Guido van Rossum | f70e43a | 1991-02-19 12:39:46 +0000 | [diff] [blame] | 1 | /*********************************************************** |
Guido van Rossum | b9f8d6e | 1995-01-04 19:08:09 +0000 | [diff] [blame] | 2 | Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam, |
| 3 | The Netherlands. |
Guido van Rossum | f70e43a | 1991-02-19 12:39:46 +0000 | [diff] [blame] | 4 | |
| 5 | All Rights Reserved |
| 6 | |
Guido van Rossum | d266eb4 | 1996-10-25 14:44:06 +0000 | [diff] [blame] | 7 | Permission to use, copy, modify, and distribute this software and its |
| 8 | documentation for any purpose and without fee is hereby granted, |
Guido van Rossum | f70e43a | 1991-02-19 12:39:46 +0000 | [diff] [blame] | 9 | provided that the above copyright notice appear in all copies and that |
Guido van Rossum | d266eb4 | 1996-10-25 14:44:06 +0000 | [diff] [blame] | 10 | both that copyright notice and this permission notice appear in |
Guido van Rossum | f70e43a | 1991-02-19 12:39:46 +0000 | [diff] [blame] | 11 | supporting documentation, and that the names of Stichting Mathematisch |
Guido van Rossum | d266eb4 | 1996-10-25 14:44:06 +0000 | [diff] [blame] | 12 | Centrum or CWI or Corporation for National Research Initiatives or |
| 13 | CNRI not be used in advertising or publicity pertaining to |
| 14 | distribution of the software without specific, written prior |
| 15 | permission. |
Guido van Rossum | f70e43a | 1991-02-19 12:39:46 +0000 | [diff] [blame] | 16 | |
Guido van Rossum | d266eb4 | 1996-10-25 14:44:06 +0000 | [diff] [blame] | 17 | While CWI is the initial source for this software, a modified version |
| 18 | is made available by the Corporation for National Research Initiatives |
| 19 | (CNRI) at the Internet address ftp://ftp.python.org. |
| 20 | |
| 21 | STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH |
| 22 | REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF |
| 23 | MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH |
| 24 | CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL |
| 25 | DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR |
| 26 | PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER |
| 27 | TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR |
| 28 | PERFORMANCE OF THIS SOFTWARE. |
Guido van Rossum | f70e43a | 1991-02-19 12:39:46 +0000 | [diff] [blame] | 29 | |
| 30 | ******************************************************************/ |
| 31 | |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 32 | /* Parser generator */ |
Guido van Rossum | 3f5da24 | 1990-12-20 15:06:42 +0000 | [diff] [blame] | 33 | /* XXX This file is not yet fully PROTOized */ |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 34 | |
| 35 | /* For a description, see the comments at end of this file */ |
| 36 | |
Guido van Rossum | 3f5da24 | 1990-12-20 15:06:42 +0000 | [diff] [blame] | 37 | #include "pgenheaders.h" |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 38 | #include "assert.h" |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 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 | |
