POSIX_TYPED_MEM_GET_INFO(P)				     POSIX Programmer's Manual				       POSIX_TYPED_MEM_GET_INFO(P)

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; therefore, the value returned is valid only while the current mapping  of  the  corre-
       sponding 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

       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 supported 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 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.

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 Technol-
       ogy -- 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(P)