MAtomic Class Reference
[OpenMaya - API module for common classes]

#include <MAtomic.h>

List of all members.

---

Detailed Description

Methods for atomic operations.

The MAtomic class implements several cross-platform atomic operations which are useful when writing a multithreaded application. Atomic operations are those that appear to happen as a single operation when viewed from other threads.

As a usage example, during reference counting in an SMP environment, it is important to ensure that decrementing and testing the counter against zero happens atomically. If coded this way:

if (--counter == 0) {}

then another thread could modify the value of counter between the decrement and the if test. The above code would therefore get the wrong value. This class provides a routine to perform the decrement and return the previous value atomically, so the above snippet could be written as:

if (MAtomic::preDecrement(&counter) == 0) {}

Static Public Member Functions
static int	preIncrement (volatile int *variable)
static int	postIncrement (volatile int *variable)
static int	increment (volatile int *variable, int incrementValue)
static int	preDecrement (volatile int *variable)
static int	postDecrement (volatile int *variable)
static int	decrement (volatile int *variable, int decrementValue)
static int	set (volatile int *variable, int newValue)
static int	compareAndSwap (volatile int *variable, int compareValue, int swapValue)

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Member Function Documentation

static int MAtomic::preIncrement

(

volatile int *

variable

)

[inline, static]

Increment variable, return value after increment

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value after incrementing

static int MAtomic::postIncrement

(

volatile int *

variable

)

[inline, static]

Increment variable, return value before increment

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value before incrementing

static int MAtomic::increment	(	volatile int *	variable,
		int	incrementValue
	)			[inline, static]

Increment variable by incrementValue, return value before increment.

Parameters:

[in]	variable	Value to be modified
[in]	incrementValue	Value by which to increment variable

Returns:

. Variable value before incrementing

static int MAtomic::preDecrement

(

volatile int *

variable

)

[inline, static]

Decrement variable, return value after increment

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value after decrementing

static int MAtomic::postDecrement

(

volatile int *

variable

)

[inline, static]

Decrement variable, return value before decrement

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value before decrementing

static int MAtomic::decrement	(	volatile int *	variable,
		int	decrementValue
	)			[inline, static]

Decrement variable by decrementValue, return value before decrement.

Parameters:

[in]	variable	Value to be modified
[in]	decrementValue	Value by which to decrement variable

Returns:

. Variable value before decrementing

static int MAtomic::set	(	volatile int *	variable,
		int	newValue
	)			[inline, static]

Set variable to newValue, return value of variable before set.

Parameters:

[in]	variable	Value to be modified
[in]	newValue	Value to which to set variable

Returns:

. Variable value before set

static int MAtomic::compareAndSwap	(	volatile int *	variable,
		int	compareValue,
		int	swapValue
	)			[inline, static]

Compare variable with compareValue and if the values are equal, sets *variable equal to swapValue. The result of the comparison is returned, true if the compare was sucessful, false otherwise.

Parameters:

[in]	variable	First value to be compared
[in]	compareValue	Second value to be compared

Returns:

. True if variable equals compareValue, otherwise false