libio/string/pcre_exec.c

/* $Id: pcre_exec.c 33 2005-10-02 20:50:00Z knight $ */

/*************************************************
*      Perl-Compatible Regular Expressions       *
*************************************************/

/* PCRE is a library of functions to support regular expressions whose syntax
and semantics are as close as possible to those of the Perl 5 language.

                       Written by Philip Hazel
           Copyright (c) 1997-2005 University of Cambridge

-----------------------------------------------------------------------------
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.

    * Neither the name of the University of Cambridge nor the names of its
      contributors may be used to endorse or promote products derived from
      this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
-----------------------------------------------------------------------------
*/


/* This module contains pcre_exec(), the externally visible function that does
pattern matching using an NFA algorithm, trying to mimic Perl as closely as
possible. There are also some static supporting functions. */


#include "pcre_internal.h"


/* Structure for building a chain of data that actually lives on the
stack, for holding the values of the subject pointer at the start of each
subpattern, so as to detect when an empty string has been matched by a
subpattern - to break infinite loops. When NO_RECURSE is set, these blocks
are on the heap, not on the stack. */

typedef struct eptrblock {
  struct eptrblock *epb_prev;
  const uschar *epb_saved_eptr;
} eptrblock;

/* Flag bits for the match() function */

#define match_condassert   0x01    /* Called to check a condition assertion */
#define match_isgroup      0x02    /* Set if start of bracketed group */

/* Non-error returns from the match() function. Error returns are externally
defined PCRE_ERROR_xxx codes, which are all negative. */

#define MATCH_MATCH        1
#define MATCH_NOMATCH      0

/* Maximum number of ints of offset to save on the stack for recursive calls.
If the offset vector is bigger, malloc is used. This should be a multiple of 3,
because the offset vector is always a multiple of 3 long. */

#define REC_STACK_SAVE_MAX 30

/* Min and max values for the common repeats; for the maxima, 0 => infinity */

static const char rep_min[] = { 0, 0, 1, 1, 0, 0 };
static const char rep_max[] = { 0, 0, 0, 0, 1, 1 };


#ifdef DEBUG
/*************************************************
*        Debugging function to print chars       *
*************************************************/

/* Print a sequence of chars in printable format, stopping at the end of the
subject if the requested.

Arguments:
  p           points to characters
  length      number to print
  is_subject  TRUE if printing from within md->start_subject
  md          pointer to matching data block, if is_subject is TRUE

Returns:     nothing
*/

static void
pchars(const uschar *p, int length, BOOL is_subject, match_data *md)
{
int c;
if (is_subject && length > md->end_subject - p) length = md->end_subject - p;
while (length-- > 0)
  if (isprint(c = *(p++))) printf("%c", c); else printf("\\x%02x", c);
}
#endif


/*************************************************
*          Match a back-reference                *
*************************************************/

/* If a back reference hasn't been set, the length that is passed is greater
than the number of characters left in the string, so the match fails.

Arguments:
  offset      index into the offset vector
  eptr        points into the subject
  length      length to be matched
  md          points to match data block
  ims         the ims flags

Returns:      TRUE if matched
*/

static BOOL
match_ref(int offset, register const uschar *eptr, int length, match_data *md,
  unsigned long int ims)
{
const uschar *p = md->start_subject + md->offset_vector[offset];

#ifdef DEBUG
if (eptr >= md->end_subject)
  printf("matching subject <null>");
else
  {
  printf("matching subject ");
  pchars(eptr, length, TRUE, md);
  }
printf(" against backref ");
pchars(p, length, FALSE, md);
printf("\n");
#endif

/* Always fail if not enough characters left */

if (length > md->end_subject - eptr) return FALSE;

/* Separate the caselesss case for speed */

if ((ims & PCRE_CASELESS) != 0)
  {
  while (length-- > 0)
    if (md->lcc[*p++] != md->lcc[*eptr++]) return FALSE;
  }
else
  { while (length-- > 0) if (*p++ != *eptr++) return FALSE; }

return TRUE;
}


/***************************************************************************
****************************************************************************
                   RECURSION IN THE match() FUNCTION

The match() function is highly recursive. Some regular expressions can cause
it to recurse thousands of times. I was writing for Unix, so I just let it
call itself recursively. This uses the stack for saving everything that has
to be saved for a recursive call. On Unix, the stack can be large, and this
works fine.

It turns out that on non-Unix systems there are problems with programs that
use a lot of stack. (This despite the fact that every last chip has oodles
of memory these days, and techniques for extending the stack have been known
for decades.) So....

There is a fudge, triggered by defining NO_RECURSE, which avoids recursive
calls by keeping local variables that need to be preserved in blocks of memory
obtained from malloc instead instead of on the stack. Macros are used to
achieve this so that the actual code doesn't look very different to what it
always used to.
****************************************************************************
***************************************************************************/


/* These versions of the macros use the stack, as normal */

#ifndef NO_RECURSE
#define REGISTER register
#define RMATCH(rx,ra,rb,rc,rd,re,rf,rg) rx = match(ra,rb,rc,rd,re,rf,rg)
#define RRETURN(ra) return ra
#else


/* These versions of the macros manage a private stack on the heap. Note
that the rd argument of RMATCH isn't actually used. It's the md argument of
match(), which never changes. */

#define REGISTER

#define RMATCH(rx,ra,rb,rc,rd,re,rf,rg)\
  {\
  heapframe *newframe = (pcre_stack_malloc)(sizeof(heapframe));\
  if (setjmp(frame->Xwhere) == 0)\
    {\
    newframe->Xeptr = ra;\
    newframe->Xecode = rb;\
    newframe->Xoffset_top = rc;\
    newframe->Xims = re;\
    newframe->Xeptrb = rf;\
    newframe->Xflags = rg;\
    newframe->Xprevframe = frame;\
    frame = newframe;\
    DPRINTF(("restarting from line %d\n", __LINE__));\
    goto HEAP_RECURSE;\
    }\
  else\
    {\
    DPRINTF(("longjumped back to line %d\n", __LINE__));\
    frame = md->thisframe;\
    rx = frame->Xresult;\
    }\
  }

#define RRETURN(ra)\
  {\
  heapframe *newframe = frame;\
  frame = newframe->Xprevframe;\
  (pcre_stack_free)(newframe);\
  if (frame != NULL)\
    {\
    frame->Xresult = ra;\
    md->thisframe = frame;\
    longjmp(frame->Xwhere, 1);\
    }\
  return ra;\
  }


