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hsregex.c

/*****************************************************************
 * HMMER - Biological sequence analysis with profile HMMs
 * Copyright (C) 1992-2003 Washington University School of Medicine
 * All Rights Reserved
 * 
 *     This source code is distributed under the terms of the
 *     GNU General Public License. See the files COPYING and LICENSE
 *     for details.
 *****************************************************************/

/*****************************************************************
 * This code is an altered version of Henry Spencer's
 * regex library. Alterations are limited to minor streamlining,
 * and some name changes to protect the SQUID namespace.
 * Henry's copyright notice appears below.
 * You can obtain the original from 
 *    ftp://ftp.zoo.toronto.edu/pub/bookregex.tar.Z
 * Thanks, Henry!
 * 
 * The magic word for compiling a testdriver: NBA_TEAM_IN_STL
 * gcc -o test -g -DNBA_TEAM_IN_STL -L. hsregex.c -lsquid -lm
 *  
 * Usage: 
 *  test <pattern> <ntok> <string>
 *  
 * SRE, Fri Aug 28 11:10:17 1998
 * CVS $Id: hsregex.c,v 1.9 2003/10/04 18:26:49 eddy Exp $
 *****************************************************************/    

#include "squidconf.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "squid.h"

/* global sqd_parse[] are managed by Strparse().
 * WARNING: TODO: this code is not threadsafe, and needs to be revised. 
 */
char *sqd_parse[10];

/* Function: Strparse()
 * 
 * Purpose:  Match a regexp to a string. Returns 1 if pattern matches,
 *           else 0.
 *
 *           Much like Perl, Strparse() makes copies of the matching
 *           substrings available via globals, sqd_parse[].
 *           sqd_parse[0] contains a copy of the complete matched
 *           text. sqd_parse[1-9] contain copies of up to nine
 *           different substrings matched within parentheses.
 *           The memory for these strings is internally managed and
 *           volatile; the next call to Strparse() may destroy them.
 *           If the caller needs the matched substrings to persist
 *           beyond a new Strparse() call, it must make its own 
 *           copies.
 *           
 *           A minor drawback of the memory management is that
 *           there will be a small amount of unfree'd memory being
 *           managed by Strparse() when a program exits; this may
 *           confuse memory debugging (Purify, dbmalloc). The
 *           general cleanup function SqdClean() is provided;
 *           you can call this before exiting.
 *           
 *           Uses an extended POSIX regular expression interface.
 *           A copylefted GNU implementation is included in the squid
 *           implementation (gnuregex.c) for use on non-POSIX compliant
 *           systems. POSIX 1003.2-compliant systems (all UNIX,
 *           some WinNT, I believe) can omit the GNU code if necessary.
 *           
 *           I built this for ease of use, not speed nor efficiency.
 *
 * Example:  Strparse("foo-...-baz", "foo-bar-baz")  returns 0
 *           Strparse("foo-(...)-baz", "foo-bar-baz")
 *              returns 0; sqd_parse[0] is "foo-bar-baz";
 *              sqd_parse[1] is "bar".
 *              
 *           A real example:   
 *            s   = ">gnl|ti|3 G10P69425RH2.T0 {SUB 81..737}  /len=657"
 *            pat = "SUB ([0-9]+)"
 *            Strparse(pat, s, 1)
 *               returns 1; sqd_parse[1] is "81".
 *              
 * Args:     rexp  - regular expression, extended POSIX form
 *           s     - string to match against
 *           ntok  - number of () substrings we will save (maximum NSUBEXP-1)
 *                   
 * Return:   1 on match, 0 if no match
 */
int
Strparse(char *rexp, char *s, int ntok)
{
  sqd_regexp *pat;
  int         code;
  int         len;
  int         i;
                        /* sanity check */
  if (ntok >= NSUBEXP )  Die("Strparse(): ntok must be <= %d", NSUBEXP-1); 

  /* Free previous global substring buffers
   */
  for (i = 0; i <= ntok; i++)
    if (sqd_parse[i] != NULL) 
      { 
      free(sqd_parse[i]);
      sqd_parse[i] = NULL;
      }

  /* Compile and match the pattern, using our modified 
   * copy of Henry Spencer's regexp library
   */
  if ((pat = sqd_regcomp(rexp)) == NULL) 
    Die("regexp compilation failed.");
  code = sqd_regexec(pat, s);

  /* Fill the global substring buffers
   */
  if (code == 1) 
    for (i = 0; i <= ntok; i++)
      if (pat->startp[i] != NULL && pat->endp[i] != NULL)
      {
        len = pat->endp[i] - pat->startp[i];
        sqd_parse[i] = (char *) MallocOrDie(sizeof(char) * (len+1));
        strncpy(sqd_parse[i], pat->startp[i], len);
        sqd_parse[i][len] = '\0';
      }

  free(pat);
  return code;
}

/* Function: SqdClean()
 * Date:     SRE, Wed Oct 29 12:52:08 1997 [TWA 721]
 * 
 * Purpose:  Clean up any squid library allocations before exiting
 *           a program, so we don't leave unfree'd memory around
 *           and confuse a malloc debugger like Purify or dbmalloc.
 */
void
SqdClean(void)
{
  int i;

