Initial revision

1 files changed, 1333 insertions, 0 deletions

diff --git a/generic/regexp.c b/generic/regexp.c
new file mode 100644
index 0000000..8254836
--- /dev/null
+++ b/generic/regexp.c
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+/*
+ * TclRegComp and TclRegExec -- TclRegSub is elsewhere
+ *
+ *	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.
+ *
+ * *** NOTE: this code has been altered slightly for use in Tcl: ***
+ * *** 1. Use ckalloc and ckfree instead of  malloc and free.	 ***
+ * *** 2. Add extra argument to regexp to specify the real	 ***
+ * ***    start of the string separately from the start of the	 ***
+ * ***    current search. This is needed to search for multiple	 ***
+ * ***    matches within a string.				 ***
+ * *** 3. Names have been changed, e.g. from regcomp to		 ***
+ * ***    TclRegComp, to avoid clashes with other 		 ***
+ * ***    regexp implementations used by applications. 		 ***
+ * *** 4. Added errMsg declaration and TclRegError procedure	 ***
+ * *** 5. Various lint-like things, such as casting arguments	 ***
+ * ***	  in procedure calls.					 ***
+ *
+ * *** NOTE: This code has been altered for use in MT-Sturdy Tcl ***
+ * *** 1. All use of static variables has been changed to access ***
+ * ***    fields of a structure.                                 ***
+ * *** 2. This in addition to changes to TclRegError makes the   ***
+ * ***    code multi-thread safe.                                ***
+ *
+ * SCCS: @(#) regexp.c 1.13 97/04/29 17:49:17
+ */
+
+#include "tclInt.h"
+#include "tclPort.h"
+
+/*
+ * The variable below is set to NULL before invoking regexp functions
+ * and checked after those functions.  If an error occurred then TclRegError
+ * will set the variable to point to a (static) error message.  This
+ * mechanism unfortunately does not support multi-threading, but the
+ * procedures TclRegError and TclGetRegError can be modified to use
+ * thread-specific storage for the variable and thereby make the code
+ * thread-safe.
+ */
+
+static char *errMsg = NULL;
+
+/*
+ * 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 TclRegComp() 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 TclRegExec() needs it and TclRegComp() 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	(OPEN+NSUBEXP)	/* 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)
+
+/*
+ * See regmagic.h for one further detail of program structure.
+ */
+
+
+/*
+ * Utility definitions.
+ */
+#ifndef CHARBITS
+#define	UCHARAT(p)	((int)*(unsigned char *)(p))
+#else
+#define	UCHARAT(p)	((int)*(p)&CHARBITS)
+#endif
+
+#define	FAIL(m)	{ TclRegError(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. */
+
+/*
+ * Global work variables for TclRegComp().
+ */
+struct regcomp_state  {
+    char *regparse;		/* Input-scan pointer. */
+    int regnpar;		/* () count. */
+    char *regcode;		/* Code-emit pointer; &regdummy = don't. */
+    long regsize;		/* Code size. */
+};
+
+static char regdummy;
+
+/*
+ * The first byte of the regexp internal "program" is actually this magic
+ * number; the start node begins in the second byte.
+ */
+#define	MAGIC	0234
+
+
+/*
+ * Forward declarations for TclRegComp()'s friends.
+ */
+
+static char *		reg _ANSI_ARGS_((int paren, int *flagp,
+			    struct regcomp_state *rcstate));
+static char *		regatom _ANSI_ARGS_((int *flagp,
+			    struct regcomp_state *rcstate));
+static char *		regbranch _ANSI_ARGS_((int *flagp,
+			    struct regcomp_state *rcstate));
+static void		regc _ANSI_ARGS_((int b,
+			    struct regcomp_state *rcstate));
+static void		reginsert _ANSI_ARGS_((int op, char *opnd,
+			    struct regcomp_state *rcstate));
+static char *		regnext _ANSI_ARGS_((char *p));
+static char *		regnode _ANSI_ARGS_((int op,
+			    struct regcomp_state *rcstate));
+static void 		regoptail _ANSI_ARGS_((char *p, char *val));
+static char *		regpiece _ANSI_ARGS_((int *flagp,
+			    struct regcomp_state *rcstate));
+static void 		regtail _ANSI_ARGS_((char *p, char *val));
+
+#ifdef STRCSPN
+static int strcspn _ANSI_ARGS_((char *s1, char *s2));
+#endif
+
+/*
+ - TclRegComp - 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.
