Manpages - mbsinit.3

mbsinit - test for initial shift state

  #include <wchar.h>

  int mbsinit(const mbstate_t *ps);

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 encodings such as ISO-2022 and UTF-7.

The initial state is the state at the beginning of conversion of a string. There are two kinds of state: the one used by multibyte to wide character conversion functions, such as *mbsrtowcs*(3), and the one used by wide character to multibyte conversion functions, such as *wcsrtombs*(3), 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 initial 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 multibyte to wide-character conversion functions like *mbrtowc*(3) do produce non-initial states when interrupted in the middle 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(state));

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.

*mbsinit*() returns nonzero if *ps is an initial state, or if ps is NULL. Otherwise, it returns 0.

For an explanation of the terms used in this section, see *attributes*(7).

POSIX.1-2001, POSIX.1-2008, C99.

The behavior of mbsinit*() depends on the *LC_CTYPE category of the current locale.

*mbrlen*(3), *mbrtowc*(3), *mbsrtowcs*(3), *wcrtomb*(3), *wcsrtombs*(3)

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