MAtomic Class Reference

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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) {}

#include <MAtomic.h>

List of all members.

Static Public Member Functions
static FORCE_INLINE int	preIncrement (volatile int *variable)
	Increment variable, return value after increment.
static FORCE_INLINE int	postIncrement (volatile int *variable)
	Increment variable, return value before increment.
static FORCE_INLINE int	increment (volatile int *variable, int incrementValue)
	Increment variable by incrementValue, return value before increment.
static FORCE_INLINE int	preDecrement (volatile int *variable)
	Decrement variable, return value after increment.
static FORCE_INLINE int	postDecrement (volatile int *variable)
	Decrement variable, return value before decrement.
static FORCE_INLINE int	decrement (volatile int *variable, int decrementValue)
	Decrement variable by decrementValue, return value before decrement.
static FORCE_INLINE int	set (volatile int *variable, int newValue)
	Set variable to newValue, return value of variable before set.
static FORCE_INLINE int	compareAndSwap (volatile int *variable, int compareValue, int swapValue)
	Compare variable with compareValue and if the values are equal, sets *variable equal to swapValue.

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Member Function Documentation

static FORCE_INLINE int preIncrement

(

volatile int *

variable

)

[inline, static]

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Increment variable, return value after increment.

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value after incrementing

static FORCE_INLINE int postIncrement

(

volatile int *

variable

)

[inline, static]

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Increment variable, return value before increment.

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value before incrementing

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

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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 FORCE_INLINE int preDecrement

(

volatile int *

variable

)

[inline, static]

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Decrement variable, return value after increment.

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value after decrementing

static FORCE_INLINE int postDecrement

(

volatile int *

variable

)

[inline, static]

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Decrement variable, return value before decrement.

Parameters:

[in]

variable

Value to be modified

Returns:

. Variable value before decrementing

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

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

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

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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
[in]	swapValue	Value to set *variable to if comparison is successful

Returns:

. True if variable equals compareValue, otherwise false