+ */
+regexp *
+TclRegComp(exp)
+char *exp;
+{
+	register regexp *r;
+	register char *scan;
+	register char *longest;
+	register int len;
+	int flags;
+	struct regcomp_state state;
+	struct regcomp_state *rcstate= &state;
+
+	if (exp == NULL)
+		FAIL("NULL argument");
+
+	/* First pass: determine size, legality. */
+	rcstate->regparse = exp;
+	rcstate->regnpar = 1;
+	rcstate->regsize = 0L;
+	rcstate->regcode = &regdummy;
+	regc(MAGIC, rcstate);
+	if (reg(0, &flags, rcstate) == NULL)
+		return(NULL);
+
+	/* Small enough for pointer-storage convention? */
+	if (rcstate->regsize >= 32767L)		/* Probably could be 65535L. */
+		FAIL("regexp too big");
+
+	/* Allocate space. */
+	r = (regexp *)ckalloc(sizeof(regexp) + (unsigned)rcstate->regsize);
+	if (r == NULL)
+		FAIL("out of space");
+
+	/* Second pass: emit code. */
+	rcstate->regparse = exp;
+	rcstate->regnpar = 1;
+	rcstate->regcode = r->program;
+	regc(MAGIC, rcstate);
+	if (reg(0, &flags, rcstate) == 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++;
+
+		/*
+		 * 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 && ((int) strlen(OPERAND(scan))) >= len) {
+					longest = OPERAND(scan);
+					len = strlen(OPERAND(scan));
+				}
+			r->regmust = longest;
+			r->regmlen = 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(paren, flagp, rcstate)
+int paren;			/* Parenthesized? */
+int *flagp;
+struct regcomp_state *rcstate;
+{
+	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 (rcstate->regnpar >= NSUBEXP)
+			FAIL("too many ()");
+		parno = rcstate->regnpar;
+		rcstate->regnpar++;
+		ret = regnode(OPEN+parno,rcstate);
+	} else
+		ret = NULL;
+
+	/* Pick up the branches, linking them together. */
+	br = regbranch(&flags,rcstate);
+	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 (*rcstate->regparse == '|') {
+		rcstate->regparse++;
+		br = regbranch(&flags,rcstate);
+		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,rcstate);	
+	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 && *rcstate->regparse++ != ')') {
+		FAIL("unmatched ()");
+	} else if (!paren && *rcstate->regparse != '\0') {
+		if (*rcstate->regparse == ')') {
+			FAIL("unmatched ()");
+		} else
+			FAIL("junk on end");	/* "Can't happen". */
+		/* NOTREACHED */
+	}
+
+	return(ret);
+}
+
+/*
+ - regbranch - one alternative of an | operator
+ *
+ * Implements the concatenation operator.
+ */
+static char *
+regbranch(flagp, rcstate)
+int *flagp;
+struct regcomp_state *rcstate;
+{
+	register char *ret;
+	register char *chain;
+	register char *latest;
+	int flags;
+
+	*flagp = WORST;		/* Tentatively. */
+
+	ret = regnode(BRANCH,rcstate);
+	chain = NULL;
+	while (*rcstate->regparse != '\0' && *rcstate->regparse != '|' &&
+				*rcstate->regparse != ')') {
+		latest = regpiece(&flags, rcstate);
+		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. */
+		(void) regnode(NOTHING,rcstate);
+
+	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(flagp, rcstate)
+int *flagp;
+struct regcomp_state *rcstate;
+{
+	register char *ret;
+	register char op;
+	register char *next;
+	int flags;
+
+	ret = regatom(&flags,rcstate);
+	if (ret == NULL)
+		return(NULL);
+
+	op = *rcstate->regparse;
+	if (!ISMULT(op)) {
+		*flagp = flags;
+		return(ret);
+	}
+
+	if (!(flags&HASWIDTH) && op != '?')
