regexec.c

   1 /* NOTE: this is derived from Henry Spencer's regexp code, and should not
   2  * confused with the original package (see point 3 below).  Thanks, Henry!
   3  */
   4
   5 /* Additional note: this code is very heavily munged from Henry's version
   6  * in places.  In some spots I've traded clarity for efficiency, so don't
   7  * blame Henry for some of the lack of readability.
   8  */
   9
  10 /* $RCSfile: regexec.c,v $$Revision: 4.0.1.4 $$Date: 92/06/08 15:25:50 $
  11  *
  12  * $Log:        regexec.c,v $
  13  * Revision 4.0.1.4  92/06/08  15:25:50  lwall
  14  * patch20: pattern modifiers i and g didn't interact right
  15  * patch20: in some cases $` and $' didn't get set by match
  16  * patch20: /x{0}/ was wrongly interpreted as /x{0,}/
  17  *
  18  * Revision 4.0.1.3  91/11/05  18:23:55  lwall
  19  * patch11: prepared for ctype implementations that don't define isascii()
  20  * patch11: initial .* in pattern had dependency on value of $*
  21  *
  22  * Revision 4.0.1.2  91/06/07  11:50:33  lwall
  23  * patch4: new copyright notice
  24  * patch4: // wouldn't use previous pattern if it started with a null character
  25  *
  26  * Revision 4.0.1.1  91/04/12  09:07:39  lwall
  27  * patch1: regexec only allocated space for 9 subexpresssions
  28  *
  29  * Revision 4.0  91/03/20  01:39:16  lwall
  30  * 4.0 baseline.
  31  *
  32  */
  33 /*SUPPRESS 112*/
  34 /*
  35  * regcomp and regexec -- regsub and regerror are not used in perl
  36  *
  37  *      Copyright (c) 1986 by University of Toronto.
  38  *      Written by Henry Spencer.  Not derived from licensed software.
  39  *
  40  *      Permission is granted to anyone to use this software for any
  41  *      purpose on any computer system, and to redistribute it freely,
  42  *      subject to the following restrictions:
  43  *
  44  *      1. The author is not responsible for the consequences of use of
  45  *              this software, no matter how awful, even if they arise
  46  *              from defects in it.
  47  *
  48  *      2. The origin of this software must not be misrepresented, either
  49  *              by explicit claim or by omission.
  50  *
  51  *      3. Altered versions must be plainly marked as such, and must not
  52  *              be misrepresented as being the original software.
  53  *
  54  ****    Alterations to Henry's code are...
  55  ****
  56  ****    Copyright (c) 1991, Larry Wall
  57  ****
  58  ****    You may distribute under the terms of either the GNU General Public
  59  ****    License or the Artistic License, as specified in the README file.
  60  *
  61  * Beware that some of this code is subtly aware of the way operator
  62  * precedence is structured in regular expressions.  Serious changes in
  63  * regular-expression syntax might require a total rethink.
  64  */
  65 #include "EXTERN.h"
  66 #include "perl.h"
  67 #include "regcomp.h"
  68
  69 #ifndef STATIC
  70 #define STATIC  static
  71 #endif
  72
  73 #ifdef DEBUGGING
  74 int regnarrate = 0;
  75 #endif
  76
  77 /*
  78  * regexec and friends
  79  */
  80
  81 /*
  82  * Global work variables for regexec().
  83  */
  84 static char *regprecomp;
  85 static char *reginput;          /* String-input pointer. */
  86 static char regprev;            /* char before regbol, \n if none */
  87 static char *regbol;            /* Beginning of input, for ^ check. */
  88 static char *regeol;            /* End of input, for $ check. */
  89 static char **regstartp;        /* Pointer to startp array. */
  90 static char **regendp;          /* Ditto for endp. */
  91 static char *reglastparen;      /* Similarly for lastparen. */
  92 static char *regtill;
  93
  94 static int regmyp_size = 0;
  95 static char **regmystartp = Null(char**);
  96 static char **regmyendp   = Null(char**);
  97
  98 /*
  99  * Forwards.
