lib/libcompat/regexp/regexp.c

   1 /* $DragonFly: src/lib/libcompat/regexp/regexp.c,v 1.3 2008/09/30 16:57:04 swildner Exp $                                                               */
   2 /*
   3  * regcomp and regexec -- regsub and regerror are elsewhere
   4  *
   5  *      Copyright (c) 1986 by University of Toronto.
   6  *      Written by Henry Spencer.  Not derived from licensed software.
   7  *
   8  *      Permission is granted to anyone to use this software for any
   9  *      purpose on any computer system, and to redistribute it freely,
  10  *      subject to the following restrictions:
  11  *
  12  *      1. The author is not responsible for the consequences of use of
  13  *              this software, no matter how awful, even if they arise
  14  *              from defects in it.
  15  *
  16  *      2. The origin of this software must not be misrepresented, either
  17  *              by explicit claim or by omission.
  18  *
  19  *      3. Altered versions must be plainly marked as such, and must not
  20  *              be misrepresented as being the original software.
  21  *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
  22  *** hoptoad!gnu, on 27 Dec 1986, to add \n as an alternative to |
  23  *** to assist in implementing egrep.
  24  *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
  25  *** hoptoad!gnu, on 27 Dec 1986, to add \< and \> for word-matching
  26  *** as in BSD grep and ex.
  27  *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
  28  *** hoptoad!gnu, on 28 Dec 1986, to optimize characters quoted with \.
  29  *** THIS IS AN ALTERED VERSION.  It was altered by James A. Woods,
  30  *** ames!jaw, on 19 June 1987, to quash a regcomp() redundancy.
  31  *
  32  * Beware that some of this code is subtly aware of the way operator
  33  * precedence is structured in regular expressions.  Serious changes in
  34  * regular-expression syntax might require a total rethink.
  35  */
  36 #include <limits.h>
  37 #include <regexp.h>
  38 #include <stdio.h>
  39 #include <ctype.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include "collate.h"
  43 #include "regmagic.h"
  44
  45 /*
  46  * The "internal use only" fields in regexp.h are present to pass info from
  47  * compile to execute that permits the execute phase to run lots faster on
  48  * simple cases.  They are:
  49  *
  50  * regstart     char that must begin a match; '\0' if none obvious
  51  * reganch      is the match anchored (at beginning-of-line only)?
  52  * regmust      string (pointer into program) that match must include, or NULL
  53  * regmlen      length of regmust string
  54  *
  55  * Regstart and reganch permit very fast decisions on suitable starting points
  56  * for a match, cutting down the work a lot.  Regmust permits fast rejection
  57  * of lines that cannot possibly match.  The regmust tests are costly enough
  58  * that regcomp() supplies a regmust only if the r.e. contains something
  59  * potentially expensive (at present, the only such thing detected is * or +
  60  * at the start of the r.e., which can involve a lot of backup).  Regmlen is
  61  * supplied because the test in regexec() needs it and regcomp() is computing
  62  * it anyway.
  63  */
  64
  65 /*
  66  * Structure for regexp "program".  This is essentially a linear encoding
  67  * of a nondeterministic finite-state machine (aka syntax charts or
  68  * "railroad normal form" in parsing technology).  Each node is an opcode
  69  * plus a "next" pointer, possibly plus an operand.  "Next" pointers of
  70  * all nodes except BRANCH implement concatenation; a "next" pointer with
  71  * a BRANCH on both ends of it is connecting two alternatives.  (Here we
  72  * have one of the subtle syntax dependencies:  an individual BRANCH (as
  73  * opposed to a collection of them) is never concatenated with anything
  74  * because of operator precedence.)  The operand of some types of node is
  75  * a literal string; for others, it is a node leading into a sub-FSM.  In
  76  * particular, the operand of a BRANCH node is the first node of the branch.
  77  * (NB this is *not* a tree structure:  the tail of the branch connects
  78  * to the thing following the set of BRANCHes.)  The opcodes are:
  79  */
  80
  81 /* definition   number  opnd?   meaning */
  82 #define END     0       /* no   End of program. */
  83 #define BOL     1       /* no   Match "" at beginning of line. */
  84 #define EOL     2       /* no   Match "" at end of line. */
  85 #define ANY     3       /* no   Match any one character. */
  86 #define ANYOF   4       /* str  Match any character in this string. */
  87 #define ANYBUT  5       /* str  Match any character not in this string. */
  88 #define BRANCH  6       /* node Match this alternative, or the next... */
  89 #define BACK    7       /* no   Match "", "next" ptr points backward. */
  90 #define EXACTLY 8       /* str  Match this string. */
  91 #define NOTHING 9       /* no   Match empty string. */
  92 #define STAR    10      /* node Match this (simple) thing 0 or more times. */
  93 #define PLUS    11      /* node Match this (simple) thing 1 or more times. */
  94 #define WORDA   12      /* no   Match "" at wordchar, where prev is nonword */
  95 #define WORDZ   13      /* no   Match "" at nonwordchar, where prev is word */
  96 #define OPEN    20      /* no   Mark this point in input as start of #n. */
  97                         /*      OPEN+1 is number 1, etc. */
  98 #define CLOSE   30      /* no   Analogous to OPEN. */
  99
 100 /*
 101  * Opcode notes:
 102  *
 103  * BRANCH       The set of branches constituting a single choice are hooked
 104  *              together with their "next" pointers, since precedence prevents
 105  *              anything being concatenated to any individual branch.  The
 106  *              "next" pointer of the last BRANCH in a choice points to the
 107  *              thing following the whole choice.  This is also where the
 108  *              final "next" pointer of each individual branch points; each
 109  *              branch starts with the operand node of a BRANCH node.