+		FAIL("*+ operand could be empty");
+	*flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);
+
+	if (op == '*' && (flags&SIMPLE))
+		reginsert(STAR, ret, rcstate);
+	else if (op == '*') {
+		/* Emit x* as (x&|), where & means "self". */
+		reginsert(BRANCH, ret, rcstate);			/* Either x */
+		regoptail(ret, regnode(BACK,rcstate));		/* and loop */
+		regoptail(ret, ret);			/* back */
+		regtail(ret, regnode(BRANCH,rcstate));		/* or */
+		regtail(ret, regnode(NOTHING,rcstate));		/* null. */
+	} else if (op == '+' && (flags&SIMPLE))
+		reginsert(PLUS, ret, rcstate);
+	else if (op == '+') {
+		/* Emit x+ as x(&|), where & means "self". */
+		next = regnode(BRANCH,rcstate);			/* Either */
+		regtail(ret, next);
+		regtail(regnode(BACK,rcstate), ret);		/* loop back */
+		regtail(next, regnode(BRANCH,rcstate));		/* or */
+		regtail(ret, regnode(NOTHING,rcstate));		/* null. */
+	} else if (op == '?') {
+		/* Emit x? as (x|) */
+		reginsert(BRANCH, ret, rcstate);			/* Either x */
+		regtail(ret, regnode(BRANCH,rcstate));		/* or */
+		next = regnode(NOTHING,rcstate);		/* null. */
+		regtail(ret, next);
+		regoptail(ret, next);
+	}
+	rcstate->regparse++;
+	if (ISMULT(*rcstate->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(flagp, rcstate)
+int *flagp;
+struct regcomp_state *rcstate;
+{
+	register char *ret;
+	int flags;
+
+	*flagp = WORST;		/* Tentatively. */
+
+	switch (*rcstate->regparse++) {
+	case '^':
+		ret = regnode(BOL,rcstate);
+		break;
+	case '$':
+		ret = regnode(EOL,rcstate);
+		break;
+	case '.':
+		ret = regnode(ANY,rcstate);
+		*flagp |= HASWIDTH|SIMPLE;
+		break;
+	case '[': {
+			register int clss;
+			register int classend;
+
+			if (*rcstate->regparse == '^') {	/* Complement of range. */
+				ret = regnode(ANYBUT,rcstate);
+				rcstate->regparse++;
+			} else
+				ret = regnode(ANYOF,rcstate);
+			if (*rcstate->regparse == ']' || *rcstate->regparse == '-')
+				regc(*rcstate->regparse++,rcstate);
+			while (*rcstate->regparse != '\0' && *rcstate->regparse != ']') {
+				if (*rcstate->regparse == '-') {
+					rcstate->regparse++;
+					if (*rcstate->regparse == ']' || *rcstate->regparse == '\0')
+						regc('-',rcstate);
+					else {
+						clss = UCHARAT(rcstate->regparse-2)+1;
+						classend = UCHARAT(rcstate->regparse);
+						if (clss > classend+1)
+							FAIL("invalid [] range");
+						for (; clss <= classend; clss++)
+							regc((char)clss,rcstate);
+						rcstate->regparse++;
+					}
+				} else
+					regc(*rcstate->regparse++,rcstate);
+			}
+			regc('\0',rcstate);
+			if (*rcstate->regparse != ']')
+				FAIL("unmatched []");
+			rcstate->regparse++;
+			*flagp |= HASWIDTH|SIMPLE;
+		}
+		break;
+	case '(':
+		ret = reg(1, &flags, rcstate);
+		if (ret == NULL)
+			return(NULL);
+		*flagp |= flags&(HASWIDTH|SPSTART);
+		break;
+	case '\0':
+	case '|':
+	case ')':
+		FAIL("internal urp");	/* Supposed to be caught earlier. */
+		/* NOTREACHED */
+	case '?':
+	case '+':
+	case '*':
+		FAIL("?+* follows nothing");
+		/* NOTREACHED */
+	case '\\':
+		if (*rcstate->regparse == '\0')
+			FAIL("trailing \\");
+		ret = regnode(EXACTLY,rcstate);
+		regc(*rcstate->regparse++,rcstate);
+		regc('\0',rcstate);
+		*flagp |= HASWIDTH|SIMPLE;
+		break;
+	default: {
+			register int len;
+			register char ender;
+
+			rcstate->regparse--;
+			len = strcspn(rcstate->regparse, META);
+			if (len <= 0)
+				FAIL("internal disaster");
+			ender = *(rcstate->regparse+len);
+			if (len > 1 && ISMULT(ender))
+				len--;		/* Back off clear of ?+* operand. */
+			*flagp |= HASWIDTH;
+			if (len == 1)
+				*flagp |= SIMPLE;
+			ret = regnode(EXACTLY,rcstate);
+			while (len > 0) {
+				regc(*rcstate->regparse++,rcstate);
+				len--;
+			}
+			regc('\0',rcstate);
+		}
+		break;
+	}
+
+	return(ret);
+}
+
+/*
+ - regnode - emit a node
+ */
+static char *			/* Location. */
+regnode(op, rcstate)
+int op;
+struct regcomp_state *rcstate;
+{
+	register char *ret;
+	register char *ptr;
+
+	ret = rcstate->regcode;
+	if (ret == &regdummy) {
+		rcstate->regsize += 3;
+		return(ret);
+	}
+
+	ptr = ret;
+	*ptr++ = (char)op;
+	*ptr++ = '\0';		/* Null "next" pointer. */
+	*ptr++ = '\0';
+	rcstate->regcode = ptr;
+
+	return(ret);
+}
+
+/*
+ - regc - emit (if appropriate) a byte of code
+ */
+static void
+regc(b, rcstate)
+int b;
+struct regcomp_state *rcstate;
+{
+	if (rcstate->regcode != &regdummy)
+		*rcstate->regcode++ = (char)b;
+	else
+		rcstate->regsize++;
+}
+
+/*
+ - reginsert - insert an operator in front of already-emitted operand
+ *
+ * Means relocating the operand.
