ossimRegExp.cpp

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//
// Copyright (C) 1991 Texas Instruments Incorporated.
//
// Permission is granted to any individual or institution to use, copy, modify,
// and distribute this software, provided that this complete copyright and
// permission notice is maintained, intact, in all copies and supporting
// documentation.
//
// Texas Instruments Incorporated provides this software "as is" without
// express or implied warranty.
//
//
// Created: MNF 06/13/89  Initial Design and Implementation
// Updated: LGO 08/09/89  Inherit from Generic
// Updated: MBN 09/07/89  Added conditional exception handling
// Updated: MBN 12/15/89  Sprinkled "const" qualifiers all over the place!
// Updated: DLS 03/22/91  New lite version
//
// This  is the header file  for the regular  expression class.   An object of
// this class contains a regular expression,  in  a special "compiled" format.
// This  compiled format consists  of  several slots   all kept as the objects
// private data.  The  RegExp class  provides a convenient  way  to  represent
// regular  expressions.  It makes it easy   to search  for  the  same regular
// expression in many different strings without having to  compile a string to
// regular expression format more than necessary.
//
// A regular  expression allows a programmer to  specify complex patterns that
// can be searched for  and  matched against the  character string of a String
// object.  In  its  simplest case, a   regular expression  is a  sequence  of
// characters with which you can search for exact character matches.  However,
// many times you may not know the exact sequence you want to find, or you may
// only want to find a match at the beginning or end of  a String.  The RegExp
// object  allows specification of  such patterns by  utilizing the  following
// regular  expression  meta-characters   (note   that  more  one  of    these
// meta-characters  can  be used in a single  regular  expression in  order to
// create complex search patterns):
//
//         ^    Match at beginning of line
//         $    Match at end of line
//         .    Match any single character
//         [ ]  Match any one character inside the brackets
//         [^ ] Match any character NOT inside the brackets
//         -    Match any character in range on either side of dash
//         *    Match preceding pattern zero or more times
//         +    Match preceding pattern one or more times
//         ?    Match preceding pattern zero or once only
//         ()   Save a matched expression and use it in a further match.
//
// There are three constructors for RegExp.  One  just creates an empty RegExp
// object.  Another creates a RegExp object  and initializes it with a regular
// expression  that is given  in  the form of a   char*.   The  third  takes a
// reference  to  a RegExp  object    as an  argument    and creates an object
// initialized with the information from the given RegExp object.
//
// The  find  member function  finds   the  first  occurence   of  the regualr
// expression of that object in the string given to find as an argument.  Find
// returns a boolean, and  if true,  mutates  the private  data appropriately.
// Find sets pointers to the beginning and end of  the thing last  found, they
// are pointers into the actual string  that was searched.   The start and end
// member functions return indicies  into the searched string that  correspond
// to the beginning   and  end pointers  respectively.   The    compile member
// function takes a char* and puts the  compiled version of the char* argument
// into the object's private data fields.  The == and  != operators only check
// the  to see  if   the compiled  regular  expression   is the same, and  the
// deep_equal functions also checks  to see if the  start and end pointers are
// the same.  The is_valid  function returns false if  program is set to NULL,
// (i.e. there is no valid compiled exression).  The set_invalid function sets
// the  program to NULL  (Warning: this deletes the compiled  expression). The
// following examples may help clarify regular expression usage:
//
//   *  The regular expression  "^hello" matches  a "hello"  only at  the
//      beginning of a  line.  It would match "hello  there" but not "hi,
//      hello there".
//
//   *  The regular expression "long$" matches a  "long"  only at the end
//      of a line. It would match "so long\0", but not "long ago".
//
//   *  The regular expression "t..t..g"  will match anything that  has a
//      "t" then any two characters, another "t", any  two characters and
//      then a "g".   It will match  "testing", or "test again" but would
//      not match "toasting"
//
//   *  The regular  expression "[1-9ab]" matches any  number one through
//      nine, and the characters  "a" and  "b".  It would match "hello 1"
//      or "begin", but would not match "no-match".
//
//   *  The  regular expression "[^1-9ab]"  matches any character that is
//      not a number one  through nine, or  an "a" or "b".   It would NOT
//      match "hello 1" or "begin", but would match "no-match".
//
//   *  The regular expression "br* " matches  something that begins with
//      a "b", is followed by zero or more "r"s, and ends in a space.  It
//      would match "brrrrr ", and "b ", but would not match "brrh ".
//
//   *  The regular expression "br+ " matches something  that begins with
//      a "b", is followed by one or more "r"s, and ends in  a space.  It
//      would match "brrrrr ",  and  "br ", but would not  match "b  " or
//      "brrh ".
//
//   *  The regular expression "br? " matches  something that begins with
//      a "b", is followed by zero or one "r"s, and ends in  a space.  It
//      would  match  "br ", and "b  ", but would not match  "brrrr "  or
//      "brrh ".
//
//   *  The regular expression "(..p)b" matches  something ending with pb
//      and beginning with whatever the two characters before the first p
//      encounterd in the line were.  It would find  "repb" in "rep drepa
//      qrepb".  The regular expression "(..p)a"  would find "repa qrepb"
//      in "rep drepa qrepb"
//
//   *  The regular expression "d(..p)" matches something ending  with p,
//      beginning with d, and having  two characters  in between that are
//      the same as the two characters before  the first p  encounterd in
//      the line.  It would match "drepa qrepb" in "rep drepa qrepb".
//

