atomic_uint32_t Class Reference

A 32-bit integer with support for atomic operations. More...

#include <atomic.hh>

Public Member Functions
uint32_t	value () const
	Return the value.
uint32_t	nonatomic_value () const
	Return the value.
	operator uint32_t () const
	Return the value.
atomic_uint32_t &	operator= (uint32_t x)
	Set the value to x.
atomic_uint32_t &	operator+= (int32_t delta)
	Atomically add delta to the value.
atomic_uint32_t &	operator-= (int32_t delta)
	Atomically subtract delta from the value.
atomic_uint32_t &	operator|= (uint32_t mask)
	Atomically bitwise-or the value with mask.
atomic_uint32_t &	operator&= (uint32_t mask)
	Atomically bitwise-and the value with mask.
void	nonatomic_inc ()
	Increment the value.
void	operator++ ()
	Atomically increment the value.
void	operator++ (int)
	Atomically increment the value.
void	nonatomic_dec ()
	Decrement the value.
void	operator-- ()
	Atomically decrement the value.
void	operator-- (int)
	Atomically decrement the value.
uint32_t	swap (uint32_t desired)
	Atomically assign the value to desired, returning the old value.
uint32_t	fetch_and_add (uint32_t delta)
	Atomically add delta to the value, returning the old value.
bool	dec_and_test ()
	Atomically decrement the value, returning true if the new value is 0.
bool	nonatomic_dec_and_test ()
	Decrement the value, returning true if the new value is 0.
uint32_t	compare_swap (uint32_t expected, uint32_t desired) CLICK_BUILTINS_DEPRECATED
bool	compare_and_swap (uint32_t expected, uint32_t desired) CLICK_BUILTINS_NONDEPRECATED
	Perform a compare-and-swap operation.

Static Public Member Functions
static uint32_t	swap (volatile uint32_t &x, uint32_t desired)
	Atomically assign the value to desired, returning the old value.
static void	inc (volatile uint32_t &x)
	Atomically increment value x.
static bool	dec_and_test (volatile uint32_t &x)
	Atomically decrement x, returning true if the new x is 0.
static uint32_t	compare_swap (volatile uint32_t &x, uint32_t expected, uint32_t desired) CLICK_BUILTINS_DEPRECATED
static bool	compare_and_swap (volatile uint32_t &x, uint32_t expected, uint32_t desired) CLICK_BUILTINS_NONDEPRECATED
	Perform a compare-and-swap operation.
static bool	use_builtins ()

Detailed Description

A 32-bit integer with support for atomic operations.

The atomic_uint32_t class represents a 32-bit integer, with support for atomic operations. The +=, -=, &=, |=, ++, and – operations are implemented using atomic instructions. There are also atomic swap(), fetch_and_add(), dec_and_test(), and compare_swap() operations.

Because of some issues with compiler implementations, atomic_uint32_t has no explicit constructor; to set an atomic_uint32_t to a value, use operator=.

The atomic_uint32_t only provides true atomic semantics when that has been implemented. It has been implemented in the Linux kernel, and at userlevel (when –enable-multithread has been defined) for x86 machines. In other situations, it's not truly atomic (because it doesn't need to be).

Member Function Documentation

value()

uint32_t atomic_uint32_t::value ( ) const

inline

Return the value.

nonatomic_value()

uint32_t atomic_uint32_t::nonatomic_value ( ) const

inline

Return the value.

operator uint32_t()

atomic_uint32_t::operator uint32_t ( ) const

inline

Return the value.

operator=()

atomic_uint32_t & atomic_uint32_t::operator= ( uint32_t  x )

inline

Set the value to x.

operator+=()

atomic_uint32_t & atomic_uint32_t::operator+= ( int32_t  delta )

inline

Atomically add delta to the value.

operator-=()

atomic_uint32_t & atomic_uint32_t::operator-= ( int32_t  delta )

inline

Atomically subtract delta from the value.

operator|=()

atomic_uint32_t & atomic_uint32_t::operator|= ( uint32_t  mask )

inline

Atomically bitwise-or the value with mask.

operator&=()

atomic_uint32_t & atomic_uint32_t::operator&= ( uint32_t  mask )

inline

Atomically bitwise-and the value with mask.

