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POSIX_TYPED_MEM_GET_INFO(3PPOSIX Programmer's ManuPOSIX_TYPED_MEM_GET_INFO(3P)

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.
NAME
       posix_typed_mem_get_info - query  typed  memory  information  (ADVANCED
       REALTIME)
SYNOPSIS
       #include <sys/mman.h>
       int posix_typed_mem_get_info(int fildes,
              struct posix_typed_mem_info *info);

DESCRIPTION
       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; there-
       fore, 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 unspec-
       ified.
       The posix_typed_mem_get_info() function may return additional implemen-
       tation-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
       Upon  successful  completion,  the  posix_typed_mem_get_info() function
       shall return zero; otherwise,  the  corresponding  error  status  value
       shall be returned.
ERRORS
       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 sup-
              ported by this function.

       This function shall not return an error code of [EINTR].
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       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  awk-
       ward  and  imprecise. The posix_typed_mem_get_info() function allows an
       application to immediately determine available memory. This is particu-
       larly  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.
FUTURE DIRECTIONS
       None.
SEE ALSO
       fstat(), mmap(), posix_typed_mem_open(), the Base Definitions volume of
       IEEE Std 1003.1-2001, <sys/mman.h>
COPYRIGHT
       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 .

IEEE/The Open Group                  2003         POSIX_TYPED_MEM_GET_INFO(3P)