/* Structure for remembering the local variables in a private frame */

typedef struct heapframe {
  struct heapframe *Xprevframe;

  /* Function arguments that may change */

  const uschar *Xeptr;
  const uschar *Xecode;
  int Xoffset_top;
  long int Xims;
  eptrblock *Xeptrb;
  int Xflags;

  /* Function local variables */

  const uschar *Xcallpat;
  const uschar *Xcharptr;
  const uschar *Xdata;
  const uschar *Xnext;
  const uschar *Xpp;
  const uschar *Xprev;
  const uschar *Xsaved_eptr;

  recursion_info Xnew_recursive;

  BOOL Xcur_is_word;
  BOOL Xcondition;
  BOOL Xminimize;
  BOOL Xprev_is_word;

  unsigned long int Xoriginal_ims;

  int Xctype;
  int Xfc;
  int Xfi;
  int Xlength;
  int Xmax;
  int Xmin;
  int Xnumber;
  int Xoffset;
  int Xop;
  int Xsave_capture_last;
  int Xsave_offset1, Xsave_offset2, Xsave_offset3;
  int Xstacksave[REC_STACK_SAVE_MAX];

  eptrblock Xnewptrb;

  /* Place to pass back result, and where to jump back to */

  int  Xresult;
  jmp_buf Xwhere;

} heapframe;

#endif


/***************************************************************************
***************************************************************************/


/*************************************************
*         Match from current position            *
*************************************************/

/* On entry ecode points to the first opcode, and eptr to the first character
in the subject string, while eptrb holds the value of eptr at the start of the
last bracketed group - used for breaking infinite loops matching zero-length
strings. This function is called recursively in many circumstances. Whenever it
returns a negative (error) response, the outer incarnation must also return the
same response.

Performance note: It might be tempting to extract commonly used fields from the
md structure (e.g. utf8, end_subject) into individual variables to improve
performance. Tests using gcc on a SPARC disproved this; in the first case, it
made performance worse.

Arguments:
   eptr        pointer in subject
   ecode       position in code
   offset_top  current top pointer
   md          pointer to "static" info for the match
   ims         current /i, /m, and /s options
   eptrb       pointer to chain of blocks containing eptr at start of
                 brackets - for testing for empty matches
   flags       can contain
                 match_condassert - this is an assertion condition
                 match_isgroup - this is the start of a bracketed group

Returns:       MATCH_MATCH if matched            )  these values are >= 0
               MATCH_NOMATCH if failed to match  )
               a negative PCRE_ERROR_xxx value if aborted by an error condition
                 (e.g. stopped by recursion limit)
*/

static int
match(REGISTER const uschar *eptr, REGISTER const uschar *ecode,
  int offset_top, match_data *md, unsigned long int ims, eptrblock *eptrb,
  int flags)
{
/* These variables do not need to be preserved over recursion in this function,
so they can be ordinary variables in all cases. Mark them with "register"
because they are used a lot in loops. */

register int  rrc;    /* Returns from recursive calls */
register int  i;      /* Used for loops not involving calls to RMATCH() */
register int  c;      /* Character values not kept over RMATCH() calls */
register BOOL utf8;   /* Local copy of UTF-8 flag for speed */

/* When recursion is not being used, all "local" variables that have to be
preserved over calls to RMATCH() are part of a "frame" which is obtained from
heap storage. Set up the top-level frame here; others are obtained from the
heap whenever RMATCH() does a "recursion". See the macro definitions above. */

#ifdef NO_RECURSE
heapframe *frame = (pcre_stack_malloc)(sizeof(heapframe));
frame->Xprevframe = NULL;            /* Marks the top level */

/* Copy in the original argument variables */

frame->Xeptr = eptr;
frame->Xecode = ecode;
frame->Xoffset_top = offset_top;
frame->Xims = ims;
frame->Xeptrb = eptrb;
frame->Xflags = flags;

/* This is where control jumps back to to effect "recursion" */

HEAP_RECURSE:

/* Macros make the argument variables come from the current frame */

#define eptr               frame->Xeptr
#define ecode              frame->Xecode
#define offset_top         frame->Xoffset_top
#define ims                frame->Xims
#define eptrb              frame->Xeptrb
#define flags              frame->Xflags

/* Ditto for the local variables */

#define callpat            frame->Xcallpat
#define data               frame->Xdata
#define next               frame->Xnext
#define pp                 frame->Xpp
#define prev               frame->Xprev
#define saved_eptr         frame->Xsaved_eptr

#define new_recursive      frame->Xnew_recursive

#define cur_is_word        frame->Xcur_is_word
#define condition          frame->Xcondition
#define minimize           frame->Xminimize
#define prev_is_word       frame->Xprev_is_word

#define original_ims       frame->Xoriginal_ims

#define ctype              frame->Xctype
#define fc                 frame->Xfc
#define fi                 frame->Xfi
#define length             frame->Xlength
#define max                frame->Xmax
#define min                frame->Xmin
#define number             frame->Xnumber
#define offset             frame->Xoffset
#define op                 frame->Xop
#define save_capture_last  frame->Xsave_capture_last
#define save_offset1       frame->Xsave_offset1
#define save_offset2       frame->Xsave_offset2
#define save_offset3       frame->Xsave_offset3
#define stacksave          frame->Xstacksave

#define newptrb            frame->Xnewptrb

/* When recursion is being used, local variables are allocated on the stack and
get preserved during recursion in the normal way. In this environment, fi and
i, and fc and c, can be the same variables. */

#else
#define fi i
#define fc c


const uschar *callpat;             /* them within each of those blocks.    */
const uschar *data;                /* However, in order to accommodate the */
const uschar *next;                /* version of this code that uses an    */
const uschar *pp;                  /* external "stack" implemented on the  */
const uschar *prev;                /* heap, it is easier to declare them   */
const uschar *saved_eptr;          /* all here, so the declarations can    */
                                   /* be cut out in a block. The only      */
recursion_info new_recursive;      /* declarations within blocks below are */
                                   /* for variables that do not have to    */
BOOL cur_is_word;                  /* be preserved over a recursive call   */
BOOL condition;                    /* to RMATCH().                         */
BOOL minimize;
BOOL prev_is_word;

unsigned long int original_ims;


int ctype;
int length;
int max;
int min;
int number;
int offset;
int op;
int save_capture_last;
int save_offset1, save_offset2, save_offset3;
int stacksave[REC_STACK_SAVE_MAX];

eptrblock newptrb;
#endif

/* OK, now we can get on with the real code of the function. Recursion is
specified by the macros RMATCH and RRETURN. When NO_RECURSE is *not* defined,
these just turn into a recursive call to match() and a "return", respectively.
However, RMATCH isn't like a function call because it's quite a complicated
macro. It has to be used in one particular way. This shouldn't, however, impact
performance when true recursion is being used. */

if (md->match_call_count++ >= md->match_limit) RRETURN(PCRE_ERROR_MATCHLIMIT);

original_ims = ims;    /* Save for resetting on ')' */
utf8 = md->utf8;       /* Local copy of the flag */

