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POSIX_TYPED_MEM_OPEN(3P) POSIX Programmer's Manual POSIX_TYPED_MEM_OPEN(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
posix_typed_mem_open — open a typed memory object (ADVANCED REALTIME)
#include <sys/mman.h>
int posix_typed_mem_open(const char *name, int oflag, int tflag);
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 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 that is the lowest numbered 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 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.
Upon successful completion, the posix_typed_mem_open() function shall
return a non-negative integer representing the lowest numbered unused
file descriptor. Otherwise, it shall return −1 and set errno to
indicate the error.
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.
None.
None.
None.
None.
close(3p), dup(3p), exec(1p), fcntl(3p), fstat(3p), ftruncate(3p),
mmap(3p), msync(3p), posix_mem_offset(3p),
posix_typed_mem_get_info(3p), umask(3p)
The Base Definitions volume of POSIX.1‐2008, fcntl.h(0p),
sys_mman.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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 2013 POSIX_TYPED_MEM_OPEN(3P)
Pages that refer to this page: sys_mman.h(0p), mmap(3p), munmap(3p), posix_mem_offset(3p), posix_typed_mem_get_info(3p)