POSIX_TYPED_MEM_OPEN(3P)                            POSIX Programmer's Manual                           POSIX_TYPED_MEM_OPEN(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       posix_typed_mem_open - open a typed memory object (ADVANCED REALTIME)

SYNOPSIS
       #include <sys/mman.h>

       int posix_typed_mem_open(const char *name, int oflag, int tflag);


DESCRIPTION
       The  posix_typed_mem_open() function shall establish a connection between the typed memory object specified by the string
       pointed to by name and a file descriptor. It shall create an open file description that refers to the typed memory object
       and  a file descriptor that refers to that open file description. The file descriptor is used by other functions to refer
       to that typed memory object. It is unspecified whether the name appears in the file system and is visible to other  func-
       tions that take pathnames as arguments. The name argument shall conform to the construction rules for a pathname. If name
       begins with the slash character, then processes calling posix_typed_mem_open() with the same value of name shall refer to
       the  same typed memory object. If name does not begin with the slash character, the effect is implementation-defined. The
       interpretation of slash characters other than the leading slash character in name is implementation-defined.

       Each typed memory object supported in a system shall be identified by a name which  specifies  not  only  its  associated
       typed  memory  pool,  but also the path or port by which it is accessed. That is, the same typed memory pool accessed via
       several different ports shall have several different corresponding names. The binding  between  names  and  typed  memory
       objects  is  established  in  an  implementation-defined  manner.  Unlike  shared  memory objects, there is no way within
       IEEE Std 1003.1-2001 for a program to create a typed memory object.

       The value of tflag shall determine how the typed memory object behaves when subsequently mapped by calls  to  mmap().  At
       most, one of the following flags defined in <sys/mman.h> may be specified:

       POSIX_TYPED_MEM_ALLOCATE
              Allocate on mmap().

       POSIX_TYPED_MEM_ALLOCATE_CONTIG
              Allocate contiguously on mmap().

       POSIX_TYPED_MEM_MAP_ALLOCATABLE
              Map on mmap(), without affecting allocatability.


       If  tflag has the flag POSIX_TYPED_MEM_ALLOCATE specified, any subsequent call to mmap() using the returned file descrip-
       tor shall result in allocation and mapping of typed memory from the specified typed memory pool. The allocated memory may
       be  a  contiguous  previously  unallocated area of the typed memory pool or several non-contiguous previously unallocated
       areas (mapped to a contiguous portion of the process address space).  If tflag has the flag POSIX_TYPED_MEM_ALLOCATE_CON-
       TIG specified, any subsequent call to mmap() using the returned file descriptor shall result in allocation and mapping of
       a single contiguous previously unallocated area of the typed memory pool (also mapped to  a  contiguous  portion  of  the
       process address space).  If tflag has none of the flags POSIX_TYPED_MEM_ALLOCATE or POSIX_TYPED_MEM_ALLOCATE_CONTIG spec-
       ified, any subsequent call to mmap() using the returned file descriptor shall map an  application-chosen  area  from  the
       specified  typed  memory  pool  such  that this mapped area becomes unavailable for allocation until unmapped by all pro-
       cesses. If tflag has the flag POSIX_TYPED_MEM_MAP_ALLOCATABLE specified, any subsequent call to mmap() using the returned
       file descriptor shall map an application-chosen area from the specified typed memory pool without an effect on the avail-
       ability of that area for allocation; that is, mapping such an object leaves each byte of the mapped area  unallocated  if
       it  was unallocated prior to the mapping or allocated if it was allocated prior to the mapping. The appropriate privilege
       to specify the POSIX_TYPED_MEM_MAP_ALLOCATABLE flag is implementation-defined.

       If successful, posix_typed_mem_open() shall return a file descriptor for the typed memory object that is the lowest  num-
       bered  file  descriptor  not  currently  open  for that process. The open file description is new, and therefore the file
       descriptor shall not share it with any other processes. It is unspecified whether the file offset is set. The  FD_CLOEXEC
       file descriptor flag associated with the new file descriptor shall be cleared.

       The   behavior   of   msync(),   ftruncate(),   and   all   file   operations   other  than  mmap(),  posix_mem_offset(),
       posix_typed_mem_get_info(), fstat(), dup(), dup2(), and close(), is unspecified when passed a file  descriptor  connected
       to a typed memory object by this function.

       The file status flags of the open file description shall be set according to the value of oflag. Applications shall spec-
       ify exactly one of the three access mode values described below and defined in the <fcntl.h>  header,  as  the  value  of
       oflag.

       O_RDONLY
              Open for read access only.

       O_WRONLY
              Open for write access only.

       O_RDWR Open for read or write access.


RETURN VALUE
       Upon successful completion, the posix_typed_mem_open() function shall return a non-negative integer representing the low-
       est numbered unused file descriptor. Otherwise, it shall return -1 and set errno to indicate the error.

ERRORS
       The posix_typed_mem_open() function shall fail if:

       EACCES The typed memory object exists and the permissions specified by oflag are denied.

       EINTR  The posix_typed_mem_open() operation was interrupted by a signal.

       EINVAL The flags specified in tflag are invalid (more than one of POSIX_TYPED_MEM_ALLOCATE, POSIX_TYPED_MEM_ALLOCATE_CON-
              TIG, or POSIX_TYPED_MEM_MAP_ALLOCATABLE is specified).

       EMFILE Too many file descriptors are currently in use by this process.

       ENAMETOOLONG
              The length of the name argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

       ENFILE Too many file descriptors are currently open in the system.

       ENOENT The named typed memory object does not exist.

       EPERM  The caller lacks the appropriate privilege to specify the flag POSIX_TYPED_MEM_MAP_ALLOCATABLE in argument tflag.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       close(),  dup(), exec(), fcntl(), fstat() , ftruncate(), mmap(), msync(), posix_mem_offset(), posix_typed_mem_get_info(),
       umask(), the Base Definitions volume of IEEE Std 1003.1-2001, <fcntl.h>, <sys/mman.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                      POSIX_TYPED_MEM_OPEN(3P)