POSIX_TYPED_MEM_OPEN(P) POSIX Programmer's Manual POSIX_TYPED_MEM_OPEN(P)NAMEposix_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
functions 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 implementa‐
tion-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 mem‐
ory 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 fol‐
lowing 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 subse‐
quent 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 contigu‐
ous 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_ALLO‐
CATE_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-cho‐
sen 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 unal‐
located 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 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 descrip‐
tor connected to a typed memory object by this function.
The file status flags of the open file description shall be set accord‐
ing 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 lowest numbered unused
file descriptor. Otherwise, it shall return -1 and set errno to indi‐
cate 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 sig‐
nal.
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 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 ALSOclose() , 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, Copyright (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.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 POSIX_TYPED_MEM_OPEN(P)