 110  *
 111  * BACK         Normal "next" pointers all implicitly point forward; BACK
 112  *              exists to make loop structures possible.
 113  *
 114  * STAR,PLUS    '?', and complex '*' and '+', are implemented as circular
 115  *              BRANCH structures using BACK.  Simple cases (one character
 116  *              per match) are implemented with STAR and PLUS for speed
 117  *              and to minimize recursive plunges.
 118  *
 119  * OPEN,CLOSE   ...are numbered at compile time.
 120  */
 121
 122 /*
 123  * A node is one char of opcode followed by two chars of "next" pointer.
 124  * "Next" pointers are stored as two 8-bit pieces, high order first.  The
 125  * value is a positive offset from the opcode of the node containing it.
 126  * An operand, if any, simply follows the node.  (Note that much of the
 127  * code generation knows about this implicit relationship.)
 128  *
 129  * Using two bytes for the "next" pointer is vast overkill for most things,
 130  * but allows patterns to get big without disasters.
 131  */
 132 #define OP(p)   (*(p))
 133 #define NEXT(p) (((*((p)+1)&0377)<<8) + (*((p)+2)&0377))
 134 #define OPERAND(p)      ((p) + 3)
 135
 136 /*
 137  * See regmagic.h for one further detail of program structure.
 138  */
 139
 140
 141 /*
 142  * Utility definitions.
 143  */
 144 #ifndef CHARBITS
 145 #define UCHARAT(p)      ((int)*(unsigned char *)(p))
 146 #else
 147 #define UCHARAT(p)      ((int)*(p)&CHARBITS)
 148 #endif
 149
 150 #define FAIL(m) { regerror(m); return(NULL); }
 151 #define ISMULT(c)       ((c) == '*' || (c) == '+' || (c) == '?')
 152
 153 /*
 154  * Flags to be passed up and down.
 155  */
 156 #define HASWIDTH        01      /* Known never to match null string. */
 157 #define SIMPLE          02      /* Simple enough to be STAR/PLUS operand. */
 158 #define SPSTART         04      /* Starts with * or +. */
 159 #define WORST           0       /* Worst case. */
 160
 161 /*
 162  * Global work variables for regcomp().
 163  */
 164 static char *regparse;          /* Input-scan pointer. */
 165 static int regnpar;             /* () count. */
 166 static char regdummy;
 167 static char *regcode;           /* Code-emit pointer; &regdummy = don't. */
 168 static long regsize;            /* Code size. */
 169
 170 /*
 171  * Forward declarations for regcomp()'s friends.
 172  */
 173 #ifndef STATIC
 174 #define STATIC  static
 175 #endif
 176 STATIC char *reg(int, int *);
 177 STATIC char *regbranch(int *);
 178 STATIC char *regpiece(int *);
 179 STATIC char *regatom(int *);
 180 STATIC char *regnode(char);
 181 STATIC char *regnext(char *);
 182 STATIC void regc(char);
 183 STATIC void reginsert(char, char *);
 184 STATIC void regtail(char *, char *);
 185 STATIC void regoptail(char *, char *);
 186 #ifdef STRCSPN
 187 STATIC int strcspn(char *, char *);
 188 #endif
 189
 190 /*
 191  - regcomp - compile a regular expression into internal code
 192  *
 193  * We can't allocate space until we know how big the compiled form will be,
 194  * but we can't compile it (and thus know how big it is) until we've got a
 195  * place to put the code.  So we cheat:  we compile it twice, once with code
 196  * generation turned off and size counting turned on, and once "for real".
 197  * This also means that we don't allocate space until we are sure that the
 198  * thing really will compile successfully, and we never have to move the
 199  * code and thus invalidate pointers into it.  (Note that it has to be in
 200  * one piece because free() must be able to free it all.)
 201  *
 202  * Beware that the optimization-preparation code in here knows about some
 203  * of the structure of the compiled regexp.
 204  */
 205 regexp *
 206 regcomp(const char *exp)
 207 {
 208         regexp *r;
 209         char *scan;
 210         char *longest;
 211         int len;
 212         int flags;
 213
 214         if (exp == NULL)
 215                 FAIL("NULL argument");
 216
 217         /* First pass: determine size, legality. */
 218 #ifdef notdef
 219         if (exp[0] == '.' && exp[1] == '*') exp += 2;  /* aid grep */
 220 #endif
 221         regparse = (char *)exp;
 222         regnpar = 1;
 223         regsize = 0L;
 224         regcode = &regdummy;
 225         regc(MAGIC);
 226         if (reg(0, &flags) == NULL)
 227                 return(NULL);
 228
 229         /* Small enough for pointer-storage convention? */
 230         if (regsize >= 32767L)          /* Probably could be 65535L. */
 231                 FAIL("regexp too big");
 232
 233         /* Allocate space. */
 234         r = (regexp *)malloc(sizeof(regexp) + (unsigned)regsize);
 235         if (r == NULL)
 236                 FAIL("out of space");
 237
 238         /* Second pass: emit code. */
 239         regparse = (char *)exp;
 240         regnpar = 1;
 241         regcode = r->program;
 242         regc(MAGIC);
 243         if (reg(0, &flags) == NULL)
 244                 return(NULL);
 245
 246         /* Dig out information for optimizations. */
 247         r->regstart = '\0';     /* Worst-case defaults. */
 248         r->reganch = 0;
 249         r->regmust = NULL;
 250         r->regmlen = 0;
 251         scan = r->program+1;                    /* First BRANCH. */
 252         if (OP(regnext(scan)) == END) {         /* Only one top-level choice. */
 253                 scan = OPERAND(scan);
 254
 255                 /* Starting-point info. */
 256                 if (OP(scan) == EXACTLY)
 257                         r->regstart = *OPERAND(scan);
 258                 else if (OP(scan) == BOL)
 259                         r->reganch++;
 260
 261                 /*
 262                  * If there's something expensive in the r.e., find the
 263                  * longest literal string that must appear and make it the
 264                  * regmust.  Resolve ties in favor of later strings, since
 265                  * the regstart check works with the beginning of the r.e.