  /* Free global substring buffers that Strparse() uses
   */
  for (i = 0; i <= 9; i++)
    if (sqd_parse[i] != NULL) {
      free(sqd_parse[i]);
      sqd_parse[i] = NULL;
    }
}



/* all code below is:
 * Copyright (c) 1986, 1993, 1995 by University of Toronto.
 * Written by Henry Spencer.  Not derived from licensed software.
 *
 * Permission is granted to anyone to use this software for any
 * purpose on any computer system, and to redistribute it in any way,
 * subject to the following restrictions:
 *
 * 1. The author is not responsible for the consequences of use of
 *    this software, no matter how awful, even if they arise
 *    from defects in it.
 *
 * 2. The origin of this software must not be misrepresented, either
 *    by explicit claim or by omission.
 * 
 * 3. Altered versions must be plainly marked as such, and must not
 *    be misrepresented (by explicit claim or omission) as being
 *    the original software.
 *
 * 4. This notice must not be removed or altered.
 */

/*
 * sqd_regcomp and sqd_regexec -- sqd_regsub and sqd_regerror are elsewhere
 */

/*
 * The first byte of the regexp internal "program" is actually this magic
 * number; the start node begins in the second byte.
 */
#define     SQD_REGMAGIC      0234

/*
 * The "internal use only" fields in regexp.h are present to pass info from
 * compile to execute that permits the execute phase to run lots faster on
 * simple cases.  They are:
 *
 * regstart char that must begin a match; '\0' if none obvious
 * reganch  is the match anchored (at beginning-of-line only)?
 * regmust  string (pointer into program) that match must include, or NULL
 * regmlen  length of regmust string
 *
 * Regstart and reganch permit very fast decisions on suitable starting points
 * for a match, cutting down the work a lot.  Regmust permits fast rejection
 * of lines that cannot possibly match.  The regmust tests are costly enough
 * that sqd_regcomp() supplies a regmust only if the r.e. contains something
 * potentially expensive (at present, the only such thing detected is * or +
 * at the start of the r.e., which can involve a lot of backup).  Regmlen is
 * supplied because the test in sqd_regexec() needs it and sqd_regcomp() is computing
 * it anyway.
 */

/*
 * Structure for regexp "program".  This is essentially a linear encoding
 * of a nondeterministic finite-state machine (aka syntax charts or
 * "railroad normal form" in parsing technology).  Each node is an opcode
 * plus a "next" pointer, possibly plus an operand.  "Next" pointers of
 * all nodes except BRANCH implement concatenation; a "next" pointer with
 * a BRANCH on both ends of it is connecting two alternatives.  (Here we
 * have one of the subtle syntax dependencies:  an individual BRANCH (as
 * opposed to a collection of them) is never concatenated with anything
 * because of operator precedence.)  The operand of some types of node is
 * a literal string; for others, it is a node leading into a sub-FSM.  In
 * particular, the operand of a BRANCH node is the first node of the branch.
 * (NB this is *not* a tree structure:  the tail of the branch connects
 * to the thing following the set of BRANCHes.)  The opcodes are:
 */

/* definition     number      opnd? meaning */
#define     END   0     /* no End of program. */
#define     BOL   1     /* no Match beginning of line. */
#define     EOL   2     /* no Match end of line. */
#define     ANY   3     /* no Match any character. */
#define     ANYOF 4     /* str      Match any of these. */
#define     ANYBUT      5     /* str      Match any but one of these. */
#define     BRANCH      6     /* node     Match this, or the next..\&. */
#define     BACK  7     /* no "next" ptr points backward. */
#define     EXACTLY     8     /* str      Match this string. */
#define     NOTHING     9     /* no Match empty string. */
#define     STAR  10    /* node     Match this 0 or more times. */
#define     PLUS  11    /* node     Match this 1 or more times. */
#define     OPEN  20    /* no Sub-RE starts here. */
                  /*    OPEN+1 is number 1, etc. */
#define     CLOSE 30    /* no Analogous to OPEN. */

/*
 * Opcode notes:
 *
 * BRANCH   The set of branches constituting a single choice are hooked
 *          together with their "next" pointers, since precedence prevents
 *          anything being concatenated to any individual branch.  The
 *          "next" pointer of the last BRANCH in a choice points to the
 *          thing following the whole choice.  This is also where the
 *          final "next" pointer of each individual branch points; each
 *          branch starts with the operand node of a BRANCH node.
 *
 * BACK           Normal "next" pointers all implicitly point forward; BACK
 *          exists to make loop structures possible.
 *
 * STAR,PLUS      '?', and complex '*' and '+', are implemented as circular
 *          BRANCH structures using BACK.  Simple cases (one character
 *          per match) are implemented with STAR and PLUS for speed
 *          and to minimize recursive plunges.
 *
 * OPEN,CLOSE     ...are numbered at compile time.
 */

