lib/libcompat/regexp/regexp.c

   1 /*
   2  * regcomp and regexec -- regsub and regerror are elsewhere
   3  *
   4  *      Copyright (c) 1986 by University of Toronto.
   5  *      Written by Henry Spencer.  Not derived from licensed software.
   6  *
   7  *      Permission is granted to anyone to use this software for any
   8  *      purpose on any computer system, and to redistribute it freely,
   9  *      subject to the following restrictions:
  10  *
  11  *      1. The author is not responsible for the consequences of use of
  12  *              this software, no matter how awful, even if they arise
  13  *              from defects in it.
  14  *
  15  *      2. The origin of this software must not be misrepresented, either
  16  *              by explicit claim or by omission.
  17  *
  18  *      3. Altered versions must be plainly marked as such, and must not
  19  *              be misrepresented as being the original software.
  20  *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
  21  *** hoptoad!gnu, on 27 Dec 1986, to add \n as an alternative to |
  22  *** to assist in implementing egrep.
  23  *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
  24  *** hoptoad!gnu, on 27 Dec 1986, to add \< and \> for word-matching
  25  *** as in BSD grep and ex.
  26  *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
  27  *** hoptoad!gnu, on 28 Dec 1986, to optimize characters quoted with \.
  28  *** THIS IS AN ALTERED VERSION.  It was altered by James A. Woods,
  29  *** ames!jaw, on 19 June 1987, to quash a regcomp() redundancy.
  30  *
  31  * Beware that some of this code is subtly aware of the way operator
  32  * precedence is structured in regular expressions.  Serious changes in
  33  * regular-expression syntax might require a total rethink.
  34  */
  35 #include <limits.h>
  36 #include <regexp.h>
  37 #include <stdio.h>
  38 #include <ctype.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41 #include "collate.h"
  42 #include "regmagic.h"
  43
  44 /*
  45  * The "internal use only" fields in regexp.h are present to pass info from
  46  * compile to execute that permits the execute phase to run lots faster on
  47  * simple cases.  They are:
  48  *
  49  * regstart     char that must begin a match; '\0' if none obvious
  50  * reganch      is the match anchored (at beginning-of-line only)?
  51  * regmust      string (pointer into program) that match must include, or NULL
  52  * regmlen      length of regmust string
  53  *
  54  * Regstart and reganch permit very fast decisions on suitable starting points
  55  * for a match, cutting down the work a lot.  Regmust permits fast rejection
  56  * of lines that cannot possibly match.  The regmust tests are costly enough
  57  * that regcomp() supplies a regmust only if the r.e. contains something
  58  * potentially expensive (at present, the only such thing detected is * or +
  59  * at the start of the r.e., which can involve a lot of backup).  Regmlen is
  60  * supplied because the test in regexec() needs it and regcomp() is computing
  61  * it anyway.
  62  */
  63
  64 /*
  65  * Structure for regexp "program".  This is essentially a linear encoding
  66  * of a nondeterministic finite-state machine (aka syntax charts or
  67  * "railroad normal form" in parsing technology).  Each node is an opcode
  68  * plus a "next" pointer, possibly plus an operand.  "Next" pointers of
  69  * all nodes except BRANCH implement concatenation; a "next" pointer with
  70  * a BRANCH on both ends of it is connecting two alternatives.  (Here we
  71  * have one of the subtle syntax dependencies:  an individual BRANCH (as
  72  * opposed to a collection of them) is never concatenated with anything
  73  * because of operator precedence.)  The operand of some types of node is
  74  * a literal string; for others, it is a node leading into a sub-FSM.  In
  75  * particular, the operand of a BRANCH node is the first node of the branch.
  76  * (NB this is *not* a tree structure:  the tail of the branch connects
  77  * to the thing following the set of BRANCHes.)  The opcodes are:
  78  */
  79
  80 /* definition   number  opnd?   meaning */
  81 #define END     0       /* no   End of program. */
  82 #define BOL     1       /* no   Match "" at beginning of line. */
  83 #define EOL     2       /* no   Match "" at end of line. */
  84 #define ANY     3       /* no   Match any one character. */
  85 #define ANYOF   4       /* str  Match any character in this string. */
  86 #define ANYBUT  5       /* str  Match any character not in this string. */
  87 #define BRANCH  6       /* node Match this alternative, or the next... */
  88 #define BACK    7       /* no   Match "", "next" ptr points backward. */
  89 #define EXACTLY 8       /* str  Match this string. */
  90 #define NOTHING 9       /* no   Match empty string. */
  91 #define STAR    10      /* node Match this (simple) thing 0 or more times. */
  92 #define PLUS    11      /* node Match this (simple) thing 1 or more times. */
  93 #define WORDA   12      /* no   Match "" at wordchar, where prev is nonword */
  94 #define WORDZ   13      /* no   Match "" at nonwordchar, where prev is word */
  95 #define OPEN    20      /* no   Mark this point in input as start of #n. */
  96                         /*      OPEN+1 is number 1, etc. */
  97 #define CLOSE   30      /* no   Analogous to OPEN. */
  98
  99 /*
 100  * Opcode notes:
 101  *
 102  * BRANCH       The set of branches constituting a single choice are hooked
 103  *              together with their "next" pointers, since precedence prevents
 104  *              anything being concatenated to any individual branch.  The
 105  *              "next" pointer of the last BRANCH in a choice points to the
 106  *              thing following the whole choice.  This is also where the
 107  *              final "next" pointer of each individual branch points; each
 108  *              branch starts with the operand node of a BRANCH node.