 100  */
 101 STATIC int regtry();
 102 STATIC int regmatch();
 103 STATIC int regrepeat();
 104
 105 extern int multiline;
 106
 107 /*
 108  - regexec - match a regexp against a string
 109  */
 110 int
 111 regexec(prog, stringarg, strend, strbeg, minend, screamer, safebase)
 112 register regexp *prog;
 113 char *stringarg;
 114 register char *strend;  /* pointer to null at end of string */
 115 char *strbeg;   /* real beginning of string */
 116 int minend;     /* end of match must be at least minend after stringarg */
 117 STR *screamer;
 118 int safebase;   /* no need to remember string in subbase */
 119 {
 120         register char *s;
 121         register int i;
 122         register char *c;
 123         register char *string = stringarg;
 124         register int tmp;
 125         int minlen = 0;         /* must match at least this many chars */
 126         int dontbother = 0;     /* how many characters not to try at end */
 127
 128         /* Be paranoid... */
 129         if (prog == NULL || string == NULL) {
 130                 fatal("NULL regexp parameter");
 131                 return(0);
 132         }
 133
 134         if (string == strbeg)   /* is ^ valid at stringarg? */
 135             regprev = '\n';
 136         else {
 137             regprev = stringarg[-1];
 138             if (!multiline && regprev == '\n')
 139                 regprev = '\0';         /* force ^ to NOT match */
 140         }
 141         regprecomp = prog->precomp;
 142         /* Check validity of program. */
 143         if (UCHARAT(prog->program) != MAGIC) {
 144                 FAIL("corrupted regexp program");
 145         }
 146
 147         if (prog->do_folding) {
 148                 i = strend - string;
 149                 New(1101,c,i+1,char);
 150                 Copy(string, c, i+1, char);
 151                 string = c;
 152                 strend = string + i;
 153                 for (s = string; s < strend; s++)
 154                         if (isUPPER(*s))
 155                                 *s = tolower(*s);
 156         }
 157
 158         /* If there is a "must appear" string, look for it. */
 159         s = string;
 160         if (prog->regmust != Nullstr &&
 161             (!(prog->reganch & ROPT_ANCH)
 162              || (multiline && prog->regback >= 0)) ) {
 163                 if (stringarg == strbeg && screamer) {
 164                         if (screamfirst[prog->regmust->str_rare] >= 0)
 165                                 s = screaminstr(screamer,prog->regmust);
 166                         else
 167                                 s = Nullch;
 168                 }
 169 #ifndef lint
 170                 else
 171                         s = fbminstr((unsigned char*)s, (unsigned char*)strend,
 172                             prog->regmust);
 173 #endif
 174                 if (!s) {
 175                         ++prog->regmust->str_u.str_useful;      /* hooray */
 176                         goto phooey;    /* not present */
 177                 }
 178                 else if (prog->regback >= 0) {
 179                         s -= prog->regback;
 180                         if (s < string)
 181                             s = string;
 182                         minlen = prog->regback + prog->regmust->str_cur;
 183                 }
 184                 else if (--prog->regmust->str_u.str_useful < 0) { /* boo */
 185                         str_free(prog->regmust);
 186                         prog->regmust = Nullstr;        /* disable regmust */
 187                         s = string;
 188                 }
 189                 else {
 190                         s = string;
 191                         minlen = prog->regmust->str_cur;
 192                 }
 193         }
 194
 195         /* Mark beginning of line for ^ . */
 196         regbol = string;
 197
 198         /* Mark end of line for $ (and such) */
 199         regeol = strend;
 200
 201         /* see how far we have to get to not match where we matched before */
 202         regtill = string+minend;
 203
 204         /* Allocate our backreference arrays */
 205         if ( regmyp_size < prog->nparens + 1 ) {
 206             /* Allocate or enlarge the arrays */
 207             regmyp_size = prog->nparens + 1;
 208             if ( regmyp_size < 10 ) regmyp_size = 10;   /* minimum */
 209             if ( regmystartp ) {
 210                 /* reallocate larger */
 211                 Renew(regmystartp,regmyp_size,char*);
 212                 Renew(regmyendp,  regmyp_size,char*);
