Mercurial > cpython-lru_cache-weakref
annotate Parser/pgen.c @ 4566:6403c94de50d legacy-trunk
Added safeguard against failure in __del__.
| author | Guido van Rossum <guido@python.org> |
|---|---|
| date | Wed, 27 Nov 1996 19:39:58 +0000 |
| parents | 65d2d8e67da3 |
| children | fae78cf8541d |
| rev | line source |
|---|---|
| 145 | 1 /*********************************************************** |
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2 Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam, |
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3 The Netherlands. |
| 145 | 4 |
| 5 All Rights Reserved | |
| 6 | |
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7 Permission to use, copy, modify, and distribute this software and its |
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8 documentation for any purpose and without fee is hereby granted, |
| 145 | 9 provided that the above copyright notice appear in all copies and that |
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10 both that copyright notice and this permission notice appear in |
| 145 | 11 supporting documentation, and that the names of Stichting Mathematisch |
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12 Centrum or CWI or Corporation for National Research Initiatives or |
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13 CNRI not be used in advertising or publicity pertaining to |
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14 distribution of the software without specific, written prior |
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15 permission. |
| 145 | 16 |
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17 While CWI is the initial source for this software, a modified version |
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18 is made available by the Corporation for National Research Initiatives |
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19 (CNRI) at the Internet address ftp://ftp.python.org. |
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20 |
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21 STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH |
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22 REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF |
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23 MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH |
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24 CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL |
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25 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR |
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26 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER |
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27 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR |
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28 PERFORMANCE OF THIS SOFTWARE. |
| 145 | 29 |
| 30 ******************************************************************/ | |
| 31 | |
| 6 | 32 /* Parser generator */ |
| 86 | 33 /* XXX This file is not yet fully PROTOized */ |
