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annotate src/expr.c @ 37:538e15927776
Added symbol handling to expression subsystem; adpated instruction handlers to the new scheme; misc fixes
| author | lost |
|---|---|
| date | Sat, 03 Jan 2009 04:20:49 +0000 |
| parents | ec0bf61a5502 |
| children | efa19ec69df9 |
| 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; | |
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70 |
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71 fprintf(stderr, "Creating operator term: %d\n", oper); |
| 17 | 72 |
| 73 t = lwasm_alloc(sizeof(lwasm_expr_term_t)); | |
| 74 t -> term_type = LWASM_TERM_OPER; | |
| 75 t -> value = oper; | |
| 76 return t; | |
| 77 } | |
| 15 | 78 |
| 17 | 79 lwasm_expr_term_t *lwasm_expr_term_create_int(int val) |
| 14 | 80 { |
| 17 | 81 lwasm_expr_term_t *t; |
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82 fprintf(stderr, "Creating integer term: %d\n", val); |
| 17 | 83 |
| 84 t = lwasm_alloc(sizeof(lwasm_expr_term_t)); | |
| 85 t -> term_type = LWASM_TERM_INT; | |
| 86 t -> value = val; | |
| 87 return t; | |
| 88 } | |
| 89 | |
| 90 lwasm_expr_term_t *lwasm_expr_term_create_sym(char *sym) | |
| 91 { | |
| 92 lwasm_expr_term_t *t; | |
| 14 | 93 |
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94 fprintf(stderr, "Creating symbol term: %s\n", sym); |
| 17 | 95 t = lwasm_alloc(sizeof(lwasm_expr_term_t)); |
| 96 t -> term_type = LWASM_TERM_SYM; | |
| 97 t -> symbol = lwasm_strdup(sym); | |
| 98 return t; | |
| 99 } | |
| 15 | 100 |
| 17 | 101 lwasm_expr_term_t *lwasm_expr_term_dup(lwasm_expr_term_t *t) |
| 102 { | |
| 103 switch (t -> term_type) | |
| 15 | 104 { |
| 17 | 105 case LWASM_TERM_INT: |
| 106 return lwasm_expr_term_create_int(t -> value); | |
| 107 | |
| 108 case LWASM_TERM_OPER: | |
| 109 return lwasm_expr_term_create_oper(t -> value); | |
| 110 | |
| 111 case LWASM_TERM_SYM: | |
| 112 return lwasm_expr_term_create_sym(t -> symbol); | |
| 113 | |
| 114 default: | |
| 115 fprintf(stderr, "lwasm_expr_term_dup(): invalid term type %d\n", t -> term_type); | |
| 116 exit(1); | |
| 117 } | |
| 118 // can't get here | |
| 119 } | |
| 120 | |
| 121 void lwasm_expr_stack_push(lwasm_expr_stack_t *s, lwasm_expr_term_t *t) | |
| 122 { | |
| 123 lwasm_expr_stack_node_t *n; | |
| 124 | |
| 125 if (!s) | |
| 126 { | |
| 127 fprintf(stderr, "lwasm_expr_stack_push(): invalid stack pointer\n"); | |
| 128 exit(1); | |
| 15 | 129 } |
| 130 | |
| 17 | 131 n = lwasm_alloc(sizeof(lwasm_expr_stack_node_t)); |
| 132 n -> next = NULL; | |
| 133 n -> prev = s -> tail; | |
| 134 n -> term = lwasm_expr_term_dup(t); | |
| 135 | |
| 136 if (s -> head) | |
| 137 { | |
| 138 s -> tail -> next = n; | |
| 139 s -> tail = n; | |
| 140 } | |
| 141 else | |
| 15 | 142 { |
| 17 | 143 s -> head = n; |
| 144 s -> tail = n; | |
| 145 } | |
| 146 } | |
| 147 | |
| 148 lwasm_expr_term_t *lwasm_expr_stack_pop(lwasm_expr_stack_t *s) | |
| 149 { | |
| 150 lwasm_expr_term_t *t; | |
| 151 lwasm_expr_stack_node_t *n; | |
| 152 | |
| 153 if (!(s -> tail)) | |
| 154 return NULL; | |
| 155 | |
| 156 n = s -> tail; | |
| 157 s -> tail = n -> prev; | |
| 158 if (!(n -> prev)) | |
| 159 { | |
| 160 s -> head = NULL; | |
| 15 | 161 } |
| 14 | 162 |
| 17 | 163 t = n -> term; |
| 164 n -> term = NULL; | |
| 165 | |