 266                  * and avoiding duplication strengthens checking.  Not a
 267                  * strong reason, but sufficient in the absence of others.
 268                  */
 269                 if (flags&SPSTART) {
 270                         longest = NULL;
 271                         len = 0;
 272                         for (; scan != NULL; scan = regnext(scan))
 273                                 if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
 274                                         longest = OPERAND(scan);
 275                                         len = strlen(OPERAND(scan));
 276                                 }
 277                         r->regmust = longest;
 278                         r->regmlen = len;
 279                 }
 280         }
 281
 282         return(r);
 283 }
 284
 285 /*
 286  - reg - regular expression, i.e. main body or parenthesized thing
 287  *
 288  * Caller must absorb opening parenthesis.
 289  *
 290  * Combining parenthesis handling with the base level of regular expression
 291  * is a trifle forced, but the need to tie the tails of the branches to what
 292  * follows makes it hard to avoid.
 293  */
 294 static char *
 295 reg(int paren, int *flagp)
 296 {
 297         char *ret;
 298         char *br;
 299         char *ender;
 300         int parno;
 301         int flags;
 302
 303         *flagp = HASWIDTH;      /* Tentatively. */
 304
 305         /* Make an OPEN node, if parenthesized. */
 306         if (paren) {
 307                 if (regnpar >= NSUBEXP)
 308                         FAIL("too many ()");
 309                 parno = regnpar;
 310                 regnpar++;
 311                 ret = regnode(OPEN+parno);
 312         } else
 313                 ret = NULL;
 314
 315         /* Pick up the branches, linking them together. */
 316         br = regbranch(&flags);
 317         if (br == NULL)
 318                 return(NULL);
 319         if (ret != NULL)
 320                 regtail(ret, br);       /* OPEN -> first. */
 321         else
 322                 ret = br;
 323         if (!(flags&HASWIDTH))
 324                 *flagp &= ~HASWIDTH;
 325         *flagp |= flags&SPSTART;
 326         while (*regparse == '|' || *regparse == '\n') {
 327                 regparse++;
 328                 br = regbranch(&flags);
 329                 if (br == NULL)
 330                         return(NULL);
 331                 regtail(ret, br);       /* BRANCH -> BRANCH. */
 332                 if (!(flags&HASWIDTH))
 333                         *flagp &= ~HASWIDTH;
 334                 *flagp |= flags&SPSTART;
 335         }
 336
 337         /* Make a closing node, and hook it on the end. */
 338         ender = regnode((paren) ? CLOSE+parno : END);
 339         regtail(ret, ender);
 340
 341         /* Hook the tails of the branches to the closing node. */
 342         for (br = ret; br != NULL; br = regnext(br))
 343                 regoptail(br, ender);
 344
 345         /* Check for proper termination. */
 346         if (paren && *regparse++ != ')') {
 347                 FAIL("unmatched ()");
 348         } else if (!paren && *regparse != '\0') {
 349                 if (*regparse == ')') {
 350                         FAIL("unmatched ()");
 351                 } else
 352                         FAIL("junk on end");    /* "Can't happen". */
 353                 /* NOTREACHED */
 354         }
 355
 356         return(ret);
 357 }
 358
 359 /*
 360  - regbranch - one alternative of an | operator
 361  *
 362  * Implements the concatenation operator.
 363  */
 364 static char *
 365 regbranch(int *flagp)
 366 {
 367         char *ret;
 368         char *chain;
 369         char *latest;
 370         int flags;
 371
 372         *flagp = WORST;         /* Tentatively. */
 373
 374         ret = regnode(BRANCH);
 375         chain = NULL;
 376         while (*regparse != '\0' && *regparse != ')' &&
 377                *regparse != '\n' && *regparse != '|') {
 378                 latest = regpiece(&flags);
 379                 if (latest == NULL)
 380                         return(NULL);
 381                 *flagp |= flags&HASWIDTH;
 382                 if (chain == NULL)      /* First piece. */
 383                         *flagp |= flags&SPSTART;
 384                 else
 385                         regtail(chain, latest);
 386                 chain = latest;
 387         }
 388         if (chain == NULL)      /* Loop ran zero times. */
 389                 (void) regnode(NOTHING);
 390
 391         return(ret);
 392 }
 393
 394 /*
 395  - regpiece - something followed by possible [*+?]
 396  *
 397  * Note that the branching code sequences used for ? and the general cases
 398  * of * and + are somewhat optimized:  they use the same NOTHING node as
 399  * both the endmarker for their branch list and the body of the last branch.
 400  * It might seem that this node could be dispensed with entirely, but the
 401  * endmarker role is not redundant.
 402  */
 403 static char *
 404 regpiece(int *flagp)
 405 {
 406         char *ret;
 407         char op;
 408         char *next;
 409         int flags;
 410
 411         ret = regatom(&flags);
 412         if (ret == NULL)
 413                 return(NULL);
 414
 415         op = *regparse;
 416         if (!ISMULT(op)) {
 417                 *flagp = flags;
 418                 return(ret);
 419         }
 420
 421         if (!(flags&HASWIDTH) && op != '?')
