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Annotation of researchv10no/cmd/paper/print2621.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * paper command: filter to print on HP2621P without dropping
        !             3:  *      characters due to intervening layers of system buffering.
        !             4:  *      This version is (hopefully) independent of strap settings.
        !             5:  *      Operates by handshaking with terminal every N characters.
        !             6:  */
        !             7: 
        !             8: #include <signal.h>
        !             9: #include <sgtty.h>
        !            10: #include <stdio.h>
        !            11: 
        !            12: #define N   25
        !            13: #define ESC '\033'
        !            14: #define DC1 '\021'
        !            15: 
        !            16: char buff[N+1];
        !            17: char enqstat[]  = {ESC, '^', DC1, DC1};
        !            18: char printon[]  = {ESC, '&', 'p', '1', '1', 'C', DC1, DC1, '\r', '\n'};
        !            19: char printoff[] = {ESC, '&', 'p', '1', '3', 'C', DC1, DC1, '\r', '\n'};
        !            20: 
        !            21: char done = 0;
        !            22: struct sgttyb oldtty, newtty;
        !            23: 
        !            24: interrupt ()
        !            25: {
        !            26:        signal (SIGINT, SIG_IGN);
        !            27:        signal (SIGQUIT, SIG_IGN);
        !            28:        signal (SIGTERM, SIG_IGN);
        !            29:        newtty.sg_flags |= RAW;
        !            30:        stty (2, &newtty);
        !            31:        write (2, printoff, sizeof printoff);
        !            32:        sleep (3);
        !            33:        stty (2, &oldtty);
        !            34:        exit (1);
        !            35: }
        !            36: 
        !            37: prepare ()
        !            38: {
        !            39:        register int n=0, c;
        !            40:        static char saveesc=0;
        !            41:        if (saveesc) {
        !            42:                buff[n++] = ESC;
        !            43:                saveesc = 0;
        !            44:        }
        !            45:        if (done)
        !            46:                return n;
        !            47:        while (n < N) {
        !            48:                c = getchar();
        !            49:                if (c == EOF) {
        !            50:                        done = 1;
        !            51:                        break;
        !            52:                }
        !            53:                if (c==ESC && n+4>=N) {
        !            54:                        saveesc = 1;
        !            55:                        break;
        !            56:                }
        !            57:                if (c == '\n')
        !            58:                        buff[n++] = '\r';
        !            59:                buff[n++] = c;
        !            60:        }
        !            61:        return n;
        !            62: }
        !            63: 
        !            64: await (c)
        !            65: int c;
        !            66: {
        !            67:        static char got;
        !            68:        while (1) {
        !            69:                if (read(2, &got, 1) != 1)
        !            70:                        interrupt ();
        !            71:                if (got == c)
        !            72:                        return;
        !            73:        }
        !            74: }
        !            75: 
        !            76: main (argc, argv)
        !            77: int argc;
        !            78: char **argv;
        !            79: {
        !            80:        register int n;
        !            81:        gtty (2, &oldtty);
        !            82:        signal (SIGINT, interrupt);
        !            83:        signal (SIGQUIT, interrupt);
        !            84:        signal (SIGTERM, interrupt);
        !            85:        newtty = oldtty;
        !            86:        newtty.sg_flags = EVENP | ODDP | CBREAK;
        !            87:        newtty.sg_flags |= n = oldtty.sg_flags & XTABS;
        !            88:        stty (2, &newtty);
        !            89:        write (2, printon, sizeof printon);
        !            90: 
        !            91:        n = 0;
        !            92:        do {
        !            93:                write (2, enqstat, sizeof enqstat);
        !            94:                write (2, buff, n);
        !            95:                n = prepare();
        !            96:                await (ESC);
        !            97:                await ('\r');
        !            98:        } while (n != 0);
        !            99: 
        !           100:        write (2, printoff, sizeof printoff);
        !           101:        write (2, enqstat, sizeof enqstat);
        !           102:        await (ESC);
        !           103:        await ('\r');
        !           104:        stty (2, &oldtty);
        !           105: }

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