| 6 | 34 |
| 35 /* For a description, see the comments at end of this file */ | |
| 36 | |
| 86 | 37 #include "pgenheaders.h" |
| 6 | 38 #include "assert.h" |
| 39 #include "token.h" | |
| 40 #include "node.h" | |
| 41 #include "grammar.h" | |
| 42 #include "metagrammar.h" | |
| 43 #include "pgen.h" | |
| 44 | |
| 45 extern int debugging; | |
| 46 | |
| 47 | |
| 48 /* PART ONE -- CONSTRUCT NFA -- Cf. Algorithm 3.2 from [Aho&Ullman 77] */ | |
| 49 | |
| 50 typedef struct _nfaarc { | |
| 51 int ar_label; | |
| 52 int ar_arrow; | |
| 53 } nfaarc; | |
| 54 | |
| 55 typedef struct _nfastate { | |
| 56 int st_narcs; | |
| 57 nfaarc *st_arc; | |
| 58 } nfastate; | |
| 59 | |
| 60 typedef struct _nfa { | |
| 61 int nf_type; | |
| 62 char *nf_name; | |
| 63 int nf_nstates; | |
| 64 nfastate *nf_state; | |
| 65 int nf_start, nf_finish; | |
| 66 } nfa; | |
| 67 | |
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68 /* Forward */ |
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69 static compile_rhs PROTO((labellist *ll, nfa *nf, node *n, int *pa, int *pb)); |
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70 static compile_alt PROTO((labellist *ll, nfa *nf, node *n, int *pa, int *pb)); |
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71 static compile_item PROTO((labellist *ll, nfa *nf, node *n, int *pa, int *pb)); |
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72 static compile_atom PROTO((labellist *ll, nfa *nf, node *n, int *pa, int *pb)); |
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73 |
| 6 | 74 static int |
| 75 addnfastate(nf) | |
| 76 nfa *nf; | |
| 77 { | |
| 78 nfastate *st; | |
| 79 | |
| 80 RESIZE(nf->nf_state, nfastate, nf->nf_nstates + 1); | |
| 81 if (nf->nf_state == NULL) | |
| 82 fatal("out of mem"); | |
| 83 st = &nf->nf_state[nf->nf_nstates++]; | |
| 84 st->st_narcs = 0; | |
| 85 st->st_arc = NULL; | |
| 86 return st - nf->nf_state; | |
| 87 } | |
| 88 | |
| 89 static void | |
| 90 addnfaarc(nf, from, to, lbl) | |
| 91 nfa *nf; | |
| 92 int from, to, lbl; | |
| 93 { | |
| 94 nfastate *st; | |
| 95 nfaarc *ar; | |
| 96 | |
| 97 st = &nf->nf_state[from]; | |
| 98 RESIZE(st->st_arc, nfaarc, st->st_narcs + 1); | |
| 99 if (st->st_arc == NULL) | |
| 100 fatal("out of mem"); | |
| 101 ar = &st->st_arc[st->st_narcs++]; | |
| 102 ar->ar_label = lbl; | |
| 103 ar->ar_arrow = to; | |
| 104 } | |
| 105 | |
| 106 static nfa * | |
| 107 newnfa(name) | |
| 108 char *name; | |
| 109 { | |
| 110 nfa *nf; | |
| 111 static type = NT_OFFSET; /* All types will be disjunct */ | |
| 112 | |
| 113 nf = NEW(nfa, 1); | |
| 114 if (nf == NULL) | |
| 115 fatal("no mem for new nfa"); | |
| 116 nf->nf_type = type++; | |
| 117 nf->nf_name = name; /* XXX strdup(name) ??? */ | |
| 118 nf->nf_nstates = 0; | |
| 119 nf->nf_state = NULL; | |
| 120 nf->nf_start = nf->nf_finish = -1; | |
| 121 return nf; | |
| 122 } | |
| 123 | |
| 124 typedef struct _nfagrammar { | |
| 125 int gr_nnfas; | |
| 126 nfa **gr_nfa; | |
| 127 labellist gr_ll; | |
| 128 } nfagrammar; | |
| 129 | |
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130 /* Forward */ |