 109  *
 110  * BACK         Normal "next" pointers all implicitly point forward; BACK
 111  *              exists to make loop structures possible.
 112  *
 113  * STAR,PLUS    '?', and complex '*' and '+', are implemented as circular
 114  *              BRANCH structures using BACK.  Simple cases (one character
 115  *              per match) are implemented with STAR and PLUS for speed
 116  *              and to minimize recursive plunges.
 117  *
 118  * OPEN,CLOSE   ...are numbered at compile time.
 119  */
 120
 121 /*
 122  * A node is one char of opcode followed by two chars of "next" pointer.
 123  * "Next" pointers are stored as two 8-bit pieces, high order first.  The
 124  * value is a positive offset from the opcode of the node containing it.
 125  * An operand, if any, simply follows the node.  (Note that much of the
 126  * code generation knows about this implicit relationship.)
 127  *
 128  * Using two bytes for the "next" pointer is vast overkill for most things,
 129  * but allows patterns to get big without disasters.
 130  */
 131 #define OP(p)   (*(p))
 132 #define NEXT(p) (((*((p)+1)&0377)<<8) + (*((p)+2)&0377))
 133 #define OPERAND(p)      ((p) + 3)
 134
 135 /*
 136  * See regmagic.h for one further detail of program structure.
 137  */
 138
 139
 140 /*
 141  * Utility definitions.
 142  */
 143 #ifndef CHARBITS
 144 #define UCHARAT(p)      ((int)*(unsigned char *)(p))
 145 #else
 146 #define UCHARAT(p)      ((int)*(p)&CHARBITS)
 147 #endif
 148
 149 #define FAIL(m) { regerror(m); return(NULL); }
 150 #define ISMULT(c)       ((c) == '*' || (c) == '+' || (c) == '?')
 151
 152 /*
 153  * Flags to be passed up and down.
 154  */
 155 #define HASWIDTH        01      /* Known never to match null string. */
 156 #define SIMPLE          02      /* Simple enough to be STAR/PLUS operand. */
 157 #define SPSTART         04      /* Starts with * or +. */
 158 #define WORST           0       /* Worst case. */
 159
 160 /*
 161  * Global work variables for regcomp().
 162  */
 163 static char *regparse;          /* Input-scan pointer. */
 164 static int regnpar;             /* () count. */
 165 static char regdummy;
 166 static char *regcode;           /* Code-emit pointer; &regdummy = don't. */
 167 static long regsize;            /* Code size. */
 168
 169 /*
 170  * Forward declarations for regcomp()'s friends.
 171  */
 172 #ifndef STATIC
 173 #define STATIC  static
 174 #endif
 175 STATIC char *reg(int, int *);
 176 STATIC char *regbranch(int *);
 177 STATIC char *regpiece(int *);
 178 STATIC char *regatom(int *);
 179 STATIC char *regnode(char);
 180 STATIC char *regnext(char *);
 181 STATIC void regc(char);
 182 STATIC void reginsert(char, char *);
 183 STATIC void regtail(char *, char *);
 184 STATIC void regoptail(char *, char *);
 185 #ifdef STRCSPN
 186 STATIC int strcspn(char *, char *);
 187 #endif
 188
 189 /*
 190  - regcomp - compile a regular expression into internal code
 191  *
 192  * We can't allocate space until we know how big the compiled form will be,
 193  * but we can't compile it (and thus know how big it is) until we've got a
 194  * place to put the code.  So we cheat:  we compile it twice, once with code
 195  * generation turned off and size counting turned on, and once "for real".
 196  * This also means that we don't allocate space until we are sure that the
 197  * thing really will compile successfully, and we never have to move the
 198  * code and thus invalidate pointers into it.  (Note that it has to be in
 199  * one piece because free() must be able to free it all.)
 200  *
 201  * Beware that the optimization-preparation code in here knows about some
 202  * of the structure of the compiled regexp.
 203  */
 204 regexp *
 205 regcomp(const char *exp)
 206 {
 207         regexp *r;
 208         char *scan;
 209         char *longest;
 210         int len;
 211         int flags;
 212
 213         if (exp == NULL)
 214                 FAIL("NULL argument");
 215
 216         /* First pass: determine size, legality. */
 217 #ifdef notdef
 218         if (exp[0] == '.' && exp[1] == '*') exp += 2;  /* aid grep */
 219 #endif
 220         regparse = (char *)exp;
 221         regnpar = 1;
 222         regsize = 0L;
 223         regcode = &regdummy;
 224         regc(MAGIC);
 225         if (reg(0, &flags) == NULL)
 226                 return(NULL);
 227
 228         /* Small enough for pointer-storage convention? */
 229         if (regsize >= 32767L)          /* Probably could be 65535L. */
 230                 FAIL("regexp too big");
 231
 232         /* Allocate space. */
 233         r = (regexp *)malloc(sizeof(regexp) + (unsigned)regsize);
 234         if (r == NULL)
 235                 FAIL("out of space");
 236
 237         /* Second pass: emit code. */
 238         regparse = (char *)exp;
 239         regnpar = 1;
 240         regcode = r->program;
 241         regc(MAGIC);
 242         if (reg(0, &flags) == NULL)
 243                 return(NULL);
 244
 245         /* Dig out information for optimizations. */
 246         r->regstart = '\0';     /* Worst-case defaults. */
 247         r->reganch = 0;
 248         r->regmust = NULL;
 249         r->regmlen = 0;
 250         scan = r->program+1;                    /* First BRANCH. */
 251         if (OP(regnext(scan)) == END) {         /* Only one top-level choice. */
 252                 scan = OPERAND(scan);
 253
 254                 /* Starting-point info. */
 255                 if (OP(scan) == EXACTLY)
 256                         r->regstart = *OPERAND(scan);
 257                 else if (OP(scan) == BOL)
 258                         r->reganch++;
 259
 260                 /*
 261                  * If there's something expensive in the r.e., find the
 262                  * longest literal string that must appear and make it the
 263                  * regmust.  Resolve ties in favor of later strings, since
 264                  * the regstart check works with the beginning of the r.e.