 422                 FAIL("*+ operand could be empty");
 423         *flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);
 424
 425         if (op == '*' && (flags&SIMPLE))
 426                 reginsert(STAR, ret);
 427         else if (op == '*') {
 428                 /* Emit x* as (x&|), where & means "self". */
 429                 reginsert(BRANCH, ret);                 /* Either x */
 430                 regoptail(ret, regnode(BACK));          /* and loop */
 431                 regoptail(ret, ret);                    /* back */
 432                 regtail(ret, regnode(BRANCH));          /* or */
 433                 regtail(ret, regnode(NOTHING));         /* null. */
 434         } else if (op == '+' && (flags&SIMPLE))
 435                 reginsert(PLUS, ret);
 436         else if (op == '+') {
 437                 /* Emit x+ as x(&|), where & means "self". */
 438                 next = regnode(BRANCH);                 /* Either */
 439                 regtail(ret, next);
 440                 regtail(regnode(BACK), ret);            /* loop back */
 441                 regtail(next, regnode(BRANCH));         /* or */
 442                 regtail(ret, regnode(NOTHING));         /* null. */
 443         } else if (op == '?') {
 444                 /* Emit x? as (x|) */
 445                 reginsert(BRANCH, ret);                 /* Either x */
 446                 regtail(ret, regnode(BRANCH));          /* or */
 447                 next = regnode(NOTHING);                /* null. */
 448                 regtail(ret, next);
 449                 regoptail(ret, next);
 450         }
 451         regparse++;
 452         if (ISMULT(*regparse))
 453                 FAIL("nested *?+");
 454
 455         return(ret);
 456 }
 457
 458 /*
 459  - regatom - the lowest level
 460  *
 461  * Optimization:  gobbles an entire sequence of ordinary characters so that
 462  * it can turn them into a single node, which is smaller to store and
 463  * faster to run.  Backslashed characters are exceptions, each becoming a
 464  * separate node; the code is simpler that way and it's not worth fixing.
 465  */
 466 static char *
 467 regatom(int *flagp)
 468 {
 469         char *ret;
 470         int flags;
 471
 472         *flagp = WORST;         /* Tentatively. */
 473
 474         switch (*regparse++) {
 475         /* FIXME: these chars only have meaning at beg/end of pat? */
 476         case '^':
 477                 ret = regnode(BOL);
 478                 break;
 479         case '$':
 480                 ret = regnode(EOL);
 481                 break;
 482         case '.':
 483                 ret = regnode(ANY);
 484                 *flagp |= HASWIDTH|SIMPLE;
 485                 break;
 486         case '[': {
 487                         int class;
 488                         int classend;
 489                         int i;
 490
 491                         if (*regparse == '^') { /* Complement of range. */
 492                                 ret = regnode(ANYBUT);
 493                                 regparse++;
 494                         } else
 495                                 ret = regnode(ANYOF);
 496                         if (*regparse == ']' || *regparse == '-')
 497                                 regc(*regparse++);
 498                         while (*regparse != '\0' && *regparse != ']') {
 499                                 if (*regparse == '-') {
 500                                         regparse++;
 501                                         if (*regparse == ']' || *regparse == '\0')
 502                                                 regc('-');
 503                                         else {
 504                                                 class = UCHARAT(regparse-2);
 505                                                 classend = UCHARAT(regparse);
 506                                                 if (__collate_load_error) {
 507                                                         if (class > classend)
 508                                                                 FAIL("invalid [] range");
 509                                                         for (class++; class <= classend; class++)
 510                                                                 regc(class);
 511                                                 } else {
 512                                                         if (__collate_range_cmp(class, classend) > 0)
 513                                                                 FAIL("invalid [] range");
 514                                                         for (i = 0; i <= UCHAR_MAX; i++)
 515                                                                 if (   i != class
 516                                                                     && __collate_range_cmp(class, i) <= 0
 517                                                                     && __collate_range_cmp(i, classend) <= 0
 518                                                                    )
 519                                                                         regc(i);
 520                                                 }
 521                                                 regparse++;
 522                                         }
 523                                 } else
 524                                         regc(*regparse++);
 525                         }
 526                         regc('\0');
 527                         if (*regparse != ']')
 528                                 FAIL("unmatched []");
 529                         regparse++;
 530                         *flagp |= HASWIDTH|SIMPLE;
 531                 }
 532                 break;
 533         case '(':
 534                 ret = reg(1, &flags);
 535                 if (ret == NULL)
 536                         return(NULL);
 537                 *flagp |= flags&(HASWIDTH|SPSTART);
 538                 break;
 539         case '\0':
 540         case '|':
 541         case '\n':
 542         case ')':
 543                 FAIL("internal urp");   /* Supposed to be caught earlier. */
 544                 break;
 545         case '?':
 546         case '+':
 547         case '*':
 548                 FAIL("?+* follows nothing");
 549                 break;
 550         case '\\':
 551                 switch (*regparse++) {
 552                 case '\0':
 553                         FAIL("trailing \\");
 554                         break;
 555                 case '<':
 556                         ret = regnode(WORDA);
 557                         break;
 558                 case '>':
 559                         ret = regnode(WORDZ);
 560                         break;
 561                 /* FIXME: Someday handle \1, \2, ... */
 562                 default:
 563                         /* Handle general quoted chars in exact-match routine */
 564                         goto de_fault;
 565                 }
 566                 break;
 567         de_fault:
 568         default:
 569                 /*
 570                  * Encode a string of characters to be matched exactly.