/*
 * A node is one char of opcode followed by two chars of "next" pointer.
 * "Next" pointers are stored as two 8-bit pieces, high order first.  The
 * value is a positive offset from the opcode of the node containing it.
 * An operand, if any, simply follows the node.  (Note that much of the
 * code generation knows about this implicit relationship.)
 *
 * Using two bytes for the "next" pointer is vast overkill for most things,
 * but allows patterns to get big without disasters.
 */
#define     OP(p)       (*(p))
#define     NEXT(p)           (((*((p)+1)&0177)<<8) + (*((p)+2)&0377))
#define     OPERAND(p)  ((p) + 3)

/*
 * Utility definitions.
 */
#define     FAIL(m)           { sqd_regerror(m); return(NULL); }
#define     ISREPN(c)   ((c) == '*' || (c) == '+' || (c) == '?')
#define     META        "^$.[()|?+*\\"

/*
 * Flags to be passed up and down.
 */
#define     HASWIDTH    01    /* Known never to match null string. */
#define     SIMPLE            02    /* Simple enough to be STAR/PLUS operand. */
#define     SPSTART           04    /* Starts with * or +. */
#define     WORST       0     /* Worst case. */

/*
 * Work-variable struct for sqd_regcomp().
 */
struct comp {
      char *regparse;         /* Input-scan pointer. */
      int regnpar;            /* () count. */
      char *regcode;          /* Code-emit pointer; &regdummy = don't. */
      char regdummy[3]; /* NOTHING, 0 next ptr */
      long regsize;           /* Code size. */
};
#define     EMITTING(cp)      ((cp)->regcode != (cp)->regdummy)

/*
 * Forward declarations for sqd_regcomp()'s friends.
 */
static char *reg(struct comp *cp, int paren, int *flagp);
static char *regbranch(struct comp *cp, int *flagp);
static char *regpiece(struct comp *cp, int *flagp);
static char *regatom(struct comp *cp, int *flagp);
static char *regnode(struct comp *cp, int op);
static char *regnext(char *node);
static void regc(struct comp *cp, int c);
static void reginsert(struct comp *cp, int op, char *opnd);
static void regtail(struct comp *cp, char *p, char *val);
static void regoptail(struct comp *cp, char *p, char *val);

/*
 - sqd_regcomp - compile a regular expression into internal code
 *
 * We can't allocate space until we know how big the compiled form will be,
 * but we can't compile it (and thus know how big it is) until we've got a
 * place to put the code.  So we cheat:  we compile it twice, once with code
 * generation turned off and size counting turned on, and once "for real".
 * This also means that we don't allocate space until we are sure that the
 * thing really will compile successfully, and we never have to move the
 * code and thus invalidate pointers into it.  (Note that it has to be in
 * one piece because free() must be able to free it all.)
 *
 * Beware that the optimization-preparation code in here knows about some
 * of the structure of the compiled regexp.
 */
sqd_regexp *
sqd_regcomp(exp)
const char *exp;
{
      register sqd_regexp *r;
      register char *scan;
      int flags;
      struct comp co;

      if (exp == NULL)
            FAIL("NULL argument to sqd_regcomp");

      /* First pass: determine size, legality. */
      co.regparse = (char *)exp;
      co.regnpar = 1;
      co.regsize = 0L;
      co.regdummy[0] = NOTHING;
      co.regdummy[1] = co.regdummy[2] = 0;
      co.regcode = co.regdummy;
      regc(&co, SQD_REGMAGIC);
      if (reg(&co, 0, &flags) == NULL)
            return(NULL);

      /* Small enough for pointer-storage convention? */
      if (co.regsize >= 0x7fffL)    /* Probably could be 0xffffL. */
            FAIL("regexp too big");

      /* Allocate space. */
      r = (sqd_regexp *)malloc(sizeof(sqd_regexp) + (size_t)co.regsize);
      if (r == NULL)
            FAIL("out of space");

      /* Second pass: emit code. */
      co.regparse = (char *)exp;
      co.regnpar = 1;
      co.regcode = r->program;
      regc(&co, SQD_REGMAGIC);
      if (reg(&co, 0, &flags) == NULL)
            return(NULL);

      /* Dig out information for optimizations. */
      r->regstart = '\0';           /* Worst-case defaults. */
      r->reganch = 0;
      r->regmust = NULL;
      r->regmlen = 0;
      scan = r->program+1;          /* First BRANCH. */
      if (OP(regnext(scan)) == END) {     /* Only one top-level choice. */
            scan = OPERAND(scan);

            /* Starting-point info. */
            if (OP(scan) == EXACTLY)
                  r->regstart = *OPERAND(scan);
            else if (OP(scan) == BOL)
                  r->reganch = 1;