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131 static compile_rule PROTO((nfagrammar *gr, node *n)); |
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132 |
| 6 | 133 static nfagrammar * |
| 134 newnfagrammar() | |
| 135 { | |
| 136 nfagrammar *gr; | |
| 137 | |
| 138 gr = NEW(nfagrammar, 1); | |
| 139 if (gr == NULL) | |
| 140 fatal("no mem for new nfa grammar"); | |
| 141 gr->gr_nnfas = 0; | |
| 142 gr->gr_nfa = NULL; | |
| 143 gr->gr_ll.ll_nlabels = 0; | |
| 144 gr->gr_ll.ll_label = NULL; | |
| 145 addlabel(&gr->gr_ll, ENDMARKER, "EMPTY"); | |
| 146 return gr; | |
| 147 } | |
| 148 | |
| 149 static nfa * | |
| 150 addnfa(gr, name) | |
| 151 nfagrammar *gr; | |
| 152 char *name; | |
| 153 { | |
| 154 nfa *nf; | |
| 155 | |
| 156 nf = newnfa(name); | |
| 157 RESIZE(gr->gr_nfa, nfa *, gr->gr_nnfas + 1); | |
| 158 if (gr->gr_nfa == NULL) | |
| 159 fatal("out of mem"); | |
| 160 gr->gr_nfa[gr->gr_nnfas++] = nf; | |
| 161 addlabel(&gr->gr_ll, NAME, nf->nf_name); | |
| 162 return nf; | |
| 163 } | |
| 164 | |
| 165 #ifdef DEBUG | |
| 166 | |
| 167 static char REQNFMT[] = "metacompile: less than %d children\n"; | |
| 168 | |
| 169 #define REQN(i, count) \ | |
| 170 if (i < count) { \ | |
| 171 fprintf(stderr, REQNFMT, count); \ | |
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172 fatal("REQN"); \ |
| 6 | 173 } else |
| 174 | |
| 175 #else | |
| 176 #define REQN(i, count) /* empty */ | |
| 177 #endif | |
| 178 | |
| 179 static nfagrammar * | |
| 180 metacompile(n) | |
| 181 node *n; | |
| 182 { | |
| 183 nfagrammar *gr; | |
| 184 int i; | |
| 185 | |
| 186 printf("Compiling (meta-) parse tree into NFA grammar\n"); | |
| 187 gr = newnfagrammar(); | |
| 188 REQ(n, MSTART); | |
| 189 i = n->n_nchildren - 1; /* Last child is ENDMARKER */ | |
| 190 n = n->n_child; | |
| 191 for (; --i >= 0; n++) { | |
| 192 if (n->n_type != NEWLINE) | |
| 193 compile_rule(gr, n); | |
| 194 } | |
| 195 return gr; | |
| 196 } | |
| 197 | |
| 198 static | |
| 199 compile_rule(gr, n) | |
| 200 nfagrammar *gr; | |
| 201 node *n; | |
| 202 { | |
| 203 nfa *nf; | |
| 204 | |
| 205 REQ(n, RULE); | |
| 206 REQN(n->n_nchildren, 4); | |
| 207 n = n->n_child; | |
| 208 REQ(n, NAME); | |
| 209 nf = addnfa(gr, n->n_str); | |
| 210 n++; | |
| 211 REQ(n, COLON); | |
| 212 n++; | |
| 213 REQ(n, RHS); | |
| 214 compile_rhs(&gr->gr_ll, nf, n, &nf->nf_start, &nf->nf_finish); | |
| 215 n++; | |
| 216 REQ(n, NEWLINE); | |
| 217 } | |
| 218 | |
| 219 static | |
| 220 compile_rhs(ll, nf, n, pa, pb) | |
| 221 labellist *ll; | |
| 222 nfa *nf; | |
| 223 node *n; | |
| 224 int *pa, *pb; | |
| 225 { | |
| 226 int i; | |
| 227 int a, b; | |
| 228 | |
| 229 REQ(n, RHS); | |
| 230 i = n->n_nchildren; | |
| 231 REQN(i, 1); | |
| 232 n = n->n_child; | |
| 233 REQ(n, ALT); | |
| 234 compile_alt(ll, nf, n, pa, pb); | |
| 235 if (--i <= 0) | |
| 236 return; | |
| 237 n++; | |
| 238 a = *pa; | |
| 239 b = *pb; | |
| 240 *pa = addnfastate(nf); | |
| 241 *pb = addnfastate(nf); | |
| 242 addnfaarc(nf, *pa, a, EMPTY); | |
| 243 addnfaarc(nf, b, *pb, EMPTY); | |
| 244 for (; --i >= 0; n++) { | |
| 245 REQ(n, VBAR); | |