| 166 lwasm_free(n); | |
| 167 | |
| 168 return t; | |
| 14 | 169 } |
| 18 | 170 |
| 171 // the following two functions are co-routines which actually parse | |
| 172 // an infix expression onto the expression stack, each returns -1 | |
| 173 // if an error is encountered | |
| 174 | |
| 175 /* | |
| 176 parse a term and push it onto the stack | |
| 177 | |
| 178 this function handles unary prefix operators (-, +, .not., .com.) | |
| 179 as well as () | |
| 180 */ | |
| 181 int lwasm_expr_parse_term(lwasm_expr_stack_t *s, const char **p) | |
| 182 { | |
| 183 lwasm_expr_term_t *t; | |
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184 fprintf(stderr, "Expression string %s\n", *p); |
| 18 | 185 eval_next: |
| 186 if (**p == '(') | |
| 187 { | |
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188 fprintf(stderr, "Starting paren\n"); |
| 18 | 189 (*p)++; |
| 190 lwasm_expr_parse_expr(s, p, 0); | |
| 191 if (**p != ')') | |
| 192 return -1; | |
| 193 (*p)++; | |
| 194 return 0; | |
| 195 } | |
| 196 | |
| 197 if (**p == '+') | |
| 198 { | |
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199 fprintf(stderr, "Unary +\n"); |
| 18 | 200 (*p)++; |
| 201 goto eval_next; | |
| 202 } | |
| 203 | |
| 204 if (**p == '-') | |
| 205 { | |
| 206 // parse expression following "-" | |
| 207 (*p)++; | |
| 208 if (lwasm_expr_parse_expr(s, p, 200) < 0) | |
| 209 return -1; | |
| 210 t = lwasm_expr_term_create_oper(LWASM_OPER_NEG); | |
| 211 lwasm_expr_stack_push(s, t); | |
| 212 lwasm_expr_term_free(t); | |
| 213 return 0; | |
| 214 } | |
| 215 | |
| 23 | 216 if (**p == '^') |
| 217 { | |
| 218 // parse expression following "^" | |
| 219 (*p)++; | |
| 220 if (lwasm_expr_parse_expr(s, p, 200) < 0) | |
| 221 return -1; | |
| 222 t = lwasm_expr_term_create_oper(LWASM_OPER_COM); | |
| 223 lwasm_expr_stack_push(s, t); | |
| 224 lwasm_expr_term_free(t); | |
| 225 return 0; | |
| 226 } | |
| 227 | |
| 18 | 228 /* |
| 229 we have an actual term here so evaluate it | |
| 230 | |
| 231 it could be one of the following: | |
| 232 | |
| 233 1. a decimal constant | |
| 234 2. a hexadecimal constant | |
| 235 3. an octal constant | |
| 236 4. a binary constant | |
| 237 5. a symbol reference | |
| 238 6. the "current" instruction address (*) | |
| 239 7. the "current" data address (.) | |
| 240 8. a "back reference" (<) | |
| 241 9. a "forward reference" (>) | |
| 242 | |
| 243 items 6 through 9 are stored as symbol references | |
| 244 | |
| 245 (a . followed by a . or a alpha char or number is a symbol) | |
| 246 */ | |
| 247 if (**p == '*' | |
| 248 || ( | |
| 249 **p == '.' | |
| 250 && (*p)[1] != '.' | |
| 251 && !((*p)[1] >= 'A' && (*p)[1] <= 'Z') | |
| 252 && !((*p)[1] >= 'a' && (*p)[1] <= 'z') | |
| 253 && !((*p)[1] >= '0' && (*p)[1] <= '9') | |
| 254 ) | |
| 255 || **p == '<' | |
| 256 || **p == '>') | |
| 257 { | |
| 258 char tstr[2]; | |
| 259 tstr[0] = **p; | |
| 260 tstr[1] = '\0'; | |
| 261 t = lwasm_expr_term_create_sym(tstr); | |
| 262 lwasm_expr_stack_push(s, t); | |
| 263 lwasm_expr_term_free(t); | |
| 264 (*p)++; | |
| 265 return 0; | |
| 266 } | |
| 267 | |
| 268 /* | |
| 269 - a symbol will be a string of characters introduced by a letter, ".", | |
| 270 "_" but NOT a number | |
| 271 - a decimal constant will consist of only digits, optionally prefixed | |
