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1/* vi: set sw=4 ts=4: */
2/*
3 * Mini expr implementation for busybox
4 *
5 * based on GNU expr Mike Parker.
6 * Copyright (C) 86, 1991-1997, 1999 Free Software Foundation, Inc.
7 *
8 * Busybox modifications
9 * Copyright (c) 2000 Edward Betts <edward@debian.org>.
10 *
11 * this program is free software; you can redistribute it and/or modify
12 * it under the terms of the gnu general public license as published by
13 * the free software foundation; either version 2 of the license, or
14 * (at your option) any later version.
15 *
16 * this program is distributed in the hope that it will be useful,
17 * but without any warranty; without even the implied warranty of
18 * merchantability or fitness for a particular purpose. see the gnu
19 * general public license for more details.
20 *
21 * you should have received a copy of the gnu general public license
22 * along with this program; if not, write to the free software
23 * foundation, inc., 59 temple place, suite 330, boston, ma 02111-1307 usa
24 *
25 */
26
27/* This program evaluates expressions. Each token (operator, operand,
28 * parenthesis) of the expression must be a seperate argument. The
29 * parser used is a reasonably general one, though any incarnation of
30 * it is language-specific. It is especially nice for expressions.
31 *
32 * No parse tree is needed; a new node is evaluated immediately.
33 * One function can handle multiple operators all of equal precedence,
34 * provided they all associate ((x op x) op x). */
35
36/* no getopt needed */
37
38#include <stdio.h>
39#include <string.h>
40#include <stdlib.h>
41#include <regex.h>
42#include <sys/types.h>
43#include "busybox.h"
44
45
46/* The kinds of value we can have. */
47enum valtype {
48 integer,
49 string
50};
51typedef enum valtype TYPE;
52
53/* A value is.... */
54struct valinfo {
55 TYPE type; /* Which kind. */
56 union { /* The value itself. */
57 int i;
58 char *s;
59 } u;
60};
61typedef struct valinfo VALUE;
62
63/* The arguments given to the program, minus the program name. */
64static char **args;
65
66static VALUE *docolon (VALUE *sv, VALUE *pv);
67static VALUE *eval (void);
68static VALUE *int_value (int i);
69static VALUE *str_value (char *s);
70static int nextarg (char *str);
71static int null (VALUE *v);
72static int toarith (VALUE *v);
73static void freev (VALUE *v);
74static void tostring (VALUE *v);
75
76int expr_main (int argc, char **argv)
77{
78 VALUE *v;
79
80 if (argc == 1) {
81 error_msg_and_die("too few arguments");
82 }
83
84 args = argv + 1;
85
86 v = eval ();
87 if (*args)
88 error_msg_and_die ("syntax error");
89
90 if (v->type == integer)
91 printf ("%d\n", v->u.i);
92 else
93 puts (v->u.s);
94
95 exit (null (v));
96}
97
98/* Return a VALUE for I. */
99
100static VALUE *int_value (int i)
101{
102 VALUE *v;
103
104 v = xmalloc (sizeof(VALUE));
105 v->type = integer;
106 v->u.i = i;
107 return v;
108}
109
110/* Return a VALUE for S. */
111
112static VALUE *str_value (char *s)
113{
114 VALUE *v;
115
116 v = xmalloc (sizeof(VALUE));
117 v->type = string;
118 v->u.s = strdup (s);
119 return v;
120}
121
122/* Free VALUE V, including structure components. */
123
124static void freev (VALUE *v)
125{
126 if (v->type == string)
127 free (v->u.s);
128 free (v);
129}
130
131/* Return nonzero if V is a null-string or zero-number. */
132
133static int null (VALUE *v)
134{
135 switch (v->type) {
136 case integer:
137 return v->u.i == 0;
138 case string:
139 return v->u.s[0] == '\0' || strcmp (v->u.s, "0") == 0;
140 default:
141 abort ();
142 }
143}
144
145/* Coerce V to a string value (can't fail). */
146
147static void tostring (VALUE *v)
148{
149 char *temp;
150
151 if (v->type == integer) {
152 temp = xmalloc (4 * (sizeof (int) / sizeof (char)));
153 sprintf (temp, "%d", v->u.i);
154 v->u.s = temp;
155 v->type = string;
156 }
157}
158
159/* Coerce V to an integer value. Return 1 on success, 0 on failure. */
160
161static int toarith (VALUE *v)
162{
163 int i;
164
165 switch (v->type) {
166 case integer:
167 return 1;
168 case string:
169 i = 0;
170 /* Don't interpret the empty string as an integer. */
171 if (v->u.s == 0)
172 return 0;
173 i = atoi(v->u.s);
174 free (v->u.s);
175 v->u.i = i;
176 v->type = integer;
177 return 1;
178 default:
179 abort ();
180 }
181}
182
183/* Return nonzero if the next token matches STR exactly.