| 246 REQN(i, 1); | |
| 247 --i; | |
| 248 n++; | |
| 249 REQ(n, ALT); | |
| 250 compile_alt(ll, nf, n, &a, &b); | |
| 251 addnfaarc(nf, *pa, a, EMPTY); | |
| 252 addnfaarc(nf, b, *pb, EMPTY); | |
| 253 } | |
| 254 } | |
| 255 | |
| 256 static | |
| 257 compile_alt(ll, nf, n, pa, pb) | |
| 258 labellist *ll; | |
| 259 nfa *nf; | |
| 260 node *n; | |
| 261 int *pa, *pb; | |
| 262 { | |
| 263 int i; | |
| 264 int a, b; | |
| 265 | |
| 266 REQ(n, ALT); | |
| 267 i = n->n_nchildren; | |
| 268 REQN(i, 1); | |
| 269 n = n->n_child; | |
| 270 REQ(n, ITEM); | |
| 271 compile_item(ll, nf, n, pa, pb); | |
| 272 --i; | |
| 273 n++; | |
| 274 for (; --i >= 0; n++) { | |
| 275 if (n->n_type == COMMA) { /* XXX Temporary */ | |
| 276 REQN(i, 1); | |
| 277 --i; | |
| 278 n++; | |
| 279 } | |
| 280 REQ(n, ITEM); | |
| 281 compile_item(ll, nf, n, &a, &b); | |
| 282 addnfaarc(nf, *pb, a, EMPTY); | |
| 283 *pb = b; | |
| 284 } | |
| 285 } | |
| 286 | |
| 287 static | |
| 288 compile_item(ll, nf, n, pa, pb) | |
| 289 labellist *ll; | |
| 290 nfa *nf; | |
| 291 node *n; | |
| 292 int *pa, *pb; | |
| 293 { | |
| 294 int i; | |
| 295 int a, b; | |
| 296 | |
| 297 REQ(n, ITEM); | |
| 298 i = n->n_nchildren; | |
| 299 REQN(i, 1); | |
| 300 n = n->n_child; | |
| 301 if (n->n_type == LSQB) { | |
| 302 REQN(i, 3); | |
| 303 n++; | |
| 304 REQ(n, RHS); | |
| 305 *pa = addnfastate(nf); | |
| 306 *pb = addnfastate(nf); | |
| 307 addnfaarc(nf, *pa, *pb, EMPTY); | |
| 308 compile_rhs(ll, nf, n, &a, &b); | |
| 309 addnfaarc(nf, *pa, a, EMPTY); | |
| 310 addnfaarc(nf, b, *pb, EMPTY); | |
| 311 REQN(i, 1); | |
| 312 n++; | |
| 313 REQ(n, RSQB); | |
| 314 } | |
| 315 else { | |
| 316 compile_atom(ll, nf, n, pa, pb); | |
| 317 if (--i <= 0) | |
| 318 return; | |
| 319 n++; | |
| 320 addnfaarc(nf, *pb, *pa, EMPTY); | |
| 321 if (n->n_type == STAR) | |
| 322 *pb = *pa; | |
| 323 else | |
| 324 REQ(n, PLUS); | |
| 325 } | |
| 326 } | |
| 327 | |
| 328 static | |
| 329 compile_atom(ll, nf, n, pa, pb) | |
| 330 labellist *ll; | |
| 331 nfa *nf; | |
| 332 node *n; | |
| 333 int *pa, *pb; | |
| 334 { | |
| 335 int i; | |
| 336 | |
| 337 REQ(n, ATOM); | |
| 338 i = n->n_nchildren; | |
| 339 REQN(i, 1); | |
| 340 n = n->n_child; | |
| 341 if (n->n_type == LPAR) { | |
| 342 REQN(i, 3); | |
| 343 n++; | |
| 344 REQ(n, RHS); | |
| 345 compile_rhs(ll, nf, n, pa, pb); | |
| 346 n++; | |
| 347 REQ(n, RPAR); | |
| 348 } | |
| 349 else if (n->n_type == NAME || n->n_type == STRING) { | |
| 350 *pa = addnfastate(nf); | |
| 351 *pb = addnfastate(nf); | |
| 352 addnfaarc(nf, *pa, *pb, addlabel(ll, n->n_type, n->n_str)); | |
| 353 } | |
| 354 else | |
| 355 REQ(n, NAME); | |
| 356 } | |
| 357 | |
| 358 static void | |
| 359 dumpstate(ll, nf, istate) | |
| 360 labellist *ll; | |
| 361 nfa *nf; | |
| 362 int istate; | |
| 363 { | |
| 364 nfastate *st; | |
| 365 int i; | |
| 366 nfaarc *ar; | |
| 367 | |
| 368 printf("%c%2d%c", | |
| 369 istate == nf->nf_start ? '*' : ' ', | |
| 370 istate, | |
| 371 istate == nf->nf_finish ? '.' : ' '); | |
| 372 st = &nf->nf_state[istate]; | |
| 373 ar = st->st_arc; | |
| 374 for (i = 0; i < st->st_narcs; i++) { | |
