forked from schacon/perl
/
regcomp.c
1653 lines (1560 loc) · 34.1 KB
/
regcomp.c
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/* regcomp.c
*/
/*
* "A fair jaw-cracker dwarf-language must be." --Samwise Gamgee
*/
/* NOTE: this is derived from Henry Spencer's regexp code, and should not
* confused with the original package (see point 3 below). Thanks, Henry!
*/
/* Additional note: this code is very heavily munged from Henry's version
* in places. In some spots I've traded clarity for efficiency, so don't
* blame Henry for some of the lack of readability.
*/
/* The names of the functions have been changed from regcomp and
* regexec to pregcomp and pregexec in order to avoid conflicts
* with the POSIX routines of the same names.
*/
/*SUPPRESS 112*/
/*
* pregcomp and pregexec -- regsub and regerror are not used in perl
*
* 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.
*
*
**** Alterations to Henry's code are...
****
**** Copyright (c) 1991-1994, Larry Wall
****
**** You may distribute under the terms of either the GNU General Public
**** License or the Artistic License, as specified in the README file.
*
* 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.
*/
#include "EXTERN.h"
#include "perl.h"
#include "INTERN.h"
#include "regcomp.h"
#ifdef MSDOS
# if defined(BUGGY_MSC6)
/* MSC 6.00A breaks on op/regexp.t test 85 unless we turn this off */
# pragma optimize("a",off)
/* But MSC 6.00A is happy with 'w', for aliases only across function calls*/
# pragma optimize("w",on )
# endif /* BUGGY_MSC6 */
#endif /* MSDOS */
#ifndef STATIC
#define STATIC static
#endif
#define ISMULT1(c) ((c) == '*' || (c) == '+' || (c) == '?')
#define ISMULT2(s) ((*s) == '*' || (*s) == '+' || (*s) == '?' || \
((*s) == '{' && regcurly(s)))
#ifdef atarist
#define PERL_META "^$.[()|?+*\\"
#else
#define META "^$.[()|?+*\\"
#endif
#ifdef SPSTART
#undef SPSTART /* dratted cpp namespace... */
#endif
/*
* Flags to be passed up and down.
*/
#define WORST 0 /* Worst case. */
#define HASWIDTH 0x1 /* Known never to match null string. */
#define SIMPLE 0x2 /* Simple enough to be STAR/PLUS operand. */
#define SPSTART 0x4 /* Starts with * or +. */
#define TRYAGAIN 0x8 /* Weeded out a declaration. */
/*
* Forward declarations for pregcomp()'s friends.
*/
static char *reg _((I32, I32 *));
static char *reganode _((char, unsigned short));
static char *regatom _((I32 *));
static char *regbranch _((I32 *));
static void regc _((char));
static char *regclass _((void));
STATIC I32 regcurly _((char *));
static char *regnode _((char));
static char *regpiece _((I32 *));
static void reginsert _((char, char *));
static void regoptail _((char *, char *));
static void regset _((char *, I32, I32));
static void regtail _((char *, char *));
static char* nextchar _((void));
/*
- pregcomp - 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.) [NB: not true in perl]
*
* Beware that the optimization-preparation code in here knows about some
* of the structure of the compiled regexp. [I'll say.]