/* At the start of a bracketed group, add the current subject pointer to the
stack of such pointers, to be re-instated at the end of the group when we hit
the closing ket. When match() is called in other circumstances, we don't add to
this stack. */

if ((flags & match_isgroup) != 0)
  {
  newptrb.epb_prev = eptrb;
  newptrb.epb_saved_eptr = eptr;
  eptrb = &newptrb;
  }

/* Now start processing the operations. */

for (;;)
  {
  op = *ecode;
  minimize = FALSE;

  /* For partial matching, remember if we ever hit the end of the subject after
  matching at least one subject character. */

  if (md->partial &&
      eptr >= md->end_subject &&
      eptr > md->start_match)
    md->hitend = TRUE;

  /* Opening capturing bracket. If there is space in the offset vector, save
  the current subject position in the working slot at the top of the vector. We
  mustn't change the current values of the data slot, because they may be set
  from a previous iteration of this group, and be referred to by a reference
  inside the group.

  If the bracket fails to match, we need to restore this value and also the
  values of the final offsets, in case they were set by a previous iteration of
  the same bracket.

  If there isn't enough space in the offset vector, treat this as if it were a
  non-capturing bracket. Don't worry about setting the flag for the error case
  here; that is handled in the code for KET. */

  if (op > OP_BRA)
    {
    number = op - OP_BRA;

    /* For extended extraction brackets (large number), we have to fish out the
    number from a dummy opcode at the start. */

    if (number > EXTRACT_BASIC_MAX)
      number = GET2(ecode, 2+LINK_SIZE);
    offset = number << 1;

#ifdef DEBUG
    printf("start bracket %d subject=", number);
    pchars(eptr, 16, TRUE, md);
    printf("\n");
#endif

    if (offset < md->offset_max)
      {
      save_offset1 = md->offset_vector[offset];
      save_offset2 = md->offset_vector[offset+1];
      save_offset3 = md->offset_vector[md->offset_end - number];
      save_capture_last = md->capture_last;

      DPRINTF(("saving %d %d %d\n", save_offset1, save_offset2, save_offset3));
      md->offset_vector[md->offset_end - number] = eptr - md->start_subject;

      do
        {
        RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims, eptrb,
          match_isgroup);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        md->capture_last = save_capture_last;
        ecode += GET(ecode, 1);
        }
      while (*ecode == OP_ALT);

      DPRINTF(("bracket %d failed\n", number));

      md->offset_vector[offset] = save_offset1;
      md->offset_vector[offset+1] = save_offset2;
      md->offset_vector[md->offset_end - number] = save_offset3;

      RRETURN(MATCH_NOMATCH);
      }

    /* Insufficient room for saving captured contents */

    else op = OP_BRA;
    }

  /* Other types of node can be handled by a switch */

  switch(op)
    {
    case OP_BRA:     /* Non-capturing bracket: optimized */
    DPRINTF(("start bracket 0\n"));
    do
      {
      RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims, eptrb,
        match_isgroup);
      if (rrc != MATCH_NOMATCH) RRETURN(rrc);
      ecode += GET(ecode, 1);
      }
    while (*ecode == OP_ALT);
    DPRINTF(("bracket 0 failed\n"));
    RRETURN(MATCH_NOMATCH);

    /* Conditional group: compilation checked that there are no more than
    two branches. If the condition is false, skipping the first branch takes us
    past the end if there is only one branch, but that's OK because that is
    exactly what going to the ket would do. */

    case OP_COND:
    if (ecode[LINK_SIZE+1] == OP_CREF) /* Condition extract or recurse test */
      {
      offset = GET2(ecode, LINK_SIZE+2) << 1;  /* Doubled ref number */
      condition = (offset == CREF_RECURSE * 2)?
        (md->recursive != NULL) :
        (offset < offset_top && md->offset_vector[offset] >= 0);
      RMATCH(rrc, eptr, ecode + (condition?
        (LINK_SIZE + 4) : (LINK_SIZE + 1 + GET(ecode, 1))),
        offset_top, md, ims, eptrb, match_isgroup);
      RRETURN(rrc);
      }

    /* The condition is an assertion. Call match() to evaluate it - setting
    the final argument TRUE causes it to stop at the end of an assertion. */

    else
      {
      RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims, NULL,
          match_condassert | match_isgroup);
      if (rrc == MATCH_MATCH)
        {
        ecode += 1 + LINK_SIZE + GET(ecode, LINK_SIZE+2);
        while (*ecode == OP_ALT) ecode += GET(ecode, 1);
        }
      else if (rrc != MATCH_NOMATCH)
        {
        RRETURN(rrc);         /* Need braces because of following else */
        }
      else ecode += GET(ecode, 1);
      RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims, eptrb,
        match_isgroup);
      RRETURN(rrc);
      }
    /* Control never reaches here */

    /* Skip over conditional reference or large extraction number data if
    encountered. */

    case OP_CREF:
    case OP_BRANUMBER:
    ecode += 3;
    break;

    /* End of the pattern. If we are in a recursion, we should restore the
    offsets appropriately and continue from after the call. */

    case OP_END:
    if (md->recursive != NULL && md->recursive->group_num == 0)
      {
      recursion_info *rec = md->recursive;
      DPRINTF(("Hit the end in a (?0) recursion\n"));
      md->recursive = rec->prevrec;
      memmove(md->offset_vector, rec->offset_save,
        rec->saved_max * sizeof(int));
      md->start_match = rec->save_start;
      ims = original_ims;
      ecode = rec->after_call;
      break;
      }

    /* Otherwise, if PCRE_NOTEMPTY is set, fail if we have matched an empty
    string - backtracking will then try other alternatives, if any. */

    if (md->notempty && eptr == md->start_match) RRETURN(MATCH_NOMATCH);
    md->end_match_ptr = eptr;          /* Record where we ended */
    md->end_offset_top = offset_top;   /* and how many extracts were taken */
    RRETURN(MATCH_MATCH);

