xref: /netbsd-src/usr.bin/m4/expr.c (revision 2a399c6883d870daece976daec6ffa7bb7f934ce) 
1 /*	$NetBSD: expr.c,v 1.8 1997/10/19 04:39:53 lukem Exp $	*/
2 
3 /*
4  * Copyright (c) 1989, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Ozan Yigit at York University.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the University of
21  *	California, Berkeley and its contributors.
22  * 4. Neither the name of the University nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  */
38 
39 #include <sys/cdefs.h>
40 #ifndef lint
41 #if 0
42 static char sccsid[] = "@(#)expr.c	8.2 (Berkeley) 4/29/95";
43 #else
44 __RCSID("$NetBSD: expr.c,v 1.8 1997/10/19 04:39:53 lukem Exp $");
45 #endif
46 #endif /* not lint */
47 
48 #include <sys/cdefs.h>
49 #include <stdio.h>
50 
51 #include "mdef.h"
52 #include "extern.h"
53 
54 /*
55  *      expression evaluator: performs a standard recursive
56  *      descent parse to evaluate any expression permissible
57  *      within the following grammar:
58  *
59  *      expr    :       query EOS
60  *      query   :       lor
61  *              |       lor "?" query ":" query
62  *      lor     :       land { "||" land }
63  *      land    :       not { "&&" not }
64  *	not	:	eqrel
65  *		|	'!' not
66  *      eqrel   :       shift { eqrelop shift }
67  *      shift   :       primary { shop primary }
68  *      primary :       term { addop term }
69  *      term    :       exp { mulop exp }
70  *	exp	:	unary { expop unary }
71  *      unary   :       factor
72  *              |       unop unary
73  *      factor  :       constant
74  *              |       "(" query ")"
75  *      constant:       num
76  *              |       "'" CHAR "'"
77  *      num     :       DIGIT
78  *              |       DIGIT num
79  *      shop    :       "<<"
80  *              |       ">>"
81  *      eqrel   :       "="
82  *              |       "=="
83  *              |       "!="
84  *      	|       "<"
85  *              |       ">"
86  *              |       "<="
87  *              |       ">="
88  *
89  *
90  *      This expression evaluator is lifted from a public-domain
91  *      C Pre-Processor included with the DECUS C Compiler distribution.
92  *      It is hacked somewhat to be suitable for m4.
93  *
94  *      Originally by:  Mike Lutz
95  *                      Bob Harper
96  */
97 
98 #define TRUE    1
99 #define FALSE   0
100 #define EOS     (char) 0
101 #define EQL     0
102 #define NEQ     1
103 #define LSS     2
104 #define LEQ     3
105 #define GTR     4
106 #define GEQ     5
107 #define OCTAL   8
108 #define DECIMAL 10
109 
110 static char *nxtch;		       /* Parser scan pointer */
111 
112 static int query __P((void));
113 static int lor __P((void));
114 static int land __P((void));
115 static int not __P((void));
116 static int eqrel __P((void));
117 static int shift __P((void));
118 static int primary __P((void));
119 static int term __P((void));
120 static int exp __P((void));
121 static int unary __P((void));
122 static int factor __P((void));
123 static int constant __P((void));
124 static int num __P((void));
125 static int geteqrel __P((void));
126 static int skipws __P((void));
127 static void experr __P((char *));
128 
129 /*
130  * For longjmp
131  */
132 #include <setjmp.h>
133 static jmp_buf expjump;
134 
135 /*
136  * macros:
137  *      ungetch - Put back the last character examined.
138  *      getch   - return the next character from expr string.