#include <cstring>
#include <cstdio>
#include <ossim/base/ossimRegExp.h>
#include <iostream>
// ossimRegExp -- Copies the given regular expression.

ossimRegExp::ossimRegExp (const ossimRegExp& rxp) :
  regstart(0),     // Internal use only
  reganch(0),      // Internal use only
  regmust(0),      // Internal use only
  regmlen(0),     // Internal use only
  program(0),   
  progsize(0),
  searchstring(0),

 // work variables
  regparse(0),
  regnpar(0),  // () count.
  regdummy(0),
  regcode(0),  // Code-emit pointer; &regdummy = don't.
  regsize(0),  // Code size.
  reginput(0),  // String-input pointer.
  regbol(0),  // Beginning of input, for ^ check.
  regstartp(0), // Pointer to startp array.
  regendp(0) // Ditto for endp.
{
   if(rxp.program)
   {
      int ind = 0; 
      this->progsize = rxp.progsize;        // Copy regular expression size
      this->program = new char[this->progsize]; // Allocate storage
      for(ind=this->progsize; ind-- != 0;)      // Copy regular expresion
         this->program[ind] = rxp.program[ind];
      this->startp[0] = rxp.startp[0];      // Copy pointers into last
      this->endp[0] = rxp.endp[0];          // Successful "find" operation
      this->regmust = rxp.regmust;          // Copy field
      if (rxp.regmust != NULL) {
         char* dum = rxp.program;
         ind = 0;
         while (dum != rxp.regmust) {
            ++dum;
            ++ind;
         }
         this->regmust = this->program + ind;
      }
      this->regstart = rxp.regstart;        // Copy starting index
      this->reganch = rxp.reganch;          // Copy remaining private data
      this->regmlen = rxp.regmlen;          // Copy remaining private data
   }
}


// operator== -- Returns true if two regular expressions have the same
// compiled program for pattern matching.

bool ossimRegExp::operator== (const ossimRegExp& rxp) const {
  if (this != &rxp) {               // Same address?
    ossim_uint32 ind = this->progsize;      // Get regular expression size
    if (ind != rxp.progsize)            // If different size regexp
      return false;             // Return failure
    while(ind-- != 0)               // Else while still characters
      if(this->program[ind] != rxp.program[ind]) // If regexp are different    
    return false;                // Return failure             
  }
  return true;                  // Else same, return success  
}


// deep_equal -- Returns true if have the same compiled regular expressions
// and the same start and end pointers.

bool ossimRegExp::deep_equal (const ossimRegExp& rxp) const {
  ossim_uint32 ind = this->progsize;        // Get regular expression size
  if (ind != rxp.progsize)          // If different size regexp
    return false;               // Return failure
  while(ind-- != 0)             // Else while still characters
    if(this->program[ind] != rxp.program[ind])  // If regexp are different    
      return false;             // Return failure             
  return (this->startp[0] == rxp.startp[0] &&   // Else if same start/end ptrs,
      this->endp[0] == rxp.endp[0]);    // Return true
}   

// The remaining code in this file is derived from the  regular expression code
// whose  copyright statement appears  below.  It has been  changed to work
// with the class concepts of C++ and COOL.

