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annotate src/expr.c @ 23:ec0bf61a5502
Added ^ (bitwise complement)
| author | lost |
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| date | Fri, 02 Jan 2009 01:32:07 +0000 |
| parents | 218aabbc3b1a |
| children | 538e15927776 |
| rev | line source |
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1 /* |
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2 expr.c |
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3 Copyright © 2008 William Astle |
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4 |
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5 This file is part of LWASM. |
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6 |
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7 LWASM is free software: you can redistribute it and/or modify it under the |
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8 terms of the GNU General Public License as published by the Free Software |
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9 Foundation, either version 3 of the License, or (at your option) any later |
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10 version. |
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11 |
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12 This program is distributed in the hope that it will be useful, but WITHOUT |
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
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15 more details. |
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16 |
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17 You should have received a copy of the GNU General Public License along with |
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18 this program. If not, see <http://www.gnu.org/licenses/>. |
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19 */ |
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20 |
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21 /* |
| 18 | 22 This file contains the actual expression evaluator |
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23 */ |
| 14 | 24 |
| 25 #define __expr_c_seen__ | |
| 15 | 26 |
| 18 | 27 #include <ctype.h> |
| 17 | 28 #include <stdio.h> |
| 15 | 29 #include <stdlib.h> |
| 18 | 30 #include <string.h> |
| 15 | 31 |
| 14 | 32 #include "expr.h" |
| 17 | 33 #include "util.h" |
| 34 | |
| 35 lwasm_expr_stack_t *lwasm_expr_stack_create(void) | |
| 36 { | |
| 37 lwasm_expr_stack_t *s; | |
| 38 | |
| 39 s = lwasm_alloc(sizeof(lwasm_expr_stack_t)); | |
| 40 s -> head = NULL; | |
| 41 s -> tail = NULL; | |
| 42 return s; | |
| 43 } | |
| 15 | 44 |
| 17 | 45 void lwasm_expr_stack_free(lwasm_expr_stack_t *s) |
| 46 { | |
| 47 while (s -> head) | |
| 48 { | |
| 49 s -> tail = s -> head; | |
| 50 s -> head = s -> head -> next; | |
| 51 lwasm_expr_term_free(s -> tail -> term); | |
| 52 lwasm_free(s -> tail); | |
| 53 } | |
| 54 lwasm_free(s); | |
| 55 } | |
| 14 | 56 |
| 17 | 57 void lwasm_expr_term_free(lwasm_expr_term_t *t) |
| 58 { | |
| 59 if (t) | |
| 60 { | |
| 61 if (t -> symbol) | |
| 62 lwasm_free(t -> symbol); | |
| 63 lwasm_free(t); | |
| 64 } | |
