mirror of https://github.com/mkerrisk/man-pages
111 lines
2.9 KiB
Groff
111 lines
2.9 KiB
Groff
.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_ONEPARA)
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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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.\" %%%LICENSE_END
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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 MBSINIT 3 2015-08-08 "GNU" "Linux Programmer's Manual"
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.SH NAME
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mbsinit \- test for initial shift state
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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 "int mbsinit(const mbstate_t *" ps );
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.fi
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.SH DESCRIPTION
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Character conversion between the multibyte representation and the wide
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character representation uses conversion state, of type
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.IR mbstate_t .
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Conversion of a string uses a finite-state machine; when it is interrupted
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after the complete conversion of a number of characters, it may need to
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save a state for processing the remaining characters.
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Such a conversion
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state is needed for the sake of encodings such as ISO-2022 and UTF-7.
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.PP
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The initial state is the state at the beginning of conversion of a string.
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There are two kinds of state: The one used by multibyte to wide character
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conversion functions, such as
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.BR mbsrtowcs (3),
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and the one used by wide
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character to multibyte conversion functions, such as
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.BR wcsrtombs (3),
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but they both fit in a
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.IR mbstate_t ,
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and they both have the same
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representation for an initial state.
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.PP
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For 8-bit encodings, all states are equivalent to the initial state.
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For multibyte encodings like UTF-8, EUC-*, BIG5 or SJIS, the wide character
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to multibyte conversion functions never produce non-initial states, but the
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multibyte to wide-character conversion functions like
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.BR mbrtowc (3)
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do
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produce non-initial states when interrupted in the middle of a character.
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.PP
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One possible way to create an
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.I mbstate_t
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in initial state is to set it to zero:
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.nf
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mbstate_t state;
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memset(&state,0,sizeof(mbstate_t));
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.fi
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.PP
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On Linux, the following works as well, but might generate compiler warnings:
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.nf
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mbstate_t state = { 0 };
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.fi
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.PP
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The function
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.BR mbsinit ()
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tests whether
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.I *ps
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corresponds to an
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initial state.
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.SH RETURN VALUE
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.BR mbsinit ()
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returns nonzero if
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.I *ps
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is an initial state, or if
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.I ps
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is NULL.
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Otherwise, it returns 0.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lb lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR mbsinit ()
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008, C99.
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.SH NOTES
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The behavior of
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.BR mbsinit ()
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depends on the
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.B LC_CTYPE
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category of the
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current locale.
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.SH SEE ALSO
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.BR mbrlen (3),
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.BR mbrtowc (3),
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.BR wcrtomb (3),
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.BR mbsrtowcs (3),
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.BR wcsrtombs (3)
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