 213             }
 214             else {
 215                 /* Initial allocation */
 216                 New(1102,regmystartp,regmyp_size,char*);
 217                 New(1102,regmyendp,  regmyp_size,char*);
 218             }
 219
 220         }
 221
 222         /* Simplest case:  anchored match need be tried only once. */
 223         /*  [unless multiline is set] */
 224         if (prog->reganch & ROPT_ANCH) {
 225                 if (regtry(prog, string))
 226                         goto got_it;
 227                 else if (multiline || (prog->reganch & ROPT_IMPLICIT)) {
 228                         if (minlen)
 229                             dontbother = minlen - 1;
 230                         strend -= dontbother;
 231                         /* for multiline we only have to try after newlines */
 232                         if (s > string)
 233                             s--;
 234                         while (s < strend) {
 235                             if (*s++ == '\n') {
 236                                 if (s < strend && regtry(prog, s))
 237                                     goto got_it;
 238                             }
 239                         }
 240                 }
 241                 goto phooey;
 242         }
 243
 244         /* Messy cases:  unanchored match. */
 245         if (prog->regstart) {
 246                 if (prog->reganch & ROPT_SKIP) {  /* we have /x+whatever/ */
 247                     /* it must be a one character string */
 248                     i = prog->regstart->str_ptr[0];
 249                     while (s < strend) {
 250                             if (*s == i) {
 251                                     if (regtry(prog, s))
 252                                             goto got_it;
 253                                     s++;
 254                                     while (s < strend && *s == i)
 255                                         s++;
 256                             }
 257                             s++;
 258                     }
 259                 }
 260                 else if (prog->regstart->str_pok == 3) {
 261                     /* We know what string it must start with. */
 262 #ifndef lint
 263                     while ((s = fbminstr((unsigned char*)s,
 264                       (unsigned char*)strend, prog->regstart)) != NULL)
 265 #else
 266                     while (s = Nullch)
 267 #endif
 268                     {
 269                             if (regtry(prog, s))
 270                                     goto got_it;
 271                             s++;
 272                     }
 273                 }
 274                 else {
 275                     c = prog->regstart->str_ptr;
 276                     while ((s = ninstr(s, strend,
 277                       c, c + prog->regstart->str_cur )) != NULL) {
 278                             if (regtry(prog, s))
 279                                     goto got_it;
 280                             s++;
 281                     }
 282                 }
 283                 goto phooey;
 284         }
 285         /*SUPPRESS 560*/
 286         if (c = prog->regstclass) {
 287                 int doevery = (prog->reganch & ROPT_SKIP) == 0;
 288
 289                 if (minlen)
 290                     dontbother = minlen - 1;
 291                 strend -= dontbother;   /* don't bother with what can't match */
 292                 tmp = 1;
 293                 /* We know what class it must start with. */
 294                 switch (OP(c)) {
 295                 case ANYOF:
 296                     c = OPERAND(c);
 297                     while (s < strend) {
 298                             i = UCHARAT(s);
 299                             if (!(c[i >> 3] & (1 << (i&7)))) {
 300                                     if (tmp && regtry(prog, s))
 301                                             goto got_it;
 302                                     else
 303                                             tmp = doevery;
 304                             }
 305                             else
 306                                     tmp = 1;
 307                             s++;
 308                     }
 309                     break;
 310                 case BOUND:
 311                     if (minlen)
 312                         dontbother++,strend--;
 313                     if (s != string) {
 314                         i = s[-1];
 315                         tmp = isALNUM(i);
 316                     }