/*
 * compile and find 
 *
 *  Copyright (c) 1986 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 freely,
 *  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 as being the original software.
 *
 * Beware that some of this code is subtly aware of the way operator
 * precedence is structured in regular expressions.  Serious changes in
 * regular-expression syntax might require a total rethink.
 */

/*
 * 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 compile() 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 find() needs it and compile() 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 "" at beginning of line.
#define EOL 2       // no   Match "" at end of line.
#define ANY 3       // no   Match any one character.
#define ANYOF   4       // str  Match any character in this string.
#define ANYBUT  5       // str  Match any character not in this
                // string.
#define BRANCH  6       // node Match this alternative, or the
                // next...
#define BACK    7       // no   Match "", "next" ptr points backward.
#define EXACTLY 8       // str  Match this string.
#define NOTHING 9       // no   Match empty string.
#define STAR    10      // node Match this (simple) thing 0 or more
                // times.
#define PLUS    11      // node Match this (simple) thing 1 or more
                // times.
#define OPEN    20      // no   Mark this point in input as start of
                // #n.
// 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)&0377)<<8) + (*((p)+2)&0377))
#define OPERAND(p)  ((p) + 3)

const unsigned char MAGIC = 0234;
/*
 * Utility definitions.
 */

#define UCHARAT(p)  ((const unsigned char*)(p))[0]


#define FAIL(m) { regerror(m); return(NULL); }
#define ISMULT(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.



//
//  COMPILE AND ASSOCIATED FUNCTIONS
//


/*
 * Global work variables for compile().
 */
// static const char* regparse; // Input-scan pointer.
// static       int   regnpar;  // () count.
// static       char  regdummy;
// static       char* regcode;  // Code-emit pointer; &regdummy = don't.
// static       long  regsize;  // Code size.

/*
 * Forward declarations for compile()'s friends.
 */
// #ifndef static
// #define  static  static
// #endif
// static       char* reg (int, int*);
// static       char* regbranch (int*);
// static       char* regpiece (int*);
// static       char* regatom (int*);
// static       char* regnode (char);
// static const char* regnext (const char*);
// static       char* regnext (char*);
// static void        regc (unsigned char);
// static void        reginsert (char, char*);
// static void        regtail (char*, const char*);
// static void        regoptail (char*, const char*);

// #ifdef STRCSPN
// static int strcspn ();
// #endif



/*
 * 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.
 */


// compile -- compile a regular expression into internal code
// for later pattern matching.

void ossimRegExp::compile (const char* exp) {
    const char* scan;
    const char* longest;
    unsigned long len;
             int         flags;

    if (exp == NULL) {
      //RAISE Error, SYM(ossimRegExp), SYM(No_Expr),
      printf ("ossimRegExp::compile(): No expression supplied.\n");
      return;
    }

    // First pass: determine size, legality.
    regparse = exp;
    regnpar = 1;
    regsize = 0L;
    regcode = &regdummy;
    regc(MAGIC);
    if(!reg(0, &flags))
      {
    printf ("ossimRegExp::compile(): Error in compile.\n");
    return;
      }
    this->startp[0] = this->endp[0] = this->searchstring = NULL;

    // Small enough for pointer-storage convention? 
    if (regsize >= 32767L) {    // Probably could be 65535L. 
      //RAISE Error, SYM(ossimRegExp), SYM(Expr_Too_Big),
      printf ("ossimRegExp::compile(): Expression too big.\n");
      return;
    }

    // Allocate space. 
//#ifndef WIN32
    if (this->program != NULL) delete [] this->program;  
//#endif
    this->program = new char[regsize];
    this->progsize = (int) regsize;

    if (this->program == NULL) {
      //RAISE Error, SYM(ossimRegExp), SYM(Out_Of_Memory),
      printf ("ossimRegExp::compile(): Out of memory.\n"); 
      return;
    }

    // Second pass: emit code.
    regparse = exp;
    regnpar = 1;
    regcode = this->program;
    regc(MAGIC);
    reg(0, &flags);

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

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

     //
     // 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) {
        longest = NULL;
        len = 0;
        for (; scan != NULL; scan = regnext(scan))
        if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
            longest = OPERAND(scan);
            len = (unsigned long)strlen(OPERAND(scan));
        }
        this->regmust = longest;
        this->regmlen = len;
    }
    }
}


/*
 - 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.
 */
char* ossimRegExp::reg (int paren, int *flagp) {
    char* ret;
    char* br;
    char* ender;
    int   parno =0;
             int   flags;

    *flagp = HASWIDTH;      // Tentatively.

