Originální popis anglicky:
posix_typed_mem_get_info - query typed memory information (
ADVANCED
REALTIME)
Návod, kniha: POSIX Programmer's Manual
#include <sys/mman.h>
int posix_typed_mem_get_info(int
fildes,
struct posix_typed_mem_info *
info);
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
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
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.
Upon successful completion, the
posix_typed_mem_get_info() function shall
return zero; otherwise, the corresponding error status value shall be
returned.
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.
None.
None.
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.
None.
fstat() ,
mmap() ,
posix_typed_mem_open() , the Base
Definitions volume of IEEE Std 1003.1-2001,
<sys/mman.h>
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
.