| 375 if (i > 0) | |
| 376 printf("\n "); | |
| 377 printf("-> %2d %s", ar->ar_arrow, | |
| 378 labelrepr(&ll->ll_label[ar->ar_label])); | |
| 379 ar++; | |
| 380 } | |
| 381 printf("\n"); | |
| 382 } | |
| 383 | |
| 384 static void | |
| 385 dumpnfa(ll, nf) | |
| 386 labellist *ll; | |
| 387 nfa *nf; | |
| 388 { | |
| 389 int i; | |
| 390 | |
| 391 printf("NFA '%s' has %d states; start %d, finish %d\n", | |
| 392 nf->nf_name, nf->nf_nstates, nf->nf_start, nf->nf_finish); | |
| 393 for (i = 0; i < nf->nf_nstates; i++) | |
| 394 dumpstate(ll, nf, i); | |
| 395 } | |
| 396 | |
| 397 | |
| 398 /* PART TWO -- CONSTRUCT DFA -- Algorithm 3.1 from [Aho&Ullman 77] */ | |
| 399 | |
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400 static void |
| 6 | 401 addclosure(ss, nf, istate) |
| 402 bitset ss; | |
| 403 nfa *nf; | |
| 404 int istate; | |
| 405 { | |
| 406 if (addbit(ss, istate)) { | |
| 407 nfastate *st = &nf->nf_state[istate]; | |
| 408 nfaarc *ar = st->st_arc; | |
| 409 int i; | |
| 410 | |
| 411 for (i = st->st_narcs; --i >= 0; ) { | |
| 412 if (ar->ar_label == EMPTY) | |
| 413 addclosure(ss, nf, ar->ar_arrow); | |
| 414 ar++; | |
| 415 } | |
| 416 } | |
| 417 } | |
| 418 | |
| 419 typedef struct _ss_arc { | |
| 420 bitset sa_bitset; | |
| 421 int sa_arrow; | |
| 422 int sa_label; | |
| 423 } ss_arc; | |
| 424 | |
| 425 typedef struct _ss_state { | |
| 426 bitset ss_ss; | |
| 427 int ss_narcs; | |
| 428 ss_arc *ss_arc; | |
| 429 int ss_deleted; | |
| 430 int ss_finish; | |
| 431 int ss_rename; | |
| 432 } ss_state; | |
| 433 | |
| 434 typedef struct _ss_dfa { | |
| 435 int sd_nstates; | |
| 436 ss_state *sd_state; | |
| 437 } ss_dfa; | |
| 438 | |
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439 /* Forward */ |
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440 static printssdfa PROTO((int xx_nstates, ss_state *xx_state, int nbits, |
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441 labellist *ll, char *msg)); |
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442 static simplify PROTO((int xx_nstates, ss_state *xx_state)); |
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443 static convert PROTO((dfa *d, int xx_nstates, ss_state *xx_state)); |
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444 |
| 6 | 445 static |
| 446 makedfa(gr, nf, d) | |
| 447 nfagrammar *gr; | |
| 448 nfa *nf; | |
| 449 dfa *d; | |
| 450 { | |
| 451 int nbits = nf->nf_nstates; | |
| 452 bitset ss; | |
| 453 int xx_nstates; | |
| 454 ss_state *xx_state, *yy; | |
| 455 ss_arc *zz; | |
| 456 int istate, jstate, iarc, jarc, ibit; | |
| 457 nfastate *st; | |
| 458 nfaarc *ar; | |
| 459 | |
| 460 ss = newbitset(nbits); | |
| 461 addclosure(ss, nf, nf->nf_start); | |
| 462 xx_state = NEW(ss_state, 1); | |
| 463 if (xx_state == NULL) | |
| 464 fatal("no mem for xx_state in makedfa"); | |
| 465 xx_nstates = 1; | |
| 466 yy = &xx_state[0]; | |
| 467 yy->ss_ss = ss; | |
| 468 yy->ss_narcs = 0; | |
| 469 yy->ss_arc = NULL; | |
| 470 yy->ss_deleted = 0; | |
| 471 yy->ss_finish = testbit(ss, nf->nf_finish); | |
| 472 if (yy->ss_finish) | |