    /* Change option settings */

    case OP_OPT:
    ims = ecode[1];
    ecode += 2;
    DPRINTF(("ims set to %02lx\n", ims));
    break;

    /* Assertion brackets. Check the alternative branches in turn - the
    matching won't pass the KET for an assertion. If any one branch matches,
    the assertion is true. Lookbehind assertions have an OP_REVERSE item at the
    start of each branch to move the current point backwards, so the code at
    this level is identical to the lookahead case. */

    case OP_ASSERT:
    case OP_ASSERTBACK:
    do
      {
      RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims, NULL,
        match_isgroup);
      if (rrc == MATCH_MATCH) break;
      if (rrc != MATCH_NOMATCH) RRETURN(rrc);
      ecode += GET(ecode, 1);
      }
    while (*ecode == OP_ALT);
    if (*ecode == OP_KET) RRETURN(MATCH_NOMATCH);

    /* If checking an assertion for a condition, return MATCH_MATCH. */

    if ((flags & match_condassert) != 0) RRETURN(MATCH_MATCH);

    /* Continue from after the assertion, updating the offsets high water
    mark, since extracts may have been taken during the assertion. */

    do ecode += GET(ecode,1); while (*ecode == OP_ALT);
    ecode += 1 + LINK_SIZE;
    offset_top = md->end_offset_top;
    continue;

    /* Negative assertion: all branches must fail to match */

    case OP_ASSERT_NOT:
    case OP_ASSERTBACK_NOT:
    do
      {
      RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims, NULL,
        match_isgroup);
      if (rrc == MATCH_MATCH) RRETURN(MATCH_NOMATCH);
      if (rrc != MATCH_NOMATCH) RRETURN(rrc);
      ecode += GET(ecode,1);
      }
    while (*ecode == OP_ALT);

    if ((flags & match_condassert) != 0) RRETURN(MATCH_MATCH);

    ecode += 1 + LINK_SIZE;
    continue;

    /* Move the subject pointer back. This occurs only at the start of
    each branch of a lookbehind assertion. If we are too close to the start to
    move back, this match function fails. When working with UTF-8 we move
    back a number of characters, not bytes. */

    case OP_REVERSE:
    /* No UTF-8 support, or not in UTF-8 mode: count is byte count */

      {
      eptr -= GET(ecode,1);
      if (eptr < md->start_subject) RRETURN(MATCH_NOMATCH);
      }

    /* Skip to next op code */

    ecode += 1 + LINK_SIZE;
    break;

    /* The callout item calls an external function, if one is provided, passing
    details of the match so far. This is mainly for debugging, though the
    function is able to force a failure. */

    case OP_CALLOUT:
    if (pcre_callout != NULL)
      {
      pcre_callout_block cb;
      cb.version          = 1;   /* Version 1 of the callout block */
      cb.callout_number   = ecode[1];
      cb.offset_vector    = md->offset_vector;
      cb.subject          = (const char *)md->start_subject;
      cb.subject_length   = md->end_subject - md->start_subject;
      cb.start_match      = md->start_match - md->start_subject;
      cb.current_position = eptr - md->start_subject;
      cb.pattern_position = GET(ecode, 2);
      cb.next_item_length = GET(ecode, 2 + LINK_SIZE);
      cb.capture_top      = offset_top/2;
      cb.capture_last     = md->capture_last;
      cb.callout_data     = md->callout_data;
      if ((rrc = (*pcre_callout)(&cb)) > 0) RRETURN(MATCH_NOMATCH);
      if (rrc < 0) RRETURN(rrc);
      }
    ecode += 2 + 2*LINK_SIZE;
    break;

    /* Recursion either matches the current regex, or some subexpression. The
    offset data is the offset to the starting bracket from the start of the
    whole pattern. (This is so that it works from duplicated subpatterns.)

    If there are any capturing brackets started but not finished, we have to
    save their starting points and reinstate them after the recursion. However,
    we don't know how many such there are (offset_top records the completed
    total) so we just have to save all the potential data. There may be up to
    65535 such values, which is too large to put on the stack, but using malloc
    for small numbers seems expensive. As a compromise, the stack is used when
    there are no more than REC_STACK_SAVE_MAX values to store; otherwise malloc
    is used. A problem is what to do if the malloc fails ... there is no way of
    returning to the top level with an error. Save the top REC_STACK_SAVE_MAX
    values on the stack, and accept that the rest may be wrong.

    There are also other values that have to be saved. We use a chained
    sequence of blocks that actually live on the stack. Thanks to Robin Houston
    for the original version of this logic. */

    case OP_RECURSE:
      {
      callpat = md->start_code + GET(ecode, 1);
      new_recursive.group_num = *callpat - OP_BRA;

      /* For extended extraction brackets (large number), we have to fish out
      the number from a dummy opcode at the start. */

      if (new_recursive.group_num > EXTRACT_BASIC_MAX)
        new_recursive.group_num = GET2(callpat, 2+LINK_SIZE);

      /* Add to "recursing stack" */

      new_recursive.prevrec = md->recursive;
      md->recursive = &new_recursive;

      /* Find where to continue from afterwards */

      ecode += 1 + LINK_SIZE;
      new_recursive.after_call = ecode;

      /* Now save the offset data. */

      new_recursive.saved_max = md->offset_end;
      if (new_recursive.saved_max <= REC_STACK_SAVE_MAX)
        new_recursive.offset_save = stacksave;
      else
        {
        new_recursive.offset_save =
          (int *)(pcre_malloc)(new_recursive.saved_max * sizeof(int));
        if (new_recursive.offset_save == NULL) RRETURN(PCRE_ERROR_NOMEMORY);
        }

      memcpy(new_recursive.offset_save, md->offset_vector,
            new_recursive.saved_max * sizeof(int));
      new_recursive.save_start = md->start_match;
      md->start_match = eptr;

      /* OK, now we can do the recursion. For each top-level alternative we
      restore the offset and recursion data. */

