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PR_OpenSharedMemory
===================
Opens an existing shared memory segment or, if one with the specified
name doesn't exist, creates a new one.
Syntax
------
.. code::
#include <prshm.h>
NSPR_API( PRSharedMemory * )
PR_OpenSharedMemory(
const char *name,
PRSize size,
PRIntn flags,
PRIntn mode
);
/* Define values for PR_OpenShareMemory(...,create) */
#define PR_SHM_CREATE 0x1 /* create if not exist */
#define PR_SHM_EXCL 0x2 /* fail if already exists */
Parameters
~~~~~~~~~~
The function has the following parameters:
name
The name of the shared memory segment.
size
The size of the shared memory segment.
flags
Options for creating the shared memory.
mode
Same as passed to :ref:`PR_Open`.
Returns
~~~~~~~
Pointer to opaque structure ``PRSharedMemory``, or ``NULL`` if an error
occurs. Retrieve the reason for the failure by calling :ref:`PR_GetError`
and :ref:`PR_GetOSError`.
Description
-----------
:ref:`PR_OpenSharedMemory` creates a new shared memory segment or
associates a previously created memory segment with the specified name.
When parameter ``create`` is (``PR_SHM_EXCL`` \| ``PR_SHM_CREATE``) and
the shared memory already exists, the function returns ``NULL`` with the
error set to ``PR_FILE_EXISTS_ERROR``.
When parameter ``create`` is ``PR_SHM_CREATE`` and the shared memory
already exists, a handle to that memory segment is returned. If the
segment does not exist, it is created and a pointer to the related
``PRSharedMemory`` structure is returned.
When parameter ``create`` is 0, and the shared memory exists, a pointer
to a ``PRSharedMemory`` structure is returned. If the shared memory does
not exist, ``NULL`` is returned with the error set to
``PR_FILE_NOT_FOUND_ERROR``.