Guido van Rossum | 71f477c | 1991-04-03 19:09:02 +0000 | [diff] [blame] | 68 | /* Forward */ |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 69 | static void compile_rhs PROTO((labellist *ll, |
| 70 | nfa *nf, node *n, int *pa, int *pb)); |
| 71 | static void compile_alt PROTO((labellist *ll, |
| 72 | nfa *nf, node *n, int *pa, int *pb)); |
| 73 | static void compile_item PROTO((labellist *ll, |
| 74 | nfa *nf, node *n, int *pa, int *pb)); |
| 75 | static void compile_atom PROTO((labellist *ll, |
| 76 | nfa *nf, node *n, int *pa, int *pb)); |
Guido van Rossum | 71f477c | 1991-04-03 19:09:02 +0000 | [diff] [blame] | 77 | |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 78 | static int |
| 79 | addnfastate(nf) |
| 80 | nfa *nf; |
| 81 | { |
| 82 | nfastate *st; |
| 83 | |
| 84 | RESIZE(nf->nf_state, nfastate, nf->nf_nstates + 1); |
| 85 | if (nf->nf_state == NULL) |
| 86 | fatal("out of mem"); |
| 87 | st = &nf->nf_state[nf->nf_nstates++]; |
| 88 | st->st_narcs = 0; |
| 89 | st->st_arc = NULL; |
| 90 | return st - nf->nf_state; |
| 91 | } |
| 92 | |
| 93 | static void |
| 94 | addnfaarc(nf, from, to, lbl) |
| 95 | nfa *nf; |
| 96 | int from, to, lbl; |
| 97 | { |
| 98 | nfastate *st; |
| 99 | nfaarc *ar; |
| 100 | |
| 101 | st = &nf->nf_state[from]; |
| 102 | RESIZE(st->st_arc, nfaarc, st->st_narcs + 1); |
| 103 | if (st->st_arc == NULL) |
| 104 | fatal("out of mem"); |
| 105 | ar = &st->st_arc[st->st_narcs++]; |
| 106 | ar->ar_label = lbl; |
| 107 | ar->ar_arrow = to; |
| 108 | } |
| 109 | |
| 110 | static nfa * |
| 111 | newnfa(name) |
| 112 | char *name; |
| 113 | { |
| 114 | nfa *nf; |
| 115 | static type = NT_OFFSET; /* All types will be disjunct */ |
| 116 | |
| 117 | nf = NEW(nfa, 1); |
| 118 | if (nf == NULL) |
| 119 | fatal("no mem for new nfa"); |
| 120 | nf->nf_type = type++; |
| 121 | nf->nf_name = name; /* XXX strdup(name) ??? */ |
| 122 | nf->nf_nstates = 0; |
| 123 | nf->nf_state = NULL; |
| 124 | nf->nf_start = nf->nf_finish = -1; |
| 125 | return nf; |
| 126 | } |
| 127 | |
| 128 | typedef struct _nfagrammar { |
| 129 | int gr_nnfas; |
| 130 | nfa **gr_nfa; |
| 131 | labellist gr_ll; |
| 132 | } nfagrammar; |
| 133 | |
Guido van Rossum | 71f477c | 1991-04-03 19:09:02 +0000 | [diff] [blame] | 134 | /* Forward */ |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 135 | static void compile_rule PROTO((nfagrammar *gr, node *n)); |
Guido van Rossum | 71f477c | 1991-04-03 19:09:02 +0000 | [diff] [blame] | 136 | |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 137 | static nfagrammar * |
| 138 | newnfagrammar() |
| 139 | { |
| 140 | nfagrammar *gr; |
| 141 | |
| 142 | gr = NEW(nfagrammar, 1); |
| 143 | if (gr == NULL) |
| 144 | fatal("no mem for new nfa grammar"); |
| 145 | gr->gr_nnfas = 0; |
| 146 | gr->gr_nfa = NULL; |
| 147 | gr->gr_ll.ll_nlabels = 0; |
| 148 | gr->gr_ll.ll_label = NULL; |
| 149 | addlabel(&gr->gr_ll, ENDMARKER, "EMPTY"); |
| 150 | return gr; |
| 151 | } |
| 152 | |
| 153 | static nfa * |
| 154 | addnfa(gr, name) |
| 155 | nfagrammar *gr; |
| 156 | char *name; |
| 157 | { |
| 158 | nfa *nf; |
| 159 | |
| 160 | nf = newnfa(name); |
| 161 | RESIZE(gr->gr_nfa, nfa *, gr->gr_nnfas + 1); |