| 473 printf("Error: nonterminal '%s' may produce empty.\n", | |
| 474 nf->nf_name); | |
| 475 | |
| 476 /* This algorithm is from a book written before | |
| 477 the invention of structured programming... */ | |
| 478 | |
| 479 /* For each unmarked state... */ | |
| 480 for (istate = 0; istate < xx_nstates; ++istate) { | |
| 481 yy = &xx_state[istate]; | |
| 482 ss = yy->ss_ss; | |
| 483 /* For all its states... */ | |
| 484 for (ibit = 0; ibit < nf->nf_nstates; ++ibit) { | |
| 485 if (!testbit(ss, ibit)) | |
| 486 continue; | |
| 487 st = &nf->nf_state[ibit]; | |
| 488 /* For all non-empty arcs from this state... */ | |
| 489 for (iarc = 0; iarc < st->st_narcs; iarc++) { | |
| 490 ar = &st->st_arc[iarc]; | |
| 491 if (ar->ar_label == EMPTY) | |
| 492 continue; | |
| 493 /* Look up in list of arcs from this state */ | |
| 494 for (jarc = 0; jarc < yy->ss_narcs; ++jarc) { | |
| 495 zz = &yy->ss_arc[jarc]; | |
| 496 if (ar->ar_label == zz->sa_label) | |
| 497 goto found; | |
| 498 } | |
| 499 /* Add new arc for this state */ | |
| 500 RESIZE(yy->ss_arc, ss_arc, yy->ss_narcs + 1); | |
| 501 if (yy->ss_arc == NULL) | |
| 502 fatal("out of mem"); | |
| 503 zz = &yy->ss_arc[yy->ss_narcs++]; | |
| 504 zz->sa_label = ar->ar_label; | |
| 505 zz->sa_bitset = newbitset(nbits); | |
| 506 zz->sa_arrow = -1; | |
| 507 found: ; | |
| 508 /* Add destination */ | |
| 509 addclosure(zz->sa_bitset, nf, ar->ar_arrow); | |
| 510 } | |
| 511 } | |
| 512 /* Now look up all the arrow states */ | |
| 513 for (jarc = 0; jarc < xx_state[istate].ss_narcs; jarc++) { | |
| 514 zz = &xx_state[istate].ss_arc[jarc]; | |
| 515 for (jstate = 0; jstate < xx_nstates; jstate++) { | |
| 516 if (samebitset(zz->sa_bitset, | |
| 517 xx_state[jstate].ss_ss, nbits)) { | |
| 518 zz->sa_arrow = jstate; | |
| 519 goto done; | |
| 520 } | |
| 521 } | |
| 522 RESIZE(xx_state, ss_state, xx_nstates + 1); | |
| 523 if (xx_state == NULL) | |
| 524 fatal("out of mem"); | |
| 525 zz->sa_arrow = xx_nstates; | |
| 526 yy = &xx_state[xx_nstates++]; | |
| 527 yy->ss_ss = zz->sa_bitset; | |
| 528 yy->ss_narcs = 0; | |
| 529 yy->ss_arc = NULL; | |
| 530 yy->ss_deleted = 0; | |
| 531 yy->ss_finish = testbit(yy->ss_ss, nf->nf_finish); | |
| 532 done: ; | |
| 533 } | |
| 534 } | |
| 535 | |
| 536 if (debugging) | |
| 537 printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll, | |
| 538 "before minimizing"); | |
| 539 | |
| 540 simplify(xx_nstates, xx_state); | |
| 541 | |
| 542 if (debugging) | |
| 543 printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll, | |
| 544 "after minimizing"); | |
| 545 | |
| 546 convert(d, xx_nstates, xx_state); | |
| 547 | |
| 548 /* XXX cleanup */ | |
| 549 } | |
| 550 | |
| 551 static | |
| 552 printssdfa(xx_nstates, xx_state, nbits, ll, msg) | |
| 553 int xx_nstates; | |
| 554 ss_state *xx_state; | |
| 555 int nbits; | |
| 556 labellist *ll; | |
| 557 char *msg; | |
| 558 { | |
| 559 int i, ibit, iarc; | |
| 560 ss_state *yy; | |
| 561 ss_arc *zz; | |
| 562 | |
| 563 printf("Subset DFA %s\n", msg); | |
| 564 for (i = 0; i < xx_nstates; i++) { | |
| 565 yy = &xx_state[i]; | |
| 566 if (yy->ss_deleted) | |
