1 /* $NetBSD: tblcmp.c,v 1.3 2014/10/30 18:44:05 christos Exp $ */
2
3 /* tblcmp - table compression routines */
4
5 /* Copyright (c) 1990 The Regents of the University of California. */
6 /* All rights reserved. */
7
8 /* This code is derived from software contributed to Berkeley by */
9 /* Vern Paxson. */
10
11 /* The United States Government has rights in this work pursuant */
12 /* to contract no. DE-AC03-76SF00098 between the United States */
13 /* Department of Energy and the University of California. */
14
15 /* This file is part of flex. */
16
17 /* Redistribution and use in source and binary forms, with or without */
18 /* modification, are permitted provided that the following conditions */
19 /* are met: */
20
21 /* 1. Redistributions of source code must retain the above copyright */
22 /* notice, this list of conditions and the following disclaimer. */
23 /* 2. Redistributions in binary form must reproduce the above copyright */
24 /* notice, this list of conditions and the following disclaimer in the */
25 /* documentation and/or other materials provided with the distribution. */
26
27 /* Neither the name of the University nor the names of its contributors */
28 /* may be used to endorse or promote products derived from this software */
29 /* without specific prior written permission. */
30
31 /* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR */
32 /* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED */
33 /* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR */
34 /* PURPOSE. */
35 #include "flexdef.h"
36 __RCSID("$NetBSD: tblcmp.c,v 1.3 2014/10/30 18:44:05 christos Exp $");
37
38
39
40 /* declarations for functions that have forward references */
41
42 void mkentry PROTO ((register int *, int, int, int, int));
43 void mkprot PROTO ((int[], int, int));
44 void mktemplate PROTO ((int[], int, int));
45 void mv2front PROTO ((int));
46 int tbldiff PROTO ((int[], int, int[]));
47
48
49 /* bldtbl - build table entries for dfa state
50 *
51 * synopsis
52 * int state[numecs], statenum, totaltrans, comstate, comfreq;
53 * bldtbl( state, statenum, totaltrans, comstate, comfreq );
54 *
55 * State is the statenum'th dfa state. It is indexed by equivalence class and
56 * gives the number of the state to enter for a given equivalence class.
57 * totaltrans is the total number of transitions out of the state. Comstate
58 * is that state which is the destination of the most transitions out of State.
59 * Comfreq is how many transitions there are out of State to Comstate.
60 *
61 * A note on terminology:
62 * "protos" are transition tables which have a high probability of
63 * either being redundant (a state processed later will have an identical
64 * transition table) or nearly redundant (a state processed later will have
65 * many of the same out-transitions). A "most recently used" queue of
66 * protos is kept around with the hope that most states will find a proto
67 * which is similar enough to be usable, and therefore compacting the
68 * output tables.
69 * "templates" are a special type of proto. If a transition table is
70 * homogeneous or nearly homogeneous (all transitions go to the same
71 * destination) then the odds are good that future states will also go
72 * to the same destination state on basically the same character set.
73 * These homogeneous states are so common when dealing with large rule
74 * sets that they merit special attention. If the transition table were
75 * simply made into a proto, then (typically) each subsequent, similar
76 * state will differ from the proto for two out-transitions. One of these
77 * out-transitions will be that character on which the proto does not go
78 * to the common destination, and one will be that character on which the
79 * state does not go to the common destination. Templates, on the other
80 * hand, go to the common state on EVERY transition character, and therefore
81 * cost only one difference.
82 */
83
bldtbl(state,statenum,totaltrans,comstate,comfreq)84 void bldtbl (state, statenum, totaltrans, comstate, comfreq)
85 int state[], statenum, totaltrans, comstate, comfreq;
86 {
87 int extptr, extrct[2][CSIZE + 1];
88 int mindiff, minprot, i, d;
89
90 /* If extptr is 0 then the first array of extrct holds the result
91 * of the "best difference" to date, which is those transitions
92 * which occur in "state" but not in the proto which, to date,
93 * has the fewest differences between itself and "state". If
94 * extptr is 1 then the second array of extrct hold the best
95 * difference. The two arrays are toggled between so that the
96 * best difference to date can be kept around and also a difference
97 * just created by checking against a candidate "best" proto.