| 162 | if (gr->gr_nfa == NULL) |
| 163 | fatal("out of mem"); |
| 164 | gr->gr_nfa[gr->gr_nnfas++] = nf; |
| 165 | addlabel(&gr->gr_ll, NAME, nf->nf_name); |
| 166 | return nf; |
| 167 | } |
| 168 | |
| 169 | #ifdef DEBUG |
| 170 | |
| 171 | static char REQNFMT[] = "metacompile: less than %d children\n"; |
| 172 | |
| 173 | #define REQN(i, count) \ |
| 174 | if (i < count) { \ |
| 175 | fprintf(stderr, REQNFMT, count); \ |
Guido van Rossum | 588633d | 1994-12-30 15:46:02 +0000 | [diff] [blame] | 176 | fatal("REQN"); \ |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 177 | } else |
| 178 | |
| 179 | #else |
| 180 | #define REQN(i, count) /* empty */ |
| 181 | #endif |
| 182 | |
| 183 | static nfagrammar * |
| 184 | metacompile(n) |
| 185 | node *n; |
| 186 | { |
| 187 | nfagrammar *gr; |
| 188 | int i; |
| 189 | |
| 190 | printf("Compiling (meta-) parse tree into NFA grammar\n"); |
| 191 | gr = newnfagrammar(); |
| 192 | REQ(n, MSTART); |
| 193 | i = n->n_nchildren - 1; /* Last child is ENDMARKER */ |
| 194 | n = n->n_child; |
| 195 | for (; --i >= 0; n++) { |
| 196 | if (n->n_type != NEWLINE) |
| 197 | compile_rule(gr, n); |
| 198 | } |
| 199 | return gr; |
| 200 | } |
| 201 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 202 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 203 | compile_rule(gr, n) |
| 204 | nfagrammar *gr; |
| 205 | node *n; |
| 206 | { |
| 207 | nfa *nf; |
| 208 | |
| 209 | REQ(n, RULE); |
| 210 | REQN(n->n_nchildren, 4); |
| 211 | n = n->n_child; |
| 212 | REQ(n, NAME); |
| 213 | nf = addnfa(gr, n->n_str); |
| 214 | n++; |
| 215 | REQ(n, COLON); |
| 216 | n++; |
| 217 | REQ(n, RHS); |
| 218 | compile_rhs(&gr->gr_ll, nf, n, &nf->nf_start, &nf->nf_finish); |
| 219 | n++; |
| 220 | REQ(n, NEWLINE); |
| 221 | } |
| 222 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 223 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 224 | compile_rhs(ll, nf, n, pa, pb) |
| 225 | labellist *ll; |
| 226 | nfa *nf; |
| 227 | node *n; |
| 228 | int *pa, *pb; |
| 229 | { |
| 230 | int i; |
| 231 | int a, b; |
| 232 | |
| 233 | REQ(n, RHS); |
| 234 | i = n->n_nchildren; |
| 235 | REQN(i, 1); |
| 236 | n = n->n_child; |
| 237 | REQ(n, ALT); |
| 238 | compile_alt(ll, nf, n, pa, pb); |
| 239 | if (--i <= 0) |
| 240 | return; |
| 241 | n++; |
| 242 | a = *pa; |
| 243 | b = *pb; |
| 244 | *pa = addnfastate(nf); |
| 245 | *pb = addnfastate(nf); |
| 246 | addnfaarc(nf, *pa, a, EMPTY); |
| 247 | addnfaarc(nf, b, *pb, EMPTY); |
| 248 | for (; --i >= 0; n++) { |
| 249 | REQ(n, VBAR); |
| 250 | REQN(i, 1); |
| 251 | --i; |
| 252 | n++; |
| 253 | REQ(n, ALT); |
| 254 | compile_alt(ll, nf, n, &a, &b); |
| 255 | addnfaarc(nf, *pa, a, EMPTY); |
| 256 | addnfaarc(nf, b, *pb, EMPTY); |
| 257 | } |
| 258 | } |
| 259 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 260 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 261 | compile_alt(ll, nf, n, pa, pb) |
| 262 | labellist *ll; |
| 263 | nfa *nf; |
| 264 | node *n; |
| 265 | int *pa, *pb; |
| 266 | { |
| 267 | int i; |
| 268 | int a, b; |
| 269 | |
| 270 | REQ(n, ALT); |
| 271 | i = n->n_nchildren; |