184 STR must not be NULL. */
185
186static int
187nextarg (char *str)
188{
189 if (*args == NULL)
190 return 0;
191 return strcmp (*args, str) == 0;
192}
193
194/* The comparison operator handling functions. */
195
196#define cmpf(name, rel) \
197static int name (l, r) VALUE *l; VALUE *r; \
198{ \
199 if (l->type == string || r->type == string) { \
200 tostring (l); \
201 tostring (r); \
202 return strcmp (l->u.s, r->u.s) rel 0; \
203 } \
204 else \
205 return l->u.i rel r->u.i; \
206}
207 cmpf (less_than, <)
208 cmpf (less_equal, <=)
209 cmpf (equal, ==)
210 cmpf (not_equal, !=)
211 cmpf (greater_equal, >=)
212 cmpf (greater_than, >)
213
214#undef cmpf
215
216/* The arithmetic operator handling functions. */
217
218#define arithf(name, op) \
219static \
220int name (l, r) VALUE *l; VALUE *r; \
221{ \
222 if (!toarith (l) || !toarith (r)) \
223 error_msg_and_die ("non-numeric argument"); \
224 return l->u.i op r->u.i; \
225}
226
227#define arithdivf(name, op) \
228static int name (l, r) VALUE *l; VALUE *r; \
229{ \
230 if (!toarith (l) || !toarith (r)) \
231 error_msg_and_die ( "non-numeric argument"); \
232 if (r->u.i == 0) \
233 error_msg_and_die ( "division by zero"); \
234 return l->u.i op r->u.i; \
235}
236
237 arithf (plus, +)
238 arithf (minus, -)
239 arithf (multiply, *)
240 arithdivf (divide, /)
241 arithdivf (mod, %)
242
243#undef arithf
244#undef arithdivf
245
246/* Do the : operator.
247 SV is the VALUE for the lhs (the string),
248 PV is the VALUE for the rhs (the pattern). */
249
250static VALUE *docolon (VALUE *sv, VALUE *pv)
251{
252 VALUE *v;
253 const char *errmsg;
254 struct re_pattern_buffer re_buffer;
255 struct re_registers re_regs;
256 int len;
257
258 tostring (sv);
259 tostring (pv);
260
261 if (pv->u.s[0] == '^') {
262 fprintf (stderr, "\
263warning: unportable BRE: `%s': using `^' as the first character\n\
264of a basic regular expression is not portable; it is being ignored",
265 pv->u.s);
266 }
267
268 len = strlen (pv->u.s);
269 memset (&re_buffer, 0, sizeof (re_buffer));
270 memset (&re_regs, 0, sizeof (re_regs));
271 re_buffer.allocated = 2 * len;
272 re_buffer.buffer = (unsigned char *) xmalloc (re_buffer.allocated);
273 re_buffer.translate = 0;
274 re_syntax_options = RE_SYNTAX_POSIX_BASIC;
275 errmsg = re_compile_pattern (pv->u.s, len, &re_buffer);
276 if (errmsg) {
277 error_msg_and_die("%s", errmsg);
278 }
279
280 len = re_match (&re_buffer, sv->u.s, strlen (sv->u.s), 0, &re_regs);
281 if (len >= 0) {
282 /* Were \(...\) used? */
283 if (re_buffer.re_nsub > 0) { /* was (re_regs.start[1] >= 0) */
284 sv->u.s[re_regs.end[1]] = '\0';
285 v = str_value (sv->u.s + re_regs.start[1]);
286 }
287 else
288 v = int_value (len);
289 }
290 else {
291 /* Match failed -- return the right kind of null. */
292 if (re_buffer.re_nsub > 0)
293 v = str_value ("");
294 else
295 v = int_value (0);
296 }
297 free (re_buffer.buffer);
298 return v;
299}
300
301/* Handle bare operands and ( expr ) syntax. */
302
303static VALUE *eval7 (void)
304{
305 VALUE *v;
306
307 if (!*args)
308 error_msg_and_die ( "syntax error");
309
310 if (nextarg ("(")) {
311 args++;
312 v = eval ();
313 if (!nextarg (")"))
314 error_msg_and_die ( "syntax error");
315 args++;
316 return v;
317 }
318
319 if (nextarg (")"))
320 error_msg_and_die ( "syntax error");
321
322 return str_value (*args++);
323}
324
325/* Handle match, substr, index, length, and quote keywords. */
326
327static VALUE *eval6 (void)
328{
329 VALUE *l, *r, *v, *i1, *i2;
330
331 if (nextarg ("quote")) {
332 args++;
333 if (!*args)
334 error_msg_and_die ( "syntax error");