98 */
99
100 extptr = 0;
101
102 /* If the state has too few out-transitions, don't bother trying to
103 * compact its tables.
104 */
105
106 if ((totaltrans * 100) < (numecs * PROTO_SIZE_PERCENTAGE))
107 mkentry (state, numecs, statenum, JAMSTATE, totaltrans);
108
109 else {
110 /* "checkcom" is true if we should only check "state" against
111 * protos which have the same "comstate" value.
112 */
113 int checkcom =
114
115 comfreq * 100 > totaltrans * CHECK_COM_PERCENTAGE;
116
117 minprot = firstprot;
118 mindiff = totaltrans;
119
120 if (checkcom) {
121 /* Find first proto which has the same "comstate". */
122 for (i = firstprot; i != NIL; i = protnext[i])
123 if (protcomst[i] == comstate) {
124 minprot = i;
125 mindiff = tbldiff (state, minprot,
126 extrct[extptr]);
127 break;
128 }
129 }
130
131 else {
132 /* Since we've decided that the most common destination
133 * out of "state" does not occur with a high enough
134 * frequency, we set the "comstate" to zero, assuring
135 * that if this state is entered into the proto list,
136 * it will not be considered a template.
137 */
138 comstate = 0;
139
140 if (firstprot != NIL) {
141 minprot = firstprot;
142 mindiff = tbldiff (state, minprot,
143 extrct[extptr]);
144 }
145 }
146
147 /* We now have the first interesting proto in "minprot". If
148 * it matches within the tolerances set for the first proto,
149 * we don't want to bother scanning the rest of the proto list
150 * to see if we have any other reasonable matches.
151 */
152
153 if (mindiff * 100 >
154 totaltrans * FIRST_MATCH_DIFF_PERCENTAGE) {
155 /* Not a good enough match. Scan the rest of the
156 * protos.
157 */
158 for (i = minprot; i != NIL; i = protnext[i]) {
159 d = tbldiff (state, i, extrct[1 - extptr]);
160 if (d < mindiff) {
161 extptr = 1 - extptr;
162 mindiff = d;
163 minprot = i;
164 }
165 }
166 }
167
168 /* Check if the proto we've decided on as our best bet is close
169 * enough to the state we want to match to be usable.
170 */
171
172 if (mindiff * 100 >
173 totaltrans * ACCEPTABLE_DIFF_PERCENTAGE) {
174 /* No good. If the state is homogeneous enough,
175 * we make a template out of it. Otherwise, we
176 * make a proto.
177 */
178
179 if (comfreq * 100 >=
180 totaltrans * TEMPLATE_SAME_PERCENTAGE)
181 mktemplate (state, statenum,
182 comstate);
183
184 else {
185 mkprot (state, statenum, comstate);
186 mkentry (state, numecs, statenum,
187 JAMSTATE, totaltrans);
188 }
189 }
190
191 else { /* use the proto */
192 mkentry (extrct[extptr], numecs, statenum,
193 prottbl[minprot], mindiff);
194
195 /* If this state was sufficiently different from the
196 * proto we built it from, make it, too, a proto.
197 */
198
199 if (mindiff * 100 >=
200 totaltrans * NEW_PROTO_DIFF_PERCENTAGE)
201 mkprot (state, statenum, comstate);
202
203 /* Since mkprot added a new proto to the proto queue,
204 * it's possible that "minprot" is no longer on the
205 * proto queue (if it happened to have been the last
206 * entry, it would have been bumped off). If it's
207 * not there, then the new proto took its physical
208 * place (though logically the new proto is at the
209 * beginning of the queue), so in that case the
210 * following call will do nothing.
211 */
212
213 mv2front (minprot);
214 }
215 }
216 }
217
218
219 /* cmptmps - compress template table entries
220 *
221 * Template tables are compressed by using the 'template equivalence
222 * classes', which are collections of transition character equivalence
223 * classes which always appear together in templates - really meta-equivalence
224 * classes.