 265                  * and avoiding duplication strengthens checking.  Not a
 266                  * strong reason, but sufficient in the absence of others.
 267                  */
 268                 if (flags&SPSTART) {
 269                         longest = NULL;
 270                         len = 0;
 271                         for (; scan != NULL; scan = regnext(scan))
 272                                 if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
 273                                         longest = OPERAND(scan);
 274                                         len = strlen(OPERAND(scan));
 275                                 }
 276                         r->regmust = longest;
 277                         r->regmlen = len;
 278                 }
 279         }
 280
 281         return(r);
 282 }
 283
 284 /*
 285  - reg - regular expression, i.e. main body or parenthesized thing
 286  *
 287  * Caller must absorb opening parenthesis.
 288  *
 289  * Combining parenthesis handling with the base level of regular expression
 290  * is a trifle forced, but the need to tie the tails of the branches to what
 291  * follows makes it hard to avoid.
 292  */
 293 static char *
 294 reg(int paren, int *flagp)
 295 {
 296         char *ret;
 297         char *br;
 298         char *ender;
 299         int parno;
 300         int flags;
 301
 302         *flagp = HASWIDTH;      /* Tentatively. */
 303
 304         /* Make an OPEN node, if parenthesized. */
 305         if (paren) {
 306                 if (regnpar >= NSUBEXP)
 307                         FAIL("too many ()");
 308                 parno = regnpar;
 309                 regnpar++;
 310                 ret = regnode(OPEN+parno);
 311         } else
 312                 ret = NULL;
 313
 314         /* Pick up the branches, linking them together. */
 315         br = regbranch(&flags);
 316         if (br == NULL)
 317                 return(NULL);
 318         if (ret != NULL)
 319                 regtail(ret, br);       /* OPEN -> first. */
 320         else
 321                 ret = br;
 322         if (!(flags&HASWIDTH))
 323                 *flagp &= ~HASWIDTH;
 324         *flagp |= flags&SPSTART;
 325         while (*regparse == '|' || *regparse == '\n') {
 326                 regparse++;
 327                 br = regbranch(&flags);
 328                 if (br == NULL)
 329                         return(NULL);
 330                 regtail(ret, br);       /* BRANCH -> BRANCH. */
 331                 if (!(flags&HASWIDTH))
 332                         *flagp &= ~HASWIDTH;
 333                 *flagp |= flags&SPSTART;
 334         }
 335
 336         /* Make a closing node, and hook it on the end. */
 337         ender = regnode((paren) ? CLOSE+parno : END);
 338         regtail(ret, ender);
 339
 340         /* Hook the tails of the branches to the closing node. */
 341         for (br = ret; br != NULL; br = regnext(br))
 342                 regoptail(br, ender);
 343
 344         /* Check for proper termination. */
 345         if (paren && *regparse++ != ')') {
 346                 FAIL("unmatched ()");
 347         } else if (!paren && *regparse != '\0') {
 348                 if (*regparse == ')') {
 349                         FAIL("unmatched ()");
 350                 } else
 351                         FAIL("junk on end");    /* "Can't happen". */
 352                 /* NOTREACHED */
 353         }
 354
 355         return(ret);
 356 }
 357
 358 /*
 359  - regbranch - one alternative of an | operator
 360  *
 361  * Implements the concatenation operator.
 362  */
 363 static char *
 364 regbranch(int *flagp)
 365 {
 366         char *ret;
 367         char *chain;
 368         char *latest;
 369         int flags;
 370
 371         *flagp = WORST;         /* Tentatively. */
 372
 373         ret = regnode(BRANCH);
 374         chain = NULL;
 375         while (*regparse != '\0' && *regparse != ')' &&
 376                *regparse != '\n' && *regparse != '|') {
 377                 latest = regpiece(&flags);
 378                 if (latest == NULL)
 379                         return(NULL);
 380                 *flagp |= flags&HASWIDTH;
 381                 if (chain == NULL)      /* First piece. */
 382                         *flagp |= flags&SPSTART;
 383                 else
 384                         regtail(chain, latest);
 385                 chain = latest;
 386         }
 387         if (chain == NULL)      /* Loop ran zero times. */
 388                 (void) regnode(NOTHING);
 389
 390         return(ret);
 391 }
 392
 393 /*
 394  - regpiece - something followed by possible [*+?]
 395  *
 396  * Note that the branching code sequences used for ? and the general cases
 397  * of * and + are somewhat optimized:  they use the same NOTHING node as
 398  * both the endmarker for their branch list and the body of the last branch.
 399  * It might seem that this node could be dispensed with entirely, but the
 400  * endmarker role is not redundant.
 401  */
 402 static char *
 403 regpiece(int *flagp)
 404 {
 405         char *ret;
 406         char op;
 407         char *next;
 408         int flags;
 409
 410         ret = regatom(&flags);
 411         if (ret == NULL)
 412                 return(NULL);
 413
 414         op = *regparse;
 415         if (!ISMULT(op)) {
 416                 *flagp = flags;
 417                 return(ret);
 418         }
 419
 420         if (!(flags&HASWIDTH) && op != '?')
