mbsinit - test for initial shift state


SYNOPSIS

       #include <wchar.h>

       int mbsinit (const mbstate_t *ps);


DESCRIPTION

       Character  conversion between the multibyte representation
       and the  wide  character  representation  uses  conversion
       state,  of  type mbstate_t.  Conversion of a string uses a
       finite-state machine; when it  is  interrupted  after  the
       complete conversion of a number of characters, it may need
       to save a state for processing the  remaining  characters.
       Such  a  conversion state is needed for the sake of encod­
       ings such as ISO-2022 and UTF-7.

       The initial state is the state at the beginning of conver­
       sion  of  a string.  There are two kinds of state: The one
       used by multibyte to wide character conversion  functions,
       such  as  mbsrtowcs, and the one used by wide character to
       multibyte conversion functions,  such  as  wcsrtombs,  but
       they  both fit in a mbstate_t, and they both have the same
       representation for an initial state.

       For 8-bit encodings, all states are equivalent to the ini­
       tial  state.   For  multibyte encodings like UTF-8, EUC-*,
       BIG5 or SJIS, the wide character to  multibyte  conversion
       functions never produce non-initial states, but the multi­
       byte to wide character conversion functions  like  mbrtowc
       do produce non-initial states when interrupted in the mid­
       dle of a character.

       One possible way to create an mbstate_t in  initial  state
       is to set it to zero:
         mbstate_t state;
         memset(&state,0,sizeof(mbstate_t));
       On  Linux, the following works as well, but might generate
       compiler warnings:
         mbstate_t state = { 0 };

       The function mbsinit tests whether *ps corresponds  to  an
       initial state.


RETURN VALUE

       mbsinit returns non-zero if *ps is an initial state, or if
       ps is a null pointer. Otherwise it returns 0.


CONFORMING TO

       ISO/ANSI C, UNIX98


SEE ALSO

       mbsrtowcs(3), wcsrtombs(3)

       The behaviour of mbsinit depends on the LC_CTYPE  category
       of the current locale.


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