Atomic Operations
[Apache Portability Runtime library]

Functions
apr_status_t	apr_atomic_init (apr_pool_t *p)
apr_uint32_t	apr_atomic_read (volatile apr_atomic_t *mem)
void	apr_atomic_set (volatile apr_atomic_t *mem, apr_uint32_t val)
void	apr_atomic_add (volatile apr_atomic_t *mem, apr_uint32_t val)
void	apr_atomic_inc (volatile apr_atomic_t *mem)
int	apr_atomic_dec (volatile apr_atomic_t *mem)
apr_uint32_t	apr_atomic_cas (volatile apr_uint32_t *mem, long with, long cmp)
void *	apr_atomic_casptr (volatile void **mem, void *with, const void *cmp)
Variables
typedef	apr_atomic_t

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Function Documentation

void apr_atomic_add	(	volatile apr_atomic_t *	mem,
		apr_uint32_t	val
	)

Add 'val' to the atomic variable

Parameters:

	mem	pointer to the atomic value
	val	the addition

apr_uint32_t apr_atomic_cas	(	volatile apr_uint32_t *	mem,
		long	with,
		long	cmp
	)

compare the atomic's value with cmp. If they are the same swap the value with 'with'

Parameters:

	mem	pointer to the atomic value
	with	what to swap it with
	cmp	the value to compare it to

Returns:

the old value of the atomic

Warning:

do not mix apr_atomic's with the CAS function. on some platforms they may be implemented by different mechanisms

void* apr_atomic_casptr	(	volatile void **	mem,
		void *	with,
		const void *	cmp
	)

compare the pointer's value with cmp. If they are the same swap the value with 'with'

Parameters:

	mem	pointer to the pointer
	with	what to swap it with
	cmp	the value to compare it to

Returns:

the old value of the pointer

int apr_atomic_dec

(

volatile apr_atomic_t *

mem

)

decrement the atomic variable by 1

Parameters:

mem

pointer to the atomic value

Returns:

zero if the value is zero, otherwise non-zero

void apr_atomic_inc

(

volatile apr_atomic_t *

mem

)

increment the atomic variable by 1

Parameters:

mem

pointer to the atomic value

apr_status_t apr_atomic_init

(

apr_pool_t *

p

)

this function is required on some platforms to initialize the atomic operation's internal structures

Parameters:

p

pool

Returns:

APR_SUCCESS on successful completion

apr_uint32_t apr_atomic_read

(

volatile apr_atomic_t *

mem

)

read the value stored in a atomic variable

Parameters:

mem

the pointer

Warning:

on certain platforms this number is not stored directly in the pointer. in others it is

void apr_atomic_set	(	volatile apr_atomic_t *	mem,
		apr_uint32_t	val
	)

set the value for atomic.

Parameters:

	mem	the pointer
	val	the value

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Variable Documentation

typedef apr_atomic_t

structure for holding a atomic value. this number >only< has a 24 bit size on some platforms

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