Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/misc/volume2/overstrike

Internet Message Format | 1991-08-07 | 4.1 KB

From: [e-mail] (Paul Vixie Esq)
Newsgroups: comp.sources.misc
Subject: v02i016: filter backspaces into multiple lines
Message-ID: <[e-mail]>
Date: 26 Jan 88 03:50:50 GMT
Approved: [e-mail]

Comp.sources.misc: Volume 2, Issue 16
Submitted-By: Paul Vixie Esq <[e-mail]>
Archive-Name: overstrike

/* noback - convert lines with backspaces to multiple lines
 * vix 16jun87 [made it leave lines containing ESC alone (for 'col -f')]
 * vix 16dec86 [add test for CR as end-of-line so that files already
 *              in overstrike format won't blow up the buffer...]
 * vix 10oct86 [written......again......sigh]
 */

#include <stdio.h>

#define    MDEPTH        10
#define    MWIDTH        256
#define    MYBUFSIZ    2000
#define    EOL        0x0A
#define    CR        0x0D
#define    TAB        0x09
#define    BS        0x08
#define    SPACE        0x20
#define    ESC        0x1B

main()
{
    int    depth[MWIDTH],        /* depth of stack for each position */
        length[MDEPTH],        /* number of positions used / level */
        data[MDEPTH][MWIDTH],    /* actual data, all positions/levels */
        buffer[MYBUFSIZ+1],    /* pre-scan buffer */
        bufptr,            /* buffer-pointer, what else? */
        has_esc,        /* flag: line has escape in it */
        i,            /* the inevitable generic integer */
        ch,            /* current character being processed */
        pos,            /* current position (0..MWIDTH-1) */
        curdepth,        /* depth of current position */
        maxdepth,        /* depth of deepest position's stack */
        end_int;        /* all useful variables end with ',' */

    /* I feel gross today. how about a goto?
     */
next_line:
    /* load a line into the pre-scan buffer
     * (I call it that because it didn't used to be here)
     */
    has_esc = 0;
    i = 0;
    do {
        ch = getchar();
        if (ch == ESC)
            has_esc++;
        if (i == MYBUFSIZ) {
            fprintf(stderr, "noback: pre-scan buffer overflow\n");
            exit(2);
        }
        buffer[i++] = ch;
    } while (ch != EOL && ch != EOF);
    buffer[i] = 0;

    /* if the line has an escape in it, write it straight out and go back
     * for another line.  escapes mean that some variable number of chars
     * following will not occupy a print position, and since we can't know
     * how many chars that will be, we don't handle the situation.
     */
    if (has_esc) {
        i = 0;
        do { putchar(buffer[i++]); }
        while (buffer[i]);
        goto next_line;
    }

    bufptr = 0;
    ch = buffer[bufptr++];

    /* we are beginning a line
     */
    for (i = 0;  i < MWIDTH;  i++)
        depth[i] = -1;
    for (i = 0;  i < MDEPTH;  i++)
        length[i] = 0;
    maxdepth = -1;
    pos = 0;

    while (ch != EOF && ch != EOL)
    {
        /* on a backspace, we send the position back one,
         * then we go get the next character.
         *
         * NOTE: backspace as first character on the line
         * is ignored.
         */
        if (ch == BS)
        {
            if (pos > 0)
                pos -= 1;
            ch = buffer[bufptr++];
            continue;
        }

        /* on a carriage-return, we set the position back
         * to the beginning of the line, then go back for
         * the next character.
         */
        if (ch == CR)
        {
            pos = 0;
            ch = buffer[bufptr++];
            continue;
        }

        /* on a tab, we skip to the tab position and continue.
         */
        if (ch == TAB)
        {
            /* increment first or it won't move from a
             * tab position.
             */
            do  {pos += 1;}  while ((pos % 8) != 0);
            ch = buffer[bufptr++];
            continue;
        }

        /* a normal character.
         *    -> push onto stack for this position
         *    -> (conditionally initialize new line)
         *    -> adjust max-length for this line
         *    -> get next character
         *    -> continue
         */
        curdepth = ++depth[pos];
        if (curdepth > maxdepth)
        {
            maxdepth = curdepth;
            for (i = 0;  i < MWIDTH;  i++)
                data[curdepth][i] = SPACE;
        }
        data[curdepth][pos] = ch;
        pos += 1;
        if (pos > length[curdepth])
            length[curdepth] = pos;
        ch = buffer[bufptr++];
    }

    /* end of line or file. either way, dump the lines out.
     * draw from the bottom up, so that the overstriking
     * characters are drawn first.  this is because on CRTs,
     * spaces (used in lines after the first for positioning)
     * are destructive.
     */
    for (i = maxdepth;  i >= 0;  i--)
    {
        for (pos = 0;  pos < length[i];  pos++)
            putchar(data[i][pos]);
        putchar(CR);
    }
    putchar(EOL);

    if (ch != EOF)
        goto next_line;

    /* end of file. bye kids...
     */
}
--
Paul A Vixie Esq
[e-mail]
{uunet,ptsfa,hoptoad}!vixie!paul
San Francisco, [phone]