 421                 FAIL("*+ operand could be empty");
 422         *flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);
 423
 424         if (op == '*' && (flags&SIMPLE))
 425                 reginsert(STAR, ret);
 426         else if (op == '*') {
 427                 /* Emit x* as (x&|), where & means "self". */
 428                 reginsert(BRANCH, ret);                 /* Either x */
 429                 regoptail(ret, regnode(BACK));          /* and loop */
 430                 regoptail(ret, ret);                    /* back */
 431                 regtail(ret, regnode(BRANCH));          /* or */
 432                 regtail(ret, regnode(NOTHING));         /* null. */
 433         } else if (op == '+' && (flags&SIMPLE))
 434                 reginsert(PLUS, ret);
 435         else if (op == '+') {
 436                 /* Emit x+ as x(&|), where & means "self". */
 437                 next = regnode(BRANCH);                 /* Either */
 438                 regtail(ret, next);
 439                 regtail(regnode(BACK), ret);            /* loop back */
 440                 regtail(next, regnode(BRANCH));         /* or */
 441                 regtail(ret, regnode(NOTHING));         /* null. */
 442         } else if (op == '?') {
 443                 /* Emit x? as (x|) */
 444                 reginsert(BRANCH, ret);                 /* Either x */
 445                 regtail(ret, regnode(BRANCH));          /* or */
 446                 next = regnode(NOTHING);                /* null. */
 447                 regtail(ret, next);
 448                 regoptail(ret, next);
 449         }
 450         regparse++;
 451         if (ISMULT(*regparse))
 452                 FAIL("nested *?+");
 453
 454         return(ret);
 455 }
 456
 457 /*
 458  - regatom - the lowest level
 459  *
 460  * Optimization:  gobbles an entire sequence of ordinary characters so that
 461  * it can turn them into a single node, which is smaller to store and
 462  * faster to run.  Backslashed characters are exceptions, each becoming a
 463  * separate node; the code is simpler that way and it's not worth fixing.
 464  */
 465 static char *
 466 regatom(int *flagp)
 467 {
 468         char *ret;
 469         int flags;
 470
 471         *flagp = WORST;         /* Tentatively. */
 472
 473         switch (*regparse++) {
 474         /* FIXME: these chars only have meaning at beg/end of pat? */
 475         case '^':
 476                 ret = regnode(BOL);
 477                 break;
 478         case '$':
 479                 ret = regnode(EOL);
 480                 break;
 481         case '.':
 482                 ret = regnode(ANY);
 483                 *flagp |= HASWIDTH|SIMPLE;
 484                 break;
 485         case '[': {
 486                         int class;
 487                         int classend;
 488                         int i;
 489
 490                         if (*regparse == '^') { /* Complement of range. */
 491                                 ret = regnode(ANYBUT);
 492                                 regparse++;
 493                         } else
 494                                 ret = regnode(ANYOF);
 495                         if (*regparse == ']' || *regparse == '-')
 496                                 regc(*regparse++);
 497                         while (*regparse != '\0' && *regparse != ']') {
 498                                 if (*regparse == '-') {
 499                                         regparse++;
 500                                         if (*regparse == ']' || *regparse == '\0')
 501                                                 regc('-');
 502                                         else {
 503                                                 class = UCHARAT(regparse-2);
 504                                                 classend = UCHARAT(regparse);
 505                                                 if (__collate_load_error) {
 506                                                         if (class > classend)
 507                                                                 FAIL("invalid [] range");
 508                                                         for (class++; class <= classend; class++)
 509                                                                 regc(class);
 510                                                 } else {
 511                                                         if (__collate_range_cmp(class, classend) > 0)
 512                                                                 FAIL("invalid [] range");
 513                                                         for (i = 0; i <= UCHAR_MAX; i++)
 514                                                                 if (   i != class
 515                                                                     && __collate_range_cmp(class, i) <= 0
 516                                                                     && __collate_range_cmp(i, classend) <= 0
 517                                                                    )
 518                                                                         regc(i);
 519                                                 }
 520                                                 regparse++;
 521                                         }
 522                                 } else
 523                                         regc(*regparse++);
 524                         }
 525                         regc('\0');
 526                         if (*regparse != ']')
 527                                 FAIL("unmatched []");
 528                         regparse++;
 529                         *flagp |= HASWIDTH|SIMPLE;
 530                 }
 531                 break;
 532         case '(':
 533                 ret = reg(1, &flags);
 534                 if (ret == NULL)
 535                         return(NULL);
 536                 *flagp |= flags&(HASWIDTH|SPSTART);
 537                 break;
 538         case '\0':
 539         case '|':
 540         case '\n':
 541         case ')':
 542                 FAIL("internal urp");   /* Supposed to be caught earlier. */
 543                 break;
 544         case '?':
 545         case '+':
 546         case '*':
 547                 FAIL("?+* follows nothing");
 548                 break;
 549         case '\\':
 550                 switch (*regparse++) {
 551                 case '\0':
 552                         FAIL("trailing \\");
 553                         break;
 554                 case '<':
 555                         ret = regnode(WORDA);
 556                         break;
 557                 case '>':
 558                         ret = regnode(WORDZ);
 559                         break;
 560                 /* FIXME: Someday handle \1, \2, ... */
 561                 default:
 562                         /* Handle general quoted chars in exact-match routine */
 563                         goto de_fault;
 564                 }
 565                 break;
 566         de_fault:
 567         default:
 568                 /*
 569                  * Encode a string of characters to be matched exactly.