| 272 with "&" | |
| 273 - a binary constant will consist of only 0s and 1s either prefixed with % | |
| 274 or suffixed with "B" | |
| 275 - a hex constant will consist of 0-9A-F either prefixed with $ or | |
| 276 suffixed with "H"; a hex number starting with A-F must be prefixed | |
| 277 with $ or start with 0 and end with H | |
| 278 - an octal constant will consist of 0-7 either prefixed with @ or | |
| 279 suffixed with "O" or "Q" | |
| 280 - an ascii constant will be a single character prefixed with a ' | |
| 281 - a double ascii constant will be two characters prefixed with a " | |
| 282 | |
| 283 */ | |
| 284 if (**p == '"') | |
| 285 { | |
| 286 // double ascii constant | |
| 287 int val; | |
| 288 (*p)++; | |
| 289 if (!**p) | |
| 290 return -1; | |
| 291 if (!*((*p)+1)) | |
| 292 return -1; | |
| 293 val = **p << 8 | *((*p) + 1); | |
| 294 (*p) += 2; | |
| 295 t = lwasm_expr_term_create_int(val); | |
| 296 lwasm_expr_stack_push(s, t); | |
| 297 lwasm_expr_term_free(t); | |
| 298 return 0; | |
| 299 } | |
| 300 else if (**p == '\'') | |
| 301 { | |
| 302 // single ascii constant | |
| 303 int val; | |
| 304 (*p)++; | |
| 305 if (!**p) | |
| 306 return -1; | |
| 307 val = **p; | |
| 308 (*p)++; | |
| 309 t = lwasm_expr_term_create_int(val); | |
| 310 lwasm_expr_stack_push(s, t); | |
| 311 lwasm_expr_term_free(t); | |
| 312 } | |
| 313 else if (**p == '&') | |
| 314 { | |
| 315 // decimal constant | |
| 316 int val = 0; | |
| 317 | |
| 318 (*p)++; | |
| 319 while (strchr("0123456789", **p)) | |
| 320 { | |
| 321 val = val * 10 + (**p - '0'); | |
| 322 (*p)++; | |
| 323 } | |
| 324 t = lwasm_expr_term_create_int(val); | |
| 325 lwasm_expr_stack_push(s, t); | |
| 326 lwasm_expr_term_free(t); | |
| 327 return 0; | |
| 328 } | |
| 329 else if (**p == '%') | |
| 330 { | |
| 331 // binary constant | |
| 332 int val = 0; | |
| 333 | |
| 334 (*p)++; | |
| 335 while (**p == '0' || **p == '1') | |
| 336 { | |
| 337 val = val * 2 + (**p - '0'); | |
| 338 (*p)++; | |
| 339 } | |
| 340 t = lwasm_expr_term_create_int(val); | |
| 341 lwasm_expr_stack_push(s, t); | |
| 342 lwasm_expr_term_free(t); | |
| 343 return 0; | |
| 344 } | |
| 345 else if (**p == '$') | |
| 346 { | |
| 347 // hexadecimal constant | |
| 348 int val = 0, val2; | |
| 349 | |
| 350 (*p)++; | |
| 351 while (strchr("0123456789ABCDEFabcdef", **p)) | |
| 352 { | |
| 353 val2 = toupper(**p) - '0'; | |
| 354 if (val2 > 9) | |
| 355 val2 -= 7; | |
| 356 val = val * 16 + val2; | |
| 357 (*p)++; | |
| 358 } | |
| 359 t = lwasm_expr_term_create_int(val); | |
| 360 lwasm_expr_stack_push(s, t); | |
| 361 lwasm_expr_term_free(t); | |
| 362 return 0; | |
| 363 } | |
| 364 else if (**p == '@') | |
| 365 { | |
| 366 // octal constant | |
| 367 int val = 0; | |
| 368 | |
| 369 (*p)++; | |
| 370 while (strchr("01234567", **p)) | |
| 371 { | |
| 372 val = val * 8 + (**p - '0'); | |
| 373 (*p)++; | |
| 374 } | |
| 375 t = lwasm_expr_term_create_int(val); | |
| 376 lwasm_expr_stack_push(s, t); | |
| 377 lwasm_expr_term_free(t); | |
| 378 return 0; | |
| 379 } | |
| 380 | |
| 381 // symbol or bare decimal or suffix identified constant here | |
| 382 // all numbers will start with a digit at this point | |
| 383 if (**p < '0' || **p > '9') | |
| 384 { | |
| 385 int l = 0; | |
| 386 char *sb; | |
| 387 | |
