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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12 posix_typed_mem_open — open a typed memory object (ADVANCED REALTIME)
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15 #include <sys/mman.h>
16 int posix_typed_mem_open(const char *name, int oflag, int tflag);
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20 The posix_typed_mem_open() function shall establish a connection
21 between the typed memory object specified by the string pointed to by
22 name and a file descriptor. It shall create an open file description
23 that refers to the typed memory object and a file descriptor that
24 refers to that open file description. The file descriptor shall be
25 allocated as described in Section 2.14, File Descriptor Allocation and
26 can be used by other functions to refer to that typed memory object. It
27 is unspecified whether the name appears in the file system and is visi‐
28 ble to other functions that take pathnames as arguments. The name argu‐
29 ment conforms to the construction rules for a pathname, except that the
30 interpretation of <slash> characters other than the leading <slash>
31 character in name is implementation-defined, and that the length limits
32 for the name argument are implementation-defined and need not be the
33 same as the pathname limits {PATH_MAX} and {NAME_MAX}. If name begins
34 with the <slash> character, then processes calling
35 posix_typed_mem_open() with the same value of name shall refer to the
36 same typed memory object. If name does not begin with the <slash> char‐
37 acter, the effect is implementation-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. The open file description is new, and
88 therefore the file descriptor shall not share it with any other pro‐
89 cesses. It is unspecified whether the file offset is set. The
90 FD_CLOEXEC file descriptor flag associated with the new file descriptor
91 shall be cleared.
92 The behavior of msync(), ftruncate(), and all file operations other
94 than mmap(), posix_mem_offset(), posix_typed_mem_get_info(), fstat(),
95 dup(), dup2(), and close(), is unspecified when passed a file descrip‐
96 tor connected to a typed memory object by this function.
97 The file status flags of the open file description shall be set accord‐
99 ing to the value of oflag. Applications shall specify exactly one of
100 the three access mode values described below and defined in the
101 <fcntl.h> header, as the value of oflag.
102 O_RDONLY Open for read access only.
104 O_WRONLY Open for write access only.
106 O_RDWR Open for read or write access.
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110 Upon successful completion, the posix_typed_mem_open() function shall
111 return a non-negative integer representing the file descriptor. Other‐
112 wise, it shall return -1 and set errno to indicate the error.
113
115 The posix_typed_mem_open() function shall fail if:
116 EACCES The typed memory object exists and the permissions specified by
118 oflag are denied.
119 EINTR The posix_typed_mem_open() operation was interrupted by a sig‐
121 nal.
122 EINVAL The flags specified in tflag are invalid (more than one of
124 POSIX_TYPED_MEM_ALLOCATE, POSIX_TYPED_MEM_ALLOCATE_CONTIG, or
125 POSIX_TYPED_MEM_MAP_ALLOCATABLE is specified).
126 EMFILE All file descriptors available to the process are currently
128 open.
129 ENFILE Too many file descriptors are currently open in the system.
131 ENOENT The named typed memory object does not exist.
133 EPERM The caller lacks appropriate privileges to specify the
135 POSIX_TYPED_MEM_MAP_ALLOCATABLE flag in the tflag argument.
136 The posix_typed_mem_open() function may fail if:
138 ENAMETOOLONG
140 The length of the name argument exceeds {_POSIX_PATH_MAX} on
141 systems that do not support the XSI option or exceeds
142 {_XOPEN_PATH_MAX} on XSI systems, or has a pathname component
143 that is longer than {_POSIX_NAME_MAX} on systems that do not
144 support the XSI option or longer than {_XOPEN_NAME_MAX} on XSI
145 systems.
146 The following sections are informative.
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150 None.
151
153 None.
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156 None.
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159 None.
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162 Section 2.14, File Descriptor Allocation, close(), dup(), exec,
163 fcntl(), fstat(), ftruncate(), mmap(), msync(), posix_mem_offset(),
164 posix_typed_mem_get_info(), umask()
165 The Base Definitions volume of POSIX.1‐2017, <fcntl.h>, <sys_mman.h>
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169 Portions of this text are reprinted and reproduced in electronic form
170 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
171 table Operating System Interface (POSIX), The Open Group Base Specifi‐
172 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
173 Electrical and Electronics Engineers, Inc and The Open Group. In the
174 event of any discrepancy between this version and the original IEEE and
175 The Open Group Standard, the original IEEE and The Open Group Standard
176 is the referee document. The original Standard can be obtained online
177 at http://www.opengroup.org/unix/online.html .
178 Any typographical or formatting errors that appear in this page are
180 most likely to have been introduced during the conversion of the source
181 files to man page format. To report such errors, see https://www.ker‐
182 nel.org/doc/man-pages/reporting_bugs.html .
183IEEE/The Open Group 2017 POSIX_TYPED_MEM_OPEN(3P)