| 65 } | |
| 66 | |
| 67 lwasm_expr_term_t *lwasm_expr_term_create_oper(int oper) | |
| 68 { | |
| 69 lwasm_expr_term_t *t; | |
| 70 | |
| 71 t = lwasm_alloc(sizeof(lwasm_expr_term_t)); | |
| 72 t -> term_type = LWASM_TERM_OPER; | |
| 73 t -> value = oper; | |
| 74 return t; | |
| 75 } | |
| 15 | 76 |
| 17 | 77 lwasm_expr_term_t *lwasm_expr_term_create_int(int val) |
| 14 | 78 { |
| 17 | 79 lwasm_expr_term_t *t; |
| 80 | |
| 81 t = lwasm_alloc(sizeof(lwasm_expr_term_t)); | |
| 82 t -> term_type = LWASM_TERM_INT; | |
| 83 t -> value = val; | |
| 84 return t; | |
| 85 } | |
| 86 | |
| 87 lwasm_expr_term_t *lwasm_expr_term_create_sym(char *sym) | |
| 88 { | |
| 89 lwasm_expr_term_t *t; | |
| 14 | 90 |
| 17 | 91 t = lwasm_alloc(sizeof(lwasm_expr_term_t)); |
| 92 t -> term_type = LWASM_TERM_SYM; | |
| 93 t -> symbol = lwasm_strdup(sym); | |
| 94 return t; | |
| 95 } | |
| 15 | 96 |
| 17 | 97 lwasm_expr_term_t *lwasm_expr_term_dup(lwasm_expr_term_t *t) |
| 98 { | |
| 99 switch (t -> term_type) | |
| 15 | 100 { |
| 17 | 101 case LWASM_TERM_INT: |
| 102 return lwasm_expr_term_create_int(t -> value); | |
| 103 | |
| 104 case LWASM_TERM_OPER: | |
| 105 return lwasm_expr_term_create_oper(t -> value); | |
| 106 | |
| 107 case LWASM_TERM_SYM: | |
| 108 return lwasm_expr_term_create_sym(t -> symbol); | |
| 109 | |
| 110 default: | |
| 111 fprintf(stderr, "lwasm_expr_term_dup(): invalid term type %d\n", t -> term_type); | |
| 112 exit(1); | |
| 113 } | |
| 114 // can't get here | |
| 115 } | |
| 116 | |
| 117 void lwasm_expr_stack_push(lwasm_expr_stack_t *s, lwasm_expr_term_t *t) | |
| 118 { | |
| 119 lwasm_expr_stack_node_t *n; | |
| 120 | |
| 121 if (!s) | |
| 122 { | |
| 123 fprintf(stderr, "lwasm_expr_stack_push(): invalid stack pointer\n"); | |
| 124 exit(1); | |
| 15 | 125 } |
| 126 | |
| 17 | 127 n = lwasm_alloc(sizeof(lwasm_expr_stack_node_t)); |
| 128 n -> next = NULL; | |
| 129 n -> prev = s -> tail; | |
| 130 n -> term = lwasm_expr_term_dup(t); | |
| 131 | |
| 132 if (s -> head) | |
| 133 { | |
| 134 s -> tail -> next = n; | |
| 135 s -> tail = n; | |
| 136 } | |
| 137 else | |
| 15 | 138 { |
| 17 | 139 s -> head = n; |
| 140 s -> tail = n; | |
| 141 } | |
| 142 } | |
| 143 | |
| 144 lwasm_expr_term_t *lwasm_expr_stack_pop(lwasm_expr_stack_t *s) | |
| 145 { | |
| 146 lwasm_expr_term_t *t; | |
| 147 lwasm_expr_stack_node_t *n; | |
| 148 | |
| 149 if (!(s -> tail)) | |
| 150 return NULL; | |
| 151 | |
| 152 n = s -> tail; | |
| 153 s -> tail = n -> prev; | |
| 154 if (!(n -> prev)) | |
| 155 { | |
| 156 s -> head = NULL; | |
| 15 | 157 } |
| 14 | 158 |
| 17 | 159 t = n -> term; |
| 160 n -> term = NULL; | |
| 161 | |
| 162 lwasm_free(n); | |
| 163 | |
| 164 return t; | |
| 14 | 165 } |
| 18 | 166 |
| 167 // the following two functions are co-routines which actually parse | |
| 168 // an infix expression onto the expression stack, each returns -1 | |
| 169 // if an error is encountered | |
| 170 | |
| 171 /* | |
| 172 parse a term and push it onto the stack | |
| 173 | |
| 174 this function handles unary prefix operators (-, +, .not., .com.) | |
| 175 as well as () | |
| 176 */ | |