139  */
140 #define ungetch()       nxtch--
141 #define getch()         *nxtch++
142 
143 int
144 expr(expbuf)
145 	char *expbuf;
146 {
147 	int rval;
148 
149 	nxtch = expbuf;
150 	if (setjmp(expjump) != 0)
151 		return FALSE;
152 
153 	rval = query();
154 	if (skipws() == EOS)
155 		return rval;
156 
157 	printf("m4: ill-formed expression.\n");
158 	return FALSE;
159 }
160 
161 /*
162  * query : lor | lor '?' query ':' query
163  */
164 static int
165 query()
166 {
167 	int bool, true_val, false_val;
168 
169 	bool = lor();
170 	if (skipws() != '?') {
171 		ungetch();
172 		return bool;
173 	}
174 
175 	true_val = query();
176 	if (skipws() != ':')
177 		experr("bad query");
178 
179 	false_val = query();
180 	return bool ? true_val : false_val;
181 }
182 
183 /*
184  * lor : land { '||' land }
185  */
186 static int
187 lor()
188 {
189 	int c, vl, vr;
190 
191 	vl = land();
192 	while ((c = skipws()) == '|') {
193 		if (getch() != '|')
194 			ungetch();
195 		vr = land();
196 		vl = vl || vr;
197 	}
198 
199 	ungetch();
200 	return vl;
201 }
202 
203 /*
204  * land : not { '&&' not }
205  */
206 static int
207 land()
208 {
209 	int c, vl, vr;
210 
211 	vl = not();
212 	while ((c = skipws()) == '&') {
213 		if (getch() != '&')
214 			ungetch();
215 		vr = not();
216 		vl = vl && vr;
217 	}
218 
219 	ungetch();
220 	return vl;
221 }
222 
223 /*
224  * not : eqrel | '!' not
225  */
226 static int
227 not()
228 {
229 	int val, c;
230 
231 	if ((c = skipws()) == '!' && getch() != '=') {
232 		ungetch();
233 		val = not();
234 		return !val;
235 	}
236 
237 	if (c == '!')
238 		ungetch();
239 	ungetch();
240 	return eqrel();
241 }
242 
243 /*
244  * eqrel : shift { eqrelop shift }
245  */
246 static int
247 eqrel()
248 {
249 	int vl, vr, eqrel;
250 
251 	vl = shift();
252 	while ((eqrel = geteqrel()) != -1) {
253 		vr = shift();
254 
255 		switch (eqrel) {
256 
257 		case EQL:
258 			vl = (vl == vr);
259 			break;
260 		case NEQ:
261 			vl = (vl != vr);
262 			break;
263 
264 		case LEQ:
265 			vl = (vl <= vr);
266 			break;
267 		case LSS:
268 			vl = (vl < vr);
269 			break;
270 		case GTR:
271 			vl = (vl > vr);
272 			break;
273 		case GEQ:
274 			vl = (vl >= vr);
275 			break;
276 		}
277 	}
278 	return vl;
279 }
280 
281 /*
282  * shift : primary { shop primary }
283  */
284 static int
285 shift()
286 {
287 	int vl, vr, c;
288 
289 	vl = primary();
290 	while (((c = skipws()) == '<' || c == '>') && getch() == c) {
291 		vr = primary();
292 
293 		if (c == '<')
294 			vl <<= vr;
295 		else
296 			vl >>= vr;
297 	}
298 
299 	if (c == '<' || c == '>')
300 		ungetch();
301 	ungetch();
302 	return vl;
303 }
304 
305 /*
306  * primary : term { addop term }
307  */
308 static int
309 primary()
310 {
311 	int c, vl, vr;
312 
313 	vl = term();
314 	while ((c = skipws()) == '+' || c == '-') {
315 		vr = term();
316 
317 		if (c == '+')
318 			vl += vr;
319 		else
320 			vl -= vr;
321 	}
322 
323 	ungetch();
324 	return vl;
325 }
326 
327 /*
328  * <term> := <exp> { <mulop> <exp> }
329  */
330 static int
331 term()
332 {
333 	int c, vl, vr;
334 
335 	vl = exp();
336 	while ((c = skipws()) == '*' || c == '/' || c == '%') {
337 		vr = exp();
338 
339 		switch (c) {
340 		case '*':
341 			vl *= vr;
342 			break;
343 		case '/':
344 			vl /= vr;
345 			break;
346 		case '%':
347 			vl %= vr;
348 			break;
349 		}
350 	}
351 	ungetch();
352 	return vl;
353 }
354 
355 /*
356  * <term> := <unary> { <expop> <unary> }
357  */
358 static int
359 exp()
360 {
361 	int c, vl, vr, n;
362 
363 	vl = unary();
364 	switch (c = skipws()) {
365 
366 	case '*':