            /*
             * If there's something expensive in the r.e., find the
             * longest literal string that must appear and make it the
             * regmust.  Resolve ties in favor of later strings, since
             * the regstart check works with the beginning of the r.e.
             * and avoiding duplication strengthens checking.  Not a
             * strong reason, but sufficient in the absence of others.
             */
            if (flags&SPSTART) {
                  register char *longest = NULL;
                  register size_t len = 0;

                  for (; scan != NULL; scan = regnext(scan))
                        if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
                              longest = OPERAND(scan);
                              len = strlen(OPERAND(scan));
                        }
                  r->regmust = longest;
                  r->regmlen = (int)len;
            }
      }

      return(r);
}

/*
 - reg - regular expression, i.e. main body or parenthesized thing
 *
 * Caller must absorb opening parenthesis.
 *
 * Combining parenthesis handling with the base level of regular expression
 * is a trifle forced, but the need to tie the tails of the branches to what
 * follows makes it hard to avoid.
 */
static char *
reg(cp, paren, flagp)
register struct comp *cp;
int paren;              /* Parenthesized? */
int *flagp;
{
      register char *ret = NULL;   /* SRE: NULL init added to silence gcc */
      register char *br;
      register char *ender;
      register int parno = 0; /* SRE: init added to silence gcc */
      int flags;

      *flagp = HASWIDTH;      /* Tentatively. */

      if (paren) {
            /* Make an OPEN node. */
            if (cp->regnpar >= NSUBEXP)
                  FAIL("too many ()");
            parno = cp->regnpar;
            cp->regnpar++;
            ret = regnode(cp, OPEN+parno);
      }

      /* Pick up the branches, linking them together. */
      br = regbranch(cp, &flags);
      if (br == NULL)
            return(NULL);
      if (paren)
            regtail(cp, ret, br);   /* OPEN -> first. */
      else
            ret = br;
      *flagp &= ~(~flags&HASWIDTH); /* Clear bit if bit 0. */
      *flagp |= flags&SPSTART;
      while (*cp->regparse == '|') {
            cp->regparse++;
            br = regbranch(cp, &flags);
            if (br == NULL)
                  return(NULL);
            regtail(cp, ret, br);   /* BRANCH -> BRANCH. */
            *flagp &= ~(~flags&HASWIDTH);
            *flagp |= flags&SPSTART;
      }

      /* Make a closing node, and hook it on the end. */
      ender = regnode(cp, (paren) ? CLOSE+parno : END);
      regtail(cp, ret, ender);

      /* Hook the tails of the branches to the closing node. */
      for (br = ret; br != NULL; br = regnext(br))
            regoptail(cp, br, ender);

      /* Check for proper termination. */
      if (paren && *cp->regparse++ != ')') {
            FAIL("unterminated ()");
      } else if (!paren && *cp->regparse != '\0') {
            if (*cp->regparse == ')') {
                  FAIL("unmatched ()");
            } else
                  FAIL("internal error: junk on end");
            /* NOTREACHED */
      }

      return(ret);
}

/*
 - regbranch - one alternative of an | operator
 *
 * Implements the concatenation operator.
 */
static char *
regbranch(cp, flagp)
register struct comp *cp;
int *flagp;
{
      register char *ret;
      register char *chain;
      register char *latest;
      int flags;
      register int c;

      *flagp = WORST;                     /* Tentatively. */

      ret = regnode(cp, BRANCH);
      chain = NULL;
      while ((c = *cp->regparse) != '\0' && c != '|' && c != ')') {
            latest = regpiece(cp, &flags);
            if (latest == NULL)
                  return(NULL);
            *flagp |= flags&HASWIDTH;
            if (chain == NULL)            /* First piece. */
                  *flagp |= flags&SPSTART;
            else
                  regtail(cp, chain, latest);
            chain = latest;
      }
      if (chain == NULL)                  /* Loop ran zero times. */
            (void) regnode(cp, NOTHING);

      return(ret);
}

/*
 - regpiece - something followed by possible [*+?]
 *
 * Note that the branching code sequences used for ? and the general cases
 * of * and + are somewhat optimized:  they use the same NOTHING node as
 * both the endmarker for their branch list and the body of the last branch.
 * It might seem that this node could be dispensed with entirely, but the
 * endmarker role is not redundant.
 */
static char *
regpiece(cp, flagp)
register struct comp *cp;
int *flagp;
{
      register char *ret;
      register char op;
      register char *next;
      int flags;

      ret = regatom(cp, &flags);
      if (ret == NULL)
            return(NULL);

      op = *cp->regparse;
      if (!ISREPN(op)) {
            *flagp = flags;
            return(ret);
      }

      if (!(flags&HASWIDTH) && op != '?')
            FAIL("*+ operand could be empty");
      switch (op) {
      case '*':   *flagp = WORST|SPSTART;             break;
      case '+':   *flagp = WORST|SPSTART|HASWIDTH;    break;
      case '?':   *flagp = WORST;                     break;
      }