    // Make an OPEN node, if parenthesized.
    if (paren) {
    if (regnpar >= NSUBEXP) {
      //RAISE Error, SYM(ossimRegExp), SYM(Too_Many_Parens),
      printf ("ossimRegExp::compile(): Too many parentheses.\n");
      return 0;
        }
    parno = regnpar;
    regnpar++;
    ret = regnode(OPEN + parno);
    }
    else
    ret = NULL;

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

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

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

    // Check for proper termination.
    if (paren && *regparse++ != ')') {
        //RAISE Error, SYM(ossimRegExp), SYM(Unmatched_Parens),
        printf ("ossimRegExp::compile(): Unmatched parentheses.\n");
    return 0;
    }
    else if (!paren && *regparse != '\0') {
        if (*regparse == ')') {
            //RAISE Error, SYM(ossimRegExp), SYM(Unmatched_Parens),
            printf ("ossimRegExp::compile(): Unmatched parentheses.\n");
        return 0;
    }
    else {
        //RAISE Error, SYM(ossimRegExp), SYM(Internal_Error),
        printf ("ossimRegExp::compile(): Internal error.\n");
        return 0;
        }
    // NOTREACHED
    }
    return (ret);
}


/*
 - regbranch - one alternative of an | operator
 *
 * Implements the concatenation operator.
 */
char* ossimRegExp::regbranch (int *flagp) {
    char* ret;
    char* chain;
    char* latest;
    int                  flags;

    *flagp = WORST;     // Tentatively.

    ret = regnode(BRANCH);
    chain = NULL;
    while (*regparse != '\0' && *regparse != '|' && *regparse != ')') {
    latest = regpiece(&flags);
    if (latest == NULL)
        return (NULL);
    *flagp |= flags & HASWIDTH;
    if (chain == NULL)  // First piece.
        *flagp |= flags & SPSTART;
    else
        regtail(chain, latest);
    chain = latest;
    }
    if (chain == NULL)      // Loop ran zero times.
    regnode(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.
 */
char* ossimRegExp::regpiece (int *flagp) {
    char* ret;
    char  op;
    char* next;
    int            flags;

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

    op = *regparse;
    if (!ISMULT(op)) {
    *flagp = flags;
    return (ret);
    }

    if (!(flags & HASWIDTH) && op != '?') {
        //RAISE Error, SYM(ossimRegExp), SYM(Empty_Operand),
        printf ("ossimRegExp::compile() : *+ operand could be empty.\n");
    return 0;
    }
    *flagp = (op != '+') ? (WORST | SPSTART) : (WORST | HASWIDTH);

    if (op == '*' && (flags & SIMPLE))
    reginsert(STAR, ret);
    else if (op == '*') {
    // Emit x* as (x&|), where & means "self".
    reginsert(BRANCH, ret); // Either x
    regoptail(ret, regnode(BACK));  // and loop
    regoptail(ret, ret);    // back
    regtail(ret, regnode(BRANCH));  // or
    regtail(ret, regnode(NOTHING)); // null.
    }
    else if (op == '+' && (flags & SIMPLE))
    reginsert(PLUS, ret);
    else if (op == '+') {
    // Emit x+ as x(&|), where & means "self".
    next = regnode(BRANCH); // Either
    regtail(ret, next);
    regtail(regnode(BACK), ret);    // loop back
    regtail(next, regnode(BRANCH)); // or
    regtail(ret, regnode(NOTHING)); // null.
    }
    else if (op == '?') {
    // Emit x? as (x|)
    reginsert(BRANCH, ret); // Either x
    regtail(ret, regnode(BRANCH));  // or
    next = regnode(NOTHING);// null.
    regtail(ret, next);
    regoptail(ret, next);
    }
    regparse++;
    if (ISMULT(*regparse)) {
        //RAISE Error, SYM(ossimRegExp), SYM(Nested_Operand),
        printf ("ossimRegExp::compile(): Nested *?+.\n");
    return 0;
    }
    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.
 */
char* ossimRegExp::regatom (int *flagp) {
    char* ret;
             int   flags;

