cds::details::marked_ptr< T, Bitmask > Class Template Reference

Marked pointer. More...

#include <cds/details/marked_ptr.h>

Public Types
typedef T	value_type
	type of value the class points to
typedef T *	pointer_type
	type of pointer

Public Member Functions
constexpr	marked_ptr () noexcept
	Constructs null marked pointer. The flag is cleared.
constexpr	marked_ptr (value_type *ptr) noexcept
	Constructs marked pointer with ptr value. The least bit(s) of ptr is the flag.
	marked_ptr (value_type *ptr, int nMask) noexcept
	Constructs marked pointer with ptr value and nMask flag. More...
	marked_ptr (marked_ptr const &src) noexcept=default
	Copy constructor.
marked_ptr &	operator= (marked_ptr const &p) noexcept=default
	Copy-assignment operator.
value_type *	ptr () const noexcept
	Returns the pointer without mark bits (real pointer) const version.
value_type *	all () const noexcept
	Returns the pointer and bits together.
uintptr_t	bits () const noexcept
	Returns the least bits of pointer according to Bitmask template argument of the class.
value_type *	operator-> () const noexcept
	Analogue for ptr.
marked_ptr	operator= (T *p) noexcept
	Assignment operator sets markup bits to zero.
marked_ptr &	operator|= (int nBits) noexcept
	Set LSB bits as bits() | nBits
marked_ptr &	operator&= (int nBits) noexcept
	Set LSB bits as bits() & nBits
marked_ptr &	operator^= (int nBits) noexcept
	Set LSB bits as bits() ^ nBits

Static Public Attributes
static constexpr const uintptr_t	bitmask = Bitmask
	bitfield bitmask
static constexpr const uintptr_t	pointer_bitmask = ~bitmask
	pointer bitmask

Private Attributes
T *	m_ptr
	pointer and its mark bits

Friends
marked_ptr	operator| (marked_ptr p, int nBits) noexcept
	Returns p |= nBits
marked_ptr	operator| (int nBits, marked_ptr p) noexcept
	Returns p |= nBits
marked_ptr	operator& (marked_ptr p, int nBits) noexcept
	Returns p &= nBits
marked_ptr	operator& (int nBits, marked_ptr p) noexcept
	Returns p &= nBits
marked_ptr	operator^ (marked_ptr p, int nBits) noexcept
	Returns p ^= nBits
marked_ptr	operator^ (int nBits, marked_ptr p) noexcept
	Returns p ^= nBits
marked_ptr	operator~ (marked_ptr p) noexcept
	Inverts LSBs of pointer p.
bool	operator== (marked_ptr p1, marked_ptr p2) noexcept
	Comparing two marked pointer including its mark bits.
bool	operator== (marked_ptr p1, value_type const *p2) noexcept
	Comparing marked pointer and raw pointer, mark bits of p1 is ignored.
bool	operator== (value_type const *p1, marked_ptr p2) noexcept
	Comparing marked pointer and raw pointer, mark bits of p2 is ignored.
bool	operator!= (marked_ptr p1, marked_ptr p2) noexcept
	Comparing two marked pointer including its mark bits.
bool	operator!= (marked_ptr p1, value_type const *p2) noexcept
	Comparing marked pointer and raw pointer, mark bits of p1 is ignored.
bool	operator!= (value_type const *p1, marked_ptr p2) noexcept
	Comparing marked pointer and raw pointer, mark bits of p2 is ignored.

Detailed Description

template<typename T, int Bitmask>
class cds::details::marked_ptr< T, Bitmask >

Marked pointer.

On the modern architectures, the default data alignment is 4 (for 32bit) or 8 byte for 64bit. Therefore, the least 2 or 3 bits of the pointer is always zero and can be used as a bitfield to store logical flags. This trick is widely used in lock-free programming to operate with the pointer and its flags atomically.

Template parameters:

• T - type of pointer
• Bitmask - bitmask of least unused bits

Constructor & Destructor Documentation

marked_ptr()

template<typename T , int Bitmask>

cds::details::marked_ptr< T, Bitmask >::marked_ptr ( value_type *  ptr, int  nMask  )

inlinenoexcept

Constructs marked pointer with ptr value and nMask flag.

The nMask argument defines the OR-bits

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

• cds/details/marked_ptr.h