      if (op == '*' && (flags&SIMPLE))
            reginsert(cp, STAR, ret);
      else if (op == '*') {
            /* Emit x* as (x&|), where & means "self". */
            reginsert(cp, BRANCH, ret);         /* Either x */
            regoptail(cp, ret, regnode(cp, BACK));    /* and loop */
            regoptail(cp, ret, ret);            /* back */
            regtail(cp, ret, regnode(cp, BRANCH));    /* or */
            regtail(cp, ret, regnode(cp, NOTHING));   /* null. */
      } else if (op == '+' && (flags&SIMPLE))
            reginsert(cp, PLUS, ret);
      else if (op == '+') {
            /* Emit x+ as x(&|), where & means "self". */
            next = regnode(cp, BRANCH);         /* Either */
            regtail(cp, ret, next);
            regtail(cp, regnode(cp, BACK), ret);      /* loop back */
            regtail(cp, next, regnode(cp, BRANCH));   /* or */
            regtail(cp, ret, regnode(cp, NOTHING));   /* null. */
      } else if (op == '?') {
            /* Emit x? as (x|) */
            reginsert(cp, BRANCH, ret);         /* Either x */
            regtail(cp, ret, regnode(cp, BRANCH));    /* or */
            next = regnode(cp, NOTHING);        /* null. */
            regtail(cp, ret, next);
            regoptail(cp, ret, next);
      }
      cp->regparse++;
      if (ISREPN(*cp->regparse))
            FAIL("nested *?+");

      return(ret);
}

/*
 - regatom - the lowest level
 *
 * Optimization:  gobbles an entire sequence of ordinary characters so that
 * it can turn them into a single node, which is smaller to store and
 * faster to run.  Backslashed characters are exceptions, each becoming a
 * separate node; the code is simpler that way and it's not worth fixing.
 */
static char *
regatom(cp, flagp)
register struct comp *cp;
int *flagp;
{
      register char *ret;
      int flags;

      *flagp = WORST;         /* Tentatively. */

      switch (*cp->regparse++) {
      case '^':
            ret = regnode(cp, BOL);
            break;
      case '$':
            ret = regnode(cp, EOL);
            break;
      case '.':
            ret = regnode(cp, ANY);
            *flagp |= HASWIDTH|SIMPLE;
            break;
      case '[': {
            register int range;
            register int rangeend;
            register int c;

            if (*cp->regparse == '^') {   /* Complement of range. */
                  ret = regnode(cp, ANYBUT);
                  cp->regparse++;
            } else
                  ret = regnode(cp, ANYOF);
            if ((c = *cp->regparse) == ']' || c == '-') {
                  regc(cp, c);
                  cp->regparse++;
            }
            while ((c = *cp->regparse++) != '\0' && c != ']') {
                  if (c != '-')
                        regc(cp, c);
                  else if ((c = *cp->regparse) == ']' || c == '\0')
                        regc(cp, '-');
                  else {
                        range = (unsigned char)*(cp->regparse-2);
                        rangeend = (unsigned char)c;
                        if (range > rangeend)
                              FAIL("invalid [] range");
                        for (range++; range <= rangeend; range++)
                              regc(cp, range);
                        cp->regparse++;
                  }
            }
            regc(cp, '\0');
            if (c != ']')
                  FAIL("unmatched []");
            *flagp |= HASWIDTH|SIMPLE;
            break;
            }
      case '(':
            ret = reg(cp, 1, &flags);
            if (ret == NULL)
                  return(NULL);
            *flagp |= flags&(HASWIDTH|SPSTART);
            break;
      case '\0':
      case '|':
      case ')':
            /* supposed to be caught earlier */
            FAIL("internal error: \\0|) unexpected");
            /*NOTREACHED*/
            break;
      case '?':
      case '+':
      case '*':
            FAIL("?+* follows nothing");
            /*NOTREACHED*/
            break;
      case '\\':
            if (*cp->regparse == '\0')
                  FAIL("trailing \\");
            ret = regnode(cp, EXACTLY);
            regc(cp, *cp->regparse++);
            regc(cp, '\0');
            *flagp |= HASWIDTH|SIMPLE;
            break;
      default: {
            register size_t len;
            register char ender;

            cp->regparse--;
            len = strcspn(cp->regparse, META);
            if (len == 0)
                  FAIL("internal error: strcspn 0");
            ender = *(cp->regparse+len);
            if (len > 1 && ISREPN(ender))
                  len--;            /* Back off clear of ?+* operand. */
            *flagp |= HASWIDTH;
            if (len == 1)
                  *flagp |= SIMPLE;
            ret = regnode(cp, EXACTLY);
            for (; len > 0; len--)
                  regc(cp, *cp->regparse++);
            regc(cp, '\0');
            break;
            }
      }

      return(ret);
}

/*
 - regnode - emit a node
 */
static char *                 /* Location. */
regnode(cp, op)
register struct comp *cp;
char op;
{
      register char *const ret = cp->regcode;
      register char *ptr;

      if (!EMITTING(cp)) {
            cp->regsize += 3;
            return(ret);
      }

      ptr = ret;
      *ptr++ = op;
      *ptr++ = '\0';          /* Null next pointer. */
      *ptr++ = '\0';
      cp->regcode = ptr;

      return(ret);
}

/*
 - regc - emit (if appropriate) a byte of code
 */
static void
regc(cp, b)
register struct comp *cp;
char b;
{
      if (EMITTING(cp))
            *cp->regcode++ = b;
      else
            cp->regsize++;
}

/*
 - reginsert - insert an operator in front of already-emitted operand
 *
 * Means relocating the operand.
 */
static void
reginsert(cp, op, opnd)
register struct comp *cp;
char op;
char *opnd;
{
      register char *place;

      if (!EMITTING(cp)) {
            cp->regsize += 3;
            return;
      }

      (void) memmove(opnd+3, opnd, (size_t)(cp->regcode - opnd));
      cp->regcode += 3;

      place = opnd;           /* Op node, where operand used to be. */
      *place++ = op;
      *place++ = '\0';
      *place++ = '\0';
}