 570                  *
 571                  * This is a bit tricky due to quoted chars and due to
 572                  * '*', '+', and '?' taking the SINGLE char previous
 573                  * as their operand.
 574                  *
 575                  * On entry, the char at regparse[-1] is going to go
 576                  * into the string, no matter what it is.  (It could be
 577                  * following a \ if we are entered from the '\' case.)
 578                  *
 579                  * Basic idea is to pick up a good char in  ch  and
 580                  * examine the next char.  If it's *+? then we twiddle.
 581                  * If it's \ then we frozzle.  If it's other magic char
 582                  * we push  ch  and terminate the string.  If none of the
 583                  * above, we push  ch  on the string and go around again.
 584                  *
 585                  *  regprev  is used to remember where "the current char"
 586                  * starts in the string, if due to a *+? we need to back
 587                  * up and put the current char in a separate, 1-char, string.
 588                  * When  regprev  is NULL,  ch  is the only char in the
 589                  * string; this is used in *+? handling, and in setting
 590                  * flags |= SIMPLE at the end.
 591                  */
 592                 {
 593                         char *regprev;
 594                         char ch;
 595
 596                         regparse--;                     /* Look at cur char */
 597                         ret = regnode(EXACTLY);
 598                         for ( regprev = NULL ; ; ) {
 599                                 ch = *regparse++;       /* Get current char */
 600                                 switch (*regparse) {    /* look at next one */
 601
 602                                 default:
 603                                         regc(ch);       /* Add cur to string */
 604                                         break;
 605
 606                                 case '.': case '[': case '(':
 607                                 case ')': case '|': case '\n':
 608                                 case '$': case '^':
 609                                 case '\0':
 610                                 /* FIXME, $ and ^ should not always be magic */
 611                                 magic:
 612                                         regc(ch);       /* dump cur char */
 613                                         goto done;      /* and we are done */
 614
 615                                 case '?': case '+': case '*':
 616                                         if (!regprev)   /* If just ch in str, */
 617                                                 goto magic;     /* use it */
 618                                         /* End mult-char string one early */
 619                                         regparse = regprev; /* Back up parse */
 620                                         goto done;
 621
 622                                 case '\\':
 623                                         regc(ch);       /* Cur char OK */
 624                                         switch (regparse[1]){ /* Look after \ */
 625                                         case '\0':
 626                                         case '<':
 627                                         case '>':
 628                                         /* FIXME: Someday handle \1, \2, ... */
 629                                                 goto done; /* Not quoted */
 630                                         default:
 631                                                 /* Backup point is \, scan                                                       * point is after it. */
 632                                                 regprev = regparse;
 633                                                 regparse++;
 634                                                 continue;       /* NOT break; */
 635                                         }
 636                                 }
 637                                 regprev = regparse;     /* Set backup point */
 638                         }
 639                 done:
 640                         regc('\0');
 641                         *flagp |= HASWIDTH;
 642                         if (!regprev)           /* One char? */
 643                                 *flagp |= SIMPLE;
 644                 }
 645                 break;
 646         }
 647
 648         return(ret);
 649 }
 650
 651 /*
 652  - regnode - emit a node
 653  */
 654 static char *                   /* Location. */
 655 regnode(char op)
 656 {
 657         char *ret;
 658         char *ptr;
 659
 660         ret = regcode;
 661         if (ret == &regdummy) {
 662                 regsize += 3;
 663                 return(ret);
 664         }
 665
 666         ptr = ret;
 667         *ptr++ = op;
 668         *ptr++ = '\0';          /* Null "next" pointer. */
 669         *ptr++ = '\0';
 670         regcode = ptr;
 671
 672         return(ret);
 673 }
 674
 675 /*
 676  - regc - emit (if appropriate) a byte of code
 677  */
 678 static void
 679 regc(char b)
 680 {
 681         if (regcode != &regdummy)
 682                 *regcode++ = b;
 683         else
 684                 regsize++;
 685 }
 686
 687 /*
 688  - reginsert - insert an operator in front of already-emitted operand
 689  *
 690  * Means relocating the operand.
 691  */
 692 static void
 693 reginsert(char op, char *opnd)
 694 {
 695         char *src;
 696         char *dst;
 697         char *place;
 698
 699         if (regcode == &regdummy) {
 700                 regsize += 3;
 701                 return;
 702         }
 703
 704         src = regcode;
 705         regcode += 3;
 706         dst = regcode;
 707         while (src > opnd)
 708                 *--dst = *--src;
 709
 710         place = opnd;           /* Op node, where operand used to be. */
 711         *place++ = op;
 712         *place++ = '\0';
 713         *place++ = '\0';
 714 }
 715
 716 /*
 717  - regtail - set the next-pointer at the end of a node chain
 718  */
 719 static void
 720 regtail(char *p, char *val)
 721 {
 722         char *scan;
 723         char *temp;
 724         int offset;
 725
 726         if (p == &regdummy)
 727                 return;
 728
 729         /* Find last node. */
 730         scan = p;
 731         for (;;) {
 732                 temp = regnext(scan);
 733                 if (temp == NULL)
 734                         break;
 735                 scan = temp;
 736         }
 737
 738         if (OP(scan) == BACK)
 739                 offset = scan - val;
 740         else
 741                 offset = val - scan;
 742         *(scan+1) = (offset>>8)&0377;
 743         *(scan+2) = offset&0377;
 744 }
 745
 746 /*
 747  - regoptail - regtail on operand of first argument; nop if operandless
 748  */
 749 static void
 750 regoptail(char *p, char *val)
 751 {
 752         /* "Operandless" and "op != BRANCH" are synonymous in practice. */
 753         if (p == NULL || p == &regdummy || OP(p) != BRANCH)
 754                 return;
 755         regtail(OPERAND(p), val);
 756 }
 757
 758 /*
 759  * regexec and friends
 760  */
 761
 762 /*
 763  * Global work variables for regexec().