| 388 // evaluate a symbol here | |
| 389 static const char *symchars = "_.$@\\abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; | |
| 390 while (strchr(symchars, (*p)[l])) | |
| 391 l++; | |
| 392 | |
| 393 if (l == 0) | |
| 394 return -1; | |
| 395 | |
| 396 sb = lwasm_alloc(l + 1); | |
| 397 sb[l] = '\0'; | |
| 398 memcpy(sb, *p, l); | |
| 399 t = lwasm_expr_term_create_sym(sb); | |
| 400 lwasm_expr_stack_push(s, t); | |
| 401 lwasm_expr_term_free(t); | |
| 402 lwasm_free(sb); | |
| 403 (*p) += l; | |
| 404 return 0; | |
| 405 } | |
| 406 | |
| 407 if (!**p) | |
| 408 return -1; | |
| 409 | |
| 410 // evaluate a suffix based constant | |
| 411 { | |
| 412 int decval = 0, binval = 0, hexval = 0, octval = 0; | |
| 413 int valtype = 15; // 1 = bin, 2 = oct, 4 = dec, 8 = hex | |
| 414 int bindone = 0; | |
| 415 int val; | |
| 416 int dval; | |
| 417 | |
| 418 while (1) | |
| 419 { | |
| 420 if (!**p || !strchr("0123456789ABCDEFabcdefqhoQHO", **p)) | |
| 421 { | |
| 422 // we can legally have bin or decimal here | |
| 423 if (bindone) | |
| 424 { | |
| 425 // we just finished a binary value | |
| 426 val = binval; | |
| 427 break; | |
| 428 } | |
| 429 else if (valtype & 4) | |
| 430 { | |
| 431 // otherwise we must be decimal (if we're still allowed one) | |
| 432 val = decval; | |
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433 fprintf(stderr, "End of decimal value\n"); |
| 18 | 434 break; |
| 435 } | |
| 436 else | |
| 437 { | |
| 438 // bad value | |
| 439 return -1; | |
| 440 } | |
| 441 } | |
| 442 | |
| 443 dval = toupper(**p); | |
| 444 (*p)++; | |
| 445 | |
| 446 if (bindone) | |
| 447 { | |
| 448 // any characters past "B" means it is not binary | |
| 449 bindone = 0; | |
| 450 valtype &= 14; | |
| 451 } | |
| 452 | |
| 453 switch (dval) | |
| 454 { | |
| 455 case 'Q': | |
| 456 case 'O': | |
| 457 if (valtype & 2) | |
| 458 { | |
| 459 val = octval; | |
| 460 valtype = -1; | |
| 461 break; | |
| 462 } | |
| 463 else | |
| 464 { | |
| 465 // not a valid octal value | |
| 466 return -1; | |
| 467 } | |
| 468 /* can't get here */ | |
| 469 | |
| 470 case 'H': | |
| 471 if (valtype & 8) | |
| 472 { | |
| 473 val = hexval; | |
| 474 valtype = -1; | |
| 475 break; | |
| 476 } | |
| 477 else | |
| 478 { | |
| 479 // not a valid hex number | |
| 480 return -1; | |
| 481 } | |
| 482 /* can't get here */ | |
| 483 | |
| 484 case 'B': | |
| 485 // this is a bit of a sticky one since B is a legit hex | |
| 486 // digit so this may or may not be the end of the number | |
| 487 // so we fall through to the digit case | |
| 488 | |
| 489 if (valtype & 1) | |
| 490 { | |
| 491 // could still be binary | |
| 492 bindone = 1; | |
| 493 valtype = 9; // hex and binary | |
| 494 } | |
| 495 /* fall through intentional */ | |
| 496 | |
| 497 default: | |
| 498 // digit | |
| 499 dval -= '0'; | |
| 500 if (dval > 9) | |
| 501 dval -= 7; | |
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502 fprintf(stderr, "Got digit: %d\n", dval); |
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503 // if (dval > 1) |
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504 // valtype &= 14; |
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505 // if (dval > 7) |
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506 // valtype &= 12; |
