/*
 * fhist - file history and comparison tools
 * Copyright (C) 1998, 2002, 2008, 2010, 2012 Peter Miller
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */

#include <common/str.h>
#include <common/sub/expr_lex.h>
#include <common/sub/expr_gram.yacc.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;
        }
    }
}


/* vim: set ts=8 sw=4 et : */
