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1 .\" Copyright (c) 2002-2004 Tim J. Robbins
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25 .\" $FreeBSD: src/lib/libc/locale/mbrlen.3,v 1.8 2004/06/30 19:32:41 ru Exp $
26 .\"
27 .Dd April 7, 2004
28 .Dt MBRLEN 3
29 .Os
30 .Sh NAME
31 .Nm mbrlen
32 .Nd "get number of bytes in a character (restartable)"
33 .Sh LIBRARY
34 .Lb libc
35 .Sh SYNOPSIS
36 .In wchar.h
37 .Ft size_t
38 .Fn mbrlen "const char * restrict s" "size_t n" "mbstate_t * restrict ps"
39 .Sh DESCRIPTION
40 The
41 .Fn mbrlen
42 function inspects at most
43 .Fa n
44 bytes pointed to by
45 .Fa s
46 to determine the number of bytes needed to complete the next
47 multibyte character.
48 .Pp
49 The
50 .Vt mbstate_t
51 argument,
52 .Fa ps ,
53 is used to keep track of the shift state.
54 If it is
55 .Dv NULL ,
56 .Fn mbrlen
57 uses an internal, static
58 .Vt mbstate_t
59 object, which is initialized to the initial conversion state
60 at program startup.
61 .Pp
62 It is equivalent to:
63 .Pp
64 .Dl "mbrtowc(NULL, s, n, ps);"
65 .Pp
66 Except that when
67 .Fa ps
68 is a
69 .Dv NULL
70 pointer,
71 .Fn mbrlen
72 uses its own static, internal
73 .Vt mbstate_t
74 object to keep track of the shift state.
75 .Sh RETURN VALUES
76 The
77 .Fn mbrlen
78 functions returns:
79 .Bl -tag -width indent
80 .It 0
81 The next
82 .Fa n
83 or fewer bytes
84 represent the null wide character
85 .Pq Li "L'\e0'" .
86 .It >0
87 The next
88 .Fa n
89 or fewer bytes
90 represent a valid character,
91 .Fn mbrlen
92 returns the number of bytes used to complete the multibyte character.
93 .It Po Vt size_t Pc Ns \-2
94 The next
95 .Fa n
96 contribute to, but do not complete, a valid multibyte character sequence,
97 and all
98 .Fa n
99 bytes have been processed.
100 .It Po Vt size_t Pc Ns \-1
101 An encoding error has occurred.
102 The next
103 .Fa n
104 or fewer bytes do not contribute to a valid multibyte character.
105 .El
106 .Sh EXAMPLES
107 A function that calculates the number of characters in a multibyte
108 character string:
109 .Bd -literal -offset indent
110 size_t
111 nchars(const char *s)
112 {
113 size_t charlen, chars;
114 mbstate_t mbs;
115
116 chars = 0;
117 memset(&mbs, 0, sizeof(mbs));
118 while ((charlen = mbrlen(s, MB_CUR_MAX, &mbs)) != 0 &&
119 charlen != (size_t)-1 && charlen != (size_t)-2) {
120 s += charlen;
121 chars++;
122 }
123
124 return (chars);
125 }
126 .Ed
127 .Sh ERRORS
128 The
129 .Fn mbrlen
130 function will fail if:
131 .Bl -tag -width Er
132 .It Bq Er EILSEQ
133 An invalid multibyte sequence was detected.
134 .It Bq Er EINVAL
135 The conversion state is invalid.
136 .El
137 .Sh SEE ALSO
138 .Xr mblen 3 ,
139 .Xr mbrtowc 3 ,
140 .Xr multibyte 3
141 .Sh STANDARDS
142 The
143 .Fn mbrlen
144 function conforms to
145 .St -isoC-99 .