| 272 | REQN(i, 1); |
| 273 | n = n->n_child; |
| 274 | REQ(n, ITEM); |
| 275 | compile_item(ll, nf, n, pa, pb); |
| 276 | --i; |
| 277 | n++; |
| 278 | for (; --i >= 0; n++) { |
| 279 | if (n->n_type == COMMA) { /* XXX Temporary */ |
| 280 | REQN(i, 1); |
| 281 | --i; |
| 282 | n++; |
| 283 | } |
| 284 | REQ(n, ITEM); |
| 285 | compile_item(ll, nf, n, &a, &b); |
| 286 | addnfaarc(nf, *pb, a, EMPTY); |
| 287 | *pb = b; |
| 288 | } |
| 289 | } |
| 290 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 291 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 292 | compile_item(ll, nf, n, pa, pb) |
| 293 | labellist *ll; |
| 294 | nfa *nf; |
| 295 | node *n; |
| 296 | int *pa, *pb; |
| 297 | { |
| 298 | int i; |
| 299 | int a, b; |
| 300 | |
| 301 | REQ(n, ITEM); |
| 302 | i = n->n_nchildren; |
| 303 | REQN(i, 1); |
| 304 | n = n->n_child; |
| 305 | if (n->n_type == LSQB) { |
| 306 | REQN(i, 3); |
| 307 | n++; |
| 308 | REQ(n, RHS); |
| 309 | *pa = addnfastate(nf); |
| 310 | *pb = addnfastate(nf); |
| 311 | addnfaarc(nf, *pa, *pb, EMPTY); |
| 312 | compile_rhs(ll, nf, n, &a, &b); |
| 313 | addnfaarc(nf, *pa, a, EMPTY); |
| 314 | addnfaarc(nf, b, *pb, EMPTY); |
| 315 | REQN(i, 1); |
| 316 | n++; |
| 317 | REQ(n, RSQB); |
| 318 | } |
| 319 | else { |
| 320 | compile_atom(ll, nf, n, pa, pb); |
| 321 | if (--i <= 0) |
| 322 | return; |
| 323 | n++; |
| 324 | addnfaarc(nf, *pb, *pa, EMPTY); |
| 325 | if (n->n_type == STAR) |
| 326 | *pb = *pa; |
| 327 | else |
| 328 | REQ(n, PLUS); |
| 329 | } |
| 330 | } |
| 331 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 332 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 333 | compile_atom(ll, nf, n, pa, pb) |
| 334 | labellist *ll; |
| 335 | nfa *nf; |
| 336 | node *n; |
| 337 | int *pa, *pb; |
| 338 | { |
| 339 | int i; |
| 340 | |
| 341 | REQ(n, ATOM); |
| 342 | i = n->n_nchildren; |
| 343 | REQN(i, 1); |
| 344 | n = n->n_child; |
| 345 | if (n->n_type == LPAR) { |
| 346 | REQN(i, 3); |
| 347 | n++; |
| 348 | REQ(n, RHS); |
| 349 | compile_rhs(ll, nf, n, pa, pb); |
| 350 | n++; |
| 351 | REQ(n, RPAR); |
| 352 | } |
| 353 | else if (n->n_type == NAME || n->n_type == STRING) { |
| 354 | *pa = addnfastate(nf); |
| 355 | *pb = addnfastate(nf); |
| 356 | addnfaarc(nf, *pa, *pb, addlabel(ll, n->n_type, n->n_str)); |
| 357 | } |
| 358 | else |
| 359 | REQ(n, NAME); |
| 360 | } |
| 361 | |
| 362 | static void |
| 363 | dumpstate(ll, nf, istate) |
| 364 | labellist *ll; |
| 365 | nfa *nf; |
| 366 | int istate; |
| 367 | { |
| 368 | nfastate *st; |
| 369 | int i; |
| 370 | nfaarc *ar; |
| 371 | |
| 372 | printf("%c%2d%c", |
| 373 | istate == nf->nf_start ? '*' : ' ', |
| 374 | istate, |
| 375 | istate == nf->nf_finish ? '.' : ' '); |
| 376 | st = &nf->nf_state[istate]; |
| 377 | ar = st->st_arc; |
| 378 | for (i = 0; i < st->st_narcs; i++) { |
| 379 | if (i > 0) |
| 380 | printf("\n "); |
| 381 | printf("-> %2d %s", ar->ar_arrow, |
| 382 | labelrepr(&ll->ll_label[ar->ar_label])); |
| 383 | ar++; |
| 384 | } |
| 385 | printf("\n"); |
| 386 | } |
| 387 | |
| 388 | static void |
| 389 | dumpnfa(ll, nf) |
| 390 | labellist *ll; |
| 391 | nfa *nf; |