+ */
+static void
+reginsert(op, opnd, rcstate)
+int op;
+char *opnd;
+struct regcomp_state *rcstate;
+{
+	register char *src;
+	register char *dst;
+	register char *place;
+
+	if (rcstate->regcode == &regdummy) {
+		rcstate->regsize += 3;
+		return;
+	}
+
+	src = rcstate->regcode;
+	rcstate->regcode += 3;
+	dst = rcstate->regcode;
+	while (src > opnd)
+		*--dst = *--src;
+
+	place = opnd;		/* Op node, where operand used to be. */
+	*place++ = (char)op;
+	*place++ = '\0';
+	*place = '\0';
+}
+
+/*
+ - regtail - set the next-pointer at the end of a node chain
+ */
+static void
+regtail(p, val)
+char *p;
+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 = scan - val;
+	else
+		offset = val - scan;
+	*(scan+1) = (char)((offset>>8)&0377);
+	*(scan+2) = (char)(offset&0377);
+}
+
+/*
+ - regoptail - regtail on operand of first argument; nop if operandless
+ */
+static void
+regoptail(p, val)
+char *p;
+char *val;
+{
+	/* "Operandless" and "op != BRANCH" are synonymous in practice. */
+	if (p == NULL || p == &regdummy || OP(p) != BRANCH)
+		return;
+	regtail(OPERAND(p), val);
+}
+
+/*
+ * TclRegExec and friends
+ */
+
+/*
+ * Global work variables for TclRegExec().
+ */
+struct regexec_state  {
+    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 _ANSI_ARGS_((regexp *prog, char *string,
+			    struct regexec_state *restate));
+static int 		regmatch _ANSI_ARGS_((char *prog,
+			    struct regexec_state *restate));
+static int 		regrepeat _ANSI_ARGS_((char *p,
+			    struct regexec_state *restate));
+
+#ifdef DEBUG
+int regnarrate = 0;
+void regdump _ANSI_ARGS_((regexp *r));
+static char *regprop _ANSI_ARGS_((char *op));
+#endif
+
+/*
+ - TclRegExec - match a regexp against a string
+ */
+int
+TclRegExec(prog, string, start)
+register regexp *prog;
+register char *string;
+char *start;
+{
+	register char *s;
+	struct regexec_state state;
+	struct regexec_state *restate= &state;
+
+	/* Be paranoid... */
+	if (prog == NULL || string == NULL) {
+		TclRegError("NULL parameter");
+		return(0);
+	}
+
+	/* Check validity of program. */
+	if (UCHARAT(prog->program) != MAGIC) {
+		TclRegError("corrupted program");
+		return(0);
+	}
+
+	/* If there is a "must appear" string, look for it. */
+	if (prog->regmust != NULL) {
+		s = string;
+		while ((s = strchr(s, prog->regmust[0])) != NULL) {
+			if (strncmp(s, prog->regmust, (size_t) prog->regmlen)
+			    == 0)
+				break;	/* Found it. */
+			s++;
+		}
+		if (s == NULL)	/* Not present. */
+			return(0);
+	}
+
+	/* Mark beginning of line for ^ . */
+	restate->regbol = start;
+
+	/* Simplest case:  anchored match need be tried only once. */
+	if (prog->reganch)
+		return(regtry(prog, string, restate));
+
+	/* Messy cases:  unanchored match. */
+	s = string;
+	if (prog->regstart != '\0')
+		/* We know what char it must start with. */
+		while ((s = strchr(s, prog->regstart)) != NULL) {
+			if (regtry(prog, s, restate))
+				return(1);
+			s++;
+		}
+	else
+		/* We don't -- general case. */
+		do {
+			if (regtry(prog, s, restate))
+				return(1);
+		} while (*s++ != '\0');
+
+	/* Failure. */
+	return(0);
+}
+
+/*
+ - regtry - try match at specific point
+ */
+static int			/* 0 failure, 1 success */
+regtry(prog, string, restate)
+regexp *prog;
+char *string;
+struct regexec_state *restate;
+{
+	register int i;
