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



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

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 shall be
       allocated as described in Section 2.14, File Descriptor Allocation and
       can be 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 functions that take pathnames as arguments. The name
       argument conforms to the construction rules for a pathname, except that
       the interpretation of <slash> characters other than the leading <slash>
       character in name is implementation-defined, and that the length limits
       for the name argument are implementation-defined and need not be the
       same as the pathname limits {PATH_MAX} and {NAME_MAX}.  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.

       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 POSIX.1-2008 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 descriptor 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_CONTIG 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 specified, 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
       processes. 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 availability 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. Appropriate
       privileges to specify the POSIX_TYPED_MEM_MAP_ALLOCATABLE flag are
       implementation-defined.

       If successful, posix__typed__mem__open() shall return a file descriptor
       for the typed memory object.  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 specify 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 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_CONTIG, or
              POSIX_TYPED_MEM_MAP_ALLOCATABLE is specified).

       EMFILE All file descriptors available to the process are currently
              open.

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

       ENOENT The named typed memory object does not exist.

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

       The posix__typed__mem__open() function may fail if:

       ENAMETOOLONG
              The length of the name argument exceeds {_POSIX_PATH_MAX} on
              systems that do not support the XSI option or exceeds
              {_XOPEN_PATH_MAX} on XSI systems, or has a pathname component
              that is longer than {_POSIX_NAME_MAX} on systems that do not
              support the XSI option or longer than {_XOPEN_NAME_MAX} on XSI
              systems.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Section 2.14, File Descriptor Allocation, close(), dup(), exec,
       fcntl(), fstat(), ftruncate(), mmap(), msync(), posix__mem__offset(),
       posix__typed__mem__get__info(), umask()

       The Base Definitions volume of POSIX.1-2017, <fcntl.h>, <sys_mman.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017              POSIX_TYPED_MEM_OPEN(3)
