prshma.h
上传用户:goldcmy89
上传日期:2017-12-03
资源大小:2246k
文件大小:8k
- /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
- /* ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is the Netscape Portable Runtime (NSPR).
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1999-2000
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either the GNU General Public License Version 2 or later (the "GPL"), or
- * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
- /*
- ** prshma.h -- NSPR Anonymous Shared Memory
- **
- ** NSPR provides an anonymous shared memory based on NSPR's PRFileMap
- ** type. The anonymous file-mapped shared memory provides an inheritable
- ** shared memory, as in: the child process inherits the shared memory.
- ** Compare the file-mapped anonymous shared memory to to a named shared
- ** memory described in prshm.h. The intent is to provide a shared
- ** memory that is accessable only by parent and child processes. ...
- ** It's a security thing.
- **
- ** Depending on the underlying platform, the file-mapped shared memory
- ** may be backed by a file. ... surprise! ... On some platforms, no
- ** real file backs the shared memory. On platforms where the shared
- ** memory is backed by a file, the file's name in the filesystem is
- ** visible to other processes for only the duration of the creation of
- ** the file, hopefully a very short time. This restricts processess
- ** that do not inherit the shared memory from opening the file and
- ** reading or writing its contents. Further, when all processes
- ** using an anonymous shared memory terminate, the backing file is
- ** deleted. ... If you are not paranoid, you're not paying attention.
- **
- ** The file-mapped shared memory requires a protocol for the parent
- ** process and child process to share the memory. NSPR provides two
- ** protocols. Use one or the other; don't mix and match.
- **
- ** In the first protocol, the job of passing the inheritable shared
- ** memory is done via helper-functions with PR_CreateProcess(). In the
- ** second protocol, the parent process is responsible for creating the
- ** child process; the parent and child are mutually responsible for
- ** passing a FileMap string. NSPR provides helper functions for
- ** extracting data from the PRFileMap object. ... See the examples
- ** below.
- **
- ** Both sides should adhere strictly to the protocol for proper
- ** operation. The pseudo-code below shows the use of a file-mapped
- ** shared memory by a parent and child processes. In the examples, the
- ** server creates the file-mapped shared memory, the client attaches to
- ** it.
- **
- ** First protocol.
- ** Server:
- **
- ** fm = PR_OpenAnonFileMap(dirName, size, FilemapProt);
- ** addr = PR_MemMap(fm);
- ** attr = PR_NewProcessAttr();
- ** PR_ProcessAttrSetInheritableFileMap( attr, fm, shmname );
- ** PR_CreateProcess(Client);
- ** PR_DestroyProcessAttr(attr);
- ** ... yadda ...
- ** PR_MemUnmap( addr );
- ** PR_CloseFileMap(fm);
- **
- **
- ** Client:
- ** ... started by server via PR_CreateProcess()
- ** fm = PR_GetInheritedFileMap( shmname );
- ** addr = PR_MemMap(fm);
- ** ... yadda ...
- ** PR_MemUnmap(addr);
- ** PR_CloseFileMap(fm);
- **
- **
- ** Second Protocol:
- ** Server:
- **
- ** fm = PR_OpenAnonFileMap(dirName, size, FilemapProt);
- ** fmstring = PR_ExportFileMapAsString( fm );
- ** addr = PR_MemMap(fm);
- ** ... application specific technique to pass fmstring to child
- ** ... yadda ... Server uses his own magic to create child
- ** PR_MemUnmap( addr );
- ** PR_CloseFileMap(fm);
- **
- **
- ** Client:
- ** ... started by server via his own magic
- ** ... application specific technique to find fmstring from parent
- ** fm = PR_ImportFileMapFromString( fmstring )
- ** addr = PR_MemMap(fm);
- ** ... yadda ...
- ** PR_MemUnmap(addr);
- ** PR_CloseFileMap(fm);
- **
- **
- ** lth. 2-Jul-1999.
- **
- ** Note: The second protocol was requested by NelsonB (7/1999); this is
- ** to accomodate servers which already create their own child processes
- ** using platform native methods.