+	register char **sp;
+	register char **ep;
+
+	restate->reginput = string;
+	restate->regstartp = prog->startp;
+	restate->regendp = prog->endp;
+
+	sp = prog->startp;
+	ep = prog->endp;
+	for (i = NSUBEXP; i > 0; i--) {
+		*sp++ = NULL;
+		*ep++ = NULL;
+	}
+	if (regmatch(prog->program + 1,restate)) {
+		prog->startp[0] = string;
+		prog->endp[0] = restate->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(prog, restate)
+char *prog;
+struct regexec_state *restate;
+{
+    register char *scan;	/* Current node. */
+    char *next;		/* Next node. */
+
+    scan = prog;
+#ifdef DEBUG
+    if (scan != NULL && regnarrate)
+	fprintf(stderr, "%s(\n", regprop(scan));
+#endif
+    while (scan != NULL) {
+#ifdef DEBUG
+	if (regnarrate)
+	    fprintf(stderr, "%s...\n", regprop(scan));
+#endif
+	next = regnext(scan);
+
+	switch (OP(scan)) {
+	    case BOL:
+		if (restate->reginput != restate->regbol) {
+		    return 0;
+		}
+		break;
+	    case EOL:
+		if (*restate->reginput != '\0') {
+		    return 0;
+		}
+		break;
+	    case ANY:
+		if (*restate->reginput == '\0') {
+		    return 0;
+		}
+		restate->reginput++;
+		break;
+	    case EXACTLY: {
+		register int len;
+		register char *opnd;
+
+		opnd = OPERAND(scan);
+		/* Inline the first character, for speed. */
+		if (*opnd != *restate->reginput) {
+		    return 0 ;
+		}
+		len = strlen(opnd);
+		if (len > 1 && strncmp(opnd, restate->reginput, (size_t) len)
+			!= 0) {
+		    return 0;
+		}
+		restate->reginput += len;
+		break;
+	    }
+	    case ANYOF:
+		if (*restate->reginput == '\0'
+			|| strchr(OPERAND(scan), *restate->reginput) == NULL) {
+		    return 0;
+		}
+		restate->reginput++;
+		break;
+	    case ANYBUT:
+		if (*restate->reginput == '\0'
+			|| strchr(OPERAND(scan), *restate->reginput) != NULL) {
+		    return 0;
+		}
+		restate->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 char *save;
+
+	doOpen:
+		no = OP(scan) - OPEN;
+		save = restate->reginput;
+
+		if (regmatch(next,restate)) {
+		    /*
+		     * Don't set startp if some later invocation of the
+		     * same parentheses already has.
+		     */
+		    if (restate->regstartp[no] == NULL) {
+			restate->regstartp[no] = save;
+		    }
+		    return 1;
+		} else {
+		    return 0;
+		}
+	    }
+	    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 char *save;
+
+	doClose:
+		no = OP(scan) - CLOSE;
+		save = restate->reginput;
+
+		if (regmatch(next,restate)) {
+				/*
+				 * Don't set endp if some later
+				 * invocation of the same parentheses
+				 * already has.
+				 */
+		    if (restate->regendp[no] == NULL)
+			restate->regendp[no] = save;
+		    return 1;
+		} else {
+		    return 0;
+		}
+	    }
+	    case BRANCH: {
+		register char *save;
+
+		if (OP(next) != BRANCH) { /* No choice. */
+		    next = OPERAND(scan); /* Avoid recursion. */
+		} else {
+		    do {
+			save = restate->reginput;
+			if (regmatch(OPERAND(scan),restate))
+			    return(1);
+			restate->reginput = save;
+			scan = regnext(scan);
+		    } while (scan != NULL && OP(scan) == BRANCH);
+		    return 0;
+		}
+		break;
+	    }
+	    case STAR:
+	    case PLUS: {
+		register char nextch;
+		register int no;
+		register char *save;
+		register int min;
+
+		/*
+		 * Lookahead to avoid useless match attempts
+		 * when we know what character comes next.
