POSIX_TYPED_MEM_GET_INFO(P) POSIX Programmer's Manual POSIX_TYPED_MEM_GET_INFO(P)
posix_typed_mem_get_info - query typed memory information (ADVANCED REALTIME)
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 suc-
cessfully 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_CON-
TIG 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_ALLO-
CATE 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.
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 appropri-
ate 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 implemen-
tations may wish to provide other attributes of typed memory objects (for example, align-
ment 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.
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 POSIX_TYPED_MEM_GET_INFO(P)