| 177 int lwasm_expr_parse_term(lwasm_expr_stack_t *s, const char **p) | |
| 178 { | |
| 179 lwasm_expr_term_t *t; | |
| 180 | |
| 181 eval_next: | |
| 182 if (**p == '(') | |
| 183 { | |
| 184 (*p)++; | |
| 185 lwasm_expr_parse_expr(s, p, 0); | |
| 186 if (**p != ')') | |
| 187 return -1; | |
| 188 (*p)++; | |
| 189 return 0; | |
| 190 } | |
| 191 | |
| 192 if (**p == '+') | |
| 193 { | |
| 194 (*p)++; | |
| 195 goto eval_next; | |
| 196 } | |
| 197 | |
| 198 if (**p == '-') | |
| 199 { | |
| 200 // parse expression following "-" | |
| 201 (*p)++; | |
| 202 if (lwasm_expr_parse_expr(s, p, 200) < 0) | |
| 203 return -1; | |
| 204 t = lwasm_expr_term_create_oper(LWASM_OPER_NEG); | |
| 205 lwasm_expr_stack_push(s, t); | |
| 206 lwasm_expr_term_free(t); | |
| 207 return 0; | |
| 208 } | |
| 209 | |
| 23 | 210 if (**p == '^') |
| 211 { | |
| 212 // parse expression following "^" | |
| 213 (*p)++; | |
| 214 if (lwasm_expr_parse_expr(s, p, 200) < 0) | |
| 215 return -1; | |
| 216 t = lwasm_expr_term_create_oper(LWASM_OPER_COM); | |
| 217 lwasm_expr_stack_push(s, t); | |
| 218 lwasm_expr_term_free(t); | |
| 219 return 0; | |
| 220 } | |
| 221 | |
| 18 | 222 /* |
| 223 we have an actual term here so evaluate it | |
| 224 | |
| 225 it could be one of the following: | |
| 226 | |
| 227 1. a decimal constant | |
| 228 2. a hexadecimal constant | |
| 229 3. an octal constant | |
| 230 4. a binary constant | |
| 231 5. a symbol reference | |
| 232 6. the "current" instruction address (*) | |
| 233 7. the "current" data address (.) | |
| 234 8. a "back reference" (<) | |
| 235 9. a "forward reference" (>) | |
| 236 | |
| 237 items 6 through 9 are stored as symbol references | |
| 238 | |
| 239 (a . followed by a . or a alpha char or number is a symbol) | |
| 240 */ | |
| 241 if (**p == '*' | |
| 242 || ( | |
| 243 **p == '.' | |
| 244 && (*p)[1] != '.' | |
| 245 && !((*p)[1] >= 'A' && (*p)[1] <= 'Z') | |
| 246 && !((*p)[1] >= 'a' && (*p)[1] <= 'z') | |
| 247 && !((*p)[1] >= '0' && (*p)[1] <= '9') | |
| 248 ) | |
| 249 || **p == '<' | |
| 250 || **p == '>') | |
| 251 { | |
| 252 char tstr[2]; | |
| 253 tstr[0] = **p; | |
| 254 tstr[1] = '\0'; | |
| 255 t = lwasm_expr_term_create_sym(tstr); | |
| 256 lwasm_expr_stack_push(s, t); | |
| 257 lwasm_expr_term_free(t); | |
| 258 (*p)++; | |
| 259 return 0; | |
| 260 } | |
| 261 | |
| 262 /* | |
| 263 - a symbol will be a string of characters introduced by a letter, ".", | |
| 264 "_" but NOT a number | |
| 265 - a decimal constant will consist of only digits, optionally prefixed | |
| 266 with "&" | |
| 267 - a binary constant will consist of only 0s and 1s either prefixed with % | |
| 268 or suffixed with "B" | |
| 269 - a hex constant will consist of 0-9A-F either prefixed with $ or | |
| 270 suffixed with "H"; a hex number starting with A-F must be prefixed | |
| 271 with $ or start with 0 and end with H | |
| 272 - an octal constant will consist of 0-7 either prefixed with @ or | |
| 273 suffixed with "O" or "Q" | |
| 274 - an ascii constant will be a single character prefixed with a ' | |
| 275 - a double ascii constant will be two characters prefixed with a " | |
| 276 | |
| 277 */ | |