    *flagp = WORST;     // Tentatively.

    switch (*regparse++) {
    case '^':
        ret = regnode(BOL);
        break;
    case '$':
        ret = regnode(EOL);
        break;
    case '.':
        ret = regnode(ANY);
        *flagp |= HASWIDTH | SIMPLE;
        break;
    case '[':{
        int    rxpclass;
        int    rxpclassend;

        if (*regparse == '^') { // Complement of range.
            ret = regnode(ANYBUT);
            regparse++;
        }
        else
            ret = regnode(ANYOF);
        if (*regparse == ']' || *regparse == '-')
            regc(*regparse++);
        while (*regparse != '\0' && *regparse != ']') {
            if (*regparse == '-') {
            regparse++;
            if (*regparse == ']' || *regparse == '\0')
                regc('-');
            else {
                rxpclass = UCHARAT(regparse - 2) + 1;
                rxpclassend = UCHARAT(regparse);
                if (rxpclass > rxpclassend + 1) {
                   //RAISE Error, SYM(ossimRegExp), SYM(Invalid_Range),
                   printf ("ossimRegExp::compile(): Invalid range in [].\n");
                   return 0;
                            }
                for (; rxpclass <= rxpclassend; rxpclass++)
                regc(rxpclass);
                regparse++;
            }
            }
            else
            regc(*regparse++);
        }
        regc('\0');
        if (*regparse != ']') {
                    //RAISE Error, SYM(ossimRegExp), SYM(Unmatched_Bracket),
                    printf ("ossimRegExp::compile(): Unmatched [].\n");
            return 0;
            }
        regparse++;
        *flagp |= HASWIDTH | SIMPLE;
        }
        break;
    case '(':
        ret = reg(1, &flags);
        if (ret == NULL)
        return (NULL);
        *flagp |= flags & (HASWIDTH | SPSTART);
        break;
    case '\0':
    case '|':
    case ')':
        //RAISE Error, SYM(ossimRegExp), SYM(Internal_Error),
            printf ("ossimRegExp::compile(): Internal error.\n"); // Never here
        return 0;
    case '?':
    case '+':
    case '*':
        //RAISE Error, SYM(ossimRegExp), SYM(No_Operand),
            printf ("ossimRegExp::compile(): ?+* follows nothing.\n");
        return 0;
    case '\\':
        if (*regparse == '\0') {
            //RAISE Error, SYM(ossimRegExp), SYM(Trailing_Backslash),
                printf ("ossimRegExp::compile(): Trailing backslash.\n");
        return 0;
            }
        ret = regnode(EXACTLY);
        regc(*regparse++);
        regc('\0');
        *flagp |= HASWIDTH | SIMPLE;
        break;
    default:{
        int    len;
        char   ender;

        regparse--;
        len = (int)strcspn(regparse, META);
        if (len <= 0) {
            //RAISE Error, SYM(ossimRegExp), SYM(Internal_Error),
                    printf ("ossimRegExp::compile(): Internal error.\n");
            return 0;
                }
        ender = *(regparse + len);
        if (len > 1 && ISMULT(ender))
            len--;  // Back off clear of ?+* operand.
        *flagp |= HASWIDTH;
        if (len == 1)
            *flagp |= SIMPLE;
        ret = regnode(EXACTLY);
        while (len > 0) {
            regc(*regparse++);
            len--;
        }
        regc('\0');
        }
        break;
    }
    return (ret);
}


/*
 - regnode - emit a node
   Location.
 */
char* ossimRegExp::regnode (char op) {
    char* ret;
    char* ptr;

    ret = regcode;
    if (ret == &regdummy) {
    regsize += 3;
    return (ret);
    }

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

    return (ret);
}


/*
 - regc - emit (if appropriate) a byte of code
 */
void ossimRegExp::regc (unsigned char b) {
    if (regcode != &regdummy)
    *regcode++ = b;
    else
    regsize++;
}


