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.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
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.\"
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" References consulted:
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.\" GNU glibc-2 source code and manual
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.\" Dinkumware C library reference http://www.dinkumware.com/
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.\" OpenGroup's Single Unix specification
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.\" http://www.UNIX-systems.org/online.html
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.\" ISO/IEC 9899:1999
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.\"
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.TH MBRTOWC 3 2001-11-22 "GNU" "Linux Programmer's Manual"
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.SH NAME
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mbrtowc \- convert a multibyte sequence to a wide character
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.SH SYNOPSIS
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.nf
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.B #include <wchar.h>
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.sp
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.BI "size_t mbrtowc(wchar_t *" pwc ", const char *" s ", size_t " n ", mbstate_t *" ps );
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.fi
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.SH DESCRIPTION
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The main case for this function is when \fIs\fP is not NULL and \fIpwc\fP is
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not NULL. In this case, the \fBmbrtowc\fP() function inspects at most \fIn\fP
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bytes of the multibyte string starting at \fIs\fP, extracts the next complete
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multibyte character, converts it to a wide character and stores it at
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\fI*pwc\fP. It updates the shift state \fI*ps\fP. If the converted wide
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character is not L'\\0', it returns the number of bytes that were consumed
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from \fIs\fP. If the converted wide character is L'\\0', it resets the shift
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state \fI*ps\fP to the initial state and returns 0.
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.PP
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If the \fIn\fP bytes starting at \fIs\fP do not contain a complete multibyte
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character, \fBmbrtowc\fP() returns \fI(size_t)(\-2)\fP. This can happen even if
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\fIn\fP >= \fIMB_CUR_MAX\fP, if the multibyte string contains redundant shift
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sequences.
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.PP
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If the multibyte string starting at \fIs\fP contains an invalid multibyte
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sequence before the next complete character, \fBmbrtowc\fP() returns
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\fI(size_t)(\-1)\fP and sets \fIerrno\fP to \fBEILSEQ\fP. In this case,
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the effects on \fI*ps\fP are undefined.
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.PP
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A different case is when \fIs\fP is not NULL but \fIpwc\fP is NULL. In this
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case the \fBmbrtowc\fP() function behaves as above, excepts that it does not
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store the converted wide character in memory.
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.PP
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A third case is when \fIs\fP is NULL. In this case, \fIpwc\fP and \fIn\fP are
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ignored. If the conversion state represented by \fI*ps\fP denotes an
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incomplete multibyte character conversion, the \fBmbrtowc\fP() function
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returns \fI(size_t)(\-1)\fP, sets \fIerrno\fP to \fBEILSEQ\fP, and
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leaves \fI*ps\fP in an undefined state. Otherwise, the \fBmbrtowc\fP() function
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puts \fI*ps\fP in the initial state and returns 0.
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.PP
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In all of the above cases, if \fIps\fP is a NULL pointer, a static anonymous
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state only known to the mbrtowc function is used instead.
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Otherwise, \fI*ps\fP must be a valid \fBmbstate_t\fP object.
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An \fBmbstate_t\fP object \fIa\fP can be initialized to the initial state
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by zeroing it, for example using
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.sp
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.RS
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memset(&a, 0, sizeof(a));
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.RE
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.SH "RETURN VALUE"
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The \fBmbrtowc\fP() function returns the number of bytes parsed from the
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multibyte sequence starting at \fIs\fP, if a non-L'\\0' wide character
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was recognized.
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It returns 0, if a L'\\0' wide character was recognized.
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It returns (size_t)(\-1)
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and sets \fIerrno\fP to \fBEILSEQ\fP, if an invalid multibyte sequence was
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encountered. It returns (size_t)(\-2) if it couldn't parse a complete multibyte
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character, meaning that \fIn\fP should be increased.
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.SH "CONFORMING TO"
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ISO/ANSI C, UNIX98
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.SH "SEE ALSO"
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.BR mbsrtowcs (3)
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.SH NOTES
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The behaviour of \fBmbrtowc\fP() depends on the LC_CTYPE category of the
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current locale.
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