Apache Portable Runtime
Typedefs | Functions
Shared Memory Routines
Apache Portability Runtime library


typedef struct apr_shm_t apr_shm_t


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_remove (const char *filename, apr_pool_t *pool)
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_detach (apr_shm_t *m)
void * apr_shm_baseaddr_get (const apr_shm_t *m)
apr_size_t apr_shm_size_get (const apr_shm_t *m)
apr_pool_tapr_shm_pool_get (const apr_shm_t *theshm)

Typedef Documentation

typedef struct apr_shm_t apr_shm_t

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

Function Documentation

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.

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.
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.

mThe shared memory segment from which to retrieve the base address.
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 accessable a shared memory segment.

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.
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_destroy ( apr_shm_t m)

Destroy a shared memory segment and associated memory.

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.

mThe shared memory structure representing the segment to detach from.
apr_pool_t* apr_shm_pool_get ( const apr_shm_t theshm)

Get the pool used by this shared memory segment.

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.

filenameThe filename associated with shared-memory segment which needs to be removed
poolThe pool used for file operations
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 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.

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