      DPRINTF(("Recursing into group %d\n", new_recursive.group_num));
      do
        {
        RMATCH(rrc, eptr, callpat + 1 + LINK_SIZE, offset_top, md, ims,
            eptrb, match_isgroup);
        if (rrc == MATCH_MATCH)
          {
          md->recursive = new_recursive.prevrec;
          if (new_recursive.offset_save != stacksave)
            (pcre_free)(new_recursive.offset_save);
          RRETURN(MATCH_MATCH);
          }
        else if (rrc != MATCH_NOMATCH) RRETURN(rrc);

        md->recursive = &new_recursive;
        memcpy(md->offset_vector, new_recursive.offset_save,
            new_recursive.saved_max * sizeof(int));
        callpat += GET(callpat, 1);
        }
      while (*callpat == OP_ALT);

      DPRINTF(("Recursion didn't match\n"));
      md->recursive = new_recursive.prevrec;
      if (new_recursive.offset_save != stacksave)
        (pcre_free)(new_recursive.offset_save);
      RRETURN(MATCH_NOMATCH);
      }
    /* Control never reaches here */

    /* "Once" brackets are like assertion brackets except that after a match,
    the point in the subject string is not moved back. Thus there can never be
    a move back into the brackets. Friedl calls these "atomic" subpatterns.
    Check the alternative branches in turn - the matching won't pass the KET
    for this kind of subpattern. If any one branch matches, we carry on as at
    the end of a normal bracket, leaving the subject pointer. */

    case OP_ONCE:
      {
      prev = ecode;
      saved_eptr = eptr;

      do
        {
        RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims,
          eptrb, match_isgroup);
        if (rrc == MATCH_MATCH) break;
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        ecode += GET(ecode,1);
        }
      while (*ecode == OP_ALT);

      /* If hit the end of the group (which could be repeated), fail */

      if (*ecode != OP_ONCE && *ecode != OP_ALT) RRETURN(MATCH_NOMATCH);

      /* Continue as from after the assertion, updating the offsets high water
      mark, since extracts may have been taken. */

      do ecode += GET(ecode,1); while (*ecode == OP_ALT);

      offset_top = md->end_offset_top;
      eptr = md->end_match_ptr;

      /* For a non-repeating ket, just continue at this level. This also
      happens for a repeating ket if no characters were matched in the group.
      This is the forcible breaking of infinite loops as implemented in Perl
      5.005. If there is an options reset, it will get obeyed in the normal
      course of events. */

      if (*ecode == OP_KET || eptr == saved_eptr)
        {
        ecode += 1+LINK_SIZE;
        break;
        }

      /* The repeating kets try the rest of the pattern or restart from the
      preceding bracket, in the appropriate order. We need to reset any options
      that changed within the bracket before re-running it, so check the next
      opcode. */

      if (ecode[1+LINK_SIZE] == OP_OPT)
        {
        ims = (ims & ~PCRE_IMS) | ecode[4];
        DPRINTF(("ims set to %02lx at group repeat\n", ims));
        }

      if (*ecode == OP_KETRMIN)
        {
        RMATCH(rrc, eptr, ecode + 1 + LINK_SIZE, offset_top, md, ims, eptrb, 0);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        RMATCH(rrc, eptr, prev, offset_top, md, ims, eptrb, match_isgroup);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        }
      else  /* OP_KETRMAX */
        {
        RMATCH(rrc, eptr, prev, offset_top, md, ims, eptrb, match_isgroup);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        RMATCH(rrc, eptr, ecode + 1+LINK_SIZE, offset_top, md, ims, eptrb, 0);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        }
      }
    RRETURN(MATCH_NOMATCH);

    /* An alternation is the end of a branch; scan along to find the end of the
    bracketed group and go to there. */

    case OP_ALT:
    do ecode += GET(ecode,1); while (*ecode == OP_ALT);
    break;

    /* BRAZERO and BRAMINZERO occur just before a bracket group, indicating
    that it may occur zero times. It may repeat infinitely, or not at all -
    i.e. it could be ()* or ()? in the pattern. Brackets with fixed upper
    repeat limits are compiled as a number of copies, with the optional ones
    preceded by BRAZERO or BRAMINZERO. */

    case OP_BRAZERO:
      {
      next = ecode+1;
      RMATCH(rrc, eptr, next, offset_top, md, ims, eptrb, match_isgroup);
      if (rrc != MATCH_NOMATCH) RRETURN(rrc);
      do next += GET(next,1); while (*next == OP_ALT);
      ecode = next + 1+LINK_SIZE;
      }
    break;

    case OP_BRAMINZERO:
      {
      next = ecode+1;
      do next += GET(next,1); while (*next == OP_ALT);
      RMATCH(rrc, eptr, next + 1+LINK_SIZE, offset_top, md, ims, eptrb,
        match_isgroup);
      if (rrc != MATCH_NOMATCH) RRETURN(rrc);
      ecode++;
      }
    break;

    /* End of a group, repeated or non-repeating. If we are at the end of
    an assertion "group", stop matching and return MATCH_MATCH, but record the
    current high water mark for use by positive assertions. Do this also
    for the "once" (not-backup up) groups. */

    case OP_KET:
    case OP_KETRMIN:
    case OP_KETRMAX:
      {
      prev = ecode - GET(ecode, 1);
      saved_eptr = eptrb->epb_saved_eptr;

      /* Back up the stack of bracket start pointers. */

      eptrb = eptrb->epb_prev;

      if (*prev == OP_ASSERT || *prev == OP_ASSERT_NOT ||
          *prev == OP_ASSERTBACK || *prev == OP_ASSERTBACK_NOT ||
          *prev == OP_ONCE)
        {
        md->end_match_ptr = eptr;      /* For ONCE */
        md->end_offset_top = offset_top;
        RRETURN(MATCH_MATCH);
        }

      /* In all other cases except a conditional group we have to check the
      group number back at the start and if necessary complete handling an
      extraction by setting the offsets and bumping the high water mark. */

      if (*prev != OP_COND)
        {
        number = *prev - OP_BRA;

        /* For extended extraction brackets (large number), we have to fish out
        the number from a dummy opcode at the start. */

        if (number > EXTRACT_BASIC_MAX) number = GET2(prev, 2+LINK_SIZE);
        offset = number << 1;

#ifdef DEBUG
        printf("end bracket %d", number);
        printf("\n");
#endif

        /* Test for a numbered group. This includes groups called as a result
        of recursion. Note that whole-pattern recursion is coded as a recurse
        into group 0, so it won't be picked up here. Instead, we catch it when
        the OP_END is reached. */

        if (number > 0)
          {
          md->capture_last = number;
          if (offset >= md->offset_max) md->offset_overflow = TRUE; else
            {
            md->offset_vector[offset] =
              md->offset_vector[md->offset_end - number];
            md->offset_vector[offset+1] = eptr - md->start_subject;
            if (offset_top <= offset) offset_top = offset + 2;
            }

