1POSIX_TYPED_MEM_OPEN(P) POSIX Programmer's Manual POSIX_TYPED_MEM_OPEN(P)
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6 posix_typed_mem_open - open a typed memory object (ADVANCED REALTIME)
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9 #include <sys/mman.h>
10 int posix_typed_mem_open(const char *name, int oflag, int tflag);
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15 The posix_typed_mem_open() function shall establish a connection
16 between the typed memory object specified by the string pointed to by
17 name and a file descriptor. It shall create an open file description
18 that refers to the typed memory object and a file descriptor that
19 refers to that open file description. The file descriptor is used by
20 other functions to refer to that typed memory object. It is unspecified
21 whether the name appears in the file system and is visible to other
22 functions that take pathnames as arguments. The name argument shall
23 conform to the construction rules for a pathname. If name begins with
24 the slash character, then processes calling posix_typed_mem_open() with
25 the same value of name shall refer to the same typed memory object. If
26 name does not begin with the slash character, the effect is implementa‐
27 tion-defined. The interpretation of slash characters other than the
28 leading slash character in name is implementation-defined.
29 Each typed memory object supported in a system shall be identified by a
31 name which specifies not only its associated typed memory pool, but
32 also the path or port by which it is accessed. That is, the same typed
33 memory pool accessed via several different ports shall have several
34 different corresponding names. The binding between names and typed mem‐
35 ory objects is established in an implementation-defined manner. Unlike
36 shared memory objects, there is no way within IEEE Std 1003.1-2001 for
37 a program to create a typed memory object.
38 The value of tflag shall determine how the typed memory object behaves
40 when subsequently mapped by calls to mmap(). At most, one of the fol‐
41 lowing flags defined in <sys/mman.h> may be specified:
42 POSIX_TYPED_MEM_ALLOCATE
44 Allocate on mmap().
45 POSIX_TYPED_MEM_ALLOCATE_CONTIG
47 Allocate contiguously on mmap().
48 POSIX_TYPED_MEM_MAP_ALLOCATABLE
50 Map on mmap(), without affecting allocatability.
51 If tflag has the flag POSIX_TYPED_MEM_ALLOCATE specified, any subse‐
54 quent call to mmap() using the returned file descriptor shall result in
55 allocation and mapping of typed memory from the specified typed memory
56 pool. The allocated memory may be a contiguous previously unallocated
57 area of the typed memory pool or several non-contiguous previously
58 unallocated areas (mapped to a contiguous portion of the process
59 address space). If tflag has the flag POSIX_TYPED_MEM_ALLOCATE_CONTIG
60 specified, any subsequent call to mmap() using the returned file
61 descriptor shall result in allocation and mapping of a single contigu‐
62 ous previously unallocated area of the typed memory pool (also mapped
63 to a contiguous portion of the process address space). If tflag has
64 none of the flags POSIX_TYPED_MEM_ALLOCATE or POSIX_TYPED_MEM_ALLO‐
65 CATE_CONTIG specified, any subsequent call to mmap() using the returned
66 file descriptor shall map an application-chosen area from the specified
67 typed memory pool such that this mapped area becomes unavailable for
68 allocation until unmapped by all processes. If tflag has the flag
69 POSIX_TYPED_MEM_MAP_ALLOCATABLE specified, any subsequent call to
70 mmap() using the returned file descriptor shall map an application-cho‐
71 sen area from the specified typed memory pool without an effect on the
72 availability of that area for allocation; that is, mapping such an
73 object leaves each byte of the mapped area unallocated if it was unal‐
74 located prior to the mapping or allocated if it was allocated prior to
75 the mapping. The appropriate privilege to specify the
76 POSIX_TYPED_MEM_MAP_ALLOCATABLE flag is implementation-defined.
77 If successful, posix_typed_mem_open() shall return a file descriptor
79 for the typed memory object that is the lowest numbered file descriptor
80 not currently open for that process. The open file description is new,
81 and therefore the file descriptor shall not share it with any other
82 processes. It is unspecified whether the file offset is set. The
83 FD_CLOEXEC file descriptor flag associated with the new file descriptor
84 shall be cleared.
85 The behavior of msync(), ftruncate(), and all file operations other
87 than mmap(), posix_mem_offset(), posix_typed_mem_get_info(), fstat(),
88 dup(), dup2(), and close(), is unspecified when passed a file descrip‐
89 tor connected to a typed memory object by this function.
90 The file status flags of the open file description shall be set accord‐
92 ing to the value of oflag. Applications shall specify exactly one of
93 the three access mode values described below and defined in the
94 <fcntl.h> header, as the value of oflag.
95 O_RDONLY
97 Open for read access only.
98 O_WRONLY
100 Open for write access only.
101 O_RDWR Open for read or write access.
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106 Upon successful completion, the posix_typed_mem_open() function shall
107 return a non-negative integer representing the lowest numbered unused
108 file descriptor. Otherwise, it shall return -1 and set errno to indi‐
109 cate the error.
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112 The posix_typed_mem_open() function shall fail if:
113 EACCES The typed memory object exists and the permissions specified by
115 oflag are denied.
116 EINTR The posix_typed_mem_open() operation was interrupted by a sig‐
118 nal.
119 EINVAL The flags specified in tflag are invalid (more than one of
121 POSIX_TYPED_MEM_ALLOCATE, POSIX_TYPED_MEM_ALLOCATE_CONTIG, or
122 POSIX_TYPED_MEM_MAP_ALLOCATABLE is specified).
123 EMFILE Too many file descriptors are currently in use by this process.
125 ENAMETOOLONG
127 The length of the name argument exceeds {PATH_MAX} or a pathname
128 component is longer than {NAME_MAX}.
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 the appropriate privilege to specify the flag
135 POSIX_TYPED_MEM_MAP_ALLOCATABLE in argument tflag.
136 The following sections are informative.
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141 None.
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144 None.
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147 None.
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150 None.
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153 close() , dup() , exec() , fcntl() , fstat() , ftruncate() , mmap() ,
154 msync() , posix_mem_offset() , posix_typed_mem_get_info() , umask() ,
155 the Base Definitions volume of IEEE Std 1003.1-2001, <fcntl.h>,
156 <sys/mman.h>
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159 Portions of this text are reprinted and reproduced in electronic form
160 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
161 -- Portable Operating System Interface (POSIX), The Open Group Base
162 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
163 Electrical and Electronics Engineers, Inc and The Open Group. In the
164 event of any discrepancy between this version and the original IEEE and
165 The Open Group Standard, the original IEEE and The Open Group Standard
166 is the referee document. The original Standard can be obtained online
167 at http://www.opengroup.org/unix/online.html .
168IEEE/The Open Group 2003 POSIX_TYPED_MEM_OPEN(P)