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POSIX_TYPED_MEM_GET_INFO(3P)SIX Programmer's ManualIX_TYPED_MEM_GET_INFO(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_get_info — query typed memory information (ADVANCED
REALTIME)
#include <sys/mman.h>
int posix_typed_mem_get_info(int fildes,
struct posix_typed_mem_info *info);
The posix_typed_mem_get_info() function shall return, in the
posix_tmi_length field of the posix_typed_mem_info structure pointed
to by info, the maximum length which may be successfully allocated by
the typed memory object designated by fildes. This maximum length
shall take into account the flag POSIX_TYPED_MEM_ALLOCATE or
POSIX_TYPED_MEM_ALLOCATE_CONTIG specified when the typed memory
object represented by fildes was opened. The maximum length is
dynamic; therefore, the value returned is valid only while the
current mapping of the corresponding typed memory pool remains
unchanged.
If fildes represents a typed memory object opened with neither the
POSIX_TYPED_MEM_ALLOCATE flag nor the POSIX_TYPED_MEM_ALLOCATE_CONTIG
flag specified, the returned value of info->posix_tmi_length is
unspecified.
The posix_typed_mem_get_info() function may return additional
implementation-defined information in other fields of the
posix_typed_mem_info structure pointed to by info.
If the memory object specified by fildes is not a typed memory
object, then the behavior of this function is undefined.
Upon successful completion, the posix_typed_mem_get_info() function
shall return zero; otherwise, the corresponding error status value
shall be returned.
The posix_typed_mem_get_info() function shall fail if:
EBADF The fildes argument is not a valid open file descriptor.
ENODEV The fildes argument is not connected to a memory object
supported by this function.
This function shall not return an error code of [EINTR].
The following sections are informative.
None.
None.
An application that needs to allocate a block of typed memory with
length dependent upon the amount of memory currently available must
either query the typed memory object to obtain the amount available,
or repeatedly invoke mmap() attempting to guess an appropriate
length. While the latter method is existing practice with malloc(),
it is awkward and imprecise. The posix_typed_mem_get_info() function
allows an application to immediately determine available memory. This
is particularly important for typed memory objects that may in some
cases be scarce resources. Note that when a typed memory pool is a
shared resource, some form of mutual-exclusion or synchronization may
be required while typed memory is being queried and allocated to
prevent race conditions.
The existing fstat() function is not suitable for this purpose. We
realize that implementations may wish to provide other attributes of
typed memory objects (for example, alignment requirements, page size,
and so on). The fstat() function returns a structure which is not
extensible and, furthermore, contains substantial information that is
inappropriate for typed memory objects.
None.
fstat(3p), mmap(3p), posix_typed_mem_open(3p)
The Base Definitions volume of POSIX.1‐2008, 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_GET_INFO(3P)
Pages that refer to this page: sys_mman.h(0p), posix_typed_mem_open(3p)