The Tor Browser: nsprpub/pr/include/prshm.h@925c144e1f1f (annotated)

nsprpub/pr/include/prshm.h@925c144e1f1f (annotated)

nsprpub/pr/include/prshm.h

Fri, 16 Jan 2015 18:13:44 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 18:13:44 +0100
branch: TOR_BUG_9701
changeset 14: 925c144e1f1f
permissions: -rw-r--r--

Integrate suggestion from review to improve consistency with existing code.

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /*
 ** prshm.h -- NSPR Shared Memory
 **
 ** NSPR Named Shared Memory API provides a cross-platform named
 ** shared-memory interface. NSPR Named Shared Memory is modeled on
 ** similar constructs in Unix and Windows operating systems. Shared
 ** memory allows multiple processes to access one or more common shared
 ** memory regions, using it as an inter-process communication channel.
 **
 ** Notes on Platform Independence:
 **   NSPR Named Shared Memory is built on the native services offered
 **   by most platforms. The NSPR Named Shared Memory API tries to
 **   provide a least common denominator interface so that it works
 **   across all supported platforms. To ensure that it works everywhere,
 **   some platform considerations must be accomodated and the protocol
 **   for using NSPR Shared Memory API must be observed.
 **
 ** Protocol:
 **   Multiple shared memories can be created using NSPR's Shared Memory
 **   feature. For each named shared memory, as defined by the name
 **   given in the PR_OpenSharedMemory() call, a protocol for using the
 **   shared memory API is required to ensure desired behavior. Failing
 **   to follow the protocol may yield unpredictable results.
 **
 **   PR_OpenSharedMemory() will create the shared memory segment, if it
 **   does not already exist, or open a connection that the existing
 **   shared memory segment if it already exists.
 **
 **   PR_AttachSharedMemory() should be called following
 **   PR_OpenSharedMemory() to map the memory segment to an address in
 **   the application's address space.
 **
 **   PR_AttachSharedMemory() may be called to re-map a shared memory
 **   segment after detaching the same PRSharedMemory object. Be
 **   sure to detach it when done.
 **
 **   PR_DetachSharedMemory() should be called to un-map the shared
 **   memory segment from the application's address space.
 **
 **   PR_CloseSharedMemory() should be called when no further use of the
 **   PRSharedMemory object is required within a process. Following a
 **   call to  PR_CloseSharedMemory() the PRSharedMemory object is
 **   invalid and cannot be reused.
 **
 **   PR_DeleteSharedMemory() should be called before process
 **   termination. After calling PR_DeleteSharedMemory() any further use
 **   of the shared memory associated with the name may cause
 **   unpredictable results.
 **
 ** Files:
 **   The name passed to PR_OpenSharedMemory() should be a valid filename
 **   for a unix platform. PR_OpenSharedMemory() creates file using the
 **   name passed in. Some platforms may mangle the name before creating
 **   the file and the shared memory.
 **
 **   The unix implementation may use SysV IPC shared memory, Posix
 **   shared memory, or memory mapped files; the filename may used to
 **   define the namespace. On Windows, the name is significant, but
 **   there is no file associated with name.
 **
 **   No assumptions about the persistence of data in the named file
 **   should be made. Depending on platform, the shared memory may be
 **   mapped onto system paging space and be discarded at process
 **   termination.
 **
 **   All names provided to PR_OpenSharedMemory() should be valid
 **   filename syntax or name syntax for shared memory for the target
 **   platform. Referenced directories should have permissions
 **   appropriate for writing.
 **
 ** Limits:
 **   Different platforms have limits on both the number and size of
 **   shared memory resources. The default system limits on some
 **   platforms may be smaller than your requirements. These limits may
 **   be adjusted on some platforms either via boot-time options or by
 **   setting the size of the system paging space to accomodate more
 **   and/or larger shared memory segment(s).
 **
 ** Security:
 **   On unix platforms, depending on implementation, contents of the
 **   backing store for the shared memory can be exposed via the file
 **   system. Set permissions and or access controls at create and attach
 **   time to ensure you get the desired security.
 **
 **   On windows platforms, no special security measures are provided.
 **
 ** Example:
 **   The test case pr/tests/nameshm1.c provides an example of use as
 **   well as testing the operation of NSPR's Named Shared Memory.
 **
 ** lth. 18-Aug-1999.
 */
