POSIX_TYPED_MEM_GET_INFO(3P)				     POSIX Programmer's Manual				      POSIX_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 correspond-
       ing 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; 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(3P)