 317                     else
 318                         tmp = isALNUM(regprev); /* assume not alphanumeric */
 319                     while (s < strend) {
 320                             i = *s;
 321                             if (tmp != isALNUM(i)) {
 322                                     tmp = !tmp;
 323                                     if (regtry(prog, s))
 324                                             goto got_it;
 325                             }
 326                             s++;
 327                     }
 328                     if ((minlen || tmp) && regtry(prog,s))
 329                             goto got_it;
 330                     break;
 331                 case NBOUND:
 332                     if (minlen)
 333                         dontbother++,strend--;
 334                     if (s != string) {
 335                         i = s[-1];
 336                         tmp = isALNUM(i);
 337                     }
 338                     else
 339                         tmp = isALNUM(regprev); /* assume not alphanumeric */
 340                     while (s < strend) {
 341                             i = *s;
 342                             if (tmp != isALNUM(i))
 343                                     tmp = !tmp;
 344                             else if (regtry(prog, s))
 345                                     goto got_it;
 346                             s++;
 347                     }
 348                     if ((minlen || !tmp) && regtry(prog,s))
 349                             goto got_it;
 350                     break;
 351                 case ALNUM:
 352                     while (s < strend) {
 353                             i = *s;
 354                             if (isALNUM(i)) {
 355                                     if (tmp && regtry(prog, s))
 356                                             goto got_it;
 357                                     else
 358                                             tmp = doevery;
 359                             }
 360                             else
 361                                     tmp = 1;
 362                             s++;
 363                     }
 364                     break;
 365                 case NALNUM:
 366                     while (s < strend) {
 367                             i = *s;
 368                             if (!isALNUM(i)) {
 369                                     if (tmp && regtry(prog, s))
 370                                             goto got_it;
 371                                     else
 372                                             tmp = doevery;
 373                             }
 374                             else
 375                                     tmp = 1;
 376                             s++;
 377                     }
 378                     break;
 379                 case SPACE:
 380                     while (s < strend) {
 381                             if (isSPACE(*s)) {
 382                                     if (tmp && regtry(prog, s))
 383                                             goto got_it;
 384                                     else
 385                                             tmp = doevery;
 386                             }
 387                             else
 388                                     tmp = 1;
 389                             s++;
 390                     }
 391                     break;
 392                 case NSPACE:
 393                     while (s < strend) {
 394                             if (!isSPACE(*s)) {
 395                                     if (tmp && regtry(prog, s))
 396                                             goto got_it;
 397                                     else
 398                                             tmp = doevery;
 399                             }
 400                             else
 401                                     tmp = 1;
 402                             s++;
 403                     }
 404                     break;
 405                 case DIGIT:
 406                     while (s < strend) {
 407                             if (isDIGIT(*s)) {
 408                                     if (tmp && regtry(prog, s))
 409                                             goto got_it;
 410                                     else
 411                                             tmp = doevery;
 412                             }
 413                             else
 414                                     tmp = 1;
 415                             s++;