/*
 - reginsert - insert an operator in front of already-emitted operand
 *
 * Means relocating the operand.
 */
void ossimRegExp::reginsert (char op, char* opnd) {
    char* src;
    char* dst;
    char* place;

    if (regcode == &regdummy) {
    regsize += 3;
    return;
    }

    src = regcode;
    regcode += 3;
    dst = regcode;
    while (src > opnd)
    *--dst = *--src;

    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
 */
void ossimRegExp::regtail (char* p, const char* val) {
    char* scan;
    char* temp;
    int   offset;

    if (p == &regdummy)
    return;

    // Find last node.
    scan = p;
    for (;;) {
    temp = regnext(scan);
    if (temp == NULL)
        break;
    scan = temp;
    }

    if (OP(scan) == BACK)
    offset = (const char*)scan - val;
    else
    offset = val - scan;
    *(scan + 1) = (offset >> 8) & 0377;
    *(scan + 2) = offset & 0377;
}


/*
 - regoptail - regtail on operand of first argument; nop if operandless
 */
void ossimRegExp::regoptail (char* p, const char* val) {
    // "Operandless" and "op != BRANCH" are synonymous in practice.
    if (p == NULL || p == &regdummy || OP(p) != BRANCH)
    return;
    regtail(OPERAND(p), val);
}



// 
//  find and friends
// 


/*
 * Global work variables for find().
 */
// static const char*  reginput;    // String-input pointer.
// static const char*  regbol;  // Beginning of input, for ^ check.
// static const char* *regstartp;   // Pointer to startp array.
// static const char* *regendp; // Ditto for endp.

/*
 * Forwards.
 */
// static int regtry (const char*, const char* *,
//         const char* *, const char*);
// static int regmatch (const char*);
// static int regrepeat (const char*);

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



// find -- Matches the regular expression to the given string.
// Returns true if found, and sets start and end indexes accordingly.

bool ossimRegExp::find (const char* string) {
    const char* s = 0;

    if(!string) return false;
    this->searchstring = string;

     // Check validity of program.
    if (!this->program || UCHARAT(this->program) != MAGIC) {
        //RAISE Error, SYM(ossimRegExp), SYM(Internal_Error),
        printf ("ossimRegExp::find(): Compiled regular expression corrupted.\n");
        return 0;
    }
    
    // If there is a "must appear" string, look for it.
    if (this->regmust != NULL) {
    s = string;
    while ((s = strchr(s, this->regmust[0])) != NULL) {
        if (strncmp(s, this->regmust, this->regmlen) == 0)
        break;      // Found it.
        s++;
    }
    if (s == NULL)      // Not present.
        return (0);
    }
     
    // Mark beginning of line for ^ .
    regbol = string;

    // Simplest case:  anchored match need be tried only once.
    if (this->reganch)
    return (regtry(string, this->startp, this->endp, this->program));
    
    // Messy cases:  unanchored match.
    s = string;
    if (this->regstart != '\0')
    // We know what char it must start with.
    while ((s = strchr(s, this->regstart)) != NULL) {
        if (regtry(s, this->startp, this->endp, this->program))
        return (1);
        s++;
      
    }
    else
    // We don't -- general case.
    do {
        if (regtry(s, this->startp, this->endp, this->program))
        return (1);
    } while (*s++ != '\0');
    
    // Failure.
    return (0);
}


/*
 - regtry - try match at specific point
   0 failure, 1 success
 */
int ossimRegExp::regtry (const char* string, const char* *start,
           const char* *end, const char* prog) {
          int    i;
    const char* *sp1;
    const char* *ep;

    reginput = string;
    regstartp = start;
    regendp = end;

    sp1 = start;
    ep = end;
    for (i = NSUBEXP; i > 0; i--) {
    *sp1++ = NULL;
    *ep++ = NULL;
    }
    if (regmatch(prog + 1)) {
    start[0] = string;
    end[0] = 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.
 * 0 failure, 1 success
 */
int ossimRegExp::regmatch (const char* prog) {
    const char* scan;   // Current node.
             const char* next;  // Next node.

    scan = prog;

    while (scan != NULL) {

    next = regnext(scan);

