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+/* -*- 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/. */
+
+/*
+** 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___ */