*/
regexp *
pregcomp(exp,xend,pm)
char* exp;
char* xend;
PMOP* pm;
{
I32 fold = pm->op_pmflags & PMf_FOLD;
register regexp *r;
register char *scan;
register SV *longish;
SV *longest;
register I32 len;
register char *first;
I32 flags;
I32 backish;
I32 backest;
I32 curback;
I32 minlen = 0;
I32 sawplus = 0;
I32 sawopen = 0;
if (exp == NULL)
croak("NULL regexp argument");
/* First pass: determine size, legality. */
regflags = pm->op_pmflags;
regparse = exp;
regxend = xend;
regprecomp = savepvn(exp,xend-exp);
regnaughty = 0;
regsawback = 0;
regnpar = 1;
regsize = 0L;
regcode = ®dummy;
regc((char)MAGIC);
if (reg(0, &flags) == NULL) {
Safefree(regprecomp);
regprecomp = Nullch;
return(NULL);
}
/* Small enough for pointer-storage convention? */
if (regsize >= 32767L) /* Probably could be 65535L. */
FAIL("regexp too big");
/* Allocate space. */
Newc(1001, r, sizeof(regexp) + (unsigned)regsize, char, regexp);
if (r == NULL)
FAIL("regexp out of space");
/* Second pass: emit code. */
r->prelen = xend-exp;
r->precomp = regprecomp;
r->subbeg = r->subbase = NULL;
regnaughty = 0;
regparse = exp;
regnpar = 1;
regcode = r->program;
regc((char)MAGIC);
if (reg(0, &flags) == NULL)
return(NULL);
/* Dig out information for optimizations. */
pm->op_pmflags = regflags;
fold = pm->op_pmflags & PMf_FOLD;
r->regstart = Nullsv; /* Worst-case defaults. */
r->reganch = 0;
r->regmust = Nullsv;
r->regback = -1;
r->regstclass = Nullch;
r->naughty = regnaughty >= 10; /* Probably an expensive pattern. */
scan = r->program+1; /* First BRANCH. */
if (OP(regnext(scan)) == END) {/* Only one top-level choice. */
scan = NEXTOPER(scan);
first = scan;
while ((OP(first) == OPEN && (sawopen = 1)) ||
(OP(first) == BRANCH && OP(regnext(first)) != BRANCH) ||
(OP(first) == PLUS) ||
(OP(first) == MINMOD) ||
(regkind[(U8)OP(first)] == CURLY && ARG1(first) > 0) ) {
if (OP(first) == PLUS)
sawplus = 1;
else
first += regarglen[(U8)OP(first)];
first = NEXTOPER(first);
}
/* Starting-point info. */
again:
if (OP(first) == EXACTLY) {
r->regstart = newSVpv(OPERAND(first)+1,*OPERAND(first));
if (SvCUR(r->regstart) > !(sawstudy|fold))
fbm_compile(r->regstart,fold);
else
sv_upgrade(r->regstart, SVt_PVBM);
}
else if (strchr(simple+2,OP(first)))
r->regstclass = first;
else if (OP(first) == BOUND || OP(first) == NBOUND)
r->regstclass = first;
else if (regkind[(U8)OP(first)] == BOL) {
r->reganch = ROPT_ANCH;
first = NEXTOPER(first);
goto again;
}
else if ((OP(first) == STAR &&
regkind[(U8)OP(NEXTOPER(first))] == ANY) &&
!(r->reganch & ROPT_ANCH) )
{
/* turn .* into ^.* with an implied $*=1 */
r->reganch = ROPT_ANCH | ROPT_IMPLICIT;
first = NEXTOPER(first);
goto again;
}
if (sawplus && (!sawopen || !regsawback))
r->reganch |= ROPT_SKIP; /* x+ must match 1st of run */
DEBUG_r(fprintf(stderr,"first %d next %d offset %d\n",
OP(first), OP(NEXTOPER(first)), first - scan));
/*
* 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.
* [Now we resolve ties in favor of the earlier string if
* it happens that curback has been invalidated, since the
* earlier string may buy us something the later one won't.]
*/
longish = newSVpv("",0);
longest = newSVpv("",0);
len = 0;
minlen = 0;
curback = 0;
backish = 0;
backest = 0;
while (OP(scan) != END) {
if (OP(scan) == BRANCH) {
if (OP(regnext(scan)) == BRANCH) {
curback = -30000;
while (OP(scan) == BRANCH)
scan = regnext(scan);
}
else /* single branch is ok */
scan = NEXTOPER(scan);
continue;
}
if (OP(scan) == UNLESSM) {
curback = -30000;
scan = regnext(scan);
continue;
}
if (OP(scan) == EXACTLY) {
char *t;
first = scan;
while (OP(t = regnext(scan)) == CLOSE)
scan = t;
minlen += *OPERAND(first);
if (curback - backish == len) {
sv_catpvn(longish, OPERAND(first)+1,
*OPERAND(first));
len += *OPERAND(first);