| 392 | { |
| 393 | int i; |
| 394 | |
| 395 | printf("NFA '%s' has %d states; start %d, finish %d\n", |
| 396 | nf->nf_name, nf->nf_nstates, nf->nf_start, nf->nf_finish); |
| 397 | for (i = 0; i < nf->nf_nstates; i++) |
| 398 | dumpstate(ll, nf, i); |
| 399 | } |
| 400 | |
| 401 | |
| 402 | /* PART TWO -- CONSTRUCT DFA -- Algorithm 3.1 from [Aho&Ullman 77] */ |
| 403 | |
Guido van Rossum | 588633d | 1994-12-30 15:46:02 +0000 | [diff] [blame] | 404 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 405 | addclosure(ss, nf, istate) |
| 406 | bitset ss; |
| 407 | nfa *nf; |
| 408 | int istate; |
| 409 | { |
| 410 | if (addbit(ss, istate)) { |
| 411 | nfastate *st = &nf->nf_state[istate]; |
| 412 | nfaarc *ar = st->st_arc; |
| 413 | int i; |
| 414 | |
| 415 | for (i = st->st_narcs; --i >= 0; ) { |
| 416 | if (ar->ar_label == EMPTY) |
| 417 | addclosure(ss, nf, ar->ar_arrow); |
| 418 | ar++; |
| 419 | } |
| 420 | } |
| 421 | } |
| 422 | |
| 423 | typedef struct _ss_arc { |
| 424 | bitset sa_bitset; |
| 425 | int sa_arrow; |
| 426 | int sa_label; |
| 427 | } ss_arc; |
| 428 | |
| 429 | typedef struct _ss_state { |
| 430 | bitset ss_ss; |
| 431 | int ss_narcs; |
| 432 | ss_arc *ss_arc; |
| 433 | int ss_deleted; |
| 434 | int ss_finish; |
| 435 | int ss_rename; |
| 436 | } ss_state; |
| 437 | |
| 438 | typedef struct _ss_dfa { |
| 439 | int sd_nstates; |
| 440 | ss_state *sd_state; |
| 441 | } ss_dfa; |
| 442 | |
Guido van Rossum | 71f477c | 1991-04-03 19:09:02 +0000 | [diff] [blame] | 443 | /* Forward */ |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 444 | static void printssdfa PROTO((int xx_nstates, ss_state *xx_state, int nbits, |
| 445 | labellist *ll, char *msg)); |
| 446 | static void simplify PROTO((int xx_nstates, ss_state *xx_state)); |
| 447 | static void convert PROTO((dfa *d, int xx_nstates, ss_state *xx_state)); |
Guido van Rossum | 71f477c | 1991-04-03 19:09:02 +0000 | [diff] [blame] | 448 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 449 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 450 | makedfa(gr, nf, d) |
| 451 | nfagrammar *gr; |
| 452 | nfa *nf; |
| 453 | dfa *d; |
| 454 | { |
| 455 | int nbits = nf->nf_nstates; |
| 456 | bitset ss; |
| 457 | int xx_nstates; |
| 458 | ss_state *xx_state, *yy; |
| 459 | ss_arc *zz; |
| 460 | int istate, jstate, iarc, jarc, ibit; |
| 461 | nfastate *st; |
| 462 | nfaarc *ar; |
| 463 | |
| 464 | ss = newbitset(nbits); |
| 465 | addclosure(ss, nf, nf->nf_start); |
| 466 | xx_state = NEW(ss_state, 1); |
| 467 | if (xx_state == NULL) |
| 468 | fatal("no mem for xx_state in makedfa"); |
| 469 | xx_nstates = 1; |
| 470 | yy = &xx_state[0]; |
| 471 | yy->ss_ss = ss; |
| 472 | yy->ss_narcs = 0; |
| 473 | yy->ss_arc = NULL; |
| 474 | yy->ss_deleted = 0; |
| 475 | yy->ss_finish = testbit(ss, nf->nf_finish); |
| 476 | if (yy->ss_finish) |
| 477 | printf("Error: nonterminal '%s' may produce empty.\n", |
| 478 | nf->nf_name); |
| 479 | |
| 480 | /* This algorithm is from a book written before |
| 481 | the invention of structured programming... */ |
| 482 | |
| 483 | /* For each unmarked state... */ |
