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Path: utzoo!watmath!clyde!bonnie!akgua!gatech!seismo!uwvax!Thomas Scott Christiansen <root@rsch.wisc.edu>
From: root@rsch.wisc.edu (Thomas Scott Christiansen)
Newsgroups: net.lang.c
Subject: Re: mildly obfuscating c
Message-ID: <464@uwvax.UUCP>
Date: Wed, 11-Dec-85 07:51:38 EST
Article-I.D.: uwvax.464
Posted: Wed Dec 11 07:51:38 1985
Date-Received: Sat, 14-Dec-85 00:39:13 EST
References: <288@epicen.UUCP> <564@puff.UUCP>
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Organization: U of Wisconsin CS Dept
Lines: 60

Thanks to all of you who have mailed me suggestions regarding my
C question on computed gotos.  No, I have not been doing too much 
FORTRAN programming.  I was actually just curious what various
systems would do with that code.  Most of you suggested that I
use a switch statement.  My own solution (which I have actually
used) is the jump table code given below.  Any routine that really 
wants to exit will do a "longjump(env,1);" to return from the msgs()
function.  Forgive me for declaring all of these functions ints;
the compiler I was using hated voids with a passion.  

tom
===================================================================
extern int superuser;
extern jmp_buf env;
extern int show_menu();

msgs() {
    int (*jump[128])();
    static beenhere = 0;
    
    load_table(jump);
    
    if (setjmp(env) == 0)
        for (;;) {
            show_menu();    
            (*jump [get_opt()])();
        } 
}

load_table( j )
    int (*j[])();
{
    register i;

    extern
        leave_comment(),enter_message(),file_transfer(),kill_message(),
        go_back(),newdir(),whos_on(),finger(),get_help(),quick_summary(),
        reset_time(),do_shell(),delete_comment(), show_comments(),
        long_summary(),say_time_on(),message_stat(),logout(),do_nothing(),
        switch_expert(),long_menu(),super_expert(),get_mesg(),toggle_pause();

    for (i=0;i < 128; i++)
        j[i] = do_nothing; 

    j [ 'C' ] = leave_comment;   j [ 'E' ] = enter_message;
    j [ 'F' ] = file_transfer;   j [ 'K' ] = kill_message;
    j [ 'M' ] = go_back;         j [ 'G' ] = logout;
    j [ 'N' ] = newdir;          j [ 'O' ] = whos_on;
    j [ 'P' ] = toggle_pause;    j [ 'Q' ] = quick_summary;
    j [ 'S' ] = long_summary;    j [ 'R' ] = get_mesg;
    j [ 'T' ] = say_time_on;     j [ 'U' ] = do_finger;
    j [ '#' ] = message_stat;    j [ 'X' ] = switch_expert;
    j [ '?' ] = long_menu;       j [ 'H' ] = long_menu;

    if ( superuser  ) { /* sysop */
        j [ '6' ] = reset_time;     j [ '7' ] = do_shell;
        j [ '8' ] = delete_comment; j [ '9' ] = show_comments;
    }
}
===================================================================