posix_mem_offset(3p) [suse man page]

POSIX_MEM_OFFSET(3P)					     POSIX Programmer's Manual					      POSIX_MEM_OFFSET(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_mem_offset - find offset and length of a mapped typed memory block (ADVANCED REALTIME)

SYNOPSIS

       #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

       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

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

ERRORS

       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

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       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_MEM_OFFSET(3P)

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)