225 */
226
cmptmps()227 void cmptmps ()
228 {
229 int tmpstorage[CSIZE + 1];
230 register int *tmp = tmpstorage, i, j;
231 int totaltrans, trans;
232
233 peakpairs = numtemps * numecs + tblend;
234
235 if (usemecs) {
236 /* Create equivalence classes based on data gathered on
237 * template transitions.
238 */
239 nummecs = cre8ecs (tecfwd, tecbck, numecs);
240 }
241
242 else
243 nummecs = numecs;
244
245 while (lastdfa + numtemps + 1 >= current_max_dfas)
246 increase_max_dfas ();
247
248 /* Loop through each template. */
249
250 for (i = 1; i <= numtemps; ++i) {
251 /* Number of non-jam transitions out of this template. */
252 totaltrans = 0;
253
254 for (j = 1; j <= numecs; ++j) {
255 trans = tnxt[numecs * i + j];
256
257 if (usemecs) {
258 /* The absolute value of tecbck is the
259 * meta-equivalence class of a given
260 * equivalence class, as set up by cre8ecs().
261 */
262 if (tecbck[j] > 0) {
263 tmp[tecbck[j]] = trans;
264
265 if (trans > 0)
266 ++totaltrans;
267 }
268 }
269
270 else {
271 tmp[j] = trans;
272
273 if (trans > 0)
274 ++totaltrans;
275 }
276 }
277
278 /* It is assumed (in a rather subtle way) in the skeleton
279 * that if we're using meta-equivalence classes, the def[]
280 * entry for all templates is the jam template, i.e.,
281 * templates never default to other non-jam table entries
282 * (e.g., another template)
283 */
284
285 /* Leave room for the jam-state after the last real state. */
286 mkentry (tmp, nummecs, lastdfa + i + 1, JAMSTATE,
287 totaltrans);
288 }
289 }
290
291
292
293 /* expand_nxt_chk - expand the next check arrays */
294
expand_nxt_chk()295 void expand_nxt_chk ()
296 {
297 register int old_max = current_max_xpairs;
298
299 current_max_xpairs += MAX_XPAIRS_INCREMENT;
300
301 ++num_reallocs;
302
303 nxt = reallocate_integer_array (nxt, current_max_xpairs);
304 chk = reallocate_integer_array (chk, current_max_xpairs);
305
306 zero_out ((char *) (chk + old_max),
307 (size_t) (MAX_XPAIRS_INCREMENT * sizeof (int)));
308 }
309
310
311 /* find_table_space - finds a space in the table for a state to be placed
312 *
313 * synopsis
314 * int *state, numtrans, block_start;
315 * int find_table_space();
316 *
317 * block_start = find_table_space( state, numtrans );
318 *
319 * State is the state to be added to the full speed transition table.
320 * Numtrans is the number of out-transitions for the state.
321 *
322 * find_table_space() returns the position of the start of the first block (in
323 * chk) able to accommodate the state
324 *
325 * In determining if a state will or will not fit, find_table_space() must take
326 * into account the fact that an end-of-buffer state will be added at [0],
327 * and an action number will be added in [-1].
328 */
329
find_table_space(state,numtrans)330 int find_table_space (state, numtrans)
331 int *state, numtrans;
332 {
333 /* Firstfree is the position of the first possible occurrence of two
334 * consecutive unused records in the chk and nxt arrays.
335 */
336 register int i;
337 register int *state_ptr, *chk_ptr;
338 register int *ptr_to_last_entry_in_state;
339
340 /* If there are too many out-transitions, put the state at the end of
341 * nxt and chk.
342 */
343 if (numtrans > MAX_XTIONS_FULL_INTERIOR_FIT) {
344 /* If table is empty, return the first available spot in
345 * chk/nxt, which should be 1.
346 */
347 if (tblend < 2)
348 return 1;
349
350 /* Start searching for table space near the end of
351 * chk/nxt arrays.
