nextlex.c

一款类linux的操作系统源码

/* 
 *  Roadrunner/pk
 *    Copyright (C) 1989-2001  Cornfed Systems, Inc.
 *
 *  The Roadrunner/pk operating system is free software; you can
 *  redistribute and/or modify it under the terms of the GNU General
 *  Public License, version 2, as published by the Free Software
 *  Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public
 *  License along with this program; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307 USA
 *
 *  More information about the Roadrunner/pk operating system of
 *  which this file is a part is available on the World-Wide Web
 *  at: http://www.cornfed.com.
 *
 */

#include <ctype.h>
#include <stdlib.h>
#include <sys/lex.h>

#define LEX_SINGLE_CHAR(TYPE)						\
    l->type = TYPE;							\
    *(s++) = ch;							\
    *s = '\0';								\
    (*pos)++

void
nextlex(char *ln, int *pos, lex_t l)
{
    char *s;
    char ch;
    int acc;

    ch = ln[*pos];
    while (isspace(ch))
	ch = ln[++(*pos)];

    s = l->s;

    if (isalpha(ch)) {
	l->type = LEX_ID;

	do {
	    *(s++) = ch;
	    ch = ln[++(*pos)];
	}
	while (isalpha(ch) || isdigit(ch));
	*s = '\0';
	return;
    }
    if (isdigit(ch)) {
	l->type = LEX_NUM;

	acc = 0;
	do {
	    *(s++) = ch;
	    acc = (acc * 10) + (ch - '0');
	    ch = ln[++(*pos)];
	}
	while (isdigit(ch));
	*s = '\0';

	l->val = acc;
	return;
    }
    switch (ch) {
    case '\0':
	l->type = LEX_EOL;
	*s = '\0';
	break;

    case '\r':
	LEX_SINGLE_CHAR(LEX_CR);
	break;
    case '\n':
	LEX_SINGLE_CHAR(LEX_LF);
	break;
    case ':':
	LEX_SINGLE_CHAR(LEX_COLON);
	break;
    case '-':
	LEX_SINGLE_CHAR(LEX_DASH);
	break;
    case '?':
	LEX_SINGLE_CHAR(LEX_QUESTION);
	break;
    case '/':
	LEX_SINGLE_CHAR(LEX_SLASH);
	break;
    case '.':
	LEX_SINGLE_CHAR(LEX_PERIOD);
	break;
    default:
	l->type = LEX_NULL;
	*s = '\0';
	(*pos)++;
    }
}