          /* Handle a recursively called group. Restore the offsets
          appropriately and continue from after the call. */

          if (md->recursive != NULL && md->recursive->group_num == number)
            {
            recursion_info *rec = md->recursive;
            DPRINTF(("Recursion (%d) succeeded - continuing\n", number));
            md->recursive = rec->prevrec;
            md->start_match = rec->save_start;
            memcpy(md->offset_vector, rec->offset_save,
              rec->saved_max * sizeof(int));
            ecode = rec->after_call;
            ims = original_ims;
            break;
            }
          }
        }

      /* Reset the value of the ims flags, in case they got changed during
      the group. */

      ims = original_ims;
      DPRINTF(("ims reset to %02lx\n", ims));

      /* For a non-repeating ket, just continue at this level. This also
      happens for a repeating ket if no characters were matched in the group.
      This is the forcible breaking of infinite loops as implemented in Perl
      5.005. If there is an options reset, it will get obeyed in the normal
      course of events. */

      if (*ecode == OP_KET || eptr == saved_eptr)
        {
        ecode += 1 + LINK_SIZE;
        break;
        }

      /* The repeating kets try the rest of the pattern or restart from the
      preceding bracket, in the appropriate order. */

      if (*ecode == OP_KETRMIN)
        {
        RMATCH(rrc, eptr, ecode + 1+LINK_SIZE, offset_top, md, ims, eptrb, 0);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        RMATCH(rrc, eptr, prev, offset_top, md, ims, eptrb, match_isgroup);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        }
      else  /* OP_KETRMAX */
        {
        RMATCH(rrc, eptr, prev, offset_top, md, ims, eptrb, match_isgroup);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        RMATCH(rrc, eptr, ecode + 1+LINK_SIZE, offset_top, md, ims, eptrb, 0);
        if (rrc != MATCH_NOMATCH) RRETURN(rrc);
        }
      }

    RRETURN(MATCH_NOMATCH);

    /* Start of subject unless notbol, or after internal newline if multiline */

    case OP_CIRC:
    if (md->notbol && eptr == md->start_subject) RRETURN(MATCH_NOMATCH);
    if ((ims & PCRE_MULTILINE) != 0)
      {
      if (eptr != md->start_subject && eptr[-1] != NEWLINE)
        RRETURN(MATCH_NOMATCH);
      ecode++;
      break;
      }
    /* ... else fall through */

    /* Start of subject assertion */

    case OP_SOD:
    if (eptr != md->start_subject) RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    /* Start of match assertion */

    case OP_SOM:
    if (eptr != md->start_subject + md->start_offset) RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    /* Assert before internal newline if multiline, or before a terminating
    newline unless endonly is set, else end of subject unless noteol is set. */

    case OP_DOLL:
    if ((ims & PCRE_MULTILINE) != 0)
      {
      if (eptr < md->end_subject)
        { if (*eptr != NEWLINE) RRETURN(MATCH_NOMATCH); }
      else
        { if (md->noteol) RRETURN(MATCH_NOMATCH); }
      ecode++;
      break;
      }
    else
      {
      if (md->noteol) RRETURN(MATCH_NOMATCH);
      if (!md->endonly)
        {
        if (eptr < md->end_subject - 1 ||
           (eptr == md->end_subject - 1 && *eptr != NEWLINE))
          RRETURN(MATCH_NOMATCH);
        ecode++;
        break;
        }
      }
    /* ... else fall through */

    /* End of subject assertion (\z) */

    case OP_EOD:
    if (eptr < md->end_subject) RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    /* End of subject or ending \n assertion (\Z) */

    case OP_EODN:
    if (eptr < md->end_subject - 1 ||
       (eptr == md->end_subject - 1 && *eptr != NEWLINE)) RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    /* Word boundary assertions */

    case OP_NOT_WORD_BOUNDARY:
    case OP_WORD_BOUNDARY:
      {

      /* More streamlined when not in UTF-8 mode */

        {
        prev_is_word = (eptr != md->start_subject) &&
          ((md->ctypes[eptr[-1]] & ctype_word) != 0);
        cur_is_word = (eptr < md->end_subject) &&
          ((md->ctypes[*eptr] & ctype_word) != 0);
        }

      /* Now see if the situation is what we want */

      if ((*ecode++ == OP_WORD_BOUNDARY)?
           cur_is_word == prev_is_word : cur_is_word != prev_is_word)
        RRETURN(MATCH_NOMATCH);
      }
    break;

    /* Match a single character type; inline for speed */

    case OP_ANY:
    if ((ims & PCRE_DOTALL) == 0 && eptr < md->end_subject && *eptr == NEWLINE)
      RRETURN(MATCH_NOMATCH);
    if (eptr++ >= md->end_subject) RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    /* Match a single byte, even in UTF-8 mode. This opcode really does match
    any byte, even newline, independent of the setting of PCRE_DOTALL. */

    case OP_ANYBYTE:
    if (eptr++ >= md->end_subject) RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    case OP_NOT_DIGIT:
    if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
    GETCHARINCTEST(c, eptr);
    if ((md->ctypes[c] & ctype_digit) != 0)
      RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    case OP_DIGIT:
    if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
    GETCHARINCTEST(c, eptr);
    if ((md->ctypes[c] & ctype_digit) == 0)
      RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    case OP_NOT_WHITESPACE:
    if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
    GETCHARINCTEST(c, eptr);
    if ((md->ctypes[c] & ctype_space) != 0)
      RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    case OP_WHITESPACE:
    if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
    GETCHARINCTEST(c, eptr);
    if ((md->ctypes[c] & ctype_space) == 0)
      RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    case OP_NOT_WORDCHAR:
    if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
    GETCHARINCTEST(c, eptr);
    if ((md->ctypes[c] & ctype_word) != 0)
      RRETURN(MATCH_NOMATCH);
    ecode++;
    break;

    case OP_WORDCHAR:
    if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
    GETCHARINCTEST(c, eptr);
    if ((md->ctypes[c] & ctype_word) == 0)
      RRETURN(MATCH_NOMATCH);
    ecode++;
    break;