352 */
353 i = tblend - numecs;
354 }
355
356 else
357 /* Start searching for table space from the beginning
358 * (skipping only the elements which will definitely not
359 * hold the new state).
360 */
361 i = firstfree;
362
363 while (1) { /* loops until a space is found */
364 while (i + numecs >= current_max_xpairs)
365 expand_nxt_chk ();
366
367 /* Loops until space for end-of-buffer and action number
368 * are found.
369 */
370 while (1) {
371 /* Check for action number space. */
372 if (chk[i - 1] == 0) {
373 /* Check for end-of-buffer space. */
374 if (chk[i] == 0)
375 break;
376
377 else
378 /* Since i != 0, there is no use
379 * checking to see if (++i) - 1 == 0,
380 * because that's the same as i == 0,
381 * so we skip a space.
382 */
383 i += 2;
384 }
385
386 else
387 ++i;
388
389 while (i + numecs >= current_max_xpairs)
390 expand_nxt_chk ();
391 }
392
393 /* If we started search from the beginning, store the new
394 * firstfree for the next call of find_table_space().
395 */
396 if (numtrans <= MAX_XTIONS_FULL_INTERIOR_FIT)
397 firstfree = i + 1;
398
399 /* Check to see if all elements in chk (and therefore nxt)
400 * that are needed for the new state have not yet been taken.
401 */
402
403 state_ptr = &state[1];
404 ptr_to_last_entry_in_state = &chk[i + numecs + 1];
405
406 for (chk_ptr = &chk[i + 1];
407 chk_ptr != ptr_to_last_entry_in_state; ++chk_ptr)
408 if (*(state_ptr++) != 0 && *chk_ptr != 0)
409 break;
410
411 if (chk_ptr == ptr_to_last_entry_in_state)
412 return i;
413
414 else
415 ++i;
416 }
417 }
418
419
420 /* inittbl - initialize transition tables
421 *
422 * Initializes "firstfree" to be one beyond the end of the table. Initializes
423 * all "chk" entries to be zero.
424 */
inittbl()425 void inittbl ()
426 {
427 register int i;
428
429 zero_out ((char *) chk,
430
431 (size_t) (current_max_xpairs * sizeof (int)));
432
433 tblend = 0;
434 firstfree = tblend + 1;
435 numtemps = 0;
436
437 if (usemecs) {
438 /* Set up doubly-linked meta-equivalence classes; these
439 * are sets of equivalence classes which all have identical
440 * transitions out of TEMPLATES.
441 */
442
443 tecbck[1] = NIL;
444
445 for (i = 2; i <= numecs; ++i) {
446 tecbck[i] = i - 1;
447 tecfwd[i - 1] = i;
448 }
449
450 tecfwd[numecs] = NIL;
451 }
452 }
453
454
455 /* mkdeftbl - make the default, "jam" table entries */
456
mkdeftbl()457 void mkdeftbl ()
458 {
459 int i;
460
461 jamstate = lastdfa + 1;
462
463 ++tblend; /* room for transition on end-of-buffer character */
464
465 while (tblend + numecs >= current_max_xpairs)
466 expand_nxt_chk ();
467
468 /* Add in default end-of-buffer transition. */
469 nxt[tblend] = end_of_buffer_state;
470 chk[tblend] = jamstate;
471
472 for (i = 1; i <= numecs; ++i) {
473 nxt[tblend + i] = 0;
474 chk[tblend + i] = jamstate;
475 }
476
477 jambase = tblend;
478
479 base[jamstate] = jambase;
480 def[jamstate] = 0;
481
482 tblend += numecs;
483 ++numtemps;
484 }
485
486
487 /* mkentry - create base/def and nxt/chk entries for transition array
488 *
489 * synopsis
490 * int state[numchars + 1], numchars, statenum, deflink, totaltrans;
491 * mkentry( state, numchars, statenum, deflink, totaltrans );
492 *
493 * "state" is a transition array "numchars" characters in size, "statenum"
494 * is the offset to be used into the base/def tables, and "deflink" is the
495 * entry to put in the "def" table entry. If "deflink" is equal to
496 * "JAMSTATE", then no attempt will be made to fit zero entries of "state"
497 * (i.e., jam entries) into the table. It is assumed that by linking to
498 * "JAMSTATE" they will be taken care of. In any case, entries in "state"
499 * marking transitions to "SAME_TRANS" are treated as though they will be
500 * taken care of by whereever "deflink" points. "totaltrans" is the total
501 * number of transitions out of the state. If it is below a certain threshold,
502 * the tables are searched for an interior spot that will accommodate the
503 * state array.