| 484 | for (istate = 0; istate < xx_nstates; ++istate) { |
| 485 | yy = &xx_state[istate]; |
| 486 | ss = yy->ss_ss; |
| 487 | /* For all its states... */ |
| 488 | for (ibit = 0; ibit < nf->nf_nstates; ++ibit) { |
| 489 | if (!testbit(ss, ibit)) |
| 490 | continue; |
| 491 | st = &nf->nf_state[ibit]; |
| 492 | /* For all non-empty arcs from this state... */ |
| 493 | for (iarc = 0; iarc < st->st_narcs; iarc++) { |
| 494 | ar = &st->st_arc[iarc]; |
| 495 | if (ar->ar_label == EMPTY) |
| 496 | continue; |
| 497 | /* Look up in list of arcs from this state */ |
| 498 | for (jarc = 0; jarc < yy->ss_narcs; ++jarc) { |
| 499 | zz = &yy->ss_arc[jarc]; |
| 500 | if (ar->ar_label == zz->sa_label) |
| 501 | goto found; |
| 502 | } |
| 503 | /* Add new arc for this state */ |
| 504 | RESIZE(yy->ss_arc, ss_arc, yy->ss_narcs + 1); |
| 505 | if (yy->ss_arc == NULL) |
| 506 | fatal("out of mem"); |
| 507 | zz = &yy->ss_arc[yy->ss_narcs++]; |
| 508 | zz->sa_label = ar->ar_label; |
| 509 | zz->sa_bitset = newbitset(nbits); |
| 510 | zz->sa_arrow = -1; |
| 511 | found: ; |
| 512 | /* Add destination */ |
| 513 | addclosure(zz->sa_bitset, nf, ar->ar_arrow); |
| 514 | } |
| 515 | } |
| 516 | /* Now look up all the arrow states */ |
| 517 | for (jarc = 0; jarc < xx_state[istate].ss_narcs; jarc++) { |
| 518 | zz = &xx_state[istate].ss_arc[jarc]; |
| 519 | for (jstate = 0; jstate < xx_nstates; jstate++) { |
| 520 | if (samebitset(zz->sa_bitset, |
| 521 | xx_state[jstate].ss_ss, nbits)) { |
| 522 | zz->sa_arrow = jstate; |
| 523 | goto done; |
| 524 | } |
| 525 | } |
| 526 | RESIZE(xx_state, ss_state, xx_nstates + 1); |
| 527 | if (xx_state == NULL) |
| 528 | fatal("out of mem"); |
| 529 | zz->sa_arrow = xx_nstates; |
| 530 | yy = &xx_state[xx_nstates++]; |
| 531 | yy->ss_ss = zz->sa_bitset; |
| 532 | yy->ss_narcs = 0; |
| 533 | yy->ss_arc = NULL; |
| 534 | yy->ss_deleted = 0; |
| 535 | yy->ss_finish = testbit(yy->ss_ss, nf->nf_finish); |
| 536 | done: ; |
| 537 | } |
| 538 | } |
| 539 | |
| 540 | if (debugging) |
| 541 | printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll, |
| 542 | "before minimizing"); |
| 543 | |
| 544 | simplify(xx_nstates, xx_state); |
| 545 | |
| 546 | if (debugging) |
| 547 | printssdfa(xx_nstates, xx_state, nbits, &gr->gr_ll, |
| 548 | "after minimizing"); |
| 549 | |
| 550 | convert(d, xx_nstates, xx_state); |
| 551 | |
| 552 | /* XXX cleanup */ |
| 553 | } |
| 554 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 555 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 556 | printssdfa(xx_nstates, xx_state, nbits, ll, msg) |
| 557 | int xx_nstates; |
| 558 | ss_state *xx_state; |
| 559 | int nbits; |
| 560 | labellist *ll; |
| 561 | char *msg; |
| 562 | { |
| 563 | int i, ibit, iarc; |
| 564 | ss_state *yy; |
| 565 | ss_arc *zz; |
| 566 | |
| 567 | printf("Subset DFA %s\n", msg); |
| 568 | for (i = 0; i < xx_nstates; i++) { |
| 569 | yy = &xx_state[i]; |
| 570 | if (yy->ss_deleted) |
| 571 | continue; |
| 572 | printf(" Subset %d", i); |
| 573 | if (yy->ss_finish) |
| 574 | printf(" (finish)"); |
| 575 | printf(" { "); |
| 576 | for (ibit = 0; ibit < nbits; ibit++) { |