 416                     }
 417                     break;
 418                 case NDIGIT:
 419                     while (s < strend) {
 420                             if (!isDIGIT(*s)) {
 421                                     if (tmp && regtry(prog, s))
 422                                             goto got_it;
 423                                     else
 424                                             tmp = doevery;
 425                             }
 426                             else
 427                                     tmp = 1;
 428                             s++;
 429                     }
 430                     break;
 431                 }
 432         }
 433         else {
 434                 if (minlen)
 435                     dontbother = minlen - 1;
 436                 strend -= dontbother;
 437                 /* We don't know much -- general case. */
 438                 do {
 439                         if (regtry(prog, s))
 440                                 goto got_it;
 441                 } while (s++ < strend);
 442         }
 443
 444         /* Failure. */
 445         goto phooey;
 446
 447     got_it:
 448         prog->subbeg = strbeg;
 449         prog->subend = strend;
 450         if ((!safebase && (prog->nparens || sawampersand)) || prog->do_folding){
 451                 strend += dontbother;   /* uncheat */
 452                 if (safebase)                   /* no need for $digit later */
 453                     s = strbeg;
 454                 else if (strbeg != prog->subbase) {
 455                     i = strend - string + (stringarg - strbeg);
 456                     s = nsavestr(strbeg,i);     /* so $digit will work later */
 457                     if (prog->subbase)
 458                             Safefree(prog->subbase);
 459                     prog->subbeg = prog->subbase = s;
 460                     prog->subend = s+i;
 461                 }
 462                 else {
 463                     i = strend - string + (stringarg - strbeg);
 464                     prog->subbeg = s = prog->subbase;
 465                     prog->subend = s+i;
 466                 }
 467                 s += (stringarg - strbeg);
 468                 for (i = 0; i <= prog->nparens; i++) {
 469                         if (prog->endp[i]) {
 470                             prog->startp[i] = s + (prog->startp[i] - string);
 471                             prog->endp[i] = s + (prog->endp[i] - string);
 472                         }
 473                 }
 474                 if (prog->do_folding)
 475                         Safefree(string);
 476         }
 477         return(1);
 478
 479     phooey:
 480         if (prog->do_folding)
 481                 Safefree(string);
 482         return(0);
 483 }
 484
 485 /*
 486  - regtry - try match at specific point
 487  */
 488 static int                      /* 0 failure, 1 success */
 489 regtry(prog, string)
 490 regexp *prog;
 491 char *string;
 492 {
 493         register int i;
 494         register char **sp;
 495         register char **ep;
 496
 497         reginput = string;
 498         regstartp = prog->startp;
 499         regendp = prog->endp;
 500         reglastparen = &prog->lastparen;
 501         prog->lastparen = 0;
 502
 503         sp = prog->startp;
 504         ep = prog->endp;
 505         if (prog->nparens) {
 506                 for (i = prog->nparens; i >= 0; i--) {
 507                         *sp++ = NULL;
 508                         *ep++ = NULL;
 509                 }
 510         }
 511         if (regmatch(prog->program + 1) && reginput >= regtill) {
 512                 prog->startp[0] = string;
 513                 prog->endp[0] = reginput;
 514                 return(1);
 515         } else
 516                 return(0);
 517 }
 518
 519 /*
 520  - regmatch - main matching routine
 521  *
 522  * Conceptually the strategy is simple:  check to see whether the current
 523  * node matches, call self recursively to see whether the rest matches,
 524  * and then act accordingly.  In practice we make some effort to avoid
 525  * recursion, in particular by going through "ordinary" nodes (that don't
 526  * need to know whether the rest of the match failed) by a loop instead of
 527  * by recursion.
 528  */
 529 /* [lwall] I've hoisted the register declarations to the outer block in order to
 530  * maybe save a little bit of pushing and popping on the stack.  It also takes
 531  * advantage of machines that use a register save mask on subroutine entry.