504 */
505
mkentry(state,numchars,statenum,deflink,totaltrans)506 void mkentry (state, numchars, statenum, deflink, totaltrans)
507 register int *state;
508 int numchars, statenum, deflink, totaltrans;
509 {
510 register int minec, maxec, i, baseaddr;
511 int tblbase, tbllast;
512
513 if (totaltrans == 0) { /* there are no out-transitions */
514 if (deflink == JAMSTATE)
515 base[statenum] = JAMSTATE;
516 else
517 base[statenum] = 0;
518
519 def[statenum] = deflink;
520 return;
521 }
522
523 for (minec = 1; minec <= numchars; ++minec) {
524 if (state[minec] != SAME_TRANS)
525 if (state[minec] != 0 || deflink != JAMSTATE)
526 break;
527 }
528
529 if (totaltrans == 1) {
530 /* There's only one out-transition. Save it for later to fill
531 * in holes in the tables.
532 */
533 stack1 (statenum, minec, state[minec], deflink);
534 return;
535 }
536
537 for (maxec = numchars; maxec > 0; --maxec) {
538 if (state[maxec] != SAME_TRANS)
539 if (state[maxec] != 0 || deflink != JAMSTATE)
540 break;
541 }
542
543 /* Whether we try to fit the state table in the middle of the table
544 * entries we have already generated, or if we just take the state
545 * table at the end of the nxt/chk tables, we must make sure that we
546 * have a valid base address (i.e., non-negative). Note that
547 * negative base addresses dangerous at run-time (because indexing
548 * the nxt array with one and a low-valued character will access
549 * memory before the start of the array.
550 */
551
552 /* Find the first transition of state that we need to worry about. */
553 if (totaltrans * 100 <= numchars * INTERIOR_FIT_PERCENTAGE) {
554 /* Attempt to squeeze it into the middle of the tables. */
555 baseaddr = firstfree;
556
557 while (baseaddr < minec) {
558 /* Using baseaddr would result in a negative base
559 * address below; find the next free slot.
560 */
561 for (++baseaddr; chk[baseaddr] != 0; ++baseaddr) ;
562 }
563
564 while (baseaddr + maxec - minec + 1 >= current_max_xpairs)
565 expand_nxt_chk ();
566
567 for (i = minec; i <= maxec; ++i)
568 if (state[i] != SAME_TRANS &&
569 (state[i] != 0 || deflink != JAMSTATE) &&
570 chk[baseaddr + i - minec] != 0) { /* baseaddr unsuitable - find another */
571 for (++baseaddr;
572 baseaddr < current_max_xpairs &&
573 chk[baseaddr] != 0; ++baseaddr) ;
574
575 while (baseaddr + maxec - minec + 1 >=
576 current_max_xpairs)
577 expand_nxt_chk ();
578
579 /* Reset the loop counter so we'll start all
580 * over again next time it's incremented.
581 */
582
583 i = minec - 1;
584 }
585 }
586
587 else {
588 /* Ensure that the base address we eventually generate is
589 * non-negative.
