POSIX_TYPED_MEM_GET_INFO(3)POSIX Programmer's ManualPOSIX_TYPED_MEM_GET_INFO(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       posix_typed_mem_get_info -- query typed memory information (AADDVVAANNCCEEDD
       RREEAALLTTIIMMEE)

SSYYNNOOPPSSIISS
       #include <sys/mman.h>

       int posix_typed_mem_get_info(int _f_i_l_d_e_s,
           struct posix_typed_mem_info *_i_n_f_o);

DDEESSCCRRIIPPTTIIOONN
       The _p_o_s_i_x___t_y_p_e_d___m_e_m___g_e_t___i_n_f_o() function shall return, in the
       _p_o_s_i_x___t_m_i___l_e_n_g_t_h field of the ppoossiixx__ttyyppeedd__mmeemm__iinnffoo structure pointed to
       by _i_n_f_o, the maximum length which may be successfully allocated by the
       typed memory object designated by _f_i_l_d_e_s.  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 _f_i_l_d_e_s 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 _f_i_l_d_e_s 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 _i_n_f_o->_p_o_s_i_x___t_m_i___l_e_n_g_t_h is
       unspecified.

       The _p_o_s_i_x___t_y_p_e_d___m_e_m___g_e_t___i_n_f_o() function may return additional
       implementation-defined information in other fields of the
       ppoossiixx__ttyyppeedd__mmeemm__iinnffoo structure pointed to by _i_n_f_o.

       If the memory object specified by _f_i_l_d_e_s is not a typed memory object,
       then the behavior of this function is undefined.

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

EERRRROORRSS
       The _p_o_s_i_x___t_y_p_e_d___m_e_m___g_e_t___i_n_f_o() function shall fail if:

       EEBBAADDFF  The _f_i_l_d_e_s argument is not a valid open file descriptor.

       EENNOODDEEVV The _f_i_l_d_e_s argument is not connected to a memory object
              supported by this function.

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

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       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 _m_m_a_p() attempting to guess an appropriate length.
       While the latter method is existing practice with _m_a_l_l_o_c(), it is
       awkward and imprecise. The _p_o_s_i_x___t_y_p_e_d___m_e_m___g_e_t___i_n_f_o() 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 _f_s_t_a_t() 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 _f_s_t_a_t() function returns a structure which is not
       extensible and, furthermore, contains substantial information that is
       inappropriate for typed memory objects.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _f_s_t_a_t(), _m_m_a_p(), _p_o_s_i_x___t_y_p_e_d___m_e_m___o_p_e_n()

       The Base Definitions volume of POSIX.1-2017, <<ssyyss__mmmmaann..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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                  2017          POSIX_TYPED_MEM_GET_INFO(3)