nonatomic_inc()

void atomic_uint32_t::nonatomic_inc ( )

inline

Increment the value.

operator++() [1/2]

void atomic_uint32_t::operator++ ( )

inline

Atomically increment the value.

operator++() [2/2]

void atomic_uint32_t::operator++ ( int  )

inline

Atomically increment the value.

nonatomic_dec()

void atomic_uint32_t::nonatomic_dec ( )

inline

Decrement the value.

operator--() [1/2]

void atomic_uint32_t::operator-- ( )

inline

Atomically decrement the value.

operator--() [2/2]

void atomic_uint32_t::operator-- ( int  )

inline

Atomically decrement the value.

swap() [1/2]

uint32_t atomic_uint32_t::swap ( uint32_t  desired )

inline

Atomically assign the value to desired, returning the old value.

Behaves like this, but in one atomic step:

uint32_t old_value = value();
*this = desired;
return old_value;

Also acts as a memory barrier.

fetch_and_add()

uint32_t atomic_uint32_t::fetch_and_add ( uint32_t  delta )

inline

Atomically add delta to the value, returning the old value.

Behaves like this, but in one atomic step:

uint32_t old_value = value();
*this += delta;
return old_value;

dec_and_test() [1/2]

bool atomic_uint32_t::dec_and_test ( )

inline

Atomically decrement the value, returning true if the new value is 0.

Behaves like this, but in one atomic step:

--*this;
return value() == 0;

nonatomic_dec_and_test()

bool atomic_uint32_t::nonatomic_dec_and_test ( )

inline

Decrement the value, returning true if the new value is 0.

Behaves like this, but in one atomic step:

--*this;
return value() == 0;

compare_and_swap() [1/2]

bool atomic_uint32_t::compare_and_swap ( uint32_t  expected, uint32_t  desired  )

inline

Perform a compare-and-swap operation.

Parameters

expected	test value
desired	new value

Returns

The actual old value. If expected is returned, the value has been set to desired.

Behaves like this, but in one atomic step:

uint32_t actual = value();
if (actual == expected)
    *this = desired;
return actual;

Also acts as a memory barrier.

Perform a compare-and-swap operation.

Parameters

expected	test value
desired	new value

Returns

True if the old value equaled expected (in which case the value was set to desired), false otherwise.

Deprecated:

Use compare_swap instead.

Behaves like this, but in one atomic step:

uint32_t old_value = value();
if (old_value == expected)
    *this = desired;
return old_value == expected;

Also acts as a memory barrier.

swap() [2/2]

uint32_t atomic_uint32_t::swap ( volatile uint32_t &  x, uint32_t  desired  )

inlinestatic

Atomically assign the value to desired, returning the old value.

Behaves like this, but in one atomic step:

uint32_t actual = x;
x = desired;
return actual;

Also acts as a memory barrier.

inc()

void atomic_uint32_t::inc ( volatile uint32_t &  x )

inlinestatic

Atomically increment value x.

dec_and_test() [2/2]

bool atomic_uint32_t::dec_and_test ( volatile uint32_t &  x )

inlinestatic

Atomically decrement x, returning true if the new x is 0.

Behaves like this, but in one atomic step:

--x;
return x == 0;

compare_and_swap() [2/2]

bool atomic_uint32_t::compare_and_swap ( volatile uint32_t &  x, uint32_t  expected, uint32_t  desired  )

inlinestatic

Perform a compare-and-swap operation.

Parameters

x	value
expected	test value
desired	new value

Returns

The actual old value. If it equaled expected, x has been set to desired.

Behaves like this, but in one atomic step:

uint32_t actual = x;
if (x == expected)
    x = desired;
return actual;

Also acts as a memory barrier.

Perform a compare-and-swap operation.

Parameters

x	value
expected	test value
desired	new value

Returns

True if the old x equaled expected (in which case x was set to desired), false otherwise.

Deprecated:

Use compare_swap instead.

Behaves like this, but in one atomic step:

uint32_t old_value = x;
if (x == expected)
    x = desired;
return old_value == expected;

Also acts as a memory barrier.

---

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

• include/click/atomic.hh