kgets.c

/*
 * Copyright (c) 2001
 *      The President and Fellows of Harvard College.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


#include <types.h>
#include <lib.h>

/*
 * Do a backspace in typed input.
 * We overwrite the current character with a space in case we're on
 * a terminal where backspace is nondestructive.
 */
static
void
backsp(void)
{
        putch('\b');
        putch(' ');
        putch('\b');
}

/*
 * Read a string off the console. Support a few of the more useful
 * common control characters. Do not include the terminating newline
 * in the buffer passed back.
 */
void
kgets(char *buf, size_t maxlen)
{
        size_t pos = 0;
        int ch;

        while (1) {
                ch = getch();
                if (ch=='\n' || ch=='\r') {
                        putch('\n');
                        break;
                }

                /* Only allow the normal 7-bit ascii */
                if (ch>=32 && ch<127 && pos < maxlen-1) {
                        putch(ch);
                        buf[pos++] = ch;
                }
                else if ((ch=='\b' || ch==127) && pos>0) {
                        /* backspace */
                        backsp();
                        pos--;
                }
                else if (ch==3) {
                        /* ^C - return empty string */
                        putch('^');
                        putch('C');
                        putch('\n');
                        pos = 0;
                        break;
                }
                else if (ch==18) {
                        /* ^R - reprint input */
                        buf[pos] = 0;
                        kprintf("^R\n%s", buf);
                }
                else if (ch==21) {
                        /* ^U - erase line */
                        while (pos > 0) {
                                backsp();
                                pos--;
                        }
                }
                else if (ch==23) {
                        /* ^W - erase word */
                        while (pos > 0 && buf[pos-1]==' ') {
                                backsp();
                                pos--;
                        }
                        while (pos > 0 && buf[pos-1]!=' ') {
                                backsp();
                                pos--;
                        }
                }
                else {
                        beep();
                }
        }

        buf[pos] = 0;
}