открыть объект типизированной памяти (РАСШИРЕННОЕ РЕАЛЬНОЕ ВРЕМЯ) (open a typed memory object (ADVANCED REALTIME))
Пролог (Prolog)
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.
Имя (Name)
posix_typed_mem_open — open a typed memory object (ADVANCED
REALTIME)
Синопсис (Synopsis)
#include <sys/mman.h>
int posix_typed_mem_open(const char *name, int oflag, int tflag);
Описание (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.
Возвращаемое значение (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.
Ошибки (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.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.14, File Descriptor Allocation, 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.1‐2017, fcntl.h(0p),
sys_mman.h(0p)