- **
- */
- #ifndef prshma_h___
- #define prshma_h___
- #include "prtypes.h"
- #include "prio.h"
- #include "prproces.h"
- PR_BEGIN_EXTERN_C
- /*
- ** PR_OpenAnonFileMap() -- Creates an anonymous file-mapped shared memory
- **
- ** Description:
- ** PR_OpenAnonFileMap() creates an anonymous shared memory. If the
- ** shared memory already exists, a handle is returned to that shared
- ** memory object.
- **
- ** On Unix platforms, PR_OpenAnonFileMap() uses 'dirName' as a
- ** directory name, without the trailing '/', to contain the anonymous
- ** file. A filename is generated for the name.
- **
- ** On Windows platforms, dirName is ignored.
- **
- ** Inputs:
- ** dirName -- A directory name to contain the anonymous file.
- ** size -- The size of the shared memory
- ** prot -- How the shared memory is mapped. See prio.h
- **
- ** Outputs:
- ** PRFileMap *
- **
- ** Returns:
- ** Pointer to PRFileMap or NULL on error.
- **
- */
- NSPR_API( PRFileMap *)
- PR_OpenAnonFileMap(
- const char *dirName,
- PRSize size,
- PRFileMapProtect prot
- );
- /*
- ** PR_ProcessAttrSetInheritableFileMap() -- Prepare FileMap for export
- ** to my children processes via PR_CreateProcess()
- **
- ** Description:
- ** PR_ProcessAttrSetInheritableFileMap() connects the PRFileMap to
- ** PRProcessAttr with shmname. A subsequent call to PR_CreateProcess()
- ** makes the PRFileMap importable by the child process.
- **
- ** Inputs:
- ** attr -- PRProcessAttr, used to pass data to PR_CreateProcess()
- ** fm -- PRFileMap structure to be passed to the child process
- ** shmname -- The name for the PRFileMap; used by child.
- **
- ** Outputs:
- ** PRFileMap *
- **
- ** Returns:
- ** PRStatus
- **
- */
- NSPR_API(PRStatus)
- PR_ProcessAttrSetInheritableFileMap(
- PRProcessAttr *attr,
- PRFileMap *fm,
- const char *shmname
- );
- /*
- ** PR_GetInheritedFileMap() -- Import a PRFileMap previously exported
- ** by my parent process via PR_CreateProcess()
- **
- ** Description:
- ** PR_GetInheritedFileMap() retrieves a PRFileMap object exported from
- ** its parent process via PR_CreateProcess().
- **
- ** Inputs:
- ** shmname -- The name provided to PR_ProcessAttrSetInheritableFileMap()
- **
- ** Outputs:
- ** PRFileMap *
- **
- ** Returns:
- ** PRFileMap pointer or NULL.
- **
- */
- NSPR_API( PRFileMap *)
- PR_GetInheritedFileMap(
- const char *shmname
- );
- /*
- ** PR_ExportFileMapAsString() -- Creates a string identifying a PRFileMap
- **
- ** Description:
- ** Creates an identifier, as a string, from a PRFileMap object
- ** previously created with PR_OpenAnonFileMap().
- **
- ** Inputs:
- ** fm -- PRFileMap pointer to be represented as a string.
- ** bufsize -- sizeof(buf)
- ** buf -- a buffer of length PR_FILEMAP_STRING_BUFSIZE
- **
- ** Outputs:
- ** buf contains the stringized PRFileMap identifier
- **
- ** Returns:
- ** PRStatus
- **
- */
- NSPR_API( PRStatus )
- PR_ExportFileMapAsString(
- PRFileMap *fm,
- PRSize bufsize,
- char *buf
- );
- #define PR_FILEMAP_STRING_BUFSIZE 128
- /*
- ** PR_ImportFileMapFromString() -- Creates a PRFileMap from the identifying string
- **
- ** Description:
- ** PR_ImportFileMapFromString() creates a PRFileMap object from a
- ** string previously created by PR_ExportFileMapAsString().
- **
- ** Inputs:
- ** fmstring -- string created by PR_ExportFileMapAsString()
- **
- ** Returns:
- ** PRFileMap pointer or NULL.
- **
- */
- NSPR_API( PRFileMap * )
- PR_ImportFileMapFromString(
- const char *fmstring
- );
- PR_END_EXTERN_C
- #endif /* prshma_h___ */