atomic_uint32_t Class Reference

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

#include <atomic.hh>

List of all members.

Public Member Functions
uint32_t	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	operator++ ()
	Atomically increment the value.
void	operator++ (int)
	Atomically increment 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.
uint32_t	compare_swap (uint32_t expected, uint32_t desired)
	Perform a compare-and-swap operation.
bool	compare_and_swap (uint32_t expected, uint32_t desired)
	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)
	Perform a compare-and-swap operation.
static bool	compare_and_swap (volatile uint32_t &x, uint32_t expected, uint32_t desired)
	Perform a compare-and-swap operation.

---

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

uint32_t atomic_uint32_t::value

(

)

const [inline]

Return the value.

atomic_uint32_t::operator uint32_t

(

)

const [inline]

Return the value.

atomic_uint32_t & atomic_uint32_t::operator=

(

uint32_t

x

)

[inline]

Set the value to x.

atomic_uint32_t & atomic_uint32_t::operator+=

(

int32_t

delta

)

[inline]

Atomically add delta to the value.

atomic_uint32_t & atomic_uint32_t::operator-=

(

int32_t

delta

)

[inline]

Atomically subtract delta from the value.

atomic_uint32_t & atomic_uint32_t::operator|=

(

uint32_t

mask

)

[inline]

Atomically bitwise-or the value with mask.

atomic_uint32_t & atomic_uint32_t::operator &=

(

uint32_t

mask

)

[inline]

Atomically bitwise-and the value with mask.

void atomic_uint32_t::operator++

(

)

[inline]

Atomically increment the value.

void atomic_uint32_t::operator++

(

int

)

[inline]

Atomically increment the value.

void atomic_uint32_t::operator--

(

)

[inline]

Atomically decrement the value.

void atomic_uint32_t::operator--

(

int

)

[inline]

Atomically decrement the value.

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.

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;

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;

uint32_t atomic_uint32_t::compare_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.

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:

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.

uint32_t atomic_uint32_t::swap	(	volatile uint32_t &	x,
		uint32_t	desired
	)			[inline, static]

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.

void atomic_uint32_t::inc

(

volatile uint32_t &

x

)

[inline, static]

Atomically increment value x.

bool atomic_uint32_t::dec_and_test

(

volatile uint32_t &

x

)

[inline, static]

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

Behaves like this, but in one atomic step:

 --x;
 return x == 0;

uint32_t atomic_uint32_t::compare_swap	(	volatile uint32_t &	x,
		uint32_t	expected,
		uint32_t	desired
	)			[inline, static]

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.

bool atomic_uint32_t::compare_and_swap	(	volatile uint32_t &	x,
		uint32_t	expected,
		uint32_t	desired
	)			[inline, static]

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.

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

• include/click/atomic.hh