rtxCheckBitBounds	(	OSCTXT *	pctxt,
		OSOCTET **	ppBits,
		OSSIZE *	pNumocts,
		OSSIZE	minRequiredBits,
		OSSIZE	preferredLimitBits
	)

Check whether the given bit string is large enough, and expand it if necessary.

Parameters

pctxt	The context to use should memory need to be allocated.
ppBits	*ppBits is a pointer to the bit string, or NULL if one has not been created. If the string is expanded, *ppBits receives a pointer to the new bit string.
pNumocts	pNumocts points to the current size of the bit string in octets. If the bit string is expanded, *pNumocts receives the new size.
minRequiredBits	The minimum number of bits needed in the bit string. On return, pBits will point to a bit string with at least this many bits.
preferredLimitBits	The number of bits over which we prefer not to go. If nonzero, no more bytes will be allocated than necessary for this many bits, unless explicitly required by minRequiredBits.

Returns

If successful, 0. Otherwise, an error code.

rtxCheckUnusedBitsZero()

int rtxCheckUnusedBitsZero	(	const OSOCTET *	pBits,
		OSSIZE	numbits
	)

This function checks to see if unused bits at the end of the given bit string are zero.

Parameters

pBits	Pointer to the octets of the bit string.
numbits	The number of bits in the bit string.

Returns

Zero if the operation is successful, or a negative status code if the operation fails. RTERR_INVBINS will be returned if bits at end are not zero.

rtxClearBit()

int rtxClearBit	(	OSOCTET *	pBits,
		OSSIZE	numbits,
		OSSIZE	bitIndex
	)

This function clears the specified zero-counted bit in the bit string.

Parameters

pBits	Pointer to octets of bit string.
numbits	Number of bits in the bit string.
bitIndex	Index of bit to be cleared. The bit with index 0 is a most significant bit in the octet with index 0.

Returns

If successful, returns the previous state of bit. If bit was set the return value is positive, if bit was not set the return value is zero. Otherwise, return value is an error code:

• RTERR_OUTOFBND = bitIndex is out of bounds

rtxGetBitCount()

OSUINT32 rtxGetBitCount

(

OSUINT32

value

)

This function returns the minimum size of the bit field required to hold the given integer value.

Parameters

value

Integer value

Returns

Minimum size of the the field in bits required to hold value.

rtxLastBitSet()

OSSIZE rtxLastBitSet	(	const OSOCTET *	pBits,
		OSSIZE	numbits
	)

This function returns the zero-counted index of the last bit set in a bit string.

Parameters

pBits	Pointer to the octets of the bit string.
numbits	The number of bits in the bit string.

Returns

Index of the last bit set in the bit string.

rtxSetBit()

int rtxSetBit	(	OSOCTET *	pBits,
		OSSIZE	numbits,
		OSSIZE	bitIndex
	)

This function sets the specified zero-counted bit in the bit string.

Parameters

pBits	Pointer to octets of bit string.
numbits	Number of bits in the bit string.
bitIndex	Index of bit to be set. The bit with index 0 is a most significant bit in the octet with index 0.

Returns

If successful, returns the previous state of bit. If bit was set the return value is positive, if bit was not set the return value is zero. Otherwise, return value is an error code:

• RTERR_OUTOFBND = bitIndex is out of bounds

rtxSetBitFlags()

OSUINT32 rtxSetBitFlags	(	OSUINT32	flags,
		OSUINT32	mask,
		OSBOOL	action
	)

This function sets one or more bits to TRUE or FALSE in a 32-bit unsigned bit flag set.

Parameters

flags	Flags to which mask will be applied.
mask	Mask with one or more bits set that will be applied to pBitMask.
action	Boolean action indicating if bits in flags should be set (TRUE) or cleared (FALSE).

Returns

Updated flags after mask is applied.

rtxTestBit()

OSBOOL rtxTestBit	(	const OSOCTET *	pBits,
		OSSIZE	numbits,
		OSSIZE	bitIndex
	)

This function tests the specified zero-counted bit in the bit string.

Parameters

pBits	Pointer to octets of bit string.
numbits	Number of bits in the bit string.
bitIndex	Index of bit to be tested. The bit with index 0 is a most significant bit in the octet with index 0.

Returns

True if bit set or false if not set or array index is beyond range of number of bits in the string.

rtxZeroUnusedBits()

int rtxZeroUnusedBits	(	OSOCTET *	pBits,
		OSSIZE	numbits
	)

This function zeros unused bits at the end of the given bit string.

Parameters

pBits	Pointer to the octets of the bit string.
numbits	The number of bits in the bit string.

Returns

Zero if the operation is successful, or a negative status code if the operation fails.