curback += *OPERAND(first);
first = regnext(scan);
}
else if (*OPERAND(first) >= len + (curback >= 0)) {
len = *OPERAND(first);
sv_setpvn(longish, OPERAND(first)+1,len);
backish = curback;
curback += len;
first = regnext(scan);
}
else
curback += *OPERAND(first);
}
else if (strchr(varies,OP(scan))) {
curback = -30000;
len = 0;
if (SvCUR(longish) > SvCUR(longest)) {
sv_setsv(longest,longish);
backest = backish;
}
sv_setpvn(longish,"",0);
if (OP(scan) == PLUS && strchr(simple,OP(NEXTOPER(scan))))
minlen++;
else if (regkind[(U8)OP(scan)] == CURLY &&
strchr(simple,OP(NEXTOPER(scan)+4)))
minlen += ARG1(scan);
}
else if (strchr(simple,OP(scan))) {
curback++;
minlen++;
len = 0;
if (SvCUR(longish) > SvCUR(longest)) {
sv_setsv(longest,longish);
backest = backish;
}
sv_setpvn(longish,"",0);
}
scan = regnext(scan);
}
/* Prefer earlier on tie, unless we can tail match latter */
if (SvCUR(longish) + (regkind[(U8)OP(first)] == EOL) >
SvCUR(longest))
{
sv_setsv(longest,longish);
backest = backish;
}
else
sv_setpvn(longish,"",0);
if (SvCUR(longest)
&&
(!r->regstart
||
!fbm_instr((unsigned char*) SvPVX(r->regstart),
(unsigned char *) SvPVX(r->regstart)
+ SvCUR(r->regstart),
longest)
)
)
{
r->regmust = longest;
if (backest < 0)
backest = -1;
r->regback = backest;
if (SvCUR(longest) > !(sawstudy || fold ||
regkind[(U8)OP(first)]==EOL))
fbm_compile(r->regmust,fold);
(void)SvUPGRADE(r->regmust, SVt_PVBM);
BmUSEFUL(r->regmust) = 100;
if (regkind[(U8)OP(first)] == EOL && SvCUR(longish))
SvTAIL_on(r->regmust);
}
else {
SvREFCNT_dec(longest);
longest = Nullsv;
}
SvREFCNT_dec(longish);
}
r->do_folding = fold;
r->nparens = regnpar - 1;
r->minlen = minlen;
Newz(1002, r->startp, regnpar, char*);
Newz(1002, r->endp, regnpar, char*);
DEBUG_r(regdump(r));
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)
I32 paren; /* Parenthesized? */
I32 *flagp;
{
register char *ret;
register char *br;
register char *ender = 0;
register I32 parno = 0;
I32 flags;
*flagp = HASWIDTH; /* Tentatively. */
/* Make an OPEN node, if parenthesized. */
if (paren) {
if (*regparse == '?') {
regparse++;
paren = *regparse++;
ret = NULL;
switch (paren) {
case ':':
case '=':
case '!':
break;
case '$':
case '@':
croak("Sequence (?%c...) not implemented", paren);
break;
case '#':
while (*regparse && *regparse != ')')
regparse++;
if (*regparse != ')')
croak("Sequence (?#... not terminated");
nextchar();
*flagp = TRYAGAIN;
return NULL;
default:
--regparse;
while (*regparse && strchr("iogmsx", *regparse))
pmflag(®flags, *regparse++);
if (*regparse != ')')
croak("Sequence (?%c...) not recognized", *regparse);
nextchar();
*flagp = TRYAGAIN;
return NULL;
}
}
else {
parno = regnpar;
regnpar++;
ret = reganode(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 == '|') {
nextchar();
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. */
switch (paren) {
case ':':
ender = regnode(NOTHING);
break;
case 1:
ender = reganode(CLOSE, parno);
break;
case '=':
case '!':
ender = regnode(SUCCEED);
*flagp &= ~HASWIDTH;
break;
case 0:
ender = regnode(END);
break;
}
regtail(ret, ender);
/* Hook the tails of the branches to the closing node. */
for (br = ret; br != NULL; br = regnext(br))
regoptail(br, ender);
if (paren == '=') {
reginsert(IFMATCH,ret);
regtail(ret, regnode(NOTHING));
}
else if (paren == '!') {
reginsert(UNLESSM,ret);
regtail(ret, regnode(NOTHING));
}
/* Check for proper termination. */
if (paren && (regparse >= regxend || *nextchar() != ')')) {
FAIL("unmatched () in regexp");
} else if (!paren && regparse < regxend) {
if (*regparse == ')') {
FAIL("unmatched () in regexp");
} else
FAIL("junk on end of regexp"); /* "Can't happen". */
/* NOTREACHED */
}
return(ret);
}
/*
- regbranch - one alternative of an | operator
*
* Implements the concatenation operator.