| 577 | if (testbit(yy->ss_ss, ibit)) |
| 578 | printf("%d ", ibit); |
| 579 | } |
| 580 | printf("}\n"); |
| 581 | for (iarc = 0; iarc < yy->ss_narcs; iarc++) { |
| 582 | zz = &yy->ss_arc[iarc]; |
| 583 | printf(" Arc to state %d, label %s\n", |
| 584 | zz->sa_arrow, |
| 585 | labelrepr(&ll->ll_label[zz->sa_label])); |
| 586 | } |
| 587 | } |
| 588 | } |
| 589 | |
| 590 | |
| 591 | /* PART THREE -- SIMPLIFY DFA */ |
| 592 | |
| 593 | /* Simplify the DFA by repeatedly eliminating states that are |
| 594 | equivalent to another oner. This is NOT Algorithm 3.3 from |
| 595 | [Aho&Ullman 77]. It does not always finds the minimal DFA, |
| 596 | but it does usually make a much smaller one... (For an example |
| 597 | of sub-optimal behaviour, try S: x a b+ | y a b+.) |
| 598 | */ |
| 599 | |
| 600 | static int |
| 601 | samestate(s1, s2) |
| 602 | ss_state *s1, *s2; |
| 603 | { |
| 604 | int i; |
| 605 | |
| 606 | if (s1->ss_narcs != s2->ss_narcs || s1->ss_finish != s2->ss_finish) |
| 607 | return 0; |
| 608 | for (i = 0; i < s1->ss_narcs; i++) { |
| 609 | if (s1->ss_arc[i].sa_arrow != s2->ss_arc[i].sa_arrow || |
| 610 | s1->ss_arc[i].sa_label != s2->ss_arc[i].sa_label) |
| 611 | return 0; |
| 612 | } |
| 613 | return 1; |
| 614 | } |
| 615 | |
| 616 | static void |
| 617 | renamestates(xx_nstates, xx_state, from, to) |
| 618 | int xx_nstates; |
| 619 | ss_state *xx_state; |
| 620 | int from, to; |
| 621 | { |
| 622 | int i, j; |
| 623 | |
| 624 | if (debugging) |
| 625 | printf("Rename state %d to %d.\n", from, to); |
| 626 | for (i = 0; i < xx_nstates; i++) { |
| 627 | if (xx_state[i].ss_deleted) |
| 628 | continue; |
| 629 | for (j = 0; j < xx_state[i].ss_narcs; j++) { |
| 630 | if (xx_state[i].ss_arc[j].sa_arrow == from) |
| 631 | xx_state[i].ss_arc[j].sa_arrow = to; |
| 632 | } |
| 633 | } |
| 634 | } |
| 635 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 636 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 637 | simplify(xx_nstates, xx_state) |
| 638 | int xx_nstates; |
| 639 | ss_state *xx_state; |
| 640 | { |
| 641 | int changes; |
Guido van Rossum | 588633d | 1994-12-30 15:46:02 +0000 | [diff] [blame] | 642 | int i, j; |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 643 | |
| 644 | do { |
| 645 | changes = 0; |
| 646 | for (i = 1; i < xx_nstates; i++) { |
| 647 | if (xx_state[i].ss_deleted) |
| 648 | continue; |
| 649 | for (j = 0; j < i; j++) { |
| 650 | if (xx_state[j].ss_deleted) |
| 651 | continue; |
| 652 | if (samestate(&xx_state[i], &xx_state[j])) { |
| 653 | xx_state[i].ss_deleted++; |
| 654 | renamestates(xx_nstates, xx_state, i, j); |
| 655 | changes++; |
| 656 | break; |
| 657 | } |
| 658 | } |
| 659 | } |
| 660 | } while (changes); |
| 661 | } |
| 662 | |
| 663 | |
| 664 | /* PART FOUR -- GENERATE PARSING TABLES */ |
| 665 | |
| 666 | /* Convert the DFA into a grammar that can be used by our parser */ |
| 667 | |
Guido van Rossum | fd8a393 | 1996-12-02 18:27:33 +0000 | [diff] [blame] | 668 | static void |
Guido van Rossum | 85a5fbb | 1990-10-14 12:07:46 +0000 | [diff] [blame] | 669 | convert(d, xx_nstates, xx_state) |
| 670 | dfa *d; |
| 671 | int xx_nstates; |
