xref: /dragonfly/lib/libc/locale/mbrlen.3 (revision d4ef6694) 
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25.\" $FreeBSD: head/lib/libc/locale/mbrlen.3 131360 2004-06-30 19:32:41Z ru $
26.\"
27.Dd December 26, 2013
28.Dt MBRLEN 3
29.Os
30.Sh NAME
31.Nm mbrlen ,
32.Nm mbrlen_l
33.Nd "get number of bytes in a character (restartable)"
34.Sh LIBRARY
35.Lb libc
36.Sh SYNOPSIS
37.In wchar.h
38.Ft size_t
39.Fn mbrlen "const char * restrict s" "size_t n" "mbstate_t * restrict ps"
40.In xlocale.h
41.Ft size_t
42.Fn mbrlen_l "const char * restrict s" "size_t n" "mbstate_t * restrict ps" "locale_t locale"
43.Sh DESCRIPTION
44The
45.Fn mbrlen
46and
47.Fn mbrlen_l
48functions inspect at most
49.Fa n
50bytes pointed to by
51.Fa s
52to determine the number of bytes needed to complete the next
53multibyte character.
54.Pp
55The
56.Vt mbstate_t
57argument,
58.Fa ps ,
59is used to keep track of the shift state.
60If it is
61.Dv NULL ,
62.Fn mbrlen
63and
64.Fn mbrlen_l
65use an internal, static
66.Vt mbstate_t
67object, which is initialized to the initial conversion state
68at program startup.
69.Pp
70It is equivalent to:
71.Pp
72.Dl "mbrtowc(NULL, s, n, ps);"
73.Pp
74Except that when
75.Fa ps
76is a
77.Dv NULL
78pointer,
79.Fn mbrlen
80and
81.Fn mbrlen_l
82use their own static, internal
83.Vt mbstate_t
84object to keep track of the shift state.
85.Pp
86The
87.Fn mbrlen_l
88function takes an explicit
89.Fa locale
90argument, whereas the
91.Fn mbrlen
92function uses the current global or per-thread locale.
93.Sh RETURN VALUES
94The
95.Fn mbrlen
96and
97.Fn mbrlen_l
98functions return:
99.Bl -tag -width indent
100.It 0
101The next
102.Fa n
103or fewer bytes
104represent the null wide character
105.Pq Li "L'\e0'" .
106.It >0
107The next
108.Fa n
109or fewer bytes
110represent a valid character,
111.Fn mbrlen
112and
113.Fn mbrlen_l
114return the number of bytes used to complete the multibyte character.
115.It Po Vt size_t Pc Ns \-2
116The next
117.Fa n
118contribute to, but do not complete, a valid multibyte character sequence,
119and all
120.Fa n
121bytes have been processed.
122.It Po Vt size_t Pc Ns \-1
123An encoding error has occurred.
124The next
125.Fa n
126or fewer bytes do not contribute to a valid multibyte character.
127.El
128.Sh EXAMPLES
129A function that calculates the number of characters in a multibyte
130character string:
131.Bd -literal -offset indent
132size_t
133nchars(const char *s)
134{
135	size_t charlen, chars;
136	mbstate_t mbs;
137
138	chars = 0;
139	memset(&mbs, 0, sizeof(mbs));
140	while ((charlen = mbrlen(s, MB_CUR_MAX, &mbs)) != 0 &&
141	    charlen != (size_t)-1 && charlen != (size_t)-2) {
142		s += charlen;
143		chars++;
144	}
145
146	return (chars);
147}
148.Ed
149.Sh ERRORS
150The
151.Fn mbrlen
152and
153.Fn mbrlen_l
154functions will fail if:
155.Bl -tag -width Er
156.It Bq Er EILSEQ
157An invalid multibyte sequence was detected.
158.It Bq Er EINVAL
159The conversion state is invalid.
160.El
161.Sh SEE ALSO
162.Xr mblen 3 ,
163.Xr mbrtowc 3 ,
164.Xr multibyte 3 ,
165.Xr xlocale 3
166.Sh STANDARDS
167The
168.Fn mbrlen
169function conforms to
170.St -isoC-99 .
171