 764  */
 765 static char *reginput;          /* String-input pointer. */
 766 static char *regbol;            /* Beginning of input, for ^ check. */
 767 static char **regstartp;        /* Pointer to startp array. */
 768 static char **regendp;          /* Ditto for endp. */
 769
 770 /*
 771  * Forwards.
 772  */
 773 STATIC int regtry();
 774 STATIC int regmatch();
 775 STATIC int regrepeat();
 776
 777 #ifdef DEBUG
 778 int regnarrate = 0;
 779 void regdump();
 780 STATIC char *regprop();
 781 #endif
 782
 783 /*
 784  - regexec - match a regexp against a string
 785  */
 786 int
 787 regexec(const regexp *prog, const char *string)
 788 {
 789         char *s;
 790         extern char *strchr();
 791
 792         /* Be paranoid... */
 793         if (prog == NULL || string == NULL) {
 794                 regerror("NULL parameter");
 795                 return(0);
 796         }
 797
 798         /* Check validity of program. */
 799         if (UCHARAT(prog->program) != MAGIC) {
 800                 regerror("corrupted program");
 801                 return(0);
 802         }
 803
 804         /* If there is a "must appear" string, look for it. */
 805         if (prog->regmust != NULL) {
 806                 s = (char *)string;
 807                 while ((s = strchr(s, prog->regmust[0])) != NULL) {
 808                         if (strncmp(s, prog->regmust, prog->regmlen) == 0)
 809                                 break;  /* Found it. */
 810                         s++;
 811                 }
 812                 if (s == NULL)  /* Not present. */
 813                         return(0);
 814         }
 815
 816         /* Mark beginning of line for ^ . */
 817         regbol = (char *)string;
 818
 819         /* Simplest case:  anchored match need be tried only once. */
 820         if (prog->reganch)
 821                 return(regtry(prog, string));
 822
 823         /* Messy cases:  unanchored match. */
 824         s = (char *)string;
 825         if (prog->regstart != '\0')
 826                 /* We know what char it must start with. */
 827                 while ((s = strchr(s, prog->regstart)) != NULL) {
 828                         if (regtry(prog, s))
 829                                 return(1);
 830                         s++;
 831                 }
 832         else
 833                 /* We don't -- general case. */
 834                 do {
 835                         if (regtry(prog, s))
 836                                 return(1);
 837                 } while (*s++ != '\0');
 838
 839         /* Failure. */
 840         return(0);
 841 }
 842
 843 /*
 844  - regtry - try match at specific point
 845  */
 846 static int                      /* 0 failure, 1 success */
 847 regtry(regexp *prog, char *string)
 848 {
 849         int i;
 850         char **sp;
 851         char **ep;
 852
 853         reginput = string;
 854         regstartp = prog->startp;
 855         regendp = prog->endp;
 856
 857         sp = prog->startp;
 858         ep = prog->endp;
 859         for (i = NSUBEXP; i > 0; i--) {
 860                 *sp++ = NULL;
 861                 *ep++ = NULL;
 862         }
 863         if (regmatch(prog->program + 1)) {
 864                 prog->startp[0] = string;
 865                 prog->endp[0] = reginput;
 866                 return(1);
 867         } else
 868                 return(0);
 869 }
 870
 871 /*
 872  - regmatch - main matching routine
 873  *
 874  * Conceptually the strategy is simple:  check to see whether the current
 875  * node matches, call self recursively to see whether the rest matches,
 876  * and then act accordingly.  In practice we make some effort to avoid
 877  * recursion, in particular by going through "ordinary" nodes (that don't
 878  * need to know whether the rest of the match failed) by a loop instead of
 879  * by recursion.
 880  */
 881 static int                      /* 0 failure, 1 success */
 882 regmatch(char *prog)
 883 {
 884         char *scan;     /* Current node. */
 885         char *next;             /* Next node. */
 886
 887         scan = prog;
 888 #ifdef DEBUG
 889         if (scan != NULL && regnarrate)
 890                 fprintf(stderr, "%s(\n", regprop(scan));
 891 #endif
 892         while (scan != NULL) {
 893 #ifdef DEBUG
 894                 if (regnarrate)
 895                         fprintf(stderr, "%s...\n", regprop(scan));
 896 #endif
 897                 next = regnext(scan);
 898
 899                 switch (OP(scan)) {
 900                 case BOL:
 901                         if (reginput != regbol)
 902                                 return(0);
 903                         break;
 904                 case EOL:
 905                         if (*reginput != '\0')
 906                                 return(0);
 907                         break;
 908                 case WORDA:
 909                         /* Must be looking at a letter, digit, or _ */
 910                         if ((!isalnum((unsigned char)*reginput)) && *reginput != '_')
 911                                 return(0);
 912                         /* Prev must be BOL or nonword */
 913                         if (reginput > regbol &&
 914                             (isalnum((unsigned char)reginput[-1]) || reginput[-1] == '_'))
 915                                 return(0);
 916                         break;
 917                 case WORDZ:
 918                         /* Must be looking at non letter, digit, or _ */
 919                         if (isalnum((unsigned char)*reginput) || *reginput == '_')
 920                                 return(0);
 921                         /* We don't care what the previous char was */
 922                         break;
 923                 case ANY:
 924                         if (*reginput == '\0')
 925                                 return(0);
 926                         reginput++;
 927                         break;
 928                 case EXACTLY: {
 929                                 int len;
 930                                 char *opnd;
 931
 932                                 opnd = OPERAND(scan);
 933                                 /* Inline the first character, for speed. */
 934                                 if (*opnd != *reginput)
 935                                         return(0);
 936                                 len = strlen(opnd);
 937                                 if (len > 1 && strncmp(opnd, reginput, len) != 0)
 938                                         return(0);
 939                                 reginput += len;
 940                         }
 941                         break;
 942                 case ANYOF:
 943                         if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) == NULL)
 944                                 return(0);
 945                         reginput++;
 946                         break;
 947                 case ANYBUT:
 948                         if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) != NULL)
 949                                 return(0);
 950                         reginput++;
 951                         break;
 952                 case NOTHING:
 953                         break;
 954                 case BACK:
 955                         break;
 956                 case OPEN+1:
 957                 case OPEN+2:
 958                 case OPEN+3:
 959                 case OPEN+4:
 960                 case OPEN+5:
 961                 case OPEN+6:
 962                 case OPEN+7:
 963                 case OPEN+8:
 964                 case OPEN+9: {
 965                                 int no;
 966                                 char *save;
 967
 968                                 no = OP(scan) - OPEN;
 969                                 save = reginput;
 970
 971                                 if (regmatch(next)) {
 972                                         /*
 973                                          * Don't set startp if some later
 974                                          * invocation of the same parentheses
 975                                          * already has.