| 278 if (**p == '"') | |
| 279 { | |
| 280 // double ascii constant | |
| 281 int val; | |
| 282 (*p)++; | |
| 283 if (!**p) | |
| 284 return -1; | |
| 285 if (!*((*p)+1)) | |
| 286 return -1; | |
| 287 val = **p << 8 | *((*p) + 1); | |
| 288 (*p) += 2; | |
| 289 t = lwasm_expr_term_create_int(val); | |
| 290 lwasm_expr_stack_push(s, t); | |
| 291 lwasm_expr_term_free(t); | |
| 292 return 0; | |
| 293 } | |
| 294 else if (**p == '\'') | |
| 295 { | |
| 296 // single ascii constant | |
| 297 int val; | |
| 298 (*p)++; | |
| 299 if (!**p) | |
| 300 return -1; | |
| 301 val = **p; | |
| 302 (*p)++; | |
| 303 t = lwasm_expr_term_create_int(val); | |
| 304 lwasm_expr_stack_push(s, t); | |
| 305 lwasm_expr_term_free(t); | |
| 306 } | |
| 307 else if (**p == '&') | |
| 308 { | |
| 309 // decimal constant | |
| 310 int val = 0; | |
| 311 | |
| 312 (*p)++; | |
| 313 while (strchr("0123456789", **p)) | |
| 314 { | |
| 315 val = val * 10 + (**p - '0'); | |
| 316 (*p)++; | |
| 317 } | |
| 318 t = lwasm_expr_term_create_int(val); | |
| 319 lwasm_expr_stack_push(s, t); | |
| 320 lwasm_expr_term_free(t); | |
| 321 return 0; | |
| 322 } | |
| 323 else if (**p == '%') | |
| 324 { | |
| 325 // binary constant | |
| 326 int val = 0; | |
| 327 | |
| 328 (*p)++; | |
| 329 while (**p == '0' || **p == '1') | |
| 330 { | |
| 331 val = val * 2 + (**p - '0'); | |
| 332 (*p)++; | |
| 333 } | |
| 334 t = lwasm_expr_term_create_int(val); | |
| 335 lwasm_expr_stack_push(s, t); | |
| 336 lwasm_expr_term_free(t); | |
| 337 return 0; | |
| 338 } | |
| 339 else if (**p == '$') | |
| 340 { | |
| 341 // hexadecimal constant | |
| 342 int val = 0, val2; | |
| 343 | |
| 344 (*p)++; | |
| 345 while (strchr("0123456789ABCDEFabcdef", **p)) | |
| 346 { | |
| 347 val2 = toupper(**p) - '0'; | |
| 348 if (val2 > 9) | |
| 349 val2 -= 7; | |
| 350 val = val * 16 + val2; | |
| 351 (*p)++; | |
| 352 } | |
| 353 t = lwasm_expr_term_create_int(val); | |
| 354 lwasm_expr_stack_push(s, t); | |
| 355 lwasm_expr_term_free(t); | |
| 356 return 0; | |
| 357 } | |
| 358 else if (**p == '@') | |
| 359 { | |
| 360 // octal constant | |
| 361 int val = 0; | |
| 362 | |
| 363 (*p)++; | |
| 364 while (strchr("01234567", **p)) | |
| 365 { | |
| 366 val = val * 8 + (**p - '0'); | |
| 367 (*p)++; | |
| 368 } | |
| 369 t = lwasm_expr_term_create_int(val); | |
| 370 lwasm_expr_stack_push(s, t); | |
| 371 lwasm_expr_term_free(t); | |
| 372 return 0; | |
| 373 } | |
| 374 | |
| 375 // symbol or bare decimal or suffix identified constant here | |
| 376 // all numbers will start with a digit at this point | |
| 377 if (**p < '0' || **p > '9') | |
| 378 { | |
| 379 int l = 0; | |
| 380 char *sb; | |
| 381 | |
| 382 // evaluate a symbol here | |
| 383 static const char *symchars = "_.$@\\abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; | |
| 384 while (strchr(symchars, (*p)[l])) | |
| 385 l++; | |
| 386 | |
| 387 if (l == 0) | |
| 388 return -1; | |
| 389 | |
| 390 sb = lwasm_alloc(l + 1); | |
| 391 sb[l] = '\0'; | |
| 392 memcpy(sb, *p, l); | |
| 393 t = lwasm_expr_term_create_sym(sb); | |
| 394 lwasm_expr_stack_push(s, t); | |
| 395 lwasm_expr_term_free(t); | |
| 396 lwasm_free(sb); | |
