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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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POSIX_TY...GET_INFO(3P) POSIX Programmer's ManualPOSIX_TY...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.1‐2017, sys_mman.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
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 2017 POSIX_TY...GET_INFO(3P)
Pages that refer to this page: sys_mman.h(0p), posix_typed_mem_open(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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