 571                  *
 572                  * This is a bit tricky due to quoted chars and due to
 573                  * '*', '+', and '?' taking the SINGLE char previous
 574                  * as their operand.
 575                  *
 576                  * On entry, the char at regparse[-1] is going to go
 577                  * into the string, no matter what it is.  (It could be
 578                  * following a \ if we are entered from the '\' case.)
 579                  *
 580                  * Basic idea is to pick up a good char in  ch  and
 581                  * examine the next char.  If it's *+? then we twiddle.
 582                  * If it's \ then we frozzle.  If it's other magic char
 583                  * we push  ch  and terminate the string.  If none of the
 584                  * above, we push  ch  on the string and go around again.
 585                  *
 586                  *  regprev  is used to remember where "the current char"
 587                  * starts in the string, if due to a *+? we need to back
 588                  * up and put the current char in a separate, 1-char, string.
 589                  * When  regprev  is NULL,  ch  is the only char in the
 590                  * string; this is used in *+? handling, and in setting
 591                  * flags |= SIMPLE at the end.
 592                  */
 593                 {
 594                         char *regprev;
 595                         char ch;
 596
 597                         regparse--;                     /* Look at cur char */
 598                         ret = regnode(EXACTLY);
 599                         for ( regprev = 0 ; ; ) {
 600                                 ch = *regparse++;       /* Get current char */
 601                                 switch (*regparse) {    /* look at next one */
 602
 603                                 default:
 604                                         regc(ch);       /* Add cur to string */
 605                                         break;
 606
 607                                 case '.': case '[': case '(':
 608                                 case ')': case '|': case '\n':
 609                                 case '$': case '^':
 610                                 case '\0':
 611                                 /* FIXME, $ and ^ should not always be magic */
 612                                 magic:
 613                                         regc(ch);       /* dump cur char */
 614                                         goto done;      /* and we are done */
 615
 616                                 case '?': case '+': case '*':
 617                                         if (!regprev)   /* If just ch in str, */
 618                                                 goto magic;     /* use it */
 619                                         /* End mult-char string one early */
 620                                         regparse = regprev; /* Back up parse */
 621                                         goto done;
 622
 623                                 case '\\':
 624                                         regc(ch);       /* Cur char OK */
 625                                         switch (regparse[1]){ /* Look after \ */
 626                                         case '\0':
 627                                         case '<':
 628                                         case '>':
 629                                         /* FIXME: Someday handle \1, \2, ... */
 630                                                 goto done; /* Not quoted */
 631                                         default:
 632                                                 /* Backup point is \, scan                                                       * point is after it. */
 633                                                 regprev = regparse;
 634                                                 regparse++;
 635                                                 continue;       /* NOT break; */
 636                                         }
 637                                 }
 638                                 regprev = regparse;     /* Set backup point */
 639                         }
 640                 done:
 641                         regc('\0');
 642                         *flagp |= HASWIDTH;
 643                         if (!regprev)           /* One char? */
 644                                 *flagp |= SIMPLE;
 645                 }
 646                 break;
 647         }
 648
 649         return(ret);
 650 }
 651
 652 /*
 653  - regnode - emit a node
 654  */
 655 static char *                   /* Location. */
 656 regnode(char op)
 657 {
 658         char *ret;
 659         char *ptr;
 660
 661         ret = regcode;
 662         if (ret == &regdummy) {
 663                 regsize += 3;
 664                 return(ret);
 665         }
 666
 667         ptr = ret;
 668         *ptr++ = op;
 669         *ptr++ = '\0';          /* Null "next" pointer. */
 670         *ptr++ = '\0';
 671         regcode = ptr;
 672
 673         return(ret);
 674 }
 675
 676 /*
 677  - regc - emit (if appropriate) a byte of code
 678  */
 679 static void
 680 regc(char b)
 681 {
 682         if (regcode != &regdummy)
 683                 *regcode++ = b;
 684         else
 685                 regsize++;
 686 }
 687
 688 /*
 689  - reginsert - insert an operator in front of already-emitted operand
 690  *
 691  * Means relocating the operand.
 692  */
 693 static void
 694 reginsert(char op, char *opnd)
 695 {
 696         char *src;
 697         char *dst;
 698         char *place;
 699
 700         if (regcode == &regdummy) {
 701                 regsize += 3;
 702                 return;
 703         }
 704
 705         src = regcode;
 706         regcode += 3;
 707         dst = regcode;
 708         while (src > opnd)
 709                 *--dst = *--src;
 710
 711         place = opnd;           /* Op node, where operand used to be. */
 712         *place++ = op;
 713         *place++ = '\0';
 714         *place++ = '\0';
 715 }
 716
 717 /*
 718  - regtail - set the next-pointer at the end of a node chain
 719  */
 720 static void
 721 regtail(char *p, char *val)
 722 {
 723         char *scan;
 724         char *temp;
 725         int offset;
 726
 727         if (p == &regdummy)
 728                 return;
 729
 730         /* Find last node. */
 731         scan = p;
 732         for (;;) {
 733                 temp = regnext(scan);
 734                 if (temp == NULL)
 735                         break;
 736                 scan = temp;
 737         }
 738
 739         if (OP(scan) == BACK)
 740                 offset = scan - val;
 741         else
 742                 offset = val - scan;
 743         *(scan+1) = (offset>>8)&0377;
 744         *(scan+2) = offset&0377;
 745 }
 746
 747 /*
 748  - regoptail - regtail on operand of first argument; nop if operandless
 749  */
 750 static void
 751 regoptail(char *p, char *val)
 752 {
 753         /* "Operandless" and "op != BRANCH" are synonymous in practice. */
 754         if (p == NULL || p == &regdummy || OP(p) != BRANCH)
 755                 return;
 756         regtail(OPERAND(p), val);
 757 }
 758
 759 /*
 760  * regexec and friends
 761  */
 762
 763 /*
 764  * Global work variables for regexec().