| 397 (*p) += l; | |
| 398 return 0; | |
| 399 } | |
| 400 | |
| 401 if (!**p) | |
| 402 return -1; | |
| 403 | |
| 404 // evaluate a suffix based constant | |
| 405 { | |
| 406 int decval = 0, binval = 0, hexval = 0, octval = 0; | |
| 407 int valtype = 15; // 1 = bin, 2 = oct, 4 = dec, 8 = hex | |
| 408 int bindone = 0; | |
| 409 int val; | |
| 410 int dval; | |
| 411 | |
| 412 while (1) | |
| 413 { | |
| 414 if (!**p || !strchr("0123456789ABCDEFabcdefqhoQHO", **p)) | |
| 415 { | |
| 416 // we can legally have bin or decimal here | |
| 417 if (bindone) | |
| 418 { | |
| 419 // we just finished a binary value | |
| 420 val = binval; | |
| 421 break; | |
| 422 } | |
| 423 else if (valtype & 4) | |
| 424 { | |
| 425 // otherwise we must be decimal (if we're still allowed one) | |
| 426 val = decval; | |
| 427 break; | |
| 428 } | |
| 429 else | |
| 430 { | |
| 431 // bad value | |
| 432 return -1; | |
| 433 } | |
| 434 } | |
| 435 | |
| 436 dval = toupper(**p); | |
| 437 (*p)++; | |
| 438 | |
| 439 if (bindone) | |
| 440 { | |
| 441 // any characters past "B" means it is not binary | |
| 442 bindone = 0; | |
| 443 valtype &= 14; | |
| 444 } | |
| 445 | |
| 446 switch (dval) | |
| 447 { | |
| 448 case 'Q': | |
| 449 case 'O': | |
| 450 if (valtype & 2) | |
| 451 { | |
| 452 val = octval; | |
| 453 valtype = -1; | |
| 454 break; | |
| 455 } | |
| 456 else | |
| 457 { | |
| 458 // not a valid octal value | |
| 459 return -1; | |
| 460 } | |
| 461 /* can't get here */ | |
| 462 | |
| 463 case 'H': | |
| 464 if (valtype & 8) | |
| 465 { | |
| 466 val = hexval; | |
| 467 valtype = -1; | |
| 468 break; | |
| 469 } | |
| 470 else | |
| 471 { | |
| 472 // not a valid hex number | |
| 473 return -1; | |
| 474 } | |
| 475 /* can't get here */ | |
| 476 | |
| 477 case 'B': | |
| 478 // this is a bit of a sticky one since B is a legit hex | |
| 479 // digit so this may or may not be the end of the number | |
| 480 // so we fall through to the digit case | |
| 481 | |
| 482 if (valtype & 1) | |
| 483 { | |
| 484 // could still be binary | |
| 485 bindone = 1; | |
| 486 valtype = 9; // hex and binary | |
| 487 } | |
| 488 /* fall through intentional */ | |
| 489 | |
| 490 default: | |
| 491 // digit | |
| 492 dval -= '0'; | |
| 493 if (dval > 9) | |
| 494 dval -= 7; | |
| 495 | |
| 496 if (valtype & 8) | |
| 497 { | |
| 498 hexval = hexval * 16 + dval; | |
| 499 } | |
| 500 if (valtype & 4) | |
| 501 { | |
| 502 if (dval > 9) | |
| 503 valtype &= 11; | |
| 504 else | |
| 505 decval = decval * 10 + dval; | |
| 506 } | |
| 507 if (valtype & 2) | |
| 508 { | |
| 509 if (dval > 7) | |
| 510 valtype &= 13; | |
| 511 else | |
| 512 octval = octval * 8 + dval; | |
| 513 } | |
| 514 if (valtype & 1) | |
| 515 { | |
| 516 if (dval > 1) | |
| 517 valtype &= 14; | |
| 518 else | |
| 519 binval = binval * 2 + dval; | |
| 520 } | |
| 521 } | |
| 522 // break out if we have a return value | |
| 523 if (valtype = -1) | |
| 524 break; | |
| 525 // return if no more valid possibilities! | |
| 526 if (valtype == 0) | |
| 527 return -1; | |
| 528 } | |
| 529 | |
| 530 // we get here when we have a value to return | |
