The mbsinit() function shall return non-zero if ps is a null
pointer, or if the pointed-to object describes an initial conversion state;
otherwise, it shall return zero.
If an mbstate_t object is altered by any of the functions described as
"restartable", and is then used with a different character sequence,
or in the other conversion direction, or with a different LC_CTYPE
category setting than on earlier function calls, the behavior is undefined.
The mbstate_t object is used to describe the current conversion state
from a particular character sequence to a wide-character sequence (or vice
versa) under the rules of a particular setting of the LC_CTYPE
category of the current locale.
The initial conversion state corresponds, for a conversion in either direction,
to the beginning of a new character sequence in the initial shift state. A
zero valued mbstate_t object is at least one way to describe an initial
conversion state. A zero valued mbstate_t object can be used to
initiate conversion involving any character sequence, in any LC_CTYPE
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html