 532  */
 533 static int                      /* 0 failure, 1 success */
 534 regmatch(prog)
 535 char *prog;
 536 {
 537         register char *scan;    /* Current node. */
 538         char *next;             /* Next node. */
 539         register int nextchar;
 540         register int n;         /* no or next */
 541         register int ln;        /* len or last */
 542         register char *s;       /* operand or save */
 543         register char *locinput = reginput;
 544
 545         nextchar = *locinput;
 546         scan = prog;
 547 #ifdef DEBUGGING
 548         if (scan != NULL && regnarrate)
 549                 fprintf(stderr, "%s(\n", regprop(scan));
 550 #endif
 551         while (scan != NULL) {
 552 #ifdef DEBUGGING
 553                 if (regnarrate)
 554                         fprintf(stderr, "%s...\n", regprop(scan));
 555 #endif
 556
 557 #ifdef REGALIGN
 558                 next = scan + NEXT(scan);
 559                 if (next == scan)
 560                     next = NULL;
 561 #else
 562                 next = regnext(scan);
 563 #endif
 564
 565                 switch (OP(scan)) {
 566                 case BOL:
 567                         if (locinput == regbol ? regprev == '\n' :
 568                             ((nextchar || locinput < regeol) &&
 569                               locinput[-1] == '\n') )
 570                         {
 571                                 /* regtill = regbol; */
 572                                 break;
 573                         }
 574                         return(0);
 575                 case EOL:
 576                         if ((nextchar || locinput < regeol) && nextchar != '\n')
 577                                 return(0);
 578                         if (!multiline && regeol - locinput > 1)
 579                                 return 0;
 580                         /* regtill = regbol; */
 581                         break;
 582                 case ANY:
 583                         if ((nextchar == '\0' && locinput >= regeol) ||
 584                           nextchar == '\n')
 585                                 return(0);
 586                         nextchar = *++locinput;
 587                         break;
 588                 case EXACTLY:
 589                         s = OPERAND(scan);
 590                         ln = *s++;
 591                         /* Inline the first character, for speed. */
 592                         if (*s != nextchar)
 593                                 return(0);
 594                         if (regeol - locinput < ln)
 595                                 return 0;
 596                         if (ln > 1 && bcmp(s, locinput, ln) != 0)
 597                                 return(0);
 598                         locinput += ln;
 599                         nextchar = *locinput;
 600                         break;
 601                 case ANYOF:
 602                         s = OPERAND(scan);
 603                         if (nextchar < 0)
 604                                 nextchar = UCHARAT(locinput);
 605                         if (s[nextchar >> 3] & (1 << (nextchar&7)))
 606                                 return(0);
 607                         if (!nextchar && locinput >= regeol)
 608                                 return 0;
 609                         nextchar = *++locinput;
 610                         break;
 611                 case ALNUM:
 612                         if (!nextchar)
 613                                 return(0);
 614                         if (!isALNUM(nextchar))
 615                                 return(0);
 616                         nextchar = *++locinput;
 617                         break;
 618                 case NALNUM:
 619                         if (!nextchar && locinput >= regeol)
 620                                 return(0);
 621                         if (isALNUM(nextchar))
 622                                 return(0);
 623                         nextchar = *++locinput;
 624                         break;
 625                 case NBOUND:
 626                 case BOUND:
 627                         if (locinput == regbol) /* was last char in word? */
 628                                 ln = isALNUM(regprev);
 629                         else
 630                                 ln = isALNUM(locinput[-1]);
 631                         n = isALNUM(nextchar); /* is next char in word? */
 632                         if ((ln == n) == (OP(scan) == BOUND))
 633                                 return(0);
 634                         break;
 635                 case SPACE:
 636                         if (!nextchar && locinput >= regeol)
 637                                 return(0);
 638                         if (!isSPACE(nextchar))
 639                                 return(0);
 640                         nextchar = *++locinput;
 641                         break;
 642                 case NSPACE:
 643                         if (!nextchar)
 644                                 return(0);
 645                         if (isSPACE(nextchar))
 646                                 return(0);
 647                         nextchar = *++locinput;
 648                         break;
 649                 case DIGIT:
 650                         if (!isDIGIT(nextchar))
 651                                 return(0);
 652                         nextchar = *++locinput;
 653                         break;
 654                 case NDIGIT:
 655                         if (!nextchar && locinput >= regeol)
 656                                 return(0);
 657                         if (isDIGIT(nextchar))
 658                                 return(0);
 659                         nextchar = *++locinput;
 660                         break;
 661                 case REF:
 662                         n = ARG1(scan);  /* which paren pair */
 663                         s = regmystartp[n];
 664                         if (!s)
 665                             return(0);
 666                         if (!regmyendp[n])
 667                             return(0);
 668                         if (s == regmyendp[n])
 669                             break;
 670                         /* Inline the first character, for speed. */
 671                         if (*s != nextchar)
 672                                 return(0);
 673                         ln = regmyendp[n] - s;
 674                         if (locinput + ln > regeol)
 675                                 return 0;
 676                         if (ln > 1 && bcmp(s, locinput, ln) != 0)
 677                                 return(0);
 678                         locinput += ln;
 679                         nextchar = *locinput;
 680                         break;
 681
 682                 case NOTHING:
 683                         break;
 684                 case BACK:
 685                         break;
 686                 case OPEN:
 687                         n = ARG1(scan);  /* which paren pair */
 688                         reginput = locinput;
 689
 690                         regmystartp[n] = locinput;      /* for REF */
 691                         if (regmatch(next)) {
 692                                 /*
 693                                  * Don't set startp if some later
 694                                  * invocation of the same parentheses
 695                                  * already has.