/*
 - regtail - set the next-pointer at the end of a node chain
 */
static void
regtail(cp, p, val)
register struct comp *cp;
char *p;
char *val;
{
      register char *scan;
      register char *temp;
      register int offset;

      if (!EMITTING(cp))
            return;

      /* Find last node. */
      for (scan = p; (temp = regnext(scan)) != NULL; scan = temp)
            continue;

      offset = (OP(scan) == BACK) ? scan - val : val - scan;
      *(scan+1) = (offset>>8)&0177;
      *(scan+2) = offset&0377;
}

/*
 - regoptail - regtail on operand of first argument; nop if operandless
 */
static void
regoptail(cp, p, val)
register struct comp *cp;
char *p;
char *val;
{
      /* "Operandless" and "op != BRANCH" are synonymous in practice. */
      if (!EMITTING(cp) || OP(p) != BRANCH)
            return;
      regtail(cp, OPERAND(p), val);
}

/*
 * sqd_regexec and friends
 */

/*
 * Work-variable struct for sqd_regexec().
 */
struct exec {
      char *reginput;         /* String-input pointer. */
      char *regbol;           /* Beginning of input, for ^ check. */
      char **regstartp; /* Pointer to startp array. */
      char **regendp;         /* Ditto for endp. */
};

/*
 * Forwards.
 */
static int regtry(struct exec *ep, sqd_regexp *rp, char *string);
static int regmatch(struct exec *ep, char *prog);
static size_t regrepeat(struct exec *ep, char *node);

#ifdef DEBUG
int regnarrate = 0;
void regdump();
static char *regprop();
#endif

/*
 - sqd_regexec - match a regexp against a string
 */
int
sqd_regexec(prog, str)
register sqd_regexp *prog;
const char *str;
{
      register char *string = (char *)str;      /* avert const poisoning */
      register char *s;
      struct exec ex;

      /* Be paranoid. */
      if (prog == NULL || string == NULL) {
            sqd_regerror("NULL argument to sqd_regexec");
            return(0);
      }

      /* Check validity of program. */
      if ((unsigned char)*prog->program != SQD_REGMAGIC) {
            sqd_regerror("corrupted regexp");
            return(0);
      }

      /* If there is a "must appear" string, look for it. */
      if (prog->regmust != NULL && strstr(string, prog->regmust) == NULL)
            return(0);

      /* Mark beginning of line for ^ . */
      ex.regbol = string;
      ex.regstartp = prog->startp;
      ex.regendp = prog->endp;

      /* Simplest case:  anchored match need be tried only once. */
      if (prog->reganch)
            return(regtry(&ex, prog, string));

      /* Messy cases:  unanchored match. */
      if (prog->regstart != '\0') {
            /* We know what char it must start with. */
            for (s = string; s != NULL; s = strchr(s+1, prog->regstart))
                  if (regtry(&ex, prog, s))
                        return(1);
            return(0);
      } else {
            /* We don't -- general case. */
            for (s = string; !regtry(&ex, prog, s); s++)
                  if (*s == '\0')
                        return(0);
            return(1);
      }
      /* NOTREACHED */
}

/*
 - regtry - try match at specific point
 */
static int              /* 0 failure, 1 success */
regtry(ep, prog, string)
register struct exec *ep;
sqd_regexp *prog;
char *string;
{
      register int i;
      register char **stp;
      register char **enp;

      ep->reginput = string;

      stp = prog->startp;
      enp = prog->endp;
      for (i = NSUBEXP; i > 0; i--) {
            *stp++ = NULL;
            *enp++ = NULL;
      }
      if (regmatch(ep, prog->program + 1)) {
            prog->startp[0] = string;
            prog->endp[0] = ep->reginput;
            return(1);
      } else
            return(0);
}

/*
 - regmatch - main matching routine
 *
 * Conceptually the strategy is simple:  check to see whether the current
 * node matches, call self recursively to see whether the rest matches,
 * and then act accordingly.  In practice we make some effort to avoid
 * recursion, in particular by going through "ordinary" nodes (that don't
 * need to know whether the rest of the match failed) by a loop instead of
 * by recursion.
 */
static int              /* 0 failure, 1 success */
regmatch(ep, prog)
register struct exec *ep;
char *prog;
{
      register char *scan;    /* Current node. */
      char *next;       /* Next node. */

#ifdef DEBUG
      if (prog != NULL && regnarrate)
            fprintf(stderr, "%s(\n", regprop(prog));
#endif
      for (scan = prog; scan != NULL; scan = next) {
#ifdef DEBUG
            if (regnarrate)
                  fprintf(stderr, "%s...\n", regprop(scan));
#endif
            next = regnext(scan);

            switch (OP(scan)) {
            case BOL:
                  if (ep->reginput != ep->regbol)
                        return(0);
                  break;
            case EOL:
                  if (*ep->reginput != '\0')
                        return(0);
                  break;
            case ANY:
                  if (*ep->reginput == '\0')
                        return(0);
                  ep->reginput++;
                  break;
            case EXACTLY: {
                  register size_t len;
                  register char *const opnd = OPERAND(scan);

