2004-11-03 13:51:07 +00:00
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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 http://www.UNIX-systems.org/online.html
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.\" ISO/IEC 9899:1999
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.\"
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.TH MBTOWC 3 2001-07-04 "GNU" "Linux Programmer's Manual"
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.SH NAME
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mbtowc \- 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 <stdlib.h>
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.sp
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.BI "int mbtowc(wchar_t *" pwc ", const char *" s ", size_t " n );
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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 \fBmbtowc\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 an internal shift state only known to the mbtowc
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function. If \fIs\fP does not point to a '\\0' byte, it returns the number
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of bytes that were consumed from \fIs\fP, otherwise it 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, or if they contain an invalid multibyte sequence, \fBmbtowc\fP()
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returns \fI-1\fP. This can happen even if \fIn\fP >= \fIMB_CUR_MAX\fP,
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if the multibyte string contains redundant shift sequences.
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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 \fBmbtowc\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. The \fBmbtowc\fP() function
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.\" The Dinkumware doc and the Single Unix specification say this, but
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.\" glibc doesn't implement this.
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resets the shift state, only known to this function, to the initial state, and
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returns non-zero if the encoding has non-trivial shift state, or zero if the
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encoding is stateless.
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.SH "RETURN VALUE"
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If \fIs\fP is not NULL, the \fBmbtowc\fP() function returns the number of
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consumed bytes starting at \fIs\fP, or 0 if \fIs\fP points to a null byte,
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or \-1 upon failure.
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.PP
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If \fIs\fP is NULL, the \fBmbtowc\fP() function returns non-zero if the encoding
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has non-trivial shift state, or zero if the encoding is stateless.
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.SH "CONFORMING TO"
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C99
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.SH "SEE ALSO"
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.BR MB_CUR_MAX (3),
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.BR mbrtowc (3),
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.BR mbstowcs (3)
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.SH NOTES
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The behaviour of \fBmbtowc\fP() depends on the LC_CTYPE category of the
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current locale.
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.PP
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This function is not multi-thread safe. The function \fBmbrtowc\fP() provides
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a better interface to the same functionality.
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