 765  */
 766 static char *reginput;          /* String-input pointer. */
 767 static char *regbol;            /* Beginning of input, for ^ check. */
 768 static char **regstartp;        /* Pointer to startp array. */
 769 static char **regendp;          /* Ditto for endp. */
 770
 771 /*
 772  * Forwards.
 773  */
 774 STATIC int regtry();
 775 STATIC int regmatch();
 776 STATIC int regrepeat();
 777
 778 #ifdef DEBUG
 779 int regnarrate = 0;
 780 void regdump();
 781 STATIC char *regprop();
 782 #endif
 783
 784 /*
 785  - regexec - match a regexp against a string
 786  */
 787 int
 788 regexec(const regexp *prog, const char *string)
 789 {
 790         char *s;
 791         extern char *strchr();
 792
 793         /* Be paranoid... */
 794         if (prog == NULL || string == NULL) {
 795                 regerror("NULL parameter");
 796                 return(0);
 797         }
 798
 799         /* Check validity of program. */
 800         if (UCHARAT(prog->program) != MAGIC) {
 801                 regerror("corrupted program");
 802                 return(0);
 803         }
 804
 805         /* If there is a "must appear" string, look for it. */
 806         if (prog->regmust != NULL) {
 807                 s = (char *)string;
 808                 while ((s = strchr(s, prog->regmust[0])) != NULL) {
 809                         if (strncmp(s, prog->regmust, prog->regmlen) == 0)
 810                                 break;  /* Found it. */
 811                         s++;
 812                 }
 813                 if (s == NULL)  /* Not present. */
 814                         return(0);
 815         }
 816
 817         /* Mark beginning of line for ^ . */
 818         regbol = (char *)string;
 819
 820         /* Simplest case:  anchored match need be tried only once. */
 821         if (prog->reganch)
 822                 return(regtry(prog, string));
 823
 824         /* Messy cases:  unanchored match. */
 825         s = (char *)string;
 826         if (prog->regstart != '\0')
 827                 /* We know what char it must start with. */
 828                 while ((s = strchr(s, prog->regstart)) != NULL) {
 829                         if (regtry(prog, s))
 830                                 return(1);
 831                         s++;
 832                 }
 833         else
 834                 /* We don't -- general case. */
 835                 do {
 836                         if (regtry(prog, s))
 837                                 return(1);
 838                 } while (*s++ != '\0');
 839
 840         /* Failure. */
 841         return(0);
 842 }
 843
 844 /*
 845  - regtry - try match at specific point
 846  */
 847 static int                      /* 0 failure, 1 success */
 848 regtry(regexp *prog, char *string)
 849 {
 850         int i;
 851         char **sp;
 852         char **ep;
 853
 854         reginput = string;
 855         regstartp = prog->startp;
 856         regendp = prog->endp;
 857
 858         sp = prog->startp;
 859         ep = prog->endp;
 860         for (i = NSUBEXP; i > 0; i--) {
 861                 *sp++ = NULL;
 862                 *ep++ = NULL;
 863         }
 864         if (regmatch(prog->program + 1)) {
 865                 prog->startp[0] = string;
 866                 prog->endp[0] = reginput;
 867                 return(1);
 868         } else
 869                 return(0);
 870 }
 871
 872 /*
 873  - regmatch - main matching routine
 874  *
 875  * Conceptually the strategy is simple:  check to see whether the current
 876  * node matches, call self recursively to see whether the rest matches,
 877  * and then act accordingly.  In practice we make some effort to avoid
 878  * recursion, in particular by going through "ordinary" nodes (that don't
 879  * need to know whether the rest of the match failed) by a loop instead of
 880  * by recursion.