590 */
591 baseaddr = MAX (tblend + 1, minec);
592 }
593
594 tblbase = baseaddr - minec;
595 tbllast = tblbase + maxec;
596
597 while (tbllast + 1 >= current_max_xpairs)
598 expand_nxt_chk ();
599
600 base[statenum] = tblbase;
601 def[statenum] = deflink;
602
603 for (i = minec; i <= maxec; ++i)
604 if (state[i] != SAME_TRANS)
605 if (state[i] != 0 || deflink != JAMSTATE) {
606 nxt[tblbase + i] = state[i];
607 chk[tblbase + i] = statenum;
608 }
609
610 if (baseaddr == firstfree)
611 /* Find next free slot in tables. */
612 for (++firstfree; chk[firstfree] != 0; ++firstfree) ;
613
614 tblend = MAX (tblend, tbllast);
615 }
616
617
618 /* mk1tbl - create table entries for a state (or state fragment) which
619 * has only one out-transition
620 */
621
mk1tbl(state,sym,onenxt,onedef)622 void mk1tbl (state, sym, onenxt, onedef)
623 int state, sym, onenxt, onedef;
624 {
625 if (firstfree < sym)
626 firstfree = sym;
627
628 while (chk[firstfree] != 0)
629 if (++firstfree >= current_max_xpairs)
630 expand_nxt_chk ();
631
632 base[state] = firstfree - sym;
633 def[state] = onedef;
634 chk[firstfree] = state;
635 nxt[firstfree] = onenxt;
636
637 if (firstfree > tblend) {
638 tblend = firstfree++;
639
640 if (firstfree >= current_max_xpairs)
641 expand_nxt_chk ();
642 }
643 }
644
645
646 /* mkprot - create new proto entry */
647
mkprot(state,statenum,comstate)648 void mkprot (state, statenum, comstate)
649 int state[], statenum, comstate;
650 {
651 int i, slot, tblbase;
652
653 if (++numprots >= MSP || numecs * numprots >= PROT_SAVE_SIZE) {
654 /* Gotta make room for the new proto by dropping last entry in
655 * the queue.
656 */
657 slot = lastprot;
658 lastprot = protprev[lastprot];
659 protnext[lastprot] = NIL;
660 }
661
662 else
663 slot = numprots;
664
665 protnext[slot] = firstprot;
666
667 if (firstprot != NIL)
668 protprev[firstprot] = slot;
669
670 firstprot = slot;
671 prottbl[slot] = statenum;
672 protcomst[slot] = comstate;
673
674 /* Copy state into save area so it can be compared with rapidly. */
675 tblbase = numecs * (slot - 1);
676
677 for (i = 1; i <= numecs; ++i)
678 protsave[tblbase + i] = state[i];
679 }
680
681
682 /* mktemplate - create a template entry based on a state, and connect the state
683 * to it
684 */
685
mktemplate(state,statenum,comstate)686 void mktemplate (state, statenum, comstate)
687 int state[], statenum, comstate;
688 {
689 int i, numdiff, tmpbase, tmp[CSIZE + 1];
690 Char transset[CSIZE + 1];
691 int tsptr;
692
693 ++numtemps;
694
695 tsptr = 0;
696
697 /* Calculate where we will temporarily store the transition table
698 * of the template in the tnxt[] array. The final transition table
699 * gets created by cmptmps().
700 */
701
702 tmpbase = numtemps * numecs;
703
704 if (tmpbase + numecs >= current_max_template_xpairs) {
705 current_max_template_xpairs +=
706 MAX_TEMPLATE_XPAIRS_INCREMENT;
707
708 ++num_reallocs;
709
710 tnxt = reallocate_integer_array (tnxt,
711 current_max_template_xpairs);
712 }
713
714 for (i = 1; i <= numecs; ++i)
715 if (state[i] == 0)
716 tnxt[tmpbase + i] = 0;
717 else {
718 transset[tsptr++] = i;
719 tnxt[tmpbase + i] = comstate;
720 }
721
722 if (usemecs)
723 mkeccl (transset, tsptr, tecfwd, tecbck, numecs, 0);
724
725 mkprot (tnxt + tmpbase, -numtemps, comstate);
726
727 /* We rely on the fact that mkprot adds things to the beginning
728 * of the proto queue.