+		 */
+		nextch = '\0';
+		if (OP(next) == EXACTLY)
+		    nextch = *OPERAND(next);
+		min = (OP(scan) == STAR) ? 0 : 1;
+		save = restate->reginput;
+		no = regrepeat(OPERAND(scan),restate);
+		while (no >= min) {
+		    /* If it could work, try it. */
+		    if (nextch == '\0' || *restate->reginput == nextch)
+			if (regmatch(next,restate))
+			    return(1);
+		    /* Couldn't or didn't -- back up. */
+		    no--;
+		    restate->reginput = save + no;
+		}
+		return(0);
+	    }
+	    case END:
+		return(1);	/* Success! */
+	    default:
+		if (OP(scan) > OPEN && OP(scan) < OPEN+NSUBEXP) {
+		    goto doOpen;
+		} else if (OP(scan) > CLOSE && OP(scan) < CLOSE+NSUBEXP) {
+		    goto doClose;
+		}
+		TclRegError("memory corruption");
+		return 0;
+	}
+
+	scan = next;
+    }
+
+    /*
+     * We get here only if there's trouble -- normally "case END" is
+     * the terminating point.
+     */
+    TclRegError("corrupted pointers");
+    return(0);
+}
+
+/*
+ - regrepeat - repeatedly match something simple, report how many
+ */
+static int
+regrepeat(p, restate)
+char *p;
+struct regexec_state *restate;
+{
+	register int count = 0;
+	register char *scan;
+	register char *opnd;
+
+	scan = restate->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. */
+		TclRegError("internal foulup");
+		count = 0;	/* Best compromise. */
+		break;
+	}
+	restate->reginput = scan;
+
+	return(count);
+}
+
+/*
+ - regnext - dig the "next" pointer out of a node
+ */
+static char *
+regnext(p)
+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);
+}
+
+#ifdef DEBUG
+
+static char *regprop();
+
+/*
+ - regdump - dump a regexp onto stdout in vaguely comprehensible form
+ */
+void
+regdump(r)
+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:
+		if (OP(op) > OPEN && OP(op) < OPEN+NSUBEXP) {
+		    sprintf(buf+strlen(buf), "OPEN%d", OP(op)-OPEN);
+		    p = NULL;
+		    break;
+		} else if (OP(op) > CLOSE && OP(op) < CLOSE+NSUBEXP) {
+		    sprintf(buf+strlen(buf), "CLOSE%d", OP(op)-CLOSE);
+		    p = NULL;
+		} else {
+		    TclRegError("corrupted opcode");
+		}
+		break;
+	}
+	if (p != NULL)
+		(void) strcat(buf, p);
+	return(buf);
+}
+#endif
+
+/*
+ * The following is provided for those people who do not have strcspn() in
+ * their C libraries.  They should get off their butts and do something
+ * about it; at least one public-domain implementation of those (highly
+ * useful) string routines has been published on Usenet.
+ */
+#ifdef STRCSPN
+/*
+ * strcspn - find length of initial segment of s1 consisting entirely
+ * of characters not from s2
+ */
+
+static int
+strcspn(s1, s2)
+char *s1;
+char *s2;
+{
+	register char *scan1;
+	register char *scan2;
+	register int count;
+
+	count = 0;
+	for (scan1 = s1; *scan1 != '\0'; scan1++) {
+		for (scan2 = s2; *scan2 != '\0';)	/* ++ moved down. */
+			if (*scan1 == *scan2++)
+				return(count);
+		count++;
+	}
+	return(count);
+}
+#endif
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclRegError --
+ *
+ *	This procedure is invoked by the regexp code when an error
+ *	occurs.  It saves the error message so it can be seen by the
+ *	code that called Spencer's code.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The value of "string" is saved in "errMsg".
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+TclRegError(string)
+    char *string;			/* Error message. */
+{
+    errMsg = string;
+}
+
+char *
+TclGetRegError()
+{
+    return errMsg;
+}