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