| 531 t = lwasm_expr_term_create_int(val); | |
| 532 lwasm_expr_stack_push(s, t); | |
| 533 lwasm_expr_term_free(t); | |
| 534 return 0; | |
| 535 } | |
| 536 /* can't get here */ | |
| 537 } | |
| 538 | |
| 539 // parse an expression and push the result onto the stack | |
| 540 // if an operator of lower precedence than the value of "prec" is found, | |
| 541 int lwasm_expr_parse_expr(lwasm_expr_stack_t *s, const char **p, int prec) | |
| 542 { | |
| 543 static const struct operinfo | |
| 544 { | |
| 545 int opernum; | |
| 546 char *operstr; | |
| 547 int operprec; | |
| 548 } operators[] = | |
| 549 { | |
| 550 { LWASM_OPER_PLUS, "+", 100 }, | |
| 551 { LWASM_OPER_MINUS, "-", 100 }, | |
| 552 { LWASM_OPER_TIMES, "*", 150 }, | |
| 553 { LWASM_OPER_DIVIDE, "/", 150 }, | |
| 554 { LWASM_OPER_MOD, "%", 150 }, | |
| 555 { LWASM_OPER_INTDIV, "\\", 150 }, | |
| 556 | |
| 557 { LWASM_OPER_NONE, "", 0 } | |
| 558 }; | |
| 559 int opern, i; | |
| 560 lwasm_expr_term_t *operterm; | |
| 561 | |
| 562 // return if we are at the end of the expression or a subexpression | |
| 563 if (!**p || isspace(**p) || **p == ')') | |
| 564 return 0; | |
| 565 | |
| 566 eval_next: | |
| 567 if (lwasm_expr_parse_term(s, p) < 0) | |
| 568 return -1; | |
| 569 | |
| 570 // expecting an operator here | |
| 571 for (opern = 0; operators[opern].opernum != LWASM_OPER_NONE; opern++) | |
| 572 { | |
| 573 for (i = 0; (*p)[i] && operators[opern].operstr[i] && (*p[i] == operators[opern].operstr[i]); i++) | |
| 574 /* do nothing */ ; | |
| 575 if (operators[opern].operstr[i] == '\0') | |
| 576 break; | |
| 577 } | |
| 578 if (operators[opern].opernum == LWASM_OPER_NONE) | |
| 579 { | |
| 580 // unrecognized operator | |
| 581 return -1; | |
| 582 } | |
| 583 | |
| 584 // the operator number in question is in opern; i is the length of the | |
| 585 // operator string | |
| 586 | |
| 587 // logic: | |
| 588 // if the precedence of this operation is <= to the "prec" flag, | |
| 589 // we simply return without advancing the input pointer; the operator | |
| 590 // will be evaluated again in the enclosing function call | |
| 591 if (operators[opern].operprec <= prec) | |
| 592 return 0; | |
| 593 | |
| 594 // logic: | |
| 595 // we have a higher precedence operator here so we will advance the | |
| 596 // input pointer to the next term and let the expression evaluator | |
| 597 // loose on it after which time we will push our operator onto the | |
| 598 // stack and then go on with the expression evaluation | |
| 599 (*p) += i; // advance input pointer | |
| 600 | |
| 601 // evaluate next expression(s) of higher precedence | |
| 602 if (lwasm_expr_parse_expr(s, p, operators[opern].operprec) < 0) | |
| 603 return -1; | |
| 604 | |
| 605 operterm = lwasm_expr_term_create_oper(operators[opern].opernum); | |
| 606 lwasm_expr_stack_push(s, operterm); | |
| 607 lwasm_expr_term_free(operterm); | |
| 608 | |
| 609 // return if we are at the end of the expression or a subexpression | |
| 610 if (!**p || isspace(**p) || **p == ')') | |
| 611 return 0; | |
| 612 | |
| 613 // continue evaluating | |
| 614 goto eval_next; | |
| 615 } | |
| 616 | |
| 617 /* | |