| 672 | ss_state *xx_state; |
| 673 | { |
| 674 | int i, j; |
| 675 | ss_state *yy; |
| 676 | ss_arc *zz; |
| 677 | |
| 678 | for (i = 0; i < xx_nstates; i++) { |
| 679 | yy = &xx_state[i]; |
| 680 | if (yy->ss_deleted) |
| 681 | continue; |
| 682 | yy->ss_rename = addstate(d); |
| 683 | } |
| 684 | |
| 685 | for (i = 0; i < xx_nstates; i++) { |
| 686 | yy = &xx_state[i]; |
| 687 | if (yy->ss_deleted) |
| 688 | continue; |
| 689 | for (j = 0; j < yy->ss_narcs; j++) { |
| 690 | zz = &yy->ss_arc[j]; |
| 691 | addarc(d, yy->ss_rename, |
| 692 | xx_state[zz->sa_arrow].ss_rename, |
| 693 | zz->sa_label); |
| 694 | } |
| 695 | if (yy->ss_finish) |
| 696 | addarc(d, yy->ss_rename, yy->ss_rename, 0); |
| 697 | } |
| 698 | |
| 699 | d->d_initial = 0; |
| 700 | } |
| 701 | |
| 702 | |
| 703 | /* PART FIVE -- GLUE IT ALL TOGETHER */ |
| 704 | |
| 705 | static grammar * |
| 706 | maketables(gr) |
| 707 | nfagrammar *gr; |
| 708 | { |
| 709 | int i; |
| 710 | nfa *nf; |
| 711 | dfa *d; |
| 712 | grammar *g; |
| 713 | |
| 714 | if (gr->gr_nnfas == 0) |
| 715 | return NULL; |
| 716 | g = newgrammar(gr->gr_nfa[0]->nf_type); |
| 717 | /* XXX first rule must be start rule */ |
| 718 | g->g_ll = gr->gr_ll; |
| 719 | |
| 720 | for (i = 0; i < gr->gr_nnfas; i++) { |
| 721 | nf = gr->gr_nfa[i]; |
| 722 | if (debugging) { |
| 723 | printf("Dump of NFA for '%s' ...\n", nf->nf_name); |
| 724 | dumpnfa(&gr->gr_ll, nf); |
| 725 | } |
| 726 | printf("Making DFA for '%s' ...\n", nf->nf_name); |
| 727 | d = adddfa(g, nf->nf_type, nf->nf_name); |
| 728 | makedfa(gr, gr->gr_nfa[i], d); |
| 729 | } |
| 730 | |
| 731 | return g; |
| 732 | } |
| 733 | |
| 734 | grammar * |
| 735 | pgen(n) |
| 736 | node *n; |
| 737 | { |
| 738 | nfagrammar *gr; |
| 739 | grammar *g; |
| 740 | |
| 741 | gr = metacompile(n); |
| 742 | g = maketables(gr); |
| 743 | translatelabels(g); |
| 744 | addfirstsets(g); |
| 745 | return g; |
| 746 | } |
| 747 | |
| 748 | |
| 749 | /* |
| 750 | |
| 751 | Description |
| 752 | ----------- |
| 753 | |
| 754 | Input is a grammar in extended BNF (using * for repetition, + for |
| 755 | at-least-once repetition, [] for optional parts, | for alternatives and |
| 756 | () for grouping). This has already been parsed and turned into a parse |
| 757 | tree. |
| 758 | |
| 759 | Each rule is considered as a regular expression in its own right. |
| 760 | It is turned into a Non-deterministic Finite Automaton (NFA), which |
| 761 | is then turned into a Deterministic Finite Automaton (DFA), which is then |
| 762 | optimized to reduce the number of states. See [Aho&Ullman 77] chapter 3, |
| 763 | or similar compiler books (this technique is more often used for lexical |
| 764 | analyzers). |
| 765 | |
| 766 | The DFA's are used by the parser as parsing tables in a special way |
| 767 | that's probably unique. Before they are usable, the FIRST sets of all |
| 768 | non-terminals are computed. |
| 769 | |
| 770 | Reference |
| 771 | --------- |
| 772 | |
| 773 | [Aho&Ullman 77] |
| 774 | Aho&Ullman, Principles of Compiler Design, Addison-Wesley 1977 |
| 775 | (first edition) |
| 776 | |
| 777 | */ |