 881  */
 882 static int                      /* 0 failure, 1 success */
 883 regmatch(char *prog)
 884 {
 885         char *scan;     /* Current node. */
 886         char *next;             /* Next node. */
 887
 888         scan = prog;
 889 #ifdef DEBUG
 890         if (scan != NULL && regnarrate)
 891                 fprintf(stderr, "%s(\n", regprop(scan));
 892 #endif
 893         while (scan != NULL) {
 894 #ifdef DEBUG
 895                 if (regnarrate)
 896                         fprintf(stderr, "%s...\n", regprop(scan));
 897 #endif
 898                 next = regnext(scan);
 899
 900                 switch (OP(scan)) {
 901                 case BOL:
 902                         if (reginput != regbol)
 903                                 return(0);
 904                         break;
 905                 case EOL:
 906                         if (*reginput != '\0')
 907                                 return(0);
 908                         break;
 909                 case WORDA:
 910                         /* Must be looking at a letter, digit, or _ */
 911                         if ((!isalnum((unsigned char)*reginput)) && *reginput != '_')
 912                                 return(0);
 913                         /* Prev must be BOL or nonword */
 914                         if (reginput > regbol &&
 915                             (isalnum((unsigned char)reginput[-1]) || reginput[-1] == '_'))
 916                                 return(0);
 917                         break;
 918                 case WORDZ:
 919                         /* Must be looking at non letter, digit, or _ */
 920                         if (isalnum((unsigned char)*reginput) || *reginput == '_')
 921                                 return(0);
 922                         /* We don't care what the previous char was */
 923                         break;
 924                 case ANY:
 925                         if (*reginput == '\0')
 926                                 return(0);
 927                         reginput++;
 928                         break;
 929                 case EXACTLY: {
 930                                 int len;
 931                                 char *opnd;
 932
 933                                 opnd = OPERAND(scan);
 934                                 /* Inline the first character, for speed. */
 935                                 if (*opnd != *reginput)
 936                                         return(0);
 937                                 len = strlen(opnd);
 938                                 if (len > 1 && strncmp(opnd, reginput, len) != 0)
 939                                         return(0);
 940                                 reginput += len;
 941                         }
 942                         break;
 943                 case ANYOF:
 944                         if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) == NULL)
 945                                 return(0);
 946                         reginput++;
 947                         break;
 948                 case ANYBUT:
 949                         if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) != NULL)
 950                                 return(0);
 951                         reginput++;
 952                         break;
 953                 case NOTHING:
 954                         break;
 955                 case BACK:
 956                         break;
 957                 case OPEN+1:
 958                 case OPEN+2:
 959                 case OPEN+3:
 960                 case OPEN+4:
 961                 case OPEN+5:
 962                 case OPEN+6:
 963                 case OPEN+7:
 964                 case OPEN+8:
 965                 case OPEN+9: {
 966                                 int no;
 967                                 char *save;
 968
 969                                 no = OP(scan) - OPEN;
 970                                 save = reginput;
 971
 972                                 if (regmatch(next)) {
 973                                         /*
 974                                          * Don't set startp if some later
 975                                          * invocation of the same parentheses
 976                                          * already has.
 977                                          */
 978                                         if (regstartp[no] == NULL)
 979                                                 regstartp[no] = save;
 980                                         return(1);
 981                                 } else
 982                                         return(0);
 983                         }
 984                         break;
 985                 case CLOSE+1:
 986                 case CLOSE+2:
 987                 case CLOSE+3:
 988                 case CLOSE+4:
 989                 case CLOSE+5:
 990                 case CLOSE+6:
 991                 case CLOSE+7:
 992                 case CLOSE+8:
 993                 case CLOSE+9: {
 994                                 int no;
 995                                 char *save;
 996
 997                                 no = OP(scan) - CLOSE;
 998                                 save = reginput;
 999
1000                                 if (regmatch(next)) {
1001                                         /*
1002                                          * Don't set endp if some later
1003                                          * invocation of the same parentheses
1004                                          * already has.
1005                                          */
1006                                         if (regendp[no] == NULL)
1007                                                 regendp[no] = save;
1008                                         return(1);
1009                                 } else
1010                                         return(0);
1011                         }
1012                         break;
1013                 case BRANCH: {
1014                                 char *save;
1015
1016                                 if (OP(next) != BRANCH)         /* No choice. */
1017                                         next = OPERAND(scan);   /* Avoid recursion. */
1018                                 else {
1019                                         do {
1020                                                 save = reginput;
1021                                                 if (regmatch(OPERAND(scan)))
1022                                                         return(1);
1023                                                 reginput = save;
1024                                                 scan = regnext(scan);
1025                                         } while (scan != NULL && OP(scan) == BRANCH);
1026                                         return(0);
1027                                         /* NOTREACHED */
1028                                 }
1029                         }
1030                         break;
1031                 case STAR:
1032                 case PLUS: {
1033                                 char nextch;
1034                                 int no;
1035                                 char *save;
1036                                 int min;
1037
1038                                 /*
1039                                  * Lookahead to avoid useless match attempts
1040                                  * when we know what character comes next.
1041                                  */
1042                                 nextch = '\0';
1043                                 if (OP(next) == EXACTLY)
1044                                         nextch = *OPERAND(next);
1045                                 min = (OP(scan) == STAR) ? 0 : 1;
1046                                 save = reginput;
1047                                 no = regrepeat(OPERAND(scan));
1048                                 while (no >= min) {
1049                                         /* If it could work, try it. */
1050                                         if (nextch == '\0' || *reginput == nextch)
1051                                                 if (regmatch(next))
1052                                                         return(1);
1053                                         /* Couldn't or didn't -- back up. */
1054                                         no--;
1055                                         reginput = save + no;
1056                                 }
1057                                 return(0);
1058                         }
1059                         break;
1060                 case END:
1061                         return(1);      /* Success! */
1062                         break;
1063                 default:
1064                         regerror("memory corruption");
1065                         return(0);
1066                         break;
1067                 }
1068
1069                 scan = next;
1070         }
1071
1072         /*
1073          * We get here only if there's trouble -- normally "case END" is
1074          * the terminating point.