 696                                  */
 697                                 if (regstartp[n] == NULL)
 698                                         regstartp[n] = locinput;
 699                                 return(1);
 700                         } else
 701                                 return(0);
 702                         /* NOTREACHED */
 703                 case CLOSE: {
 704                                 n = ARG1(scan);  /* which paren pair */
 705                                 reginput = locinput;
 706
 707                                 regmyendp[n] = locinput;        /* for REF */
 708                                 if (regmatch(next)) {
 709                                         /*
 710                                          * Don't set endp if some later
 711                                          * invocation of the same parentheses
 712                                          * already has.
 713                                          */
 714                                         if (regendp[n] == NULL) {
 715                                                 regendp[n] = locinput;
 716                                                 if (n > *reglastparen)
 717                                                     *reglastparen = n;
 718                                         }
 719                                         return(1);
 720                                 } else
 721                                         return(0);
 722                         }
 723                         /*NOTREACHED*/
 724                 case BRANCH: {
 725                                 if (OP(next) != BRANCH)         /* No choice. */
 726                                         next = NEXTOPER(scan);  /* Avoid recursion. */
 727                                 else {
 728                                         do {
 729                                                 reginput = locinput;
 730                                                 if (regmatch(NEXTOPER(scan)))
 731                                                         return(1);
 732 #ifdef REGALIGN
 733                                                 /*SUPPRESS 560*/
 734                                                 if (n = NEXT(scan))
 735                                                     scan += n;
 736                                                 else
 737                                                     scan = NULL;
 738 #else
 739                                                 scan = regnext(scan);
 740 #endif
 741                                         } while (scan != NULL && OP(scan) == BRANCH);
 742                                         return(0);
 743                                         /* NOTREACHED */
 744                                 }
 745                         }
 746                         break;
 747                 case CURLY:
 748                         ln = ARG1(scan);  /* min to match */
 749                         n  = ARG2(scan);  /* max to match */
 750                         scan = NEXTOPER(scan) + 4;
 751                         goto repeat;
 752                 case STAR:
 753                         ln = 0;
 754                         n = 32767;
 755                         scan = NEXTOPER(scan);
 756                         goto repeat;
 757                 case PLUS:
 758                         /*
 759                          * Lookahead to avoid useless match attempts
 760                          * when we know what character comes next.