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507 // if (dval > 9) |
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508 // valtype &= 8; |
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509 |
| 18 | 510 if (valtype & 8) |
| 511 { | |
| 512 hexval = hexval * 16 + dval; | |
| 513 } | |
| 514 if (valtype & 4) | |
| 515 { | |
| 516 if (dval > 9) | |
| 517 valtype &= 11; | |
| 518 else | |
| 519 decval = decval * 10 + dval; | |
| 520 } | |
| 521 if (valtype & 2) | |
| 522 { | |
| 523 if (dval > 7) | |
| 524 valtype &= 13; | |
| 525 else | |
| 526 octval = octval * 8 + dval; | |
| 527 } | |
| 528 if (valtype & 1) | |
| 529 { | |
| 530 if (dval > 1) | |
| 531 valtype &= 14; | |
| 532 else | |
| 533 binval = binval * 2 + dval; | |
| 534 } | |
| 535 } | |
| 536 // break out if we have a return value | |
|
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537 if (valtype == -1) |
| 18 | 538 break; |
| 539 // return if no more valid possibilities! | |
| 540 if (valtype == 0) | |
| 541 return -1; | |
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542 val = decval; // in case we fall through |
| 18 | 543 } |
| 544 | |
| 545 // we get here when we have a value to return | |
| 546 t = lwasm_expr_term_create_int(val); | |
| 547 lwasm_expr_stack_push(s, t); | |
| 548 lwasm_expr_term_free(t); | |
| 549 return 0; | |
| 550 } | |
| 551 /* can't get here */ | |
| 552 } | |
| 553 | |
| 554 // parse an expression and push the result onto the stack | |
| 555 // if an operator of lower precedence than the value of "prec" is found, | |
| 556 int lwasm_expr_parse_expr(lwasm_expr_stack_t *s, const char **p, int prec) | |
| 557 { | |
| 558 static const struct operinfo | |
| 559 { | |
| 560 int opernum; | |
| 561 char *operstr; | |
| 562 int operprec; | |
| 563 } operators[] = | |
| 564 { | |
| 565 { LWASM_OPER_PLUS, "+", 100 }, | |
| 566 { LWASM_OPER_MINUS, "-", 100 }, | |
| 567 { LWASM_OPER_TIMES, "*", 150 }, | |
| 568 { LWASM_OPER_DIVIDE, "/", 150 }, | |
| 569 { LWASM_OPER_MOD, "%", 150 }, | |
| 570 { LWASM_OPER_INTDIV, "\\", 150 }, | |
| 571 | |
| 572 { LWASM_OPER_NONE, "", 0 } | |
| 573 }; | |
| 574 int opern, i; | |
| 575 lwasm_expr_term_t *operterm; | |
| 576 | |
| 577 // return if we are at the end of the expression or a subexpression | |
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578 if (!**p || isspace(**p) || **p == ')' || **p == ',') |
| 18 | 579 return 0; |
| 580 | |
| 581 if (lwasm_expr_parse_term(s, p) < 0) | |
| 582 return -1; | |
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583 |
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584 eval_next: |
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585 if (!**p || isspace(**p) || **p == ')' || **p == ',') |
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586 return 0; |
| 18 | 587 |
| 588 // expecting an operator here | |
| 589 for (opern = 0; operators[opern].opernum != LWASM_OPER_NONE; opern++) | |
| 590 { | |
| 591 for (i = 0; (*p)[i] && operators[opern].operstr[i] && (*p[i] == operators[opern].operstr[i]); i++) | |
| 592 /* do nothing */ ; | |
| 593 if (operators[opern].operstr[i] == '\0') | |
| 594 break; | |
| 595 } | |
| 596 if (operators[opern].opernum == LWASM_OPER_NONE) | |
| 597 { | |
| 598 // unrecognized operator | |
| 599 return -1; | |
| 600 } | |
| 601 | |
