Atomic Operations

Functions
apr_status_t	apr_atomic_init (apr_pool_t *p)
apr_uint32_t	apr_atomic_read32 (volatile apr_uint32_t *mem)
void	apr_atomic_set32 (volatile apr_uint32_t *mem, apr_uint32_t val)
apr_uint32_t	apr_atomic_add32 (volatile apr_uint32_t *mem, apr_uint32_t val)
void	apr_atomic_sub32 (volatile apr_uint32_t *mem, apr_uint32_t val)
apr_uint32_t	apr_atomic_inc32 (volatile apr_uint32_t *mem)
int	apr_atomic_dec32 (volatile apr_uint32_t *mem)
apr_uint32_t	apr_atomic_cas32 (volatile apr_uint32_t *mem, apr_uint32_t with, apr_uint32_t cmp)
apr_uint32_t	apr_atomic_xchg32 (volatile apr_uint32_t *mem, apr_uint32_t val)
void *	apr_atomic_casptr (volatile void **mem, void *with, const void *cmp)
void *	apr_atomic_xchgptr (volatile void **mem, void *with)

Detailed Description

Function Documentation

apr_uint32_t apr_atomic_add32	(	volatile apr_uint32_t *	mem,
		apr_uint32_t	val
	)

atomically add 'val' to an apr_uint32_t

Parameters

mem	pointer to the object
val	amount to add

Returns

old value pointed to by mem

apr_uint32_t apr_atomic_cas32	(	volatile apr_uint32_t *	mem,
		apr_uint32_t	with,
		apr_uint32_t	cmp
	)

compare an apr_uint32_t's value with 'cmp'. If they are the same swap the value with 'with'

Parameters

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

Returns

the old value of *mem

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_dec32

(

volatile apr_uint32_t *

mem

)

atomically decrement an apr_uint32_t by 1

Parameters

mem	pointer to the atomic value

Returns

zero if the value becomes zero on decrement, otherwise non-zero

apr_uint32_t apr_atomic_inc32

(

volatile apr_uint32_t *

mem

)

atomically increment an apr_uint32_t by 1

Parameters

mem	pointer to the object

Returns

old value pointed to by mem

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

Remarks

Programs do NOT need to call this directly. APR will call this automatically from apr_initialize.

apr_uint32_t apr_atomic_read32

(

volatile apr_uint32_t *

mem

)

atomically read an apr_uint32_t from memory

Parameters

mem	the pointer

void apr_atomic_set32	(	volatile apr_uint32_t *	mem,
		apr_uint32_t	val
	)

atomically set an apr_uint32_t in memory

Parameters

mem	pointer to the object
val	value that the object will assume

void apr_atomic_sub32	(	volatile apr_uint32_t *	mem,
		apr_uint32_t	val
	)

atomically subtract 'val' from an apr_uint32_t

Parameters

mem	pointer to the object
val	amount to subtract

apr_uint32_t apr_atomic_xchg32	(	volatile apr_uint32_t *	mem,
		apr_uint32_t	val
	)

exchange an apr_uint32_t's value with 'val'.

Parameters

mem	pointer to the value
val	what to swap it with

Returns

the old value of *mem

void* apr_atomic_xchgptr	(	volatile void **	mem,
		void *	with
	)

exchange a pair of pointer values

Parameters

mem	pointer to the pointer
with	what to swap it with

Returns

the old value of the pointer