| 567 continue; | |
| 568 printf(" Subset %d", i); | |
| 569 if (yy->ss_finish) | |
| 570 printf(" (finish)"); | |
| 571 printf(" { "); | |
| 572 for (ibit = 0; ibit < nbits; ibit++) { | |
| 573 if (testbit(yy->ss_ss, ibit)) | |
| 574 printf("%d ", ibit); | |
| 575 } | |
| 576 printf("}\n"); | |
| 577 for (iarc = 0; iarc < yy->ss_narcs; iarc++) { | |
| 578 zz = &yy->ss_arc[iarc]; | |
| 579 printf(" Arc to state %d, label %s\n", | |
| 580 zz->sa_arrow, | |
| 581 labelrepr(&ll->ll_label[zz->sa_label])); | |
| 582 } | |
| 583 } | |
| 584 } | |
| 585 | |
| 586 | |
| 587 /* PART THREE -- SIMPLIFY DFA */ | |
| 588 | |
| 589 /* Simplify the DFA by repeatedly eliminating states that are | |
| 590 equivalent to another oner. This is NOT Algorithm 3.3 from | |
| 591 [Aho&Ullman 77]. It does not always finds the minimal DFA, | |
| 592 but it does usually make a much smaller one... (For an example | |
| 593 of sub-optimal behaviour, try S: x a b+ | y a b+.) | |
| 594 */ | |
| 595 | |
| 596 static int | |
| 597 samestate(s1, s2) | |
| 598 ss_state *s1, *s2; | |
| 599 { | |
| 600 int i; | |
| 601 | |
| 602 if (s1->ss_narcs != s2->ss_narcs || s1->ss_finish != s2->ss_finish) | |
| 603 return 0; | |
| 604 for (i = 0; i < s1->ss_narcs; i++) { | |
| 605 if (s1->ss_arc[i].sa_arrow != s2->ss_arc[i].sa_arrow || | |
| 606 s1->ss_arc[i].sa_label != s2->ss_arc[i].sa_label) | |
| 607 return 0; | |
| 608 } | |
| 609 return 1; | |
| 610 } | |
| 611 | |
| 612 static void | |
| 613 renamestates(xx_nstates, xx_state, from, to) | |
| 614 int xx_nstates; | |
| 615 ss_state *xx_state; | |
| 616 int from, to; | |
| 617 { | |
| 618 int i, j; | |
| 619 | |
| 620 if (debugging) | |
| 621 printf("Rename state %d to %d.\n", from, to); | |
| 622 for (i = 0; i < xx_nstates; i++) { | |
| 623 if (xx_state[i].ss_deleted) | |
| 624 continue; | |
| 625 for (j = 0; j < xx_state[i].ss_narcs; j++) { | |
| 626 if (xx_state[i].ss_arc[j].sa_arrow == from) | |
| 627 xx_state[i].ss_arc[j].sa_arrow = to; | |
| 628 } | |
| 629 } | |
| 630 } | |
| 631 | |
| 632 static | |
| 633 simplify(xx_nstates, xx_state) | |
| 634 int xx_nstates; | |
| 635 ss_state *xx_state; | |
| 636 { | |
| 637 int changes; | |
|
2044
281e40652e23
Parser/tokenizer.c (tok_nextc): zap tok->buf after freeing;
Guido van Rossum <guido@python.org>
parents:
1848
diff
changeset
|
638 int i, j; |
| 6 | 639 |
| 640 do { | |
| 641 changes = 0; | |
| 642 for (i = 1; i < xx_nstates; i++) { | |
| 643 if (xx_state[i].ss_deleted) | |
| 644 continue; | |
| 645 for (j = 0; j < i; j++) { | |
| 646 if (xx_state[j].ss_deleted) | |
| 647 continue; | |
| 648 if (samestate(&xx_state[i], &xx_state[j])) { | |
| 649 xx_state[i].ss_deleted++; | |
| 650 renamestates(xx_nstates, xx_state, i, j); | |
| 651 changes++; | |
| 652 break; | |
| 653 } | |
| 654 } | |
| 655 } | |
| 656 } while (changes); | |
| 657 } | |
| 658 | |
| 659 | |
| 660 /* PART FOUR -- GENERATE PARSING TABLES */ | |
| 661 | |
| 662 /* Convert the DFA into a grammar that can be used by our parser */ | |
| 663 | |
| 664 static | |
| 665 convert(d, xx_nstates, xx_state) | |
| 666 dfa *d; | |
| 667 int xx_nstates; | |