367 		if (getch() != '*') {
368 			ungetch();
369 			break;
370 		}
371 
372 	case '^':
373 		vr = exp();
374 		n = 1;
375 		while (vr-- > 0)
376 			n *= vl;
377 		return n;
378 	}
379 
380 	ungetch();
381 	return vl;
382 }
383 
384 /*
385  * unary : factor | unop unary
386  */
387 static int
388 unary()
389 {
390 	int val, c;
391 
392 	if ((c = skipws()) == '+' || c == '-' || c == '~') {
393 		val = unary();
394 
395 		switch (c) {
396 		case '+':
397 			return val;
398 		case '-':
399 			return -val;
400 		case '~':
401 			return ~val;
402 		}
403 	}
404 
405 	ungetch();
406 	return factor();
407 }
408 
409 /*
410  * factor : constant | '(' query ')'
411  */
412 static int
413 factor()
414 {
415 	int val;
416 
417 	if (skipws() == '(') {
418 		val = query();
419 		if (skipws() != ')')
420 			experr("bad factor");
421 		return val;
422 	}
423 
424 	ungetch();
425 	return constant();
426 }
427 
428 /*
429  * constant: num | 'char'
430  * Note: constant() handles multi-byte constants
431  */
432 static int
433 constant()
434 {
435 	int i;
436 	int value;
437 	char c;
438 	int v[sizeof(int)];
439 
440 	if (skipws() != '\'') {
441 		ungetch();
442 		return num();
443 	}
444 	for (i = 0; i < sizeof(int); i++) {
445 		if ((c = getch()) == '\'') {
446 			ungetch();
447 			break;
448 		}
449 		if (c == '\\') {
450 			switch (c = getch()) {
451 			case '0':
452 			case '1':
453 			case '2':
454 			case '3':
455 			case '4':
456 			case '5':
457 			case '6':
458 			case '7':
459 				ungetch();
460 				c = num();
461 				break;
462 			case 'n':
463 				c = 012;
464 				break;
465 			case 'r':
466 				c = 015;
467 				break;
468 			case 't':
469 				c = 011;
470 				break;
471 			case 'b':
472 				c = 010;
473 				break;
474 			case 'f':
475 				c = 014;
476 				break;
477 			}
478 		}
479 		v[i] = c;
480 	}
481 	if (i == 0 || getch() != '\'')
482 		experr("illegal character constant");
483 	for (value = 0; --i >= 0;) {
484 		value <<= 8;
485 		value += v[i];
486 	}
487 	return value;
488 }
489 
490 /*
491  * num : digit | num digit
492  */
493 static int
494 num()
495 {
496 	int rval, c, base;
497 	int ndig;
498 
499 	base = ((c = skipws()) == '0') ? OCTAL : DECIMAL;
500 	rval = 0;
501 	ndig = 0;
502 	while (c >= '0' && c <= (base == OCTAL ? '7' : '9')) {
503 		rval *= base;
504 		rval += (c - '0');
505 		c = getch();
506 		ndig++;
507 	}
508 	ungetch();
509 
510 	if (ndig == 0)
511 		experr("bad constant");
512 
513 	return rval;
514 
515 }
516 
517 /*
518  * eqrel : '=' | '==' | '!=' | '<' | '>' | '<=' | '>='
519  */
520 static int
521 geteqrel()
522 {
523 	int c1, c2;
524 
525 	c1 = skipws();
526 	c2 = getch();
527 
528 	switch (c1) {
529 
530 	case '=':
531 		if (c2 != '=')
532 			ungetch();
533 		return EQL;
534 
535 	case '!':
536 		if (c2 == '=')
537 			return NEQ;
538 		ungetch();
539 		ungetch();
540 		return -1;
541 
542 	case '<':
543 		if (c2 == '=')
544 			return LEQ;
545 		ungetch();
546 		return LSS;
547 
548 	case '>':
549 		if (c2 == '=')
550 			return GEQ;
551 		ungetch();
552 		return GTR;
553 
554 	default:
555 		ungetch();
556 		ungetch();
557 		return -1;
558 	}
559 }
560 
561 /*
562  * Skip over any white space and return terminating char.
563  */
564 static int
565 skipws()
566 {
567 	char c;
568 
569 	while ((c = getch()) <= ' ' && c > EOS)
570 		;
571 	return c;
572 }
573 
574 /*
575  * resets environment to eval(), prints an error
576  * and forces eval to return FALSE.
577  */
578 static void
579 experr(msg)
580 	char *msg;
581 {
582 	printf("m4: %s in expr.\n", msg);
583 	longjmp(expjump, -1);
584 }
585