/*
 * Mach Operating System
 * Copyright (c) 1991,1990 Carnegie Mellon University
 * All Rights Reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 *
 * $FreeBSD: src/sys/ddb/db_expr.c,v 1.13 1999/08/28 00:41:07 peter Exp $
 */

/*
 *      Author: David B. Golub, Carnegie Mellon University
 *      Date:   7/90
 */
#include <sys/param.h>

#include <ddb/ddb.h>
#include <ddb/db_lex.h>
#include <ddb/db_access.h>
#include <ddb/db_command.h>

static boolean_t        db_add_expr (db_expr_t *valuep);
static boolean_t        db_mult_expr (db_expr_t *valuep);
static boolean_t        db_shift_expr (db_expr_t *valuep);
static boolean_t        db_term (db_expr_t *valuep);
static boolean_t        db_unary (db_expr_t *valuep);

static boolean_t
db_term(db_expr_t *valuep)
{
        int     t;

        t = db_read_token();
        if (t == tIDENT) {
            if (!db_value_of_name(db_tok_string, valuep)) {
                db_error("Symbol not found\n");
                /*NOTREACHED*/
            }
            return (TRUE);
        }
        if (t == tNUMBER) {
            *valuep = (db_expr_t)db_tok_number;
            return (TRUE);
        }
        if (t == tDOT) {
            *valuep = (db_expr_t)db_dot;
            return (TRUE);
        }
        if (t == tDOTDOT) {
            *valuep = (db_expr_t)db_prev;
            return (TRUE);
        }
        if (t == tPLUS) {
            *valuep = (db_expr_t) db_next;
            return (TRUE);
        }
        if (t == tDITTO) {
            *valuep = (db_expr_t)db_last_addr;
            return (TRUE);
        }
        if (t == tDOLLAR) {
            if (!db_get_variable(valuep))
                return (FALSE);
            return (TRUE);
        }
        if (t == tLPAREN) {
            if (!db_expression(valuep)) {
                db_error("Syntax error\n");
                /*NOTREACHED*/
            }
            t = db_read_token();
            if (t != tRPAREN) {
                db_error("Syntax error\n");
                /*NOTREACHED*/
            }
            return (TRUE);
        }
        db_unread_token(t);
        return (FALSE);
}

static boolean_t
db_unary(db_expr_t *valuep)
{
        int     t;

        t = db_read_token();
        if (t == tMINUS) {
            if (!db_unary(valuep)) {
                db_error("Syntax error\n");
                /*NOTREACHED*/
            }
            *valuep = -*valuep;
            return (TRUE);
        }
        if (t == tSTAR) {
            /* indirection */
            if (!db_unary(valuep)) {
                db_error("Syntax error\n");
                /*NOTREACHED*/
            }
            *valuep = db_get_value((db_addr_t)*valuep, sizeof(int), FALSE);
            return (TRUE);
        }
        db_unread_token(t);
        return (db_term(valuep));
}

static boolean_t
db_mult_expr(db_expr_t *valuep)
{
        db_expr_t       lhs, rhs;
        int             t;

        *valuep = 0;    /* silence gcc */

        if (!db_unary(&lhs))
            return (FALSE);

        t = db_read_token();
        while (t == tSTAR || t == tSLASH || t == tPCT || t == tHASH) {
            if (!db_term(&rhs)) {
                db_error("Syntax error\n");
                /*NOTREACHED*/
            }
            if (t == tSTAR)
                lhs *= rhs;
            else {
                if (rhs == 0) {
                    db_error("Divide by 0\n");
                    /*NOTREACHED*/
                }
                if (t == tSLASH)
                    lhs /= rhs;
                else if (t == tPCT)
                    lhs %= rhs;
                else
                    lhs = roundup(lhs, rhs);
            }
            t = db_read_token();
        }
        db_unread_token(t);
        *valuep = lhs;
        return (TRUE);
}

static boolean_t
db_add_expr(db_expr_t *valuep)
{
        db_expr_t       lhs, rhs;
        int             t;

        *valuep = 0;    /* silence gcc */

        if (!db_mult_expr(&lhs))
            return (FALSE);

        t = db_read_token();
        while (t == tPLUS || t == tMINUS) {
            if (!db_mult_expr(&rhs)) {
                db_error("Syntax error\n");
                /*NOTREACHED*/
            }
            if (t == tPLUS)
                lhs += rhs;
            else
                lhs -= rhs;
            t = db_read_token();
        }
        db_unread_token(t);
        *valuep = lhs;
        return (TRUE);
}

static boolean_t
db_shift_expr(db_expr_t *valuep)
{
        db_expr_t       lhs, rhs;
        int             t;

        if (!db_add_expr(&lhs))
            return (FALSE);

        t = db_read_token();
        while (t == tSHIFT_L || t == tSHIFT_R) {
            if (!db_add_expr(&rhs)) {
                db_error("Syntax error\n");
                /*NOTREACHED*/
            }
            if (rhs < 0) {
                db_error("Negative shift amount\n");
                /*NOTREACHED*/
            }
            if (t == tSHIFT_L)
                lhs <<= rhs;
            else {
                /* Shift right is unsigned */
                lhs = (unsigned) lhs >> rhs;
            }
            t = db_read_token();
        }
        db_unread_token(t);
        *valuep = lhs;
        return (TRUE);
}

int
db_expression(db_expr_t *valuep)
{
        return (db_shift_expr(valuep));
}