*/
static char *
regbranch(flagp)
I32 *flagp;
{
register char *ret;
register char *chain;
register char *latest;
I32 flags = 0;
*flagp = WORST; /* Tentatively. */
ret = regnode(BRANCH);
chain = NULL;
regparse--;
nextchar();
while (regparse < regxend && *regparse != '|' && *regparse != ')') {
flags &= ~TRYAGAIN;
latest = regpiece(&flags);
if (latest == NULL) {
if (flags & TRYAGAIN)
continue;
return(NULL);
}
*flagp |= flags&HASWIDTH;
if (chain == NULL) /* First piece. */
*flagp |= flags&SPSTART;
else {
regnaughty++;
regtail(chain, latest);
}
chain = latest;
}
if (chain == NULL) /* Loop ran zero times. */
(void) 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(flagp)
I32 *flagp;
{
register char *ret;
register char op;
register char *next;
I32 flags;
char *origparse = regparse;
char *maxpos;
I32 min;
I32 max = 32767;
ret = regatom(&flags);
if (ret == NULL) {
if (flags & TRYAGAIN)
*flagp |= TRYAGAIN;
return(NULL);
}
op = *regparse;
if (op == '(' && regparse[1] == '?' && regparse[2] == '#') {
while (op && op != ')')
op = *++regparse;
if (op) {
nextchar();
op = *regparse;
}
}
if (op == '{' && regcurly(regparse)) {
next = regparse + 1;
maxpos = Nullch;
while (isDIGIT(*next) || *next == ',') {
if (*next == ',') {
if (maxpos)
break;
else
maxpos = next;
}
next++;
}
if (*next == '}') { /* got one */
if (!maxpos)
maxpos = next;
regparse++;
min = atoi(regparse);
if (*maxpos == ',')
maxpos++;
else
maxpos = regparse;
max = atoi(maxpos);
if (!max && *maxpos != '0')
max = 32767; /* meaning "infinity" */
regparse = next;
nextchar();
do_curly:
if ((flags&SIMPLE)) {
regnaughty += 2 + regnaughty / 2;
reginsert(CURLY, ret);
}
else {
regnaughty += 4 + regnaughty; /* compound interest */
regtail(ret, regnode(WHILEM));
reginsert(CURLYX,ret);
regtail(ret, regnode(NOTHING));
}
if (min > 0)
*flagp = (WORST|HASWIDTH);
if (max && max < min)
croak("Can't do {n,m} with n > m");
if (regcode != ®dummy) {
#ifdef REGALIGN
*(unsigned short *)(ret+3) = min;
*(unsigned short *)(ret+5) = max;
#else
ret[3] = min >> 8; ret[4] = min & 0377;
ret[5] = max >> 8; ret[6] = max & 0377;
#endif
}
goto nest_check;
}
}
if (!ISMULT1(op)) {
*flagp = flags;
return(ret);
}
nextchar();
*flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);
if (op == '*' && (flags&SIMPLE)) {
reginsert(STAR, ret);
regnaughty += 4;
}
else if (op == '*') {
min = 0;
goto do_curly;
} else if (op == '+' && (flags&SIMPLE)) {
reginsert(PLUS, ret);
regnaughty += 3;
}
else if (op == '+') {
min = 1;
goto do_curly;
} else if (op == '?') {
min = 0; max = 1;
goto do_curly;
}
nest_check:
if (dowarn && regcode != ®dummy && !(flags&HASWIDTH) && max > 10000) {
warn("%.*s matches null string many times",
regparse - origparse, origparse);
}
if (*regparse == '?') {
nextchar();
reginsert(MINMOD, ret);
#ifdef REGALIGN
regtail(ret, ret + 4);
#else
regtail(ret, ret + 3);
#endif
}
if (ISMULT2(regparse))
FAIL("nested *?+ in regexp");
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.
*
* [Yes, it is worth fixing, some scripts can run twice the speed.]
*/
static char *
regatom(flagp)
I32 *flagp;
{
register char *ret = 0;
I32 flags;
*flagp = WORST; /* Tentatively. */
tryagain:
switch (*regparse) {
case '^':
nextchar();
if (regflags & PMf_MULTILINE)
ret = regnode(MBOL);
else if (regflags & PMf_SINGLELINE)
ret = regnode(SBOL);
else
ret = regnode(BOL);
break;
case '$':
nextchar();
if (regflags & PMf_MULTILINE)
ret = regnode(MEOL);
else if (regflags & PMf_SINGLELINE)
ret = regnode(SEOL);
else
ret = regnode(EOL);
break;
case '.':
nextchar();
if (regflags & PMf_SINGLELINE)
ret = regnode(SANY);
else
ret = regnode(ANY);
regnaughty++;
*flagp |= HASWIDTH|SIMPLE;
break;
case '[':
