/*
 *      cook - file construction tool
 *      Copyright (C) 1997, 2006, 2007 Peter Miller;
 *      All rights reserved.
 *
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2 of the License, or
 *      (at your option) any later version.
 *
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY 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, USA.
 *
 * MANIFEST: functions to manipulate expr_lexs
 */

#include <common/str.h>
#include <common/sub/expr_lex.h>
#include <common/sub/expr_gram.gen.h>


static string_ty *text;
static size_t   pos;


void
sub_expr_lex_open(string_ty *s)
{
    text = s;
    pos = 0;
}


void
sub_expr_lex_close(void)
{
    text = 0;
    pos = 0;
}


static int
lex_getc(void)
{
    int             c;

    if (!text || pos >= text->str_length)
        c = 0;
    else
        c = (unsigned char)text->str_text[pos];
    ++pos;
    return c;
}


static void
lex_getc_undo(int c)
{
    (void)c;
    if (pos > 0)
        --pos;
}



int
sub_expr_gram_lex(void)
{
    int             c;
    long            n;

    for (;;)
    {
        c = lex_getc();
        switch (c)
        {
        case 0:
            return 0;

        case '(':
            return LP;

        case ')':
            return RP;

        case '-':
            return MINUS;

        case '+':
            return PLUS;

        case '*':
            return MUL;

        case '/':
            return DIV;

        case ' ':
        case '\t':
        case '\n':
        case '\f':
            break;

        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
            n = 0;
            for (;;)
            {
                n = n * 10 + c - '0';
                c = lex_getc();
                switch (c)
                {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                    continue;

                default:
                    break;
                }
                lex_getc_undo(c);
                break;
            }
            sub_expr_gram_lval.lv_number = n;
            return NUMBER;

        default:
            return JUNK;
        }
    }
}