729 */
730
731 numdiff = tbldiff (state, firstprot, tmp);
732 mkentry (tmp, numecs, statenum, -numtemps, numdiff);
733 }
734
735
736 /* mv2front - move proto queue element to front of queue */
737
mv2front(qelm)738 void mv2front (qelm)
739 int qelm;
740 {
741 if (firstprot != qelm) {
742 if (qelm == lastprot)
743 lastprot = protprev[lastprot];
744
745 protnext[protprev[qelm]] = protnext[qelm];
746
747 if (protnext[qelm] != NIL)
748 protprev[protnext[qelm]] = protprev[qelm];
749
750 protprev[qelm] = NIL;
751 protnext[qelm] = firstprot;
752 protprev[firstprot] = qelm;
753 firstprot = qelm;
754 }
755 }
756
757
758 /* place_state - place a state into full speed transition table
759 *
760 * State is the statenum'th state. It is indexed by equivalence class and
761 * gives the number of the state to enter for a given equivalence class.
762 * Transnum is the number of out-transitions for the state.
763 */
764
place_state(state,statenum,transnum)765 void place_state (state, statenum, transnum)
766 int *state, statenum, transnum;
767 {
768 register int i;
769 register int *state_ptr;
770 int position = find_table_space (state, transnum);
771
772 /* "base" is the table of start positions. */
773 base[statenum] = position;
774
775 /* Put in action number marker; this non-zero number makes sure that
776 * find_table_space() knows that this position in chk/nxt is taken
777 * and should not be used for another accepting number in another
778 * state.
779 */
780 chk[position - 1] = 1;
781
782 /* Put in end-of-buffer marker; this is for the same purposes as
783 * above.
784 */
785 chk[position] = 1;
786
787 /* Place the state into chk and nxt. */
788 state_ptr = &state[1];
789
790 for (i = 1; i <= numecs; ++i, ++state_ptr)
791 if (*state_ptr != 0) {
792 chk[position + i] = i;
793 nxt[position + i] = *state_ptr;
794 }
795
796 if (position + numecs > tblend)
797 tblend = position + numecs;
798 }
799
800
801 /* stack1 - save states with only one out-transition to be processed later
802 *
803 * If there's room for another state on the "one-transition" stack, the
804 * state is pushed onto it, to be processed later by mk1tbl. If there's
805 * no room, we process the sucker right now.
806 */
807
stack1(statenum,sym,nextstate,deflink)808 void stack1 (statenum, sym, nextstate, deflink)
809 int statenum, sym, nextstate, deflink;
810 {
811 if (onesp >= ONE_STACK_SIZE - 1)
812 mk1tbl (statenum, sym, nextstate, deflink);
813
814 else {
815 ++onesp;
816 onestate[onesp] = statenum;
817 onesym[onesp] = sym;
818 onenext[onesp] = nextstate;
819 onedef[onesp] = deflink;
820 }
821 }
822
823
824 /* tbldiff - compute differences between two state tables
825 *
826 * "state" is the state array which is to be extracted from the pr'th
827 * proto. "pr" is both the number of the proto we are extracting from
828 * and an index into the save area where we can find the proto's complete
829 * state table. Each entry in "state" which differs from the corresponding
830 * entry of "pr" will appear in "ext".
831 *
832 * Entries which are the same in both "state" and "pr" will be marked
833 * as transitions to "SAME_TRANS" in "ext". The total number of differences
834 * between "state" and "pr" is returned as function value. Note that this
835 * number is "numecs" minus the number of "SAME_TRANS" entries in "ext".
836 */
837
tbldiff(state,pr,ext)838 int tbldiff (state, pr, ext)
839 int state[], pr, ext[];
840 {
841 register int i, *sp = state, *ep = ext, *protp;
842 register int numdiff = 0;
843
844 protp = &protsave[numecs * (pr - 1)];
845
846 for (i = numecs; i > 0; --i) {
847 if (*++protp == *++sp)
848 *++ep = SAME_TRANS;
849 else {
850 *++ep = *sp;
851 ++numdiff;
852 }
853 }
854
855 return numdiff;
856 }
857