1MBRTOWC(3P) POSIX Programmer's Manual MBRTOWC(3P)
2
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.
10
12 mbrtowc — convert a character to a wide-character code (restartable)
13
15 #include <wchar.h>
16 size_t mbrtowc(wchar_t *restrict pwc, const char *restrict s,
18 size_t n, mbstate_t *restrict ps);
19
21 The functionality described on this reference page is aligned with the
22 ISO C standard. Any conflict between the requirements described here
23 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
24 defers to the ISO C standard.
25 If s is a null pointer, the mbrtowc() function shall be equivalent to
27 the call:
28 mbrtowc(NULL, "", 1, ps)
31 In this case, the values of the arguments pwc and n are ignored.
33 If s is not a null pointer, the mbrtowc() function shall inspect at
35 most n bytes beginning at the byte pointed to by s to determine the
36 number of bytes needed to complete the next character (including any
37 shift sequences). If the function determines that the next character is
38 completed, it shall determine the value of the corresponding wide char‐
39 acter and then, if pwc is not a null pointer, shall store that value in
40 the object pointed to by pwc. If the corresponding wide character is
41 the null wide character, the resulting state described shall be the
42 initial conversion state.
43 If ps is a null pointer, the mbrtowc() function shall use its own
45 internal mbstate_t object, which shall be initialized at program start-
46 up to the initial conversion state. Otherwise, the mbstate_t object
47 pointed to by ps shall be used to completely describe the current con‐
48 version state of the associated character sequence. The implementation
49 shall behave as if no function defined in this volume of POSIX.1‐2017
50 calls mbrtowc().
51 The behavior of this function is affected by the LC_CTYPE category of
53 the current locale.
54 The mbrtowc() function need not be thread-safe if called with a NULL ps
56 argument.
57 The mbrtowc() function shall not change the setting of errno if suc‐
59 cessful.
60
62 The mbrtowc() function shall return the first of the following that
63 applies:
64 0 If the next n or fewer bytes complete the character that
66 corresponds to the null wide character (which is the value
67 stored).
68 between 1 and n inclusive
70 If the next n or fewer bytes complete a valid character
71 (which is the value stored); the value returned shall be
72 the number of bytes that complete the character.
73 (size_t)-2 If the next n bytes contribute to an incomplete but poten‐
75 tially valid character, and all n bytes have been processed
76 (no value is stored). When n has at least the value of the
77 {MB_CUR_MAX} macro, this case can only occur if s points at
78 a sequence of redundant shift sequences (for implementa‐
79 tions with state-dependent encodings).
80 (size_t)-1 If an encoding error occurs, in which case the next n or
82 fewer bytes do not contribute to a complete and valid char‐
83 acter (no value is stored). In this case, [EILSEQ] shall be
84 stored in errno and the conversion state is undefined.
85
87 The mbrtowc() function shall fail if:
88 EILSEQ An invalid character sequence is detected. In the POSIX locale
90 an [EILSEQ] error cannot occur since all byte values are valid
91 characters.
92 The mbrtowc() function may fail if:
94 EINVAL ps points to an object that contains an invalid conversion
96 state.
97 The following sections are informative.
99
101 None.
102
104 None.
105
107 None.
108
110 None.
111
113 mbsinit(), mbsrtowcs()
114 The Base Definitions volume of POSIX.1‐2017, <wchar.h>
116
118 Portions of this text are reprinted and reproduced in electronic form
119 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
120 table Operating System Interface (POSIX), The Open Group Base Specifi‐
121 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
122 Electrical and Electronics Engineers, Inc and The Open Group. In the
123 event of any discrepancy between this version and the original IEEE and
124 The Open Group Standard, the original IEEE and The Open Group Standard
125 is the referee document. The original Standard can be obtained online
126 at http://www.opengroup.org/unix/online.html .
127 Any typographical or formatting errors that appear in this page are
129 most likely to have been introduced during the conversion of the source
130 files to man page format. To report such errors, see https://www.ker‐
131 nel.org/doc/man-pages/reporting_bugs.html .
132IEEE/The Open Group 2017 MBRTOWC(3P)