#ident  "@(#)stty-euc-dependency.txt	1.1 98/03/25 SMI"
								1/14/1998
								Ienup Sung
								is@eng.sun.com
Brief analysis of EUC dependency in stty(1)
-------------------------------------------

0. Overview

This memo is to provide a brief analysis result. The scope of the analysis is
restricted to I18N and EUC dependency.


1. Header files

The stty.c and sttyparse.c includes following EUC specific headers:

	/usr/include/sys/eucioctl.h
	/usr/include/getwidth.h

The first one is to have 'eucioc_t' data structure type and necessary
macros. The second one is to have getwidth() function prototype which is
only for the locales that have EUC as its codeset.
Also, stty.h header file at the same directory contains EUCW flag definitnion.


2. stty.c and sttyparse.c

The version number of stty.c is 1.18 and last modified at 7/1/1996.
The version number of sttyparse.c is 1.18 and last modified at 4/13/1995.

After setlocale() invocation, the main() calls 'getwidth(&wp)' so that 'wp'
will contain necessary EUC codeset specific information. And then it calls
'get_ttymode()' that will collect the current EUC settings for the ldterm.

If user specified -a option with the stty(1) command, 'pramodes()' function
will be invoked so that "eucw" and "scrw" can be printed.

After that, the main() routine calls 'sttyparse()' that parses and processes
user specified modes. Especially if the user specified "defeucw", it will
save the current locale's EUC codeset info, i.e., byte length and screen
width of each EUC codeset, into the 'wp'. Also, if the current locale is
a multibyte one and one or more of -raw, cooked or sane is specified,
the ISTRIP flag will be cleared from the input mode flag and, from
the control mode flag, CS7 and PARENB will be cleared and instead CS8 will be
set.

After that, the main() rountine calls 'set_ttymode()' that checks whether
EUCW flag has set for this terminal and if so, it will send EUC_WSET ioctl
command downstream with the 'kwp' that is retrived or changed from
the 'get_ttymode()' and/or 'sttyparse()'.


3. Related functions in stty.c and sttyparse.c

int
main(int argc, char *argv[])

int
get_ttymode(int fd, struct termio *termio, struct termios *termios,
	struct stio *stermio, struct winsize *winsize, struct eucioc *kwp)

void
pramodes()

char *
sttyparse(int argc, char *argv[], int term, struct termio *ocb,
	struct termios *cb, struct termiox *termiox, struct winsize *winsize,
	eucwidth_t *wp, struct eucioc *kwp)

int
set_sttymode(int fd, struct termio *termio, struct termios *termios,
	struct stio *stermio, struct termiox *termiox, struct winsize *winsize,
	struct winsize *owinsize, struct eucioc *kwp)