Bitwise operation for state machine Post: 302880914

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Top Forums Programming Bitwise operation for state machine Post 302880914 by Don Cragun on Tuesday 24th of December 2013 01:44:30 PM

12-24-2013

Registered User

Quote:

Originally Posted by RudiC

To be on the safe side, you might want to AND the STATE operand with 0xF8 as well, and check that in STATE only one bit is set...

Agreed. I'm just not sure that we have a true specification of what this macro is supposed to do yet. I've worked on a lot of finite state machines, but the state changes described for this project still seem unusual to me. There seems to be a state0, but instead of having a bit identifying state0; it is identified by being not in state1, state2, or state3.

I was expecting to hear that my suggested change is a step in the right direction, but still isn't doing some things right. Should INA_SAVE_APP_STATE(state4) really clear state1, state2, and state3 from appState? Shouldn't there be some way to clear state4 through state8? Shouldn't there be a macro to initialize the state? (Maybe the header always defines appState to be an extern int (or char); but we haven't seen any evidence of that yet, and these macros won't behave as desired if appState is an uninitialized variable allocated on the stack.) There is no defined error mechanism. (What should happen if one calls INA_SAVE_APP_STATE(state1 | state2)?) Et cetera.

I'm still hoping for an actual set of specifications of the allowed state transitions, what happens when an illegal state is passed in, etc.

Don Cragun

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mbsinit

MBSINIT(3)						     Linux Programmer's Manual							MBSINIT(3)

NAME

       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 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 wcsr-
       tombs(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(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 nonzero if *ps is an initial state, or if ps is NULL.	Otherwise, it returns 0.

ATTRIBUTES

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

       +----------+---------------+---------+
       |Interface | Attribute	  | Value   |
       +----------+---------------+---------+
       |mbsinit() | Thread safety | MT-Safe |
       +----------+---------------+---------+
CONFORMING TO

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

NOTES

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

SEE ALSO

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

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

GNU
								    2016-10-08								MBSINIT(3)