| 618 actually evaluate an expression | |
| 619 | |
| 620 This happens in two stages. The first stage merely parses the expression into | |
| 621 a lwasm_expr_stack_t * which is then evaluated as much as possible before the | |
| 622 result is returned. | |
| 623 | |
| 624 Returns NULL on a parse error or otherwise invalid expression. *outp will | |
| 625 contain the pointer to the next character after the expression if and only | |
| 626 if there is no error. In the case of an error, *outp is undefined. | |
| 627 */ | |
| 628 lwasm_expr_stack_t *lwasm_expr_eval(const char *inp, const char **outp) | |
| 629 { | |
| 630 lwasm_expr_stack_t *s; | |
| 631 const char *p; | |
| 632 | |
| 633 // actually parse the expression | |
| 634 p = inp; | |
| 635 s = lwasm_expr_stack_create(); | |
| 636 if (lwasm_expr_parse_expr(s, &p, 0) < 0) | |
| 637 goto cleanup_error; | |
| 638 | |
| 639 // save end of expression | |
| 640 if (outp) | |
| 641 (*outp) = p; | |
| 642 | |
| 643 // return potentially partial expression | |
| 644 if (lwasm_expr_reval(s) < 0) | |
| 645 goto cleanup_error; | |
| 646 | |
| 647 return s; | |
| 648 | |
| 649 cleanup_error: | |
| 650 lwasm_expr_stack_free(s); | |
| 651 return NULL; | |
| 652 } | |
| 653 | |
| 654 /* | |
| 655 take an expression stack s and scan for operations that can be completed | |
| 656 | |
| 657 return -1 on error, 0 on no error | |
| 658 | |
| 659 possible errors are: division by zero or unknown operator | |
| 660 | |
| 661 theory of operation: | |
| 662 | |
| 663 scan the stack for an operator which has two constants preceding it (binary) | |
| 664 or 1 constant preceding it (unary) and if found, perform the calculation | |
| 665 and replace the operator and its operands with the result | |
| 666 | |
| 667 repeat the scan until no futher simplications are found or if there are no | |
| 668 further operators or only a single term remains | |
| 669 | |
| 670 */ | |
| 671 int lwasm_expr_reval(lwasm_expr_stack_t *s) | |
| 672 { | |
| 673 lwasm_expr_stack_node_t *n; | |
| 674 | |
| 675 next_iter: | |
| 676 // a single term | |
| 677 if (s -> head == s -> tail) | |
| 678 return 0; | |
| 679 | |
| 680 // search for an operator | |
| 681 for (n = s -> head; n; n = n -> next) | |
| 682 { | |
| 683 if (n -> term -> term_type == LWASM_TERM_OPER) | |
| 684 { | |
| 685 if (n -> term -> value == LWASM_OPER_NEG | |
| 686 || n -> term -> value == LWASM_OPER_COM | |
| 687 ) | |
| 688 { | |
| 689 // unary operator | |
| 690 if (n -> prev && n -> prev -> term -> term_type == LWASM_TERM_INT) | |
| 691 { | |
| 692 // a unary operator we can resolve | |
| 693 // we do the op then remove the term "n" is pointing at | |
| 694 if (n -> term -> value == LWASM_OPER_NEG) | |
| 695 { | |
| 696 n -> prev -> term -> value = -(n -> prev -> term -> value); | |
| 697 } | |
| 698 else if (n -> term -> value == LWASM_OPER_COM) | |
| 699 { | |
| 700 n -> prev -> term -> value = ~(n -> prev -> term -> value); | |
| 701 } | |
| 702 n -> prev -> next = n -> next; | |
| 703 if (n -> next) | |
| 704 n -> next -> prev = n -> prev; | |
| 705 else | |
| 706 s -> tail = n -> prev; | |
| 707 | |
| 708 lwasm_expr_term_free(n -> term); | |
