CMake/Source/cmRegularExpression.cxx

/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile$
  Language:  C++
  Date:      $Date$
  Version:   $Revision$

Copyright (c) 2001 Insight Consortium
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

 * Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.

 * Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

 * The name of the Insight Consortium, nor the names of any consortium members,
   nor of any contributors, may be used to endorse or promote products derived
   from this software without specific prior written permission.

  * Modified source versions must be plainly marked as such, and must not be
    misrepresented as being the original software.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS ``AS IS''
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

=========================================================================*/
//
// 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
//

#include "cmRegularExpression.h"	// Include class specification 
#include "cmStandardIncludes.h"
#include <stdio.h>

// cmRegularExpression -- Copies the given regular expression.
cmRegularExpression::cmRegularExpression (const cmRegularExpression& rxp) {
  int ind; 
  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 cmRegularExpression::operator== (const cmRegularExpression& rxp) const {
  if (this != &rxp) {				// Same address?
    int 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 cmRegularExpression::deep_equal (const cmRegularExpression& rxp) const {
  int 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 (register const char*);
static       char* regnext (register 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 cmRegularExpression::compile (const char* exp) {
    register const char* scan;
    register const char* longest;
    register unsigned long len;
             int         flags;

    if (exp == NULL) {
      //RAISE Error, SYM(cmRegularExpression), SYM(No_Expr),
      printf ("cmRegularExpression::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 ("cmRegularExpression::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(cmRegularExpression), SYM(Expr_Too_Big),
      printf ("cmRegularExpression::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(cmRegularExpression), SYM(Out_Of_Memory),
      printf ("cmRegularExpression::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 = 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.
 */
static char* reg (int paren, int *flagp) {
    register char* ret;
    register char* br;
    register char* ender;
    register int   parno =0;
             int   flags;

    *flagp = HASWIDTH;		// Tentatively.

    // Make an OPEN node, if parenthesized.
    if (paren) {
	if (regnpar >= NSUBEXP) {
	  //RAISE Error, SYM(cmRegularExpression), SYM(Too_Many_Parens),
	  printf ("cmRegularExpression::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(cmRegularExpression), SYM(Unmatched_Parens),
        printf ("cmRegularExpression::compile(): Unmatched parentheses.\n");
	return 0;
    }
    else if (!paren && *regparse != '\0') {
        if (*regparse == ')') {
            //RAISE Error, SYM(cmRegularExpression), SYM(Unmatched_Parens),
            printf ("cmRegularExpression::compile(): Unmatched parentheses.\n");
	    return 0;
	}
	else {
	    //RAISE Error, SYM(cmRegularExpression), SYM(Internal_Error),
	    printf ("cmRegularExpression::compile(): Internal error.\n");
	    return 0;
        }
	// NOTREACHED
    }
    return (ret);
}


/*
 - regbranch - one alternative of an | operator
 *
 * Implements the concatenation operator.
 */
static char* regbranch (int *flagp) {
    register char* ret;
    register char* chain;
    register 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.
 */
static char* regpiece (int *flagp) {
    register char* ret;
    register char  op;
    register 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(cmRegularExpression), SYM(Empty_Operand),
        printf ("cmRegularExpression::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(cmRegularExpression), SYM(Nested_Operand),
        printf ("cmRegularExpression::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.
 */
static char* regatom (int *flagp) {
    register 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 '[':{
		register int    rxpclass;
		register 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(cmRegularExpression), SYM(Invalid_Range),
			       printf ("cmRegularExpression::compile(): Invalid range in [].\n");
			       return 0;
                            }
			    for (; rxpclass <= rxpclassend; rxpclass++)
				regc(rxpclass);
			    regparse++;
			}
		    }
		    else
			regc(*regparse++);
		}
		regc('\0');
		if (*regparse != ']') {
                    //RAISE Error, SYM(cmRegularExpression), SYM(Unmatched_Bracket),
                    printf ("cmRegularExpression::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(cmRegularExpression), SYM(Internal_Error),
            printf ("cmRegularExpression::compile(): Internal error.\n"); // Never here
	    return 0;
	case '?':
	case '+':
	case '*':
	    //RAISE Error, SYM(cmRegularExpression), SYM(No_Operand),
            printf ("cmRegularExpression::compile(): ?+* follows nothing.\n");
	    return 0;
	case '\\':
	    if (*regparse == '\0') {
	        //RAISE Error, SYM(cmRegularExpression), SYM(Trailing_Backslash),
                printf ("cmRegularExpression::compile(): Trailing backslash.\n");
		return 0;
            }
	    ret = regnode(EXACTLY);
	    regc(*regparse++);
	    regc('\0');
	    *flagp |= HASWIDTH | SIMPLE;
	    break;
	default:{
		register int    len;
		register char   ender;

		regparse--;
		len = strcspn(regparse, META);
		if (len <= 0) {
		    //RAISE Error, SYM(cmRegularExpression), SYM(Internal_Error),
                    printf ("cmRegularExpression::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.
 */
static char* regnode (char op) {
    register char* ret;
    register 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
 */
static void 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.
 */
static void reginsert (char op, char* opnd) {
    register char* src;
    register char* dst;
    register 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
 */
static void regtail (char* p, const char* val) {
    register char* scan;
    register char* temp;
    register 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
 */
static void 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

bool cmRegularExpression::find (std::string const& s) 
{
  return find(s.c_str());
}



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

bool cmRegularExpression::find (const char* string) {
    register const char* s;

    this->searchstring = string;

     // Check validity of program.
    if (!this->program || UCHARAT(this->program) != MAGIC) {
        //RAISE Error, SYM(cmRegularExpression), SYM(Internal_Error),
        printf ("cmRegularExpression::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) != 0);
    
    // 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
 */
static int regtry (const char* string, const char* *start,
		   const char* *end, const char* prog) {
    register       int    i;
    register const char* *sp1;
    register 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
 */
static int regmatch (const char* prog) {
    register 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:{
		    register int         len;
		    register const char* opnd;

		    opnd = OPERAND(scan);
		    // Inline the first character, for speed.
		    if (*opnd != *reginput)
			return (0);
		    len = 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:{
		    register       int    no;
		    register 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:{
		    register       int    no;
		    register 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:{
	      
	      register 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:{
	      register char   nextch;
		    register int        no;
		    register const char* save;
		    register 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(cmRegularExpression), SYM(Internal_Error),
                printf ("cmRegularExpression::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(cmRegularExpression), SYM(Internal_Error),
    printf ("cmRegularExpression::find(): Internal error -- corrupted pointers.\n");
    return (0);
}


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

    scan = reginput;
    opnd = OPERAND(p);
    switch (OP(p)) {
	case ANY:
	    count = 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(cmRegularExpression), SYM(Internal_Error),
	    printf ("cm RegularExpression::find(): Internal error.\n");
	    return 0;
    }
    reginput = scan;
    return (count);
}


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


static char* regnext (register char* p) {
    register 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);
}