| 602 // the operator number in question is in opern; i is the length of the | |
| 603 // operator string | |
| 604 | |
| 605 // logic: | |
| 606 // if the precedence of this operation is <= to the "prec" flag, | |
| 607 // we simply return without advancing the input pointer; the operator | |
| 608 // will be evaluated again in the enclosing function call | |
| 609 if (operators[opern].operprec <= prec) | |
| 610 return 0; | |
| 611 | |
| 612 // logic: | |
| 613 // we have a higher precedence operator here so we will advance the | |
| 614 // input pointer to the next term and let the expression evaluator | |
| 615 // loose on it after which time we will push our operator onto the | |
| 616 // stack and then go on with the expression evaluation | |
| 617 (*p) += i; // advance input pointer | |
| 618 | |
| 619 // evaluate next expression(s) of higher precedence | |
| 620 if (lwasm_expr_parse_expr(s, p, operators[opern].operprec) < 0) | |
| 621 return -1; | |
| 622 | |
| 623 operterm = lwasm_expr_term_create_oper(operators[opern].opernum); | |
| 624 lwasm_expr_stack_push(s, operterm); | |
| 625 lwasm_expr_term_free(operterm); | |
| 626 | |
| 627 // return if we are at the end of the expression or a subexpression | |
| 628 if (!**p || isspace(**p) || **p == ')') | |
| 629 return 0; | |
| 630 | |
| 631 // continue evaluating | |
| 632 goto eval_next; | |
| 633 } | |
| 634 | |
| 635 /* | |
| 636 actually evaluate an expression | |
| 637 | |
| 638 This happens in two stages. The first stage merely parses the expression into | |
| 639 a lwasm_expr_stack_t * which is then evaluated as much as possible before the | |
| 640 result is returned. | |
| 641 | |
| 642 Returns NULL on a parse error or otherwise invalid expression. *outp will | |
| 643 contain the pointer to the next character after the expression if and only | |
| 644 if there is no error. In the case of an error, *outp is undefined. | |
| 645 */ | |
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646 lwasm_expr_stack_t *lwasm_expr_eval(const char *inp, const char **outp, int (*sfunc)(char *sym, void *state, int *val), void *state) |
| 18 | 647 { |
| 648 lwasm_expr_stack_t *s; | |
| 649 const char *p; | |
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650 int rval; |
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651 |
| 18 | 652 // actually parse the expression |
| 653 p = inp; | |
| 654 s = lwasm_expr_stack_create(); | |
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655 |
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656 rval = lwasm_expr_parse_expr(s, &p, 0); |
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657 if (rval < 0) |
| 18 | 658 goto cleanup_error; |
| 659 | |
| 660 // save end of expression | |
| 661 if (outp) | |
| 662 (*outp) = p; | |
| 663 | |
| 664 // return potentially partial expression | |
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665 if (lwasm_expr_reval(s, sfunc, state) < 0) |
| 18 | 666 goto cleanup_error; |
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667 |
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668 if (lwasm_expr_is_constant(s)) |
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669 fprintf(stderr, "Constant expression evaluates to: %d\n", lwasm_expr_get_value(s)); |
| 18 | 670 |
| 671 return s; | |
| 672 | |
| 673 cleanup_error: | |
