posix_typed_mem_get_info(3p) — Linux manual page



PROLOG         top

       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.

NAME         top

       posix_typed_mem_get_info — query typed memory information

SYNOPSIS         top

       #include <sys/mman.h>

       int posix_typed_mem_get_info(int fildes,
           struct posix_typed_mem_info *info);

DESCRIPTION         top

       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
       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.

RETURN VALUE         top

       Upon successful completion, the posix_typed_mem_get_info()
       function shall return zero; otherwise, the corresponding error
       status value shall be returned.

ERRORS         top

       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.

EXAMPLES         top




RATIONALE         top

       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.



SEE ALSO         top

       fstat(3p), mmap(3p), posix_typed_mem_open(3p)

       The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)

COPYRIGHT         top

       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)