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

            opnd = OPERAND(scan);
            // Inline the first character, for speed.
            if (*opnd != *reginput)
            return (0);
            len = (int)strlen(opnd);
            if (len > 1 && strncmp(opnd, reginput, len) != 0)
            return (0);
            reginput += len;
        }
        break;
        case ANYOF:
        if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) == NULL)
            return (0);
        reginput++;
        break;
        case ANYBUT:
        if (*reginput == '\0' || strchr(OPERAND(scan), *reginput) != NULL)
            return (0);
        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:{
                  int    no;
            const char* save;

            no = OP(scan) - OPEN;
            save = reginput;

            if (regmatch(next)) {

            //
            // Don't set startp if some later invocation of the
            // same parentheses already has. 
            //
            if (regstartp[no] == NULL)
                regstartp[no] = save;
            return (1);
            }
            else
            return (0);
        }
//      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:{
                  int    no;
            const char* save;

            no = OP(scan) - CLOSE;
            save = reginput;

            if (regmatch(next)) {

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

            if (OP(next) != BRANCH) // No choice.
            next = OPERAND(scan);   // Avoid recursion.
            else {
            do {
                save = reginput;
                if (regmatch(OPERAND(scan)))
                return (1);
                reginput = save;
                scan = regnext(scan);
            } while (scan != NULL && OP(scan) == BRANCH);
            return (0);
            // NOTREACHED
            }
        }
        break;
        case STAR:
        case PLUS:{
          char   nextch;
            int        no;
            const char* save;
            int        min_no;

            //
            // Lookahead to avoid useless match attempts when we know
            // what character comes next. 
            //
            nextch = '\0';
            if (OP(next) == EXACTLY)
            nextch = *OPERAND(next);
            min_no = (OP(scan) == STAR) ? 0 : 1;
            save = reginput;
            no = regrepeat(OPERAND(scan));
            while (no >= min_no) {
            // If it could work, try it.
            if (nextch == '\0' || *reginput == nextch)
                if (regmatch(next))
                return (1);
            // Couldn't or didn't -- back up.
            no--;
            reginput = save + no;
            }
            return (0);
        }
//      break;
        case END:
        return (1); // Success!

        default:
            //RAISE Error, SYM(ossimRegExp), SYM(Internal_Error),
                printf ("ossimRegExp::find(): Internal error -- memory corrupted.\n");
        return 0;
    }
    scan = next;
    }

    // 
    //  We get here only if there's trouble -- normally "case END" is the
    //  terminating point. 
    // 
    //RAISE Error, SYM(ossimRegExp), SYM(Internal_Error),
    printf ("ossimRegExp::find(): Internal error -- corrupted pointers.\n");
    return (0);
}


/*
 - regrepeat - repeatedly match something simple, report how many
 */
int ossimRegExp::regrepeat (const char* p) {
          int   count = 0;
    const char* scan;
    const char* opnd;

    scan = reginput;
    opnd = OPERAND(p);
    switch (OP(p)) {
    case ANY:
        count = (int)strlen(scan);
        scan += count;
        break;
    case EXACTLY:
        while (*opnd == *scan) {
        count++;
        scan++;
        }
        break;
    case ANYOF:
        while (*scan != '\0' && strchr(opnd, *scan) != NULL) {
        count++;
        scan++;
        }
        break;
    case ANYBUT:
        while (*scan != '\0' && strchr(opnd, *scan) == NULL) {
        count++;
        scan++;
        }
        break;
    default:        // Oh dear.  Called inappropriately.
        //RAISE Error, SYM(ossimRegExp), SYM(Internal_Error),
        printf ("ossimRegExp::find(): Internal error.\n");
        return 0;
    }
    reginput = scan;
    return (count);
}


/*
 - regnext - dig the "next" pointer out of a node
 */
const char* ossimRegExp::regnext (const char* p) {
    int offset;

    if (p == &regdummy)
    return (NULL);

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

    if (OP(p) == BACK)
    return (p - offset);
    else
    return (p + offset);
}


char* ossimRegExp::regnext (char* p) {
    int offset;

    if (p == &regdummy)
    return (NULL);

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

    if (OP(p) == BACK)
    return (p - offset);
    else
    return (p + offset);
}