 976                                          */
 977                                         if (regstartp[no] == NULL)
 978                                                 regstartp[no] = save;
 979                                         return(1);
 980                                 } else
 981                                         return(0);
 982                         }
 983                         break;
 984                 case CLOSE+1:
 985                 case CLOSE+2:
 986                 case CLOSE+3:
 987                 case CLOSE+4:
 988                 case CLOSE+5:
 989                 case CLOSE+6:
 990                 case CLOSE+7:
 991                 case CLOSE+8:
 992                 case CLOSE+9: {
 993                                 int no;
 994                                 char *save;
 995
 996                                 no = OP(scan) - CLOSE;
 997                                 save = reginput;
 998
 999                                 if (regmatch(next)) {
1000                                         /*
1001                                          * Don't set endp if some later
1002                                          * invocation of the same parentheses
1003                                          * already has.
1004                                          */
1005                                         if (regendp[no] == NULL)
1006                                                 regendp[no] = save;
1007                                         return(1);
1008                                 } else
1009                                         return(0);
1010                         }
1011                         break;
1012                 case BRANCH: {
1013                                 char *save;
1014
1015                                 if (OP(next) != BRANCH)         /* No choice. */
1016                                         next = OPERAND(scan);   /* Avoid recursion. */
1017                                 else {
1018                                         do {
1019                                                 save = reginput;
1020                                                 if (regmatch(OPERAND(scan)))
1021                                                         return(1);
1022                                                 reginput = save;
1023                                                 scan = regnext(scan);
1024                                         } while (scan != NULL && OP(scan) == BRANCH);
1025                                         return(0);
1026                                         /* NOTREACHED */
1027                                 }
1028                         }
1029                         break;
1030                 case STAR:
1031                 case PLUS: {
1032                                 char nextch;
1033                                 int no;
1034                                 char *save;
1035                                 int min;
1036
1037                                 /*
1038                                  * Lookahead to avoid useless match attempts
1039                                  * when we know what character comes next.
1040                                  */
1041                                 nextch = '\0';
1042                                 if (OP(next) == EXACTLY)
1043                                         nextch = *OPERAND(next);
1044                                 min = (OP(scan) == STAR) ? 0 : 1;
1045                                 save = reginput;
1046                                 no = regrepeat(OPERAND(scan));
1047                                 while (no >= min) {
1048                                         /* If it could work, try it. */
1049                                         if (nextch == '\0' || *reginput == nextch)
1050                                                 if (regmatch(next))
1051                                                         return(1);
1052                                         /* Couldn't or didn't -- back up. */
1053                                         no--;
1054                                         reginput = save + no;
1055                                 }
1056                                 return(0);
1057                         }
1058                         break;
1059                 case END:
1060                         return(1);      /* Success! */
1061                         break;
1062                 default:
1063                         regerror("memory corruption");
1064                         return(0);
1065                         break;
1066                 }
1067
1068                 scan = next;
1069         }
1070
1071         /*
1072          * We get here only if there's trouble -- normally "case END" is
1073          * the terminating point.
