man3/mbtowc.3

   1 .\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
   2 .\"
   3 .\" %%%LICENSE_START(GPLv2+_DOC_ONEPARA)
   4 .\" This is free documentation; you can redistribute it and/or
   5 .\" modify it under the terms of the GNU General Public License as
   6 .\" published by the Free Software Foundation; either version 2 of
   7 .\" the License, or (at your option) any later version.
   8 .\" %%%LICENSE_END
   9 .\"
  10 .\" References consulted:
  11 .\"   GNU glibc-2 source code and manual
  12 .\"   Dinkumware C library reference http://www.dinkumware.com/
  13 .\"   OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
  14 .\"   ISO/IEC 9899:1999
  15 .\"
  16 .TH MBTOWC 3  2011-09-28 "GNU" "Linux Programmer's Manual"
  17 .SH NAME
  18 mbtowc \- convert a multibyte sequence to a wide character
  19 .SH SYNOPSIS
  20 .nf
  21 .B #include <stdlib.h>
  22 .sp
  23 .BI "int mbtowc(wchar_t *" pwc ", const char *" s ", size_t " n );
  24 .fi
  25 .SH DESCRIPTION
  26 The main case for this function is when \fIs\fP is not NULL and \fIpwc\fP is
  27 not NULL.
  28 In this case, the
  29 .BR mbtowc ()
  30 function inspects at most \fIn\fP
  31 bytes of the multibyte string starting at \fIs\fP,
  32 extracts the next complete
  33 multibyte character, converts it to a wide character and stores it at
  34 \fI*pwc\fP.
  35 It updates an internal shift state only known to the
  36 .BR mbtowc ()
  37 function.
  38 If \fIs\fP does not point to a null byte (\(aq\\0\(aq), it returns the number
  39 of bytes that were consumed from \fIs\fP, otherwise it returns 0.
  40 .PP
  41 If the \fIn\fP bytes starting at \fIs\fP do not contain a complete multibyte
  42 character, or if they contain an invalid multibyte sequence,
  43 .BR mbtowc ()
  44 returns \-1.
  45 This can happen even if \fIn\fP >= \fIMB_CUR_MAX\fP,
  46 if the multibyte string contains redundant shift sequences.
  47 .PP
  48 A different case is when \fIs\fP is not NULL but \fIpwc\fP is NULL.
  49 In this
  50 case the
  51 .BR mbtowc ()
  52 function behaves as above, except that it does not
  53 store the converted wide character in memory.
  54 .PP
  55 A third case is when \fIs\fP is NULL.
  56 In this case, \fIpwc\fP and \fIn\fP are
  57 ignored.
  58 The
  59 .BR mbtowc ()
  60 function
  61 .\" The Dinkumware doc and the Single UNIX specification say this, but
  62 .\" glibc doesn't implement this.
  63 resets the shift state, only known to this function,
  64 to the initial state, and
  65 returns nonzero if the encoding has nontrivial shift state, or zero if the
  66 encoding is stateless.
  67 .SH RETURN VALUE
  68 If \fIs\fP is not NULL, the
  69 .BR mbtowc ()
  70 function returns the number of
  71 consumed bytes starting at \fIs\fP, or 0 if \fIs\fP points to a null byte,
  72 or \-1 upon failure.
  73 .PP
  74 If \fIs\fP is NULL, the
  75 .BR mbtowc ()
  76 function
  77 returns nonzero if the encoding
  78 has nontrivial shift state, or zero if the encoding is stateless.
  79 .SH CONFORMING TO
  80 C99.
  81 .SH NOTES
  82 The behavior of
  83 .BR mbtowc ()
  84 depends on the
  85 .B LC_CTYPE
  86 category of the
  87 current locale.
  88 .PP
  89 This function is not multithread safe.
  90 The function
  91 .BR mbrtowc (3)
  92 provides
  93 a better interface to the same functionality.
  94 .SH SEE ALSO
  95 .BR MB_CUR_MAX (3),
  96 .BR mbrtowc (3),
  97 .BR mbstowcs (3)