335 return str_value (*args++);
336 }
337 else if (nextarg ("length")) {
338 args++;
339 r = eval6 ();
340 tostring (r);
341 v = int_value (strlen (r->u.s));
342 freev (r);
343 return v;
344 }
345 else if (nextarg ("match")) {
346 args++;
347 l = eval6 ();
348 r = eval6 ();
349 v = docolon (l, r);
350 freev (l);
351 freev (r);
352 return v;
353 }
354 else if (nextarg ("index")) {
355 args++;
356 l = eval6 ();
357 r = eval6 ();
358 tostring (l);
359 tostring (r);
360 v = int_value (strcspn (l->u.s, r->u.s) + 1);
361 if (v->u.i == (int) strlen (l->u.s) + 1)
362 v->u.i = 0;
363 freev (l);
364 freev (r);
365 return v;
366 }
367 else if (nextarg ("substr")) {
368 args++;
369 l = eval6 ();
370 i1 = eval6 ();
371 i2 = eval6 ();
372 tostring (l);
373 if (!toarith (i1) || !toarith (i2)
374 || i1->u.i > (int) strlen (l->u.s)
375 || i1->u.i <= 0 || i2->u.i <= 0)
376 v = str_value ("");
377 else {
378 v = xmalloc (sizeof(VALUE));
379 v->type = string;
380 v->u.s = strncpy ((char *) xmalloc (i2->u.i + 1),
381 l->u.s + i1->u.i - 1, i2->u.i);
382 v->u.s[i2->u.i] = 0;
383 }
384 freev (l);
385 freev (i1);
386 freev (i2);
387 return v;
388 }
389 else
390 return eval7 ();
391}
392
393/* Handle : operator (pattern matching).
394 Calls docolon to do the real work. */
395
396static VALUE *eval5 (void)
397{
398 VALUE *l, *r, *v;
399
400 l = eval6 ();
401 while (nextarg (":")) {
402 args++;
403 r = eval6 ();
404 v = docolon (l, r);
405 freev (l);
406 freev (r);
407 l = v;
408 }
409 return l;
410}
411
412/* Handle *, /, % operators. */
413
414static VALUE *eval4 (void)
415{
416 VALUE *l, *r;
417 int (*fxn) (), val;
418
419 l = eval5 ();
420 while (1) {
421 if (nextarg ("*"))
422 fxn = multiply;
423 else if (nextarg ("/"))
424 fxn = divide;
425 else if (nextarg ("%"))
426 fxn = mod;
427 else
428 return l;
429 args++;
430 r = eval5 ();
431 val = (*fxn) (l, r);
432 freev (l);
433 freev (r);
434 l = int_value (val);
435 }
436}
437
438/* Handle +, - operators. */
439
440static VALUE *eval3 (void)
441{
442 VALUE *l, *r;
443 int (*fxn) (), val;
444
445 l = eval4 ();
446 while (1) {
447 if (nextarg ("+"))
448 fxn = plus;
449 else if (nextarg ("-"))
450 fxn = minus;
451 else
452 return l;
453 args++;
454 r = eval4 ();
455 val = (*fxn) (l, r);
456 freev (l);
457 freev (r);
458 l = int_value (val);
459 }
460}
461
462/* Handle comparisons. */
463
464static VALUE *eval2 (void)
465{
466 VALUE *l, *r;
467 int (*fxn) (), val;
468
469 l = eval3 ();
470 while (1) {
471 if (nextarg ("<"))
472 fxn = less_than;
473 else if (nextarg ("<="))
474 fxn = less_equal;
475 else if (nextarg ("=") || nextarg ("=="))
476 fxn = equal;
477 else if (nextarg ("!="))
478 fxn = not_equal;
479 else if (nextarg (">="))
480 fxn = greater_equal;
481 else if (nextarg (">"))
482 fxn = greater_than;
483 else
484 return l;
485 args++;
486 r = eval3 ();
487 toarith (l);
488 toarith (r);
489 val = (*fxn) (l, r);
490 freev (l);
491 freev (r);
492 l = int_value (val);
493 }
494}
495
496/* Handle &. */
497
498static VALUE *eval1 (void)
499{
500 VALUE *l, *r;
501
502 l = eval2 ();
503 while (nextarg ("&")) {
504 args++;
505 r = eval2 ();
506 if (null (l) || null (r)) {
507 freev (l);
508 freev (r);
509 l = int_value (0);
510 }
511 else
512 freev (r);
513 }
514 return l;
515}
516
517/* Handle |. */
518
519static VALUE *eval (void)
520{
521 VALUE *l, *r;
522
523 l = eval1 ();
524 while (nextarg ("|")) {
525 args++;
526 r = eval1 ();
527 if (null (l)) {
528 freev (l);
529 l = r;
530 }
531 else
532 freev (r);
533 }
534 return l;
535}
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