1POSIX_TYPED_MEM_OPEN(3P) POSIX Programmer's Manual POSIX_TYPED_MEM_OPEN(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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13 posix_typed_mem_open — open a typed memory object (ADVANCED REALTIME)
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16 #include <sys/mman.h>
17 int posix_typed_mem_open(const char *name, int oflag, int tflag);
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21 The posix_typed_mem_open() function shall establish a connection
22 between the typed memory object specified by the string pointed to by
23 name and a file descriptor. It shall create an open file description
24 that refers to the typed memory object and a file descriptor that
25 refers to that open file description. The file descriptor is used by
26 other functions to refer to that typed memory object. It is unspecified
27 whether the name appears in the file system and is visible to other
28 functions that take pathnames as arguments. The name argument conforms
29 to the construction rules for a pathname, except that the interpreta‐
30 tion of <slash> characters other than the leading <slash> character in
31 name is implementation-defined, and that the length limits for the name
32 argument are implementation-defined and need not be the same as the
33 pathname limits {PATH_MAX} and {NAME_MAX}. If name begins with the
34 <slash> character, then processes calling posix_typed_mem_open() with
35 the same value of name shall refer to the same typed memory object. If
36 name does not begin with the <slash> character, the effect is implemen‐
37 tation-defined.
38 Each typed memory object supported in a system shall be identified by a
40 name which specifies not only its associated typed memory pool, but
41 also the path or port by which it is accessed. That is, the same typed
42 memory pool accessed via several different ports shall have several
43 different corresponding names. The binding between names and typed mem‐
44 ory objects is established in an implementation-defined manner. Unlike
45 shared memory objects, there is no way within POSIX.1‐2008 for a pro‐
46 gram to create a typed memory object.
47 The value of tflag shall determine how the typed memory object behaves
49 when subsequently mapped by calls to mmap(). At most, one of the fol‐
50 lowing flags defined in <sys/mman.h> may be specified:
51 POSIX_TYPED_MEM_ALLOCATE
53 Allocate on mmap().
54 POSIX_TYPED_MEM_ALLOCATE_CONTIG
56 Allocate contiguously on mmap().
57 POSIX_TYPED_MEM_MAP_ALLOCATABLE
59 Map on mmap(), without affecting allocatability.
60 If tflag has the flag POSIX_TYPED_MEM_ALLOCATE specified, any subse‐
62 quent call to mmap() using the returned file descriptor shall result in
63 allocation and mapping of typed memory from the specified typed memory
64 pool. The allocated memory may be a contiguous previously unallocated
65 area of the typed memory pool or several non-contiguous previously
66 unallocated areas (mapped to a contiguous portion of the process
67 address space). If tflag has the flag POSIX_TYPED_MEM_ALLOCATE_CONTIG
68 specified, any subsequent call to mmap() using the returned file
69 descriptor shall result in allocation and mapping of a single contigu‐
70 ous previously unallocated area of the typed memory pool (also mapped
71 to a contiguous portion of the process address space). If tflag has
72 none of the flags POSIX_TYPED_MEM_ALLOCATE or POSIX_TYPED_MEM_ALLO‐
73 CATE_CONTIG specified, any subsequent call to mmap() using the returned
74 file descriptor shall map an application-chosen area from the specified
75 typed memory pool such that this mapped area becomes unavailable for
76 allocation until unmapped by all processes. If tflag has the flag
77 POSIX_TYPED_MEM_MAP_ALLOCATABLE specified, any subsequent call to
78 mmap() using the returned file descriptor shall map an application-cho‐
79 sen area from the specified typed memory pool without an effect on the
80 availability of that area for allocation; that is, mapping such an
81 object leaves each byte of the mapped area unallocated if it was unal‐
82 located prior to the mapping or allocated if it was allocated prior to
83 the mapping. Appropriate privileges to specify the
84 POSIX_TYPED_MEM_MAP_ALLOCATABLE flag are implementation-defined.
85 If successful, posix_typed_mem_open() shall return a file descriptor
87 for the typed memory object that is the lowest numbered file descriptor
88 not currently open for that process. The open file description is new,
89 and therefore the file descriptor shall not share it with any other
90 processes. It is unspecified whether the file offset is set. The
91 FD_CLOEXEC file descriptor flag associated with the new file descriptor
92 shall be cleared.
93 The behavior of msync(), ftruncate(), and all file operations other
95 than mmap(), posix_mem_offset(), posix_typed_mem_get_info(), fstat(),
96 dup(), dup2(), and close(), is unspecified when passed a file descrip‐
97 tor connected to a typed memory object by this function.
98 The file status flags of the open file description shall be set accord‐
100 ing to the value of oflag. Applications shall specify exactly one of
101 the three access mode values described below and defined in the
102 <fcntl.h> header, as the value of oflag.
103 O_RDONLY Open for read access only.
105 O_WRONLY Open for write access only.
107 O_RDWR Open for read or write access.
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111 Upon successful completion, the posix_typed_mem_open() function shall
112 return a non-negative integer representing the lowest numbered unused
113 file descriptor. Otherwise, it shall return −1 and set errno to indi‐
114 cate the error.
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117 The posix_typed_mem_open() function shall fail if:
118 EACCES The typed memory object exists and the permissions specified by
120 oflag are denied.
121 EINTR The posix_typed_mem_open() operation was interrupted by a sig‐
123 nal.
124 EINVAL The flags specified in tflag are invalid (more than one of
126 POSIX_TYPED_MEM_ALLOCATE, POSIX_TYPED_MEM_ALLOCATE_CONTIG, or
127 POSIX_TYPED_MEM_MAP_ALLOCATABLE is specified).
128 EMFILE All file descriptors available to the process are currently
130 open.
131 ENFILE Too many file descriptors are currently open in the system.
133 ENOENT The named typed memory object does not exist.
135 EPERM The caller lacks appropriate privileges to specify the
137 POSIX_TYPED_MEM_MAP_ALLOCATABLE flag in the tflag argument.
138 The posix_typed_mem_open() function may fail if:
140 ENAMETOOLONG
142 The length of the name argument exceeds {_POSIX_PATH_MAX} on
143 systems that do not support the XSI option or exceeds
144 {_XOPEN_PATH_MAX} on XSI systems, or has a pathname component
145 that is longer than {_POSIX_NAME_MAX} on systems that do not
146 support the XSI option or longer than {_XOPEN_NAME_MAX} on XSI
147 systems.
148 The following sections are informative.
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152 None.
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155 None.
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158 None.
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161 None.
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164 close(), dup(), exec, fcntl(), fstat(), ftruncate(), mmap(), msync(),
165 posix_mem_offset(), posix_typed_mem_get_info(), umask()
166 The Base Definitions volume of POSIX.1‐2008, <fcntl.h>, <sys_mman.h>
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170 Portions of this text are reprinted and reproduced in electronic form
171 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
172 -- Portable Operating System Interface (POSIX), The Open Group Base
173 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
174 cal and Electronics Engineers, Inc and The Open Group. (This is
175 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
176 event of any discrepancy between this version and the original IEEE and
177 The Open Group Standard, the original IEEE and The Open Group Standard
178 is the referee document. The original Standard can be obtained online
179 at http://www.unix.org/online.html .
180 Any typographical or formatting errors that appear in this page are
182 most likely to have been introduced during the conversion of the source
183 files to man page format. To report such errors, see https://www.ker‐
184 nel.org/doc/man-pages/reporting_bugs.html .
185IEEE/The Open Group 2013 POSIX_TYPED_MEM_OPEN(3P)