                  /* Inline the first character, for speed. */
                  if (*opnd != *ep->reginput)
                        return(0);
                  len = strlen(opnd);
                  if (len > 1 && strncmp(opnd, ep->reginput, len) != 0)
                        return(0);
                  ep->reginput += len;
                  break;
                  }
            case ANYOF:
                  if (*ep->reginput == '\0' ||
                              strchr(OPERAND(scan), *ep->reginput) == NULL)
                        return(0);
                  ep->reginput++;
                  break;
            case ANYBUT:
                  if (*ep->reginput == '\0' ||
                              strchr(OPERAND(scan), *ep->reginput) != NULL)
                        return(0);
                  ep->reginput++;
                  break;
            case NOTHING:
                  break;
            case BACK:
                  break;
            case OPEN+1: case OPEN+2: case OPEN+3:
            case OPEN+4: case OPEN+5: case OPEN+6:
            case OPEN+7: case OPEN+8: case OPEN+9: {
                  register const int no = OP(scan) - OPEN;
                  register char *const input = ep->reginput;

                  if (regmatch(ep, next)) {
                        /*
                         * Don't set startp if some later
                         * invocation of the same parentheses
                         * already has.
                         */
                        if (ep->regstartp[no] == NULL)
                              ep->regstartp[no] = input;
                        return(1);
                  } else
                        return(0);
                  /*NOTREACHED*/
                  break;
                    }
            case CLOSE+1: case CLOSE+2: case CLOSE+3:
            case CLOSE+4: case CLOSE+5: case CLOSE+6:
            case CLOSE+7: case CLOSE+8: case CLOSE+9: {
                  register const int no = OP(scan) - CLOSE;
                  register char *const input = ep->reginput;

                  if (regmatch(ep, next)) {
                        /*
                         * Don't set endp if some later
                         * invocation of the same parentheses
                         * already has.
                         */
                        if (ep->regendp[no] == NULL)
                              ep->regendp[no] = input;
                        return(1);
                  } else
                        return(0);
                  /*NOTREACHED*/
                  break;
                  }
            case BRANCH: {
                  register char *const save = ep->reginput;

                  if (OP(next) != BRANCH)       /* No choice. */
                        next = OPERAND(scan);   /* Avoid recursion. */
                  else {
                        while (OP(scan) == BRANCH) {
                              if (regmatch(ep, OPERAND(scan)))
                                    return(1);
                              ep->reginput = save;
                              scan = regnext(scan);
                        }
                        return(0);
                        /*NOTREACHED*/
                  }
                  break;
                  }
            case STAR: case PLUS: {
                  register const char nextch =
                        (OP(next) == EXACTLY) ? *OPERAND(next) : '\0';
                  register size_t no;
                  register char *const save = ep->reginput;
                  register const size_t min = (OP(scan) == STAR) ? 0 : 1;

                  for (no = regrepeat(ep, OPERAND(scan)) + 1; no > min; no--) {
                        ep->reginput = save + no - 1;
                        /* If it could work, try it. */
                        if (nextch == '\0' || *ep->reginput == nextch)
                              if (regmatch(ep, next))
                                    return(1);
                  }
                  return(0);
                  /*NOTREACHED*/
                  break;
                  }
            case END:
                  return(1);  /* Success! */
                  break;
            default:
                  sqd_regerror("regexp corruption");
                  return(0);
                  /*NOTREACHED*/
                  break;
            }
      }

      /*
       * We get here only if there's trouble -- normally "case END" is
       * the terminating point.
       */
      sqd_regerror("corrupted pointers");
      return(0);
}

/*
 - regrepeat - report how many times something simple would match
 */
static size_t
regrepeat(ep, node)
register struct exec *ep;
char *node;
{
      register size_t count;
      register char *scan;
      register char ch;

      switch (OP(node)) {
      case ANY:
            return(strlen(ep->reginput));
            break;
      case EXACTLY:
            ch = *OPERAND(node);
            count = 0;
            for (scan = ep->reginput; *scan == ch; scan++)
                  count++;
            return(count);
            /*NOTREACHED*/
            break;
      case ANYOF:
            return(strspn(ep->reginput, OPERAND(node)));
            break;
      case ANYBUT:
            return(strcspn(ep->reginput, OPERAND(node)));
            break;
      default:          /* Oh dear.  Called inappropriately. */
            sqd_regerror("internal error: bad call of regrepeat");
            return(0);  /* Best compromise. */
                /*NOTREACHED*/
            break;
      }
      /* NOTREACHED */
}

/*
 - regnext - dig the "next" pointer out of a node
 */
static char *
regnext(p)
register char *p;
{
      register const int offset = NEXT(p);

      if (offset == 0)
            return(NULL);

      return((OP(p) == BACK) ? p-offset : p+offset);
}

#ifdef DEBUG

static char *regprop();