    /* Match a back reference, possibly repeatedly. Look past the end of the
    item to see if there is repeat information following. The code is similar
    to that for character classes, but repeated for efficiency. Then obey
    similar code to character type repeats - written out again for speed.
    However, if the referenced string is the empty string, always treat
    it as matched, any number of times (otherwise there could be infinite
    loops). */

    case OP_REF:
      {
      offset = GET2(ecode, 1) << 1;               /* Doubled ref number */
      ecode += 3;                                 /* Advance past item */

      /* If the reference is unset, set the length to be longer than the amount
      of subject left; this ensures that every attempt at a match fails. We
      can't just fail here, because of the possibility of quantifiers with zero
      minima. */

      length = (offset >= offset_top || md->offset_vector[offset] < 0)?
        md->end_subject - eptr + 1 :
        md->offset_vector[offset+1] - md->offset_vector[offset];

      /* Set up for repetition, or handle the non-repeated case */

      switch (*ecode)
        {
        case OP_CRSTAR:
        case OP_CRMINSTAR:
        case OP_CRPLUS:
        case OP_CRMINPLUS:
        case OP_CRQUERY:
        case OP_CRMINQUERY:
        c = *ecode++ - OP_CRSTAR;
        minimize = (c & 1) != 0;
        min = rep_min[c];                 /* Pick up values from tables; */
        max = rep_max[c];                 /* zero for max => infinity */
        if (max == 0) max = INT_MAX;
        break;

        case OP_CRRANGE:
        case OP_CRMINRANGE:
        minimize = (*ecode == OP_CRMINRANGE);
        min = GET2(ecode, 1);
        max = GET2(ecode, 3);
        if (max == 0) max = INT_MAX;
        ecode += 5;
        break;

        default:               /* No repeat follows */
        if (!match_ref(offset, eptr, length, md, ims)) RRETURN(MATCH_NOMATCH);
        eptr += length;
        continue;              /* With the main loop */
        }

      /* If the length of the reference is zero, just continue with the
      main loop. */

      if (length == 0) continue;

      /* First, ensure the minimum number of matches are present. We get back
      the length of the reference string explicitly rather than passing the
      address of eptr, so that eptr can be a register variable. */

      for (i = 1; i <= min; i++)
        {
        if (!match_ref(offset, eptr, length, md, ims)) RRETURN(MATCH_NOMATCH);
        eptr += length;
        }

      /* If min = max, continue at the same level without recursion.
      They are not both allowed to be zero. */

      if (min == max) continue;

      /* If minimizing, keep trying and advancing the pointer */

      if (minimize)
        {
        for (fi = min;; fi++)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          if (fi >= max || !match_ref(offset, eptr, length, md, ims))
            RRETURN(MATCH_NOMATCH);
          eptr += length;
          }
        /* Control never gets here */
        }

      /* If maximizing, find the longest string and work backwards */

      else
        {
        pp = eptr;
        for (i = min; i < max; i++)
          {
          if (!match_ref(offset, eptr, length, md, ims)) break;
          eptr += length;
          }
        while (eptr >= pp)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          eptr -= length;
          }
        RRETURN(MATCH_NOMATCH);
        }
      }
    /* Control never gets here */


    /* Match a bit-mapped character class, possibly repeatedly. This op code is
    used when all the characters in the class have values in the range 0-255,
    and either the matching is caseful, or the characters are in the range
    0-127 when UTF-8 processing is enabled. The only difference between
    OP_CLASS and OP_NCLASS occurs when a data character outside the range is
    encountered.

    First, look past the end of the item to see if there is repeat information
    following. Then obey similar code to character type repeats - written out
    again for speed. */

    case OP_NCLASS:
    case OP_CLASS:
      {
      data = ecode + 1;                /* Save for matching */
      ecode += 33;                     /* Advance past the item */

      switch (*ecode)
        {
        case OP_CRSTAR:
        case OP_CRMINSTAR:
        case OP_CRPLUS:
        case OP_CRMINPLUS:
        case OP_CRQUERY:
        case OP_CRMINQUERY:
        c = *ecode++ - OP_CRSTAR;
        minimize = (c & 1) != 0;
        min = rep_min[c];                 /* Pick up values from tables; */
        max = rep_max[c];                 /* zero for max => infinity */
        if (max == 0) max = INT_MAX;
        break;

        case OP_CRRANGE:
        case OP_CRMINRANGE:
        minimize = (*ecode == OP_CRMINRANGE);
        min = GET2(ecode, 1);
        max = GET2(ecode, 3);
        if (max == 0) max = INT_MAX;
        ecode += 5;
        break;

        default:               /* No repeat follows */
        min = max = 1;
        break;
        }

      /* First, ensure the minimum number of matches are present. */

      /* Not UTF-8 mode */
        {
        for (i = 1; i <= min; i++)
          {
          if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
          c = *eptr++;
          if ((data[c/8] & (1 << (c&7))) == 0) RRETURN(MATCH_NOMATCH);
          }
        }

      /* If max == min we can continue with the main loop without the
      need to recurse. */

      if (min == max) continue;

      /* If minimizing, keep testing the rest of the expression and advancing
      the pointer while it matches the class. */

      if (minimize)
        {
        /* Not UTF-8 mode */
          {
          for (fi = min;; fi++)
            {
            RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
            if (rrc != MATCH_NOMATCH) RRETURN(rrc);
            if (fi >= max || eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
            c = *eptr++;
            if ((data[c/8] & (1 << (c&7))) == 0) RRETURN(MATCH_NOMATCH);
            }
          }
        /* Control never gets here */
        }

      /* If maximizing, find the longest possible run, then work backwards. */

      else
        {
        pp = eptr;

          /* Not UTF-8 mode */
          {
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject) break;
            c = *eptr;
            if ((data[c/8] & (1 << (c&7))) == 0) break;
            eptr++;
            }
          while (eptr >= pp)
            {
            RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
            eptr--;
            if (rrc != MATCH_NOMATCH) RRETURN(rrc);
            }
          }

        RRETURN(MATCH_NOMATCH);
        }
      }
    /* Control never gets here */


    /* Match a single character, casefully */

    case OP_CHAR:
    /* Non-UTF-8 mode */
      {
      if (md->end_subject - eptr < 1) RRETURN(MATCH_NOMATCH);
      if (ecode[1] != *eptr++) RRETURN(MATCH_NOMATCH);
      ecode += 2;
      }
    break;