| 674 lwasm_expr_stack_free(s); | |
| 675 return NULL; | |
| 676 } | |
| 677 | |
| 678 /* | |
| 679 take an expression stack s and scan for operations that can be completed | |
| 680 | |
| 681 return -1 on error, 0 on no error | |
| 682 | |
| 683 possible errors are: division by zero or unknown operator | |
| 684 | |
| 685 theory of operation: | |
| 686 | |
| 687 scan the stack for an operator which has two constants preceding it (binary) | |
| 688 or 1 constant preceding it (unary) and if found, perform the calculation | |
| 689 and replace the operator and its operands with the result | |
| 690 | |
| 691 repeat the scan until no futher simplications are found or if there are no | |
| 692 further operators or only a single term remains | |
| 693 | |
| 694 */ | |
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695 int lwasm_expr_reval(lwasm_expr_stack_t *s, int (*sfunc)(char *sym, void *state, int *val), void *state) |
| 18 | 696 { |
| 697 lwasm_expr_stack_node_t *n; | |
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698 int sval; |
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699 |
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700 // resolve symbols |
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701 // symbols that do not resolve to a constant are left alone |
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702 for (n = s -> head; n; n = n -> next) |
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703 { |
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704 if (n -> term -> term_type == LWASM_TERM_SYM) |
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705 { |
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706 if (sfunc(n -> term -> symbol, state, &sval) == 0) |
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707 { |
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708 n -> term -> term_type = LWASM_TERM_INT; |
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709 n -> term -> value = sval; |
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710 lwasm_free(n -> term -> symbol); |
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711 n -> term -> symbol = NULL; |
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712 } |
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713 } |
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714 } |
| 18 | 715 |
| 716 next_iter: | |
| 717 // a single term | |
| 718 if (s -> head == s -> tail) | |
| 719 return 0; | |
| 720 | |
| 721 // search for an operator | |
| 722 for (n = s -> head; n; n = n -> next) | |
| 723 { | |
| 724 if (n -> term -> term_type == LWASM_TERM_OPER) | |
| 725 { | |
| 726 if (n -> term -> value == LWASM_OPER_NEG | |
| 727 || n -> term -> value == LWASM_OPER_COM | |
| 728 ) | |
| 729 { | |
| 730 // unary operator | |
| 731 if (n -> prev && n -> prev -> term -> term_type == LWASM_TERM_INT) | |
| 732 { | |
| 733 // a unary operator we can resolve | |
| 734 // we do the op then remove the term "n" is pointing at | |
| 735 if (n -> term -> value == LWASM_OPER_NEG) | |
| 736 { | |
| 737 n -> prev -> term -> value = -(n -> prev -> term -> value); | |
| 738 } | |
| 739 else if (n -> term -> value == LWASM_OPER_COM) | |
| 740 { | |
| 741 n -> prev -> term -> value = ~(n -> prev -> term -> value); | |
| 742 } | |
| 743 n -> prev -> next = n -> next; | |