1075          */
1076         regerror("corrupted pointers");
1077         return(0);
1078 }
1079
1080 /*
1081  - regrepeat - repeatedly match something simple, report how many
1082  */
1083 static int
1084 regrepeat(char *p)
1085 {
1086         int count = 0;
1087         char *scan;
1088         char *opnd;
1089
1090         scan = reginput;
1091         opnd = OPERAND(p);
1092         switch (OP(p)) {
1093         case ANY:
1094                 count = strlen(scan);
1095                 scan += count;
1096                 break;
1097         case EXACTLY:
1098                 while (*opnd == *scan) {
1099                         count++;
1100                         scan++;
1101                 }
1102                 break;
1103         case ANYOF:
1104                 while (*scan != '\0' && strchr(opnd, *scan) != NULL) {
1105                         count++;
1106                         scan++;
1107                 }
1108                 break;
1109         case ANYBUT:
1110                 while (*scan != '\0' && strchr(opnd, *scan) == NULL) {
1111                         count++;
1112                         scan++;
1113                 }
1114                 break;
1115         default:                /* Oh dear.  Called inappropriately. */
1116                 regerror("internal foulup");
1117                 count = 0;      /* Best compromise. */
1118                 break;
1119         }
1120         reginput = scan;
1121
1122         return(count);
1123 }
1124
1125 /*
1126  - regnext - dig the "next" pointer out of a node
1127  */
1128 static char *
1129 regnext(char *p)
1130 {
1131         int offset;
1132
1133         if (p == &regdummy)
1134                 return(NULL);
1135
1136         offset = NEXT(p);
1137         if (offset == 0)
1138                 return(NULL);
1139
1140         if (OP(p) == BACK)
1141                 return(p-offset);
1142         else
1143                 return(p+offset);
1144 }
1145
1146 #ifdef DEBUG
1147
1148 STATIC char *regprop();
1149
1150 /*
1151  - regdump - dump a regexp onto stdout in vaguely comprehensible form
1152  */
1153 void
1154 regdump(regexp *r)
1155 {
1156         char *s;
1157         char op = EXACTLY;      /* Arbitrary non-END op. */
1158         char *next;
1159         extern char *strchr();
1160
1161
1162         s = r->program + 1;
1163         while (op != END) {     /* While that wasn't END last time... */
1164                 op = OP(s);
1165                 printf("%2d%s", s-r->program, regprop(s));      /* Where, what. */
1166                 next = regnext(s);
1167                 if (next == NULL)               /* Next ptr. */
1168                         printf("(0)");
1169                 else
1170                         printf("(%d)", (s-r->program)+(next-s));
1171                 s += 3;
1172                 if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
1173                         /* Literal string, where present. */
1174                         while (*s != '\0') {
1175                                 putchar(*s);
1176                                 s++;
1177                         }
1178                         s++;
1179                 }
1180                 putchar('\n');
1181         }
1182
1183         /* Header fields of interest. */
1184         if (r->regstart != '\0')
1185                 printf("start `%c' ", r->regstart);
1186         if (r->reganch)
1187                 printf("anchored ");
1188         if (r->regmust != NULL)
1189                 printf("must have \"%s\"", r->regmust);
1190         printf("\n");
1191 }
1192
1193 /*
1194  - regprop - printable representation of opcode
1195  */
1196 static char *
1197 regprop(char *op)
1198 {
1199         char *p;
1200         static char buf[50];
1201
1202         (void) strcpy(buf, ":");
1203
1204         switch (OP(op)) {
1205         case BOL:
1206                 p = "BOL";
1207                 break;
1208         case EOL:
1209                 p = "EOL";
1210                 break;
1211         case ANY:
1212                 p = "ANY";
1213                 break;
1214         case ANYOF:
1215                 p = "ANYOF";
1216                 break;
1217         case ANYBUT:
1218                 p = "ANYBUT";
1219                 break;
1220         case BRANCH:
1221                 p = "BRANCH";
1222                 break;
1223         case EXACTLY:
1224                 p = "EXACTLY";
1225                 break;
1226         case NOTHING:
1227                 p = "NOTHING";
1228                 break;
1229         case BACK:
1230                 p = "BACK";
1231                 break;
1232         case END:
1233                 p = "END";
1234                 break;
1235         case OPEN+1:
1236         case OPEN+2:
1237         case OPEN+3:
1238         case OPEN+4:
1239         case OPEN+5:
1240         case OPEN+6:
1241         case OPEN+7:
1242         case OPEN+8:
1243         case OPEN+9:
1244                 sprintf(buf+strlen(buf), "OPEN%d", OP(op)-OPEN);
1245                 p = NULL;
1246                 break;
1247         case CLOSE+1:
1248         case CLOSE+2:
1249         case CLOSE+3:
1250         case CLOSE+4:
1251         case CLOSE+5:
1252         case CLOSE+6:
1253         case CLOSE+7:
1254         case CLOSE+8:
1255         case CLOSE+9:
1256                 sprintf(buf+strlen(buf), "CLOSE%d", OP(op)-CLOSE);
1257                 p = NULL;
1258                 break;
1259         case STAR:
1260                 p = "STAR";
1261                 break;
1262         case PLUS:
1263                 p = "PLUS";
1264                 break;
1265         case WORDA:
1266                 p = "WORDA";
1267                 break;
1268         case WORDZ:
1269                 p = "WORDZ";
1270                 break;
1271         default:
1272                 regerror("corrupted opcode");
1273                 break;
1274         }
1275         if (p != NULL)
1276                 (void) strcat(buf, p);
1277         return(buf);
1278 }
1279 #endif
1280
1281 /*
1282  * The following is provided for those people who do not have strcspn() in
1283  * their C libraries.  They should get off their butts and do something
1284  * about it; at least one public-domain implementation of those (highly
1285  * useful) string routines has been published on Usenet.
1286  */
1287 #ifdef STRCSPN
1288 /*
1289  * strcspn - find length of initial segment of s1 consisting entirely
1290  * of characters not from s2
1291  */
1292
1293 static int
1294 strcspn(char *s1, char *s2)
1295 {
1296         char *scan1;
1297         char *scan2;
1298         int count;
1299
1300         count = 0;
1301         for (scan1 = s1; *scan1 != '\0'; scan1++) {
1302                 for (scan2 = s2; *scan2 != '\0';)       /* ++ moved down. */
1303                         if (*scan1 == *scan2++)
1304                                 return(count);
1305                 count++;
1306         }
1307         return(count);
1308 }
1309 #endif