 #ifndef prshm_h___
 #define prshm_h___
 #include "prtypes.h"
 #include "prio.h"
 PR_BEGIN_EXTERN_C
 /*
 ** Declare opaque type PRSharedMemory.
 */
 typedef struct PRSharedMemory PRSharedMemory;
 /*
 ** FUNCTION: PR_OpenSharedMemory()
 **
 ** DESCRIPTION:
 **   PR_OpenSharedMemory() creates a new shared-memory segment or
 **   associates a previously created memory segment with 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 is returned. If the shared memory does
 **   not exist, NULL is returned with the error set to
 **   PR_FILE_NOT_FOUND_ERROR.
 **
 ** INPUTS:
 **   name -- the name the shared-memory segment is known as.
 **   size -- the size of the shared memory segment.
 **   flags -- Options for creating the shared memory
 **   mode -- Same as is passed to PR_Open()
 **
 ** OUTPUTS:
 **   The shared memory is allocated.
 **
 ** RETURNS: Pointer to opaque structure PRSharedMemory or NULL.
 **   NULL is returned on error. The reason for the error can be
 **   retrieved via PR_GetError() and PR_GetOSError();
 **
 */
 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 */
 /*
 ** FUNCTION: PR_AttachSharedMemory()
 **
 ** DESCRIPTION:
 ** PR_AttachSharedMemory() maps the shared-memory described by
 ** shm to the current process.
 **
 ** INPUTS:
 **   shm -- The handle returned from PR_OpenSharedMemory().
 **   flags -- options for mapping the shared memory.
 **   PR_SHM_READONLY causes the memory to be attached
 **   read-only.
 **
 ** OUTPUTS:
 **   On success, the shared memory segment represented by shm is mapped
 **   into the process' address space.
 **
 ** RETURNS: Address where shared memory is mapped, or NULL.
 **   NULL is returned on error. The reason for the error can be
 **   retrieved via PR_GetError() and PR_GetOSError();
 **
 **
 */
 NSPR_API( void * )
     PR_AttachSharedMemory(
         PRSharedMemory *shm,
         PRIntn  flags
 );
 /* Define values for PR_AttachSharedMemory(...,flags) */
 #define PR_SHM_READONLY 0x01
 /*
 ** FUNCTION: PR_DetachSharedMemory()
 **
 ** DESCRIPTION:
 **   PR_DetachSharedMemory() detaches the shared-memory described
 **   by shm.
 **
 ** INPUTS:
 **   shm -- The handle returned from PR_OpenSharedMemory().
 **   addr -- The address at which the memory was attached.
 **
 ** OUTPUTS:
 **   The shared memory mapped to an address via a previous call to
 **   PR_AttachSharedMemory() is unmapped.
 **
 ** RETURNS: PRStatus
 **
 */
 NSPR_API( PRStatus )
     PR_DetachSharedMemory(
         PRSharedMemory *shm,
         void  *addr
 );
 /*
 ** FUNCTION: PR_CloseSharedMemory()
 **
 ** DESCRIPTION:
 **   PR_CloseSharedMemory() closes the shared-memory described by
 **   shm.
 **
 ** INPUTS:
 **   shm -- The handle returned from PR_OpenSharedMemory().
 **
 ** OUTPUTS:
 **   the shared memory represented by shm is closed
 **
 ** RETURNS: PRStatus
 **
 */
 NSPR_API( PRStatus )
     PR_CloseSharedMemory(
         PRSharedMemory *shm
 );
 /*
 ** FUNCTION: PR_DeleteSharedMemory()
 **
 ** DESCRIPTION:
 **   The shared memory resource represented by name is released.
 **
 ** INPUTS:
 **   name -- the name the shared-memory segment
 **
 ** OUTPUTS:
 **   depending on platform, resources may be returned to the underlying
 **   operating system.
 **
 ** RETURNS: PRStatus
 **
 */
 NSPR_API( PRStatus )
     PR_DeleteSharedMemory(
         const char *name
 );
 PR_END_EXTERN_C
 #endif /* prshm_h___ */

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nsprpub/pr/include/prshm.h@925c144e1f1f (annotated)

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