Opens an existing shared memory segment or, if one with the specified name doesn't exist, creates a new one.

Syntax

#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 PR_Open.

Returns

Pointer to opaque structure PRSharedMemory, or NULL if an error occurs. Retrieve the reason for the failure by calling PR_GetError and PR_GetOSError.

Description

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.