man3/mbsinit.3

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  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 MBSINIT 3  2016-10-08 "GNU" "Linux Programmer's Manual"
  17 .SH NAME
  18 mbsinit \- test for initial shift state
  19 .SH SYNOPSIS
  20 .nf
  21 .B #include <wchar.h>
  22 .PP
  23 .BI "int mbsinit(const mbstate_t *" ps );
  24 .fi
  25 .SH DESCRIPTION
  26 Character conversion between the multibyte representation and the wide
  27 character representation uses conversion state, of type
  28 .IR mbstate_t .
  29 Conversion of a string uses a finite-state machine; when it is interrupted
  30 after the complete conversion of a number of characters, it may need to
  31 save a state for processing the remaining characters.
  32 Such a conversion
  33 state is needed for the sake of encodings such as ISO-2022 and UTF-7.
  34 .PP
  35 The initial state is the state at the beginning of conversion of a string.
  36 There are two kinds of state: the one used by multibyte to wide character
  37 conversion functions, such as
  38 .BR mbsrtowcs (3),
  39 and the one used by wide
  40 character to multibyte conversion functions, such as
  41 .BR wcsrtombs (3),
  42 but they both fit in a
  43 .IR mbstate_t ,
  44 and they both have the same
  45 representation for an initial state.
  46 .PP
  47 For 8-bit encodings, all states are equivalent to the initial state.
  48 For multibyte encodings like UTF-8, EUC-*, BIG5 or SJIS, the wide character
  49 to multibyte conversion functions never produce non-initial states, but the
  50 multibyte to wide-character conversion functions like
  51 .BR mbrtowc (3)
  52 do
  53 produce non-initial states when interrupted in the middle of a character.
  54 .PP
  55 One possible way to create an
  56 .I mbstate_t
  57 in initial state is to set it to zero:
  58 .PP
  59 .in +4n
  60 .EX
  61 mbstate_t state;
  62 memset(&state,0,sizeof(mbstate_t));
  63 .EE
  64 .in
  65 .PP
  66 On Linux, the following works as well, but might generate compiler warnings:
  67 .PP
  68 .in +4n
  69 .EX
  70 mbstate_t state = { 0 };
  71 .EE
  72 .in
  73 .PP
  74 The function
  75 .BR mbsinit ()
  76 tests whether
  77 .I *ps
  78 corresponds to an
  79 initial state.
  80 .SH RETURN VALUE
  81 .BR mbsinit ()
  82 returns nonzero if
  83 .I *ps
  84 is an initial state, or if
  85 .I ps
  86 is NULL.
  87 Otherwise, it returns 0.
  88 .SH ATTRIBUTES
  89 For an explanation of the terms used in this section, see
  90 .BR attributes (7).
  91 .TS
  92 allbox;
  93 lb lb lb
  94 l l l.
  95 Interface       Attribute       Value
  96 T{
  97 .BR mbsinit ()
  98 T}      Thread safety   MT-Safe
  99 .TE
 100 .SH CONFORMING TO
 101 POSIX.1-2001, POSIX.1-2008, C99.
 102 .SH NOTES
 103 The behavior of
 104 .BR mbsinit ()
 105 depends on the
 106 .B LC_CTYPE
 107 category of the
 108 current locale.
 109 .SH SEE ALSO
 110 .BR mbrlen (3),
 111 .BR mbrtowc (3),
 112 .BR mbsrtowcs (3),
 113 .BR wcrtomb (3),
 114 .BR wcsrtombs (3)