PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

POSIX_MEM_OFFSET(3P)      POSIX Programmer's Manual     POSIX_MEM_OFFSET(3P)

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_mem_offset — find offset and length of a mapped typed memory
       block (ADVANCED REALTIME)

SYNOPSIS         top

       #include <sys/mman.h>

       int posix_mem_offset(const void *restrict addr, size_t len,
           off_t *restrict off, size_t *restrict contig_len,
           int *restrict fildes);

DESCRIPTION         top

       The posix_mem_offset() function shall return in the variable pointed
       to by off a value that identifies the offset (or location), within a
       memory object, of the memory block currently mapped at addr.  The
       function shall return in the variable pointed to by fildes, the
       descriptor used (via mmap()) to establish the mapping which contains
       addr.  If that descriptor was closed since the mapping was
       established, the returned value of fildes shall be −1. The len
       argument specifies the length of the block of the memory object the
       user wishes the offset for; upon return, the value pointed to by
       contig_len shall equal either len, or the length of the largest
       contiguous block of the memory object that is currently mapped to the
       calling process starting at addr, whichever is smaller.

       If the memory object mapped at addr is a typed memory object, then if
       the off and contig_len values obtained by calling posix_mem_offset()
       are used in a call to mmap() with a file descriptor that refers to
       the same memory pool as fildes (either through the same port or
       through a different port), and that was opened with neither the
       POSIX_TYPED_MEM_ALLOCATE nor the POSIX_TYPED_MEM_ALLOCATE_CONTIG
       flag, the typed memory area that is mapped shall be exactly the same
       area that was mapped at addr in the address space of the process that
       called posix_mem_offset().

       If the memory object specified by fildes is not a typed memory
       object, then the behavior of this function is implementation-defined.

RETURN VALUE         top

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

ERRORS         top

       The posix_mem_offset() function shall fail if:

       EACCES The process has not mapped a memory object supported by this
              function at the given address addr.

       This function shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       mmap(3p), posix_typed_mem_open(3p)

       The Base Definitions volume of POSIX.1‐2008, sys_mman.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                POSIX_MEM_OFFSET(3P)

Pages that refer to this page: sys_mman.h(0p)posix_typed_mem_open(3p)