| 709 lwasm_free(n); | |
| 710 break; | |
| 711 } | |
| 712 } | |
| 713 else | |
| 714 { | |
| 715 // binary operator | |
| 716 if (n -> prev && n -> prev -> prev && n -> prev -> term -> term_type == LWASM_TERM_INT && n -> prev -> prev -> term -> term_type == LWASM_TERM_INT) | |
| 717 { | |
| 718 // a binary operator we can resolve | |
| 719 switch (n -> term -> value) | |
| 720 { | |
| 721 case LWASM_OPER_PLUS: | |
| 722 n -> prev -> prev -> term -> value += n -> prev -> term -> value; | |
| 723 break; | |
| 724 | |
| 725 case LWASM_OPER_MINUS: | |
| 726 n -> prev -> prev -> term -> value -= n -> prev -> term -> value; | |
| 727 break; | |
| 728 | |
| 729 case LWASM_OPER_TIMES: | |
| 730 n -> prev -> prev -> term -> value *= n -> prev -> term -> value; | |
| 731 break; | |
| 732 | |
| 733 case LWASM_OPER_DIVIDE: | |
| 734 if (n -> prev -> term -> value == 0) | |
| 735 return -1; | |
| 736 n -> prev -> prev -> term -> value /= n -> prev -> term -> value; | |
| 737 break; | |
| 738 | |
| 739 case LWASM_OPER_MOD: | |
| 740 if (n -> prev -> term -> value == 0) | |
| 741 return -1; | |
| 742 n -> prev -> prev -> term -> value %= n -> prev -> term -> value; | |
| 743 break; | |
| 744 | |
| 745 case LWASM_OPER_INTDIV: | |
| 746 if (n -> prev -> term -> value == 0) | |
| 747 return -1; | |
| 748 n -> prev -> prev -> term -> value /= n -> prev -> term -> value; | |
| 749 break; | |
| 750 | |
| 751 case LWASM_OPER_BWAND: | |
| 752 n -> prev -> prev -> term -> value &= n -> prev -> term -> value; | |
| 753 break; | |
| 754 | |
| 755 case LWASM_OPER_BWOR: | |
| 756 n -> prev -> prev -> term -> value |= n -> prev -> term -> value; | |
| 757 break; | |
| 758 | |
| 759 case LWASM_OPER_BWXOR: | |
| 760 n -> prev -> prev -> term -> value ^= n -> prev -> term -> value; | |
| 761 break; | |
| 762 | |
| 763 case LWASM_OPER_AND: | |
| 764 n -> prev -> prev -> term -> value = (n -> prev -> term -> value && n -> prev -> prev -> term -> value) ? 1 : 0; | |
| 765 break; | |
| 766 | |
| 767 case LWASM_OPER_OR: | |
| 768 n -> prev -> prev -> term -> value = (n -> prev -> term -> value || n -> prev -> prev -> term -> value) ? 1 : 0; | |
| 769 break; | |
| 770 | |
| 771 default: | |
| 772 // return error if unknown operator! | |
| 773 return -1; | |
| 774 } | |
| 775 | |
| 776 // now remove the two unneeded entries from the stack | |
| 777 n -> prev -> prev -> next = n -> next; | |
| 778 if (n -> next) | |
| 779 n -> next -> prev = n -> prev -> prev; | |
| 780 else | |
| 781 s -> tail = n -> prev -> prev; | |
| 782 | |
| 783 lwasm_expr_term_free(n -> term); | |
| 784 lwasm_expr_term_free(n -> prev -> term); | |
| 785 lwasm_free(n -> prev); | |
| 786 lwasm_free(n); | |
| 787 break; | |
| 788 } | |
| 789 } | |
| 790 } | |
| 791 } | |
| 792 // note for the terminally confused about dynamic memory and pointers: | |
| 793 // n will not be NULL even after the lwasm_free calls above so | |
| 794 // this test will still work (n will be a dangling pointer) | |
| 795 // (n will only be NULL if we didn't find any operators to simplify) | |
| 796 if (n) | |
| 797 goto next_iter; | |
| 798 | |
| 799 return 0; | |
| 800 } |