/*
 - regdump - dump a regexp onto stdout in vaguely comprehensible form
 */
void
regdump(r)
sqd_regexp *r;
{
      register char *s;
      register char op = EXACTLY;   /* Arbitrary non-END op. */
      register char *next;


      s = r->program + 1;
      while (op != END) {     /* While that wasn't END last time... */
            op = OP(s);
            printf("%2d%s", s-r->program, regprop(s));      /* Where, what. */
            next = regnext(s);
            if (next == NULL)       /* Next ptr. */
                  printf("(0)");
            else 
                  printf("(%d)", (s-r->program)+(next-s));
            s += 3;
            if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
                  /* Literal string, where present. */
                  while (*s != '\0') {
                        putchar(*s);
                        s++;
                  }
                  s++;
            }
            putchar('\n');
      }

      /* Header fields of interest. */
      if (r->regstart != '\0')
            printf("start `%c' ", r->regstart);
      if (r->reganch)
            printf("anchored ");
      if (r->regmust != NULL)
            printf("must have \"%s\"", r->regmust);
      printf("\n");
}

/*
 - regprop - printable representation of opcode
 */
static char *
regprop(op)
char *op;
{
      register char *p;
      static char buf[50];

      (void) strcpy(buf, ":");

      switch (OP(op)) {
      case BOL:
            p = "BOL";
            break;
      case EOL:
            p = "EOL";
            break;
      case ANY:
            p = "ANY";
            break;
      case ANYOF:
            p = "ANYOF";
            break;
      case ANYBUT:
            p = "ANYBUT";
            break;
      case BRANCH:
            p = "BRANCH";
            break;
      case EXACTLY:
            p = "EXACTLY";
            break;
      case NOTHING:
            p = "NOTHING";
            break;
      case BACK:
            p = "BACK";
            break;
      case END:
            p = "END";
            break;
      case OPEN+1:
      case OPEN+2:
      case OPEN+3:
      case OPEN+4:
      case OPEN+5:
      case OPEN+6:
      case OPEN+7:
      case OPEN+8:
      case OPEN+9:
            sprintf(buf+strlen(buf), "OPEN%d", OP(op)-OPEN);
            p = NULL;
            break;
      case CLOSE+1:
      case CLOSE+2:
      case CLOSE+3:
      case CLOSE+4:
      case CLOSE+5:
      case CLOSE+6:
      case CLOSE+7:
      case CLOSE+8:
      case CLOSE+9:
            sprintf(buf+strlen(buf), "CLOSE%d", OP(op)-CLOSE);
            p = NULL;
            break;
      case STAR:
            p = "STAR";
            break;
      case PLUS:
            p = "PLUS";
            break;
      default:
            sqd_regerror("corrupted opcode");
            break;
      }
      if (p != NULL)
            (void) strcat(buf, p);
      return(buf);
}
#endif


/*
 - sqd_regsub - perform substitutions after a regexp match
 */
void
sqd_regsub(rp, source, dest)
const sqd_regexp *rp;
const char *source;
char *dest;
{
      register sqd_regexp * const prog = (sqd_regexp *)rp;
      register char *src = (char *)source;
      register char *dst = dest;
      register char c;
      register int no;
      register size_t len;

      if (prog == NULL || source == NULL || dest == NULL) {
            sqd_regerror("NULL parameter to sqd_regsub");
            return;
      }
      if ((unsigned char)*(prog->program) != SQD_REGMAGIC) {
            sqd_regerror("damaged regexp");
            return;
      }

      while ((c = *src++) != '\0') {
            if (c == '&')
                  no = 0;
            else if (c == '\\' && isdigit((int) (*src)))
                  no = *src++ - '0';
            else
                  no = -1;

            if (no < 0) {     /* Ordinary character. */
                  if (c == '\\' && (*src == '\\' || *src == '&'))
                        c = *src++;
                  *dst++ = c;
            } else if (prog->startp[no] != NULL && prog->endp[no] != NULL &&
                              prog->endp[no] > prog->startp[no]) {
                  len = prog->endp[no] - prog->startp[no];
                  (void) strncpy(dst, prog->startp[no], len);
                  dst += len;
                  if (*(dst-1) == '\0') { /* strncpy hit NUL. */
                        sqd_regerror("damaged match string");
                        return;
                  }
            }
      }
      *dst++ = '\0';
}


void
sqd_regerror(s)
char *s;
{
  fprintf(stderr, "regexp(3): %s\n", s);
  exit(EXIT_FAILURE);
  /* NOTREACHED */
}

#ifdef NBA_TEAM_IN_STL
int
main(int argc, char **argv)
{
  char *pat;
  int   ntok;
  char *s;
  int   status;

  pat  = argv[1];
  ntok = atoi(argv[2]);
  s    = argv[3];

  status = Strparse(pat, s, ntok);
  if (status == 0) {
    printf("no match\n");
  } else {
    int i;
    printf("MATCH.\n");
    for (i = 1; i <= ntok; i++) 
      printf("matched token %1d:  %s\n", i, sqd_parse[i]);
  }
}
#endif /*NBA_TEAM_IN_STL*/

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