Originální popis anglicky:
posix_typed_mem_open - open a typed memory object (
ADVANCED REALTIME)
Návod, kniha: POSIX Programmer's Manual
#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 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 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. 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
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
- 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.
None.
None.
None.
None.
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>
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
.