regparse++;
ret = regclass();
*flagp |= HASWIDTH|SIMPLE;
break;
case '(':
nextchar();
ret = reg(1, &flags);
if (ret == NULL) {
if (flags & TRYAGAIN)
goto tryagain;
return(NULL);
}
*flagp |= flags&(HASWIDTH|SPSTART);
break;
case '|':
case ')':
if (flags & TRYAGAIN) {
*flagp |= TRYAGAIN;
return NULL;
}
croak("internal urp in regexp at /%s/", regparse);
/* Supposed to be caught earlier. */
break;
case '?':
case '+':
case '*':
FAIL("?+* follows nothing in regexp");
break;
case '\\':
switch (*++regparse) {
case 'A':
ret = regnode(SBOL);
*flagp |= SIMPLE;
nextchar();
break;
case 'G':
ret = regnode(GBOL);
*flagp |= SIMPLE;
nextchar();
break;
case 'Z':
ret = regnode(SEOL);
*flagp |= SIMPLE;
nextchar();
break;
case 'w':
ret = regnode(ALNUM);
*flagp |= HASWIDTH|SIMPLE;
nextchar();
break;
case 'W':
ret = regnode(NALNUM);
*flagp |= HASWIDTH|SIMPLE;
nextchar();
break;
case 'b':
ret = regnode(BOUND);
*flagp |= SIMPLE;
nextchar();
break;
case 'B':
ret = regnode(NBOUND);
*flagp |= SIMPLE;
nextchar();
break;
case 's':
ret = regnode(SPACE);
*flagp |= HASWIDTH|SIMPLE;
nextchar();
break;
case 'S':
ret = regnode(NSPACE);
*flagp |= HASWIDTH|SIMPLE;
nextchar();
break;
case 'd':
ret = regnode(DIGIT);
*flagp |= HASWIDTH|SIMPLE;
nextchar();
break;
case 'D':
ret = regnode(NDIGIT);
*flagp |= HASWIDTH|SIMPLE;
nextchar();
break;
case 'n':
case 'r':
case 't':
case 'f':
case 'e':
case 'a':
case 'x':
case 'c':
case '0':
goto defchar;
case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
{
I32 num = atoi(regparse);
if (num > 9 && num >= regnpar)
goto defchar;
else {
regsawback = 1;
ret = reganode(REF, num);
*flagp |= HASWIDTH;
while (isDIGIT(*regparse))
regparse++;
regparse--;
nextchar();
}
}
break;
case '\0':
if (regparse >= regxend)
FAIL("trailing \\ in regexp");
/* FALL THROUGH */
default:
goto defchar;
}
break;
case '#':
if (regflags & PMf_EXTENDED) {
while (regparse < regxend && *regparse != '\n') regparse++;
if (regparse < regxend)
goto tryagain;
}
/* FALL THROUGH */
default: {
register I32 len;
register char ender;
register char *p;
char *oldp;
I32 numlen;
regparse++;
defchar:
ret = regnode(EXACTLY);
regc(0); /* save spot for len */
for (len = 0, p = regparse - 1;
len < 127 && p < regxend;
len++)
{
oldp = p;
switch (*p) {
case '^':
case '$':
case '.':
case '[':
case '(':
case ')':
case '|':
goto loopdone;
case '\\':
switch (*++p) {
case 'A':
case 'G':
case 'Z':
case 'w':
case 'W':
case 'b':
case 'B':
case 's':
case 'S':
case 'd':
case 'D':
--p;
goto loopdone;
case 'n':
ender = '\n';
p++;
break;
case 'r':
ender = '\r';
p++;
break;
case 't':
ender = '\t';
p++;
break;
case 'f':
ender = '\f';
p++;
break;
case 'e':
ender = '\033';
p++;
break;
case 'a':
ender = '\007';
p++;
break;
case 'x':
ender = scan_hex(++p, 2, &numlen);
p += numlen;
break;
case 'c':
p++;
ender = *p++;
if (isLOWER(ender))
ender = toUPPER(ender);
ender ^= 64;
break;
case '0': case '1': case '2': case '3':case '4':
case '5': case '6': case '7': case '8':case '9':
if (*p == '0' ||
(isDIGIT(p[1]) && atoi(p) >= regnpar) ) {
ender = scan_oct(p, 3, &numlen);
p += numlen;
}
else {
--p;
goto loopdone;
}
break;
case '\0':
if (p >= regxend)
FAIL("trailing \\ in regexp");
/* FALL THROUGH */
default:
ender = *p++;
break;
}
break;
case '#':
if (regflags & PMf_EXTENDED) {
while (p < regxend && *p != '\n') p++;
}
/* FALL THROUGH */
case ' ': case '\t': case '\n': case '\r': case '\f': case '\v':
if (regflags & PMf_EXTENDED) {
p++;
len--;
continue;
}
/* FALL THROUGH */
default:
ender = *p++;
break;
}
if (regflags & PMf_FOLD && isUPPER(ender))
ender = toLOWER(ender);
if (ISMULT2(p)) { /* Back off on ?+*. */
if (len)
p = oldp;
else {
len++;
regc(ender);