| 744 if (n -> next) | |
| 745 n -> next -> prev = n -> prev; | |
| 746 else | |
| 747 s -> tail = n -> prev; | |
| 748 | |
| 749 lwasm_expr_term_free(n -> term); | |
| 750 lwasm_free(n); | |
| 751 break; | |
| 752 } | |
| 753 } | |
| 754 else | |
| 755 { | |
| 756 // binary operator | |
| 757 if (n -> prev && n -> prev -> prev && n -> prev -> term -> term_type == LWASM_TERM_INT && n -> prev -> prev -> term -> term_type == LWASM_TERM_INT) | |
| 758 { | |
| 759 // a binary operator we can resolve | |
| 760 switch (n -> term -> value) | |
| 761 { | |
| 762 case LWASM_OPER_PLUS: | |
| 763 n -> prev -> prev -> term -> value += n -> prev -> term -> value; | |
| 764 break; | |
| 765 | |
| 766 case LWASM_OPER_MINUS: | |
| 767 n -> prev -> prev -> term -> value -= n -> prev -> term -> value; | |
| 768 break; | |
| 769 | |
| 770 case LWASM_OPER_TIMES: | |
| 771 n -> prev -> prev -> term -> value *= n -> prev -> term -> value; | |
| 772 break; | |
| 773 | |
| 774 case LWASM_OPER_DIVIDE: | |
| 775 if (n -> prev -> term -> value == 0) | |
| 776 return -1; | |
| 777 n -> prev -> prev -> term -> value /= n -> prev -> term -> value; | |
| 778 break; | |
| 779 | |
| 780 case LWASM_OPER_MOD: | |
| 781 if (n -> prev -> term -> value == 0) | |
| 782 return -1; | |
| 783 n -> prev -> prev -> term -> value %= n -> prev -> term -> value; | |
| 784 break; | |
| 785 | |
| 786 case LWASM_OPER_INTDIV: | |
| 787 if (n -> prev -> term -> value == 0) | |
| 788 return -1; | |
| 789 n -> prev -> prev -> term -> value /= n -> prev -> term -> value; | |
| 790 break; | |
| 791 | |
| 792 case LWASM_OPER_BWAND: | |
| 793 n -> prev -> prev -> term -> value &= n -> prev -> term -> value; | |
| 794 break; | |
| 795 | |
| 796 case LWASM_OPER_BWOR: | |
| 797 n -> prev -> prev -> term -> value |= n -> prev -> term -> value; | |
| 798 break; | |
| 799 | |
| 800 case LWASM_OPER_BWXOR: | |
| 801 n -> prev -> prev -> term -> value ^= n -> prev -> term -> value; | |
| 802 break; | |
| 803 | |
| 804 case LWASM_OPER_AND: | |
| 805 n -> prev -> prev -> term -> value = (n -> prev -> term -> value && n -> prev -> prev -> term -> value) ? 1 : 0; | |
| 806 break; | |
| 807 | |
| 808 case LWASM_OPER_OR: | |
| 809 n -> prev -> prev -> term -> value = (n -> prev -> term -> value || n -> prev -> prev -> term -> value) ? 1 : 0; | |
| 810 break; | |
| 811 | |
| 812 default: | |
| 813 // return error if unknown operator! | |
| 814 return -1; | |
| 815 } | |
| 816 | |
| 817 // now remove the two unneeded entries from the stack | |
| 818 n -> prev -> prev -> next = n -> next; | |
| 819 if (n -> next) | |
| 820 n -> next -> prev = n -> prev -> prev; | |
| 821 else | |
| 822 s -> tail = n -> prev -> prev; | |
| 823 | |
| 824 lwasm_expr_term_free(n -> term); | |
| 825 lwasm_expr_term_free(n -> prev -> term); | |
| 826 lwasm_free(n -> prev); | |
| 827 lwasm_free(n); | |
| 828 break; | |
| 829 } | |
| 830 } | |
| 831 } | |
| 832 } | |
| 833 // note for the terminally confused about dynamic memory and pointers: | |
| 834 // n will not be NULL even after the lwasm_free calls above so | |
| 835 // this test will still work (n will be a dangling pointer) | |
| 836 // (n will only be NULL if we didn't find any operators to simplify) | |
| 837 if (n) | |
| 838 goto next_iter; | |
| 839 | |
| 840 return 0; | |
| 841 } |