| 668 ss_state *xx_state; | |
| 669 { | |
| 670 int i, j; | |
| 671 ss_state *yy; | |
| 672 ss_arc *zz; | |
| 673 | |
| 674 for (i = 0; i < xx_nstates; i++) { | |
| 675 yy = &xx_state[i]; | |
| 676 if (yy->ss_deleted) | |
| 677 continue; | |
| 678 yy->ss_rename = addstate(d); | |
| 679 } | |
| 680 | |
| 681 for (i = 0; i < xx_nstates; i++) { | |
| 682 yy = &xx_state[i]; | |
| 683 if (yy->ss_deleted) | |
| 684 continue; | |
| 685 for (j = 0; j < yy->ss_narcs; j++) { | |
| 686 zz = &yy->ss_arc[j]; | |
| 687 addarc(d, yy->ss_rename, | |
| 688 xx_state[zz->sa_arrow].ss_rename, | |
| 689 zz->sa_label); | |
| 690 } | |
| 691 if (yy->ss_finish) | |
| 692 addarc(d, yy->ss_rename, yy->ss_rename, 0); | |
| 693 } | |
| 694 | |
| 695 d->d_initial = 0; | |
| 696 } | |
| 697 | |
| 698 | |
| 699 /* PART FIVE -- GLUE IT ALL TOGETHER */ | |
| 700 | |
| 701 static grammar * | |
| 702 maketables(gr) | |
| 703 nfagrammar *gr; | |
| 704 { | |
| 705 int i; | |
| 706 nfa *nf; | |
| 707 dfa *d; | |
| 708 grammar *g; | |
| 709 | |
| 710 if (gr->gr_nnfas == 0) | |
| 711 return NULL; | |
| 712 g = newgrammar(gr->gr_nfa[0]->nf_type); | |
| 713 /* XXX first rule must be start rule */ | |
| 714 g->g_ll = gr->gr_ll; | |
| 715 | |
| 716 for (i = 0; i < gr->gr_nnfas; i++) { | |
| 717 nf = gr->gr_nfa[i]; | |
| 718 if (debugging) { | |
| 719 printf("Dump of NFA for '%s' ...\n", nf->nf_name); | |
| 720 dumpnfa(&gr->gr_ll, nf); | |
| 721 } | |
| 722 printf("Making DFA for '%s' ...\n", nf->nf_name); | |
| 723 d = adddfa(g, nf->nf_type, nf->nf_name); | |
| 724 makedfa(gr, gr->gr_nfa[i], d); | |
| 725 } | |
| 726 | |
| 727 return g; | |
| 728 } | |
| 729 | |
| 730 grammar * | |
| 731 pgen(n) | |
| 732 node *n; | |
| 733 { | |
| 734 nfagrammar *gr; | |
| 735 grammar *g; | |
| 736 | |
| 737 gr = metacompile(n); | |
| 738 g = maketables(gr); | |
| 739 translatelabels(g); | |
| 740 addfirstsets(g); | |
| 741 return g; | |
| 742 } | |
| 743 | |
| 744 | |
| 745 /* | |
| 746 | |
| 747 Description | |
| 748 ----------- | |
| 749 | |
| 750 Input is a grammar in extended BNF (using * for repetition, + for | |
| 751 at-least-once repetition, [] for optional parts, | for alternatives and | |
| 752 () for grouping). This has already been parsed and turned into a parse | |
| 753 tree. | |
| 754 | |
| 755 Each rule is considered as a regular expression in its own right. | |
| 756 It is turned into a Non-deterministic Finite Automaton (NFA), which | |
| 757 is then turned into a Deterministic Finite Automaton (DFA), which is then | |
| 758 optimized to reduce the number of states. See [Aho&Ullman 77] chapter 3, | |
| 759 or similar compiler books (this technique is more often used for lexical | |
| 760 analyzers). | |
| 761 | |
| 762 The DFA's are used by the parser as parsing tables in a special way | |
| 763 that's probably unique. Before they are usable, the FIRST sets of all | |
| 764 non-terminals are computed. | |
| 765 | |
| 766 Reference | |
| 767 --------- | |
| 768 | |
| 769 [Aho&Ullman 77] | |
| 770 Aho&Ullman, Principles of Compiler Design, Addison-Wesley 1977 | |
| 771 (first edition) | |
| 772 | |
| 773 */ |