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 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.
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 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.
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 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 .
/The Open Group 2003 POSIX_TYPED_MEM_GET_INFO(P)