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qShm.c File Reference

Shared Memory Handling API. More…

Functions
int	qShmInit (const char *keyfile, int keyid, size_t size, bool ifexistdestroy)
	Initialize shared-memory.
int	qShmGetId (const char *keyfile, int keyid)
	Get shared memory identifier by keyfile and keyid which are used for qShmInit().
void *	qShmGet (int shmid)
	Get a pointer of shared memory.
bool	qShmFree (int shmid)
	De-allocate shared memory.

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Detailed Description

Shared Memory Handling API.

Note:

   [your header file]
   struct SharedData {
     (... structrue definitions ...)
   }
   [shared memory creater]
   // create shared memory
   int shmid = qShmInit("/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 *)qShmGet(shmid);
   if(sdata == NULL) {
     printf("ERROR: Can't get shared memory.n");
     return -1;
   }
   [shared memory user]
   // get shared memory id
   int shmid = qShmGetId("/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 *)qShmGet(shmid);
   if(sdata == NULL) {
     printf("ERROR: Can't get shared memory.n");
     return -1;
   }

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Function Documentation

int qShmInit	(	const char *	keyfile,
		int	keyid,
		size_t	size,
		bool	ifexistdestroy
	)

Initialize shared-memory.

Parameters:

	keyfile	seed for generating unique IPC key
	keyid	seed for generating unique IPC key
	size	size of shared memory
	ifexistdestroy	set to true for if shared memory already exists, try to destroy it first

Returns:

non-negative shared memory identifier if successful, otherwise returns -1

int qShmGetId	(	const char *	keyfile,
		int	keyid
	)

Get shared memory identifier by keyfile and keyid which are used for qShmInit().

Parameters:

	keyfile	seed for generating unique IPC key
	keyid	seed for generating unique IPC key

Returns:

non-negative shared memory identifier if successful, otherwise returns -1

void* qShmGet

(

int

shmid

)

Get a pointer of shared memory.

Parameters:

shmid

shared memory identifier

Returns:

a pointer of shared memory

bool qShmFree

(

int

shmid

)

De-allocate shared memory.

Parameters:

shmid

shared memory identifier

Returns:

true if successful, otherwise returns false

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