qshm.c File Reference

Shared-memory APIs. More...

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Functions
int	qshm_init (const char *keyfile, int keyid, size_t size, bool recreate)
	Initialize shared memory.
int	qshm_getid (const char *keyfile, int keyid)
	Get the identifier of existing shared memory.
void *	qshm_get (int shmid)
	Get a pointer to shared memory.
bool	qshm_free (int shmid)
	Free shared memory.

Detailed Description

Shared-memory APIs.

Note

[your header file]
struct SharedData {
  (... structrue definitions ...)
}
 
[shared memory creater]
// create shared memory
int shmid = qshm_init("/some/file/for/generating/unique/key", 's', sizeof(struct SharedData), true);
if(shmid < 0) {
  printf("ERROR: Can't initialize shared memory.\n");
  return -1;
}
 
// get shared memory pointer
struct SharedData *sdata = (SharedData *)qshm_get(shmid);
if(sdata == NULL) {
  printf("ERROR: Can't get shared memory.\n");
  return -1;
}
 
[shared memory user]
// get shared memory id
int shmid = qshm_getid("/some/file/for/generating/unique/key", 's');
if(shmid < 0) {
  printf("ERROR: Can't get shared memory id.\n");
  return -1;
}
 
// get shared memory pointer
struct SharedData *sdata = (SharedData *)qshm_get(shmid);
if(sdata == NULL) {
  printf("ERROR: Can't get shared memory.\n");
  return -1;
}

Definition in file qshm.c.

Function Documentation

qshm_init()

int qshm_init	(	const char *	keyfile,
		int	keyid,
		size_t	size,
		bool	recreate )

Initialize shared memory.

Parameters

keyfile	seed used to generate a unique IPC key
keyid	seed used to generate a unique IPC key
size	size of the shared memory
recreate	set to true to recreate the shared memory if it already exists

Returns

non-negative shared memory identifier on success, or -1 on failure.

Definition at line 91 of file qshm.c.

qshm_getid()

int qshm_getid	(	const char *	keyfile,
		int	keyid )

Get the identifier of existing shared memory.

Parameters

keyfile	seed used to generate a unique IPC key
keyid	seed used to generate a unique IPC key

Returns

non-negative shared memory identifier on success, or -1 on failure.

Definition at line 127 of file qshm.c.

qshm_get()

void * qshm_get

(

int

shmid

)

Get a pointer to shared memory.

Parameters

shmid

shared memory identifier

Returns

pointer to shared memory, or NULL on failure.

Definition at line 149 of file qshm.c.

qshm_free()

bool qshm_free

(

int

shmid

)

Free shared memory.

Parameters

shmid

shared memory identifier

Returns

true on success, otherwise false.

Definition at line 167 of file qshm.c.