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Collaboration diagram for Shared Memory Routines:

Macros

#define APR_SHM_NS_LOCAL
 
#define APR_SHM_NS_GLOBAL
 

Typedefs

typedef struct apr_shm_t apr_shm_t
 

Functions

apr_status_t apr_shm_create (apr_shm_t **m, apr_size_t reqsize, const char *filename, apr_pool_t *pool)
 
apr_status_t apr_shm_create_ex (apr_shm_t **m, apr_size_t reqsize, const char *filename, apr_pool_t *pool, apr_int32_t flags)
 
apr_status_t apr_shm_remove (const char *filename, apr_pool_t *pool)
 
apr_status_t apr_shm_delete (apr_shm_t *m)
 
apr_status_t apr_shm_destroy (apr_shm_t *m)
 
apr_status_t apr_shm_attach (apr_shm_t **m, const char *filename, apr_pool_t *pool)
 
apr_status_t apr_shm_attach_ex (apr_shm_t **m, const char *filename, apr_pool_t *pool, apr_int32_t flags)
 
apr_status_t apr_shm_detach (apr_shm_t *m)
 
voidapr_shm_baseaddr_get (const apr_shm_t *m)
 
apr_size_t apr_shm_size_get (const apr_shm_t *m)
 
 APR_PERMS_SET_IMPLEMENT (shm)
 
 APR_POOL_DECLARE_ACCESSOR (shm)
 

Detailed Description

Macro Definition Documentation

#define APR_SHM_NS_GLOBAL
Value:
2 /* Create or attach to named shared memory
* segment in the "Global" namespace on
* Windows. (Ignored on other platforms.)
*/
#define APR_SHM_NS_LOCAL
Value:
1 /* Create or attach to named shared memory
* segment in the "Local" namespace on
* Windows. (Ignored on other platforms.)
* By default, the "Global" namespace is
* used for privileged processes and the
* "Local" namespace is used otherwise.
*/

Special processing flags for apr_shm_create_ex() and apr_shm_attach_ex().

Typedef Documentation

typedef struct apr_shm_t apr_shm_t

Private, platform-specific data struture representing a shared memory segment.

Function Documentation

APR_PERMS_SET_IMPLEMENT ( shm  )

Set shared memory permissions.

APR_POOL_DECLARE_ACCESSOR ( shm  )

Get the pool used by this shared memory segment.

apr_status_t apr_shm_attach ( apr_shm_t **  m,
const char *  filename,
apr_pool_t pool 
)

Attach to a shared memory segment that was created by another process.

Parameters
mThe shared memory structure to create.
filenameThe file used to create the original segment. (This MUST match the original filename.)
poolthe pool from which to allocate the shared memory structure for this process.
apr_status_t apr_shm_attach_ex ( apr_shm_t **  m,
const char *  filename,
apr_pool_t pool,
apr_int32_t  flags 
)

Attach to a shared memory segment that was created by another process, with platform-specific processing.

Parameters
mThe shared memory structure to create.
filenameThe file used to create the original segment. (This MUST match the original filename.)
poolthe pool from which to allocate the shared memory structure for this process.
flagsmask of APR_SHM_* (defined above)
void* apr_shm_baseaddr_get ( const apr_shm_t m)

Retrieve the base address of the shared memory segment. NOTE: This address is only usable within the callers address space, since this API does not guarantee that other attaching processes will maintain the same address mapping.

Parameters
mThe shared memory segment from which to retrieve the base address.
Returns
address, aligned by APR_ALIGN_DEFAULT.
apr_status_t apr_shm_create ( apr_shm_t **  m,
apr_size_t  reqsize,
const char *  filename,
apr_pool_t pool 
)

Create and make accessible a shared memory segment with default properties.

Parameters
mThe shared memory structure to create.
reqsizeThe desired size of the segment.
filenameThe file to use for shared memory on platforms that require it.
poolthe pool from which to allocate the shared memory structure.
Remarks
A note about Anonymous vs. Named shared memory segments: Not all plaforms support anonymous shared memory segments, but in some cases it is prefered over other types of shared memory implementations. Passing a NULL 'file' parameter to this function will cause the subsystem to use anonymous shared memory segments. If such a system is not available, APR_ENOTIMPL is returned.
A note about allocation sizes: On some platforms it is necessary to store some metainformation about the segment within the actual segment. In order to supply the caller with the requested size it may be necessary for the implementation to request a slightly greater segment length from the subsystem. In all cases, the apr_shm_baseaddr_get() function will return the first usable byte of memory.
apr_status_t apr_shm_create_ex ( apr_shm_t **  m,
apr_size_t  reqsize,
const char *  filename,
apr_pool_t pool,
apr_int32_t  flags 
)

Create and make accessible a shared memory segment with platform- specific processing.

Parameters
mThe shared memory structure to create.
reqsizeThe desired size of the segment.
filenameThe file to use for shared memory on platforms that require it.
poolthe pool from which to allocate the shared memory structure.
flagsmask of APR_SHM_* (defined above)
Remarks
A note about Anonymous vs. Named shared memory segments: Not all plaforms support anonymous shared memory segments, but in some cases it is prefered over other types of shared memory implementations. Passing a NULL 'file' parameter to this function will cause the subsystem to use anonymous shared memory segments. If such a system is not available, APR_ENOTIMPL is returned.
A note about allocation sizes: On some platforms it is necessary to store some metainformation about the segment within the actual segment. In order to supply the caller with the requested size it may be necessary for the implementation to request a slightly greater segment length from the subsystem. In all cases, the apr_shm_baseaddr_get() function will return the first usable byte of memory.
apr_status_t apr_shm_delete ( apr_shm_t m)

Delete named resource associated with a shared memory segment, preventing attachments to the resource.

Parameters
mThe shared memory segment structure to delete.
Remarks
This function is only supported on platforms which support name-based shared memory segments, and will return APR_ENOTIMPL on platforms without such support. Removing the file while the shm is in use is not entirely portable, caller may use this to enhance obscurity of the resource, but be prepared for the call to fail, and for concurrent attempts to create a resource of the same name to also fail. The pool cleanup of apr_shm_create (apr_shm_destroy) also removes the named resource.
apr_status_t apr_shm_destroy ( apr_shm_t m)

Destroy a shared memory segment and associated memory.

Parameters
mThe shared memory segment structure to destroy.
apr_status_t apr_shm_detach ( apr_shm_t m)

Detach from a shared memory segment without destroying it.

Parameters
mThe shared memory structure representing the segment to detach from.
apr_status_t apr_shm_remove ( const char *  filename,
apr_pool_t pool 
)

Remove named resource associated with a shared memory segment, preventing attachments to the resource, but not destroying it.

Parameters
filenameThe filename associated with shared-memory segment which needs to be removed
poolThe pool used for file operations
Remarks
This function is only supported on platforms which support name-based shared memory segments, and will return APR_ENOTIMPL on platforms without such support. Removing the file while the shm is in use is not entirely portable, caller may use this to enhance obscurity of the resource, but be prepared for the call to fail, and for concurrent attempts to create a resource of the same name to also fail. The pool cleanup of apr_shm_create (apr_shm_destroy) also removes the named resource.
apr_size_t apr_shm_size_get ( const apr_shm_t m)

Retrieve the length of a shared memory segment in bytes.

Parameters
mThe shared memory segment from which to retrieve the segment length.