db_expr.c revision 798 
1/*
2 * Mach Operating System
3 * Copyright (c) 1991,1990 Carnegie Mellon University
4 * All Rights Reserved.
5 *
6 * Permission to use, copy, modify and distribute this software and its
7 * documentation is hereby granted, provided that both the copyright
8 * notice and this permission notice appear in all copies of the
9 * software, derivative works or modified versions, and any portions
10 * thereof, and that both notices appear in supporting documentation.
11 *
12 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
13 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
14 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
15 *
16 * Carnegie Mellon requests users of this software to return to
17 *
18 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
19 *  School of Computer Science
20 *  Carnegie Mellon University
21 *  Pittsburgh PA 15213-3890
22 *
23 * any improvements or extensions that they make and grant Carnegie the
24 * rights to redistribute these changes.
25 *
26 *	$Id: db_expr.c,v 1.2 1993/10/16 16:47:14 rgrimes Exp $
27 */
28
29/*
30 *	Author: David B. Golub, Carnegie Mellon University
31 *	Date:	7/90
32 */
33#include "param.h"
34#include "systm.h"
35#include "proc.h"
36#include "ddb/ddb.h"
37#include <ddb/db_lex.h>
38#include <ddb/db_access.h>
39#include <ddb/db_command.h>
40
41boolean_t
42db_term(valuep)
43	db_expr_t *valuep;
44{
45	int	t;
46
47	t = db_read_token();
48	if (t == tIDENT) {
49	    if (!db_value_of_name(db_tok_string, valuep)) {
50		db_error("Symbol not found\n");
51		/*NOTREACHED*/
52	    }
53	    return (TRUE);
54	}
55	if (t == tNUMBER) {
56	    *valuep = (db_expr_t)db_tok_number;
57	    return (TRUE);
58	}
59	if (t == tDOT) {
60	    *valuep = (db_expr_t)db_dot;
61	    return (TRUE);
62	}
63	if (t == tDOTDOT) {
64	    *valuep = (db_expr_t)db_prev;
65	    return (TRUE);
66	}
67	if (t == tPLUS) {
68	    *valuep = (db_expr_t) db_next;
69	    return (TRUE);
70	}
71	if (t == tDITTO) {
72	    *valuep = (db_expr_t)db_last_addr;
73	    return (TRUE);
74	}
75	if (t == tDOLLAR) {
76	    if (!db_get_variable(valuep))
77		return (FALSE);
78	    return (TRUE);
79	}
80	if (t == tLPAREN) {
81	    if (!db_expression(valuep)) {
82		db_error("Syntax error\n");
83		/*NOTREACHED*/
84	    }
85	    t = db_read_token();
86	    if (t != tRPAREN) {
87		db_error("Syntax error\n");
88		/*NOTREACHED*/
89	    }
90	    return (TRUE);
91	}
92	db_unread_token(t);
93	return (FALSE);
94}
95
96boolean_t
97db_unary(valuep)
98	db_expr_t *valuep;
99{
100	int	t;
101
102	t = db_read_token();
103	if (t == tMINUS) {
104	    if (!db_unary(valuep)) {
105		db_error("Syntax error\n");
106		/*NOTREACHED*/
107	    }
108	    *valuep = -*valuep;
109	    return (TRUE);
110	}
111	if (t == tSTAR) {
112	    /* indirection */
113	    if (!db_unary(valuep)) {
114		db_error("Syntax error\n");
115		/*NOTREACHED*/
116	    }
117	    *valuep = db_get_value((db_addr_t)*valuep, sizeof(int), FALSE);
118	    return (TRUE);
119	}
120	db_unread_token(t);
121	return (db_term(valuep));
122}
123
124boolean_t
125db_mult_expr(valuep)
126	db_expr_t *valuep;
127{
128	db_expr_t	lhs, rhs;
129	int		t;
130
131	if (!db_unary(&lhs))
132	    return (FALSE);
133
134	t = db_read_token();
135	while (t == tSTAR || t == tSLASH || t == tPCT || t == tHASH) {
136	    if (!db_term(&rhs)) {
137		db_error("Syntax error\n");
138		/*NOTREACHED*/
139	    }
140	    if (t == tSTAR)
141		lhs *= rhs;
142	    else {
143		if (rhs == 0) {
144		    db_error("Divide by 0\n");
145		    /*NOTREACHED*/
146		}
147		if (t == tSLASH)
148		    lhs /= rhs;
149		else if (t == tPCT)
150		    lhs %= rhs;
151		else
152		    lhs = ((lhs+rhs-1)/rhs)*rhs;
153	    }
154	    t = db_read_token();
155	}
156	db_unread_token(t);
157	*valuep = lhs;
158	return (TRUE);
159}
160
161boolean_t
162db_add_expr(valuep)
163	db_expr_t *valuep;
164{
165	db_expr_t	lhs, rhs;
166	int		t;
167
168	if (!db_mult_expr(&lhs))
169	    return (FALSE);
170
171	t = db_read_token();
172	while (t == tPLUS || t == tMINUS) {
173	    if (!db_mult_expr(&rhs)) {
174		db_error("Syntax error\n");
175		/*NOTREACHED*/
176	    }
177	    if (t == tPLUS)
178		lhs += rhs;
179	    else
180		lhs -= rhs;
181	    t = db_read_token();
182	}
183	db_unread_token(t);
184	*valuep = lhs;
185	return (TRUE);
186}
187
188boolean_t
189db_shift_expr(valuep)
190	db_expr_t *valuep;
191{
192	db_expr_t	lhs, rhs;
193	int		t;
194
195	if (!db_add_expr(&lhs))
196	    return (FALSE);
197
198	t = db_read_token();
199	while (t == tSHIFT_L || t == tSHIFT_R) {
200	    if (!db_add_expr(&rhs)) {
201		db_error("Syntax error\n");
202		/*NOTREACHED*/
203	    }
204	    if (rhs < 0) {
205		db_error("Negative shift amount\n");
206		/*NOTREACHED*/
207	    }
208	    if (t == tSHIFT_L)
209		lhs <<= rhs;
210	    else {
211		/* Shift right is unsigned */
212		lhs = (unsigned) lhs >> rhs;
213	    }
214	    t = db_read_token();
215	}
216	db_unread_token(t);
217	*valuep = lhs;
218	return (TRUE);
219}
220
221int
222db_expression(valuep)
223	db_expr_t *valuep;
224{
225	return (db_shift_expr(valuep));
226}
227