 761                          */
 762                         ln = 1;
 763                         n = 32767;
 764                         scan = NEXTOPER(scan);
 765                     repeat:
 766                         if (OP(next) == EXACTLY)
 767                                 nextchar = *(OPERAND(next)+1);
 768                         else
 769                                 nextchar = -1000;
 770                         reginput = locinput;
 771                         n = regrepeat(scan, n);
 772                         if (!multiline && OP(next) == EOL && ln < n)
 773                             ln = n;                     /* why back off? */
 774                         while (n >= ln) {
 775                                 /* If it could work, try it. */
 776                                 if (nextchar == -1000 || *reginput == nextchar)
 777                                         if (regmatch(next))
 778                                                 return(1);
 779                                 /* Couldn't or didn't -- back up. */
 780                                 n--;
 781                                 reginput = locinput + n;
 782                         }
 783                         return(0);
 784                 case END:
 785                         reginput = locinput; /* put where regtry can find it */
 786                         return(1);      /* Success! */
 787                 default:
 788                         printf("%x %d\n",scan,scan[1]);
 789                         FAIL("regexp memory corruption");
 790                 }
 791
 792                 scan = next;
 793         }
 794
 795         /*
 796          * We get here only if there's trouble -- normally "case END" is
 797          * the terminating point.
 798          */
 799         FAIL("corrupted regexp pointers");
 800         /*NOTREACHED*/
 801 #ifdef lint
 802         return 0;
 803 #endif
 804 }
 805
 806 /*
 807  - regrepeat - repeatedly match something simple, report how many
 808  */
 809 /*
 810  * [This routine now assumes that it will only match on things of length 1.
 811  * That was true before, but now we assume scan - reginput is the count,
 812  * rather than incrementing count on every character.]
 813  */
 814 static int
 815 regrepeat(p, max)
 816 char *p;
 817 int max;
 818 {
 819         register char *scan;
 820         register char *opnd;
 821         register int c;
 822         register char *loceol = regeol;
 823
 824         scan = reginput;
 825         if (max != 32767 && max < loceol - scan)
 826             loceol = scan + max;
 827         opnd = OPERAND(p);
 828         switch (OP(p)) {
 829         case ANY:
 830                 while (scan < loceol && *scan != '\n')
 831                         scan++;
 832                 break;
 833         case EXACTLY:           /* length of string is 1 */
 834                 opnd++;
 835                 while (scan < loceol && *opnd == *scan)
 836                         scan++;
 837                 break;
 838         case ANYOF:
 839                 c = UCHARAT(scan);
 840                 while (scan < loceol && !(opnd[c >> 3] & (1 << (c & 7)))) {
 841                         scan++;
 842                         c = UCHARAT(scan);
 843                 }
 844                 break;
 845         case ALNUM:
 846                 while (scan < loceol && isALNUM(*scan))
 847                         scan++;
 848                 break;
 849         case NALNUM:
 850                 while (scan < loceol && !isALNUM(*scan))
 851                         scan++;
 852                 break;
 853         case SPACE:
 854                 while (scan < loceol && isSPACE(*scan))
 855                         scan++;
 856                 break;
 857         case NSPACE:
 858                 while (scan < loceol && !isSPACE(*scan))
 859                         scan++;
 860                 break;
 861         case DIGIT:
 862                 while (scan < loceol && isDIGIT(*scan))
 863                         scan++;
 864                 break;
 865         case NDIGIT:
 866                 while (scan < loceol && !isDIGIT(*scan))
 867                         scan++;
 868                 break;
 869         default:                /* Oh dear.  Called inappropriately. */
 870                 FAIL("internal regexp foulup");
 871                 /* NOTREACHED */
 872         }
 873
 874         c = scan - reginput;
 875         reginput = scan;
 876
 877         return(c);
 878 }
 879
 880 /*
 881  - regnext - dig the "next" pointer out of a node
 882  *
 883  * [Note, when REGALIGN is defined there are two places in regmatch()
 884  * that bypass this code for speed.]
 885  */
 886 char *
 887 regnext(p)
 888 register char *p;
 889 {
 890         register int offset;
 891
 892         if (p == &regdummy)
 893                 return(NULL);
 894
 895         offset = NEXT(p);
 896         if (offset == 0)
 897                 return(NULL);
 898
 899 #ifdef REGALIGN
 900         return(p+offset);
 901 #else
 902         if (OP(p) == BACK)
 903                 return(p-offset);
 904         else
 905                 return(p+offset);
 906 #endif
 907 }