1074          */
1075         regerror("corrupted pointers");
1076         return(0);
1077 }
1078
1079 /*
1080  - regrepeat - repeatedly match something simple, report how many
1081  */
1082 static int
1083 regrepeat(char *p)
1084 {
1085         int count = 0;
1086         char *scan;
1087         char *opnd;
1088
1089         scan = reginput;
1090         opnd = OPERAND(p);
1091         switch (OP(p)) {
1092         case ANY:
1093                 count = strlen(scan);
1094                 scan += count;
1095                 break;
1096         case EXACTLY:
1097                 while (*opnd == *scan) {
1098                         count++;
1099                         scan++;
1100                 }
1101                 break;
1102         case ANYOF:
1103                 while (*scan != '\0' && strchr(opnd, *scan) != NULL) {
1104                         count++;
1105                         scan++;
1106                 }
1107                 break;
1108         case ANYBUT:
1109                 while (*scan != '\0' && strchr(opnd, *scan) == NULL) {
1110                         count++;
1111                         scan++;
1112                 }
1113                 break;
1114         default:                /* Oh dear.  Called inappropriately. */
1115                 regerror("internal foulup");
1116                 count = 0;      /* Best compromise. */
1117                 break;
1118         }
1119         reginput = scan;
1120
1121         return(count);
1122 }
1123
1124 /*
1125  - regnext - dig the "next" pointer out of a node
1126  */
1127 static char *
1128 regnext(char *p)
1129 {
1130         int offset;
1131
1132         if (p == &regdummy)
1133                 return(NULL);
1134
1135         offset = NEXT(p);
1136         if (offset == 0)
1137                 return(NULL);
1138
1139         if (OP(p) == BACK)
1140                 return(p-offset);
1141         else
1142                 return(p+offset);
1143 }
1144
1145 #ifdef DEBUG
1146
1147 STATIC char *regprop();
1148
1149 /*
1150  - regdump - dump a regexp onto stdout in vaguely comprehensible form
1151  */
1152 void
1153 regdump(regexp *r)
1154 {
1155         char *s;
1156         char op = EXACTLY;      /* Arbitrary non-END op. */
1157         char *next;
1158         extern char *strchr();
1159
1160
1161         s = r->program + 1;
1162         while (op != END) {     /* While that wasn't END last time... */
1163                 op = OP(s);
1164                 printf("%2d%s", s-r->program, regprop(s));      /* Where, what. */
1165                 next = regnext(s);
1166                 if (next == NULL)               /* Next ptr. */
1167                         printf("(0)");
1168                 else
1169                         printf("(%d)", (s-r->program)+(next-s));
1170                 s += 3;
1171                 if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
1172                         /* Literal string, where present. */
1173                         while (*s != '\0') {
1174                                 putchar(*s);
1175                                 s++;
1176                         }
1177                         s++;
1178                 }
1179                 putchar('\n');
1180         }
1181
1182         /* Header fields of interest. */
1183         if (r->regstart != '\0')
1184                 printf("start `%c' ", r->regstart);
1185         if (r->reganch)
1186                 printf("anchored ");
1187         if (r->regmust != NULL)
1188                 printf("must have \"%s\"", r->regmust);
1189         printf("\n");
1190 }
1191
1192 /*
1193  - regprop - printable representation of opcode
1194  */
1195 static char *
1196 regprop(char *op)
1197 {
1198         char *p;
1199         static char buf[50];
1200
1201         (void) strcpy(buf, ":");
1202
1203         switch (OP(op)) {
1204         case BOL:
1205                 p = "BOL";
1206                 break;
1207         case EOL:
1208                 p = "EOL";
1209                 break;
1210         case ANY:
1211                 p = "ANY";
1212                 break;
1213         case ANYOF:
1214                 p = "ANYOF";
1215                 break;
1216         case ANYBUT:
1217                 p = "ANYBUT";
1218                 break;
1219         case BRANCH:
1220                 p = "BRANCH";
1221                 break;
1222         case EXACTLY:
1223                 p = "EXACTLY";
1224                 break;
1225         case NOTHING:
1226                 p = "NOTHING";
1227                 break;
1228         case BACK:
1229                 p = "BACK";
1230                 break;
1231         case END:
1232                 p = "END";
1233                 break;
1234         case OPEN+1:
1235         case OPEN+2:
1236         case OPEN+3:
1237         case OPEN+4:
1238         case OPEN+5:
1239         case OPEN+6:
1240         case OPEN+7:
1241         case OPEN+8:
1242         case OPEN+9:
1243                 sprintf(buf+strlen(buf), "OPEN%d", OP(op)-OPEN);
1244                 p = NULL;
1245                 break;
1246         case CLOSE+1:
1247         case CLOSE+2:
1248         case CLOSE+3:
1249         case CLOSE+4:
1250         case CLOSE+5:
1251         case CLOSE+6:
1252         case CLOSE+7:
1253         case CLOSE+8:
1254         case CLOSE+9:
1255                 sprintf(buf+strlen(buf), "CLOSE%d", OP(op)-CLOSE);
1256                 p = NULL;
1257                 break;
1258         case STAR:
1259                 p = "STAR";
1260                 break;
1261         case PLUS:
1262                 p = "PLUS";
1263                 break;
1264         case WORDA:
1265                 p = "WORDA";
1266                 break;
1267         case WORDZ:
1268                 p = "WORDZ";
1269                 break;
1270         default:
1271                 regerror("corrupted opcode");
1272                 break;
1273         }
1274         if (p != NULL)
1275                 (void) strcat(buf, p);
1276         return(buf);
1277 }
1278 #endif
1279
1280 /*
1281  * The following is provided for those people who do not have strcspn() in
1282  * their C libraries.  They should get off their butts and do something
1283  * about it; at least one public-domain implementation of those (highly
1284  * useful) string routines has been published on Usenet.
1285  */
1286 #ifdef STRCSPN
1287 /*
1288  * strcspn - find length of initial segment of s1 consisting entirely
1289  * of characters not from s2
1290  */
1291
1292 static int
1293 strcspn(char *s1, char *s2)
1294 {
1295         char *scan1;
1296         char *scan2;
1297         int count;
1298
1299         count = 0;
1300         for (scan1 = s1; *scan1 != '\0'; scan1++) {
1301                 for (scan2 = s2; *scan2 != '\0';)       /* ++ moved down. */
1302                         if (*scan1 == *scan2++)
1303                                 return(count);
1304                 count++;
1305         }
1306         return(count);
1307 }
1308 #endif