    /* Match a single character, caselessly */

    case OP_CHARNC:
    /* Non-UTF-8 mode */
      {
      if (md->end_subject - eptr < 1) RRETURN(MATCH_NOMATCH);
      if (md->lcc[ecode[1]] != md->lcc[*eptr++]) RRETURN(MATCH_NOMATCH);
      ecode += 2;
      }
    break;

    /* Match a single character repeatedly; different opcodes share code. */

    case OP_EXACT:
    min = max = GET2(ecode, 1);
    ecode += 3;
    goto REPEATCHAR;

    case OP_UPTO:
    case OP_MINUPTO:
    min = 0;
    max = GET2(ecode, 1);
    minimize = *ecode == OP_MINUPTO;
    ecode += 3;
    goto REPEATCHAR;

    case OP_STAR:
    case OP_MINSTAR:
    case OP_PLUS:
    case OP_MINPLUS:
    case OP_QUERY:
    case OP_MINQUERY:
    c = *ecode++ - OP_STAR;
    minimize = (c & 1) != 0;
    min = rep_min[c];                 /* Pick up values from tables; */
    max = rep_max[c];                 /* zero for max => infinity */
    if (max == 0) max = INT_MAX;

    /* Common code for all repeated single-character matches. We can give
    up quickly if there are fewer than the minimum number of characters left in
    the subject. */

    REPEATCHAR:
    /* When not in UTF-8 mode, load a single-byte character. */
      {
      if (min > md->end_subject - eptr) RRETURN(MATCH_NOMATCH);
      fc = *ecode++;
      }

    /* The value of fc at this point is always less than 256, though we may or
    may not be in UTF-8 mode. The code is duplicated for the caseless and
    caseful cases, for speed, since matching characters is likely to be quite
    common. First, ensure the minimum number of matches are present. If min =
    max, continue at the same level without recursing. Otherwise, if
    minimizing, keep trying the rest of the expression and advancing one
    matching character if failing, up to the maximum. Alternatively, if
    maximizing, find the maximum number of characters and work backwards. */

    DPRINTF(("matching %c{%d,%d} against subject %.*s\n", fc, min, max,
      max, eptr));

    if ((ims & PCRE_CASELESS) != 0)
      {
      fc = md->lcc[fc];
      for (i = 1; i <= min; i++)
        if (fc != md->lcc[*eptr++]) RRETURN(MATCH_NOMATCH);
      if (min == max) continue;
      if (minimize)
        {
        for (fi = min;; fi++)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          if (fi >= max || eptr >= md->end_subject ||
              fc != md->lcc[*eptr++])
            RRETURN(MATCH_NOMATCH);
          }
        /* Control never gets here */
        }
      else
        {
        pp = eptr;
        for (i = min; i < max; i++)
          {
          if (eptr >= md->end_subject || fc != md->lcc[*eptr]) break;
          eptr++;
          }
        while (eptr >= pp)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          eptr--;
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          }
        RRETURN(MATCH_NOMATCH);
        }
      /* Control never gets here */
      }

    /* Caseful comparisons (includes all multi-byte characters) */

    else
      {
      for (i = 1; i <= min; i++) if (fc != *eptr++) RRETURN(MATCH_NOMATCH);
      if (min == max) continue;
      if (minimize)
        {
        for (fi = min;; fi++)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          if (fi >= max || eptr >= md->end_subject || fc != *eptr++)
            RRETURN(MATCH_NOMATCH);
          }
        /* Control never gets here */
        }
      else
        {
        pp = eptr;
        for (i = min; i < max; i++)
          {
          if (eptr >= md->end_subject || fc != *eptr) break;
          eptr++;
          }
        while (eptr >= pp)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          eptr--;
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          }
        RRETURN(MATCH_NOMATCH);
        }
      }
    /* Control never gets here */

    /* Match a negated single one-byte character. The character we are
    checking can be multibyte. */

    case OP_NOT:
    if (eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
    ecode++;
    GETCHARINCTEST(c, eptr);
    if ((ims & PCRE_CASELESS) != 0)
      {
      c = md->lcc[c];
      if (md->lcc[*ecode++] == c) RRETURN(MATCH_NOMATCH);
      }
    else
      {
      if (*ecode++ == c) RRETURN(MATCH_NOMATCH);
      }
    break;

    /* Match a negated single one-byte character repeatedly. This is almost a
    repeat of the code for a repeated single character, but I haven't found a
    nice way of commoning these up that doesn't require a test of the
    positive/negative option for each character match. Maybe that wouldn't add
    very much to the time taken, but character matching *is* what this is all
    about... */

    case OP_NOTEXACT:
    min = max = GET2(ecode, 1);
    ecode += 3;
    goto REPEATNOTCHAR;

    case OP_NOTUPTO:
    case OP_NOTMINUPTO:
    min = 0;
    max = GET2(ecode, 1);
    minimize = *ecode == OP_NOTMINUPTO;
    ecode += 3;
    goto REPEATNOTCHAR;

    case OP_NOTSTAR:
    case OP_NOTMINSTAR:
    case OP_NOTPLUS:
    case OP_NOTMINPLUS:
    case OP_NOTQUERY:
    case OP_NOTMINQUERY:
    c = *ecode++ - OP_NOTSTAR;
    minimize = (c & 1) != 0;
    min = rep_min[c];                 /* Pick up values from tables; */
    max = rep_max[c];                 /* zero for max => infinity */
    if (max == 0) max = INT_MAX;

    /* Common code for all repeated single-byte matches. We can give up quickly
    if there are fewer than the minimum number of bytes left in the
    subject. */

    REPEATNOTCHAR:
    if (min > md->end_subject - eptr) RRETURN(MATCH_NOMATCH);
    fc = *ecode++;

    /* The code is duplicated for the caseless and caseful cases, for speed,
    since matching characters is likely to be quite common. First, ensure the
    minimum number of matches are present. If min = max, continue at the same
    level without recursing. Otherwise, if minimizing, keep trying the rest of
    the expression and advancing one matching character if failing, up to the
    maximum. Alternatively, if maximizing, find the maximum number of
    characters and work backwards. */

    DPRINTF(("negative matching %c{%d,%d} against subject %.*s\n", fc, min, max,
      max, eptr));

    if ((ims & PCRE_CASELESS) != 0)
      {
      fc = md->lcc[fc];

      /* Not UTF-8 mode */
        {
        for (i = 1; i <= min; i++)
          if (fc == md->lcc[*eptr++]) RRETURN(MATCH_NOMATCH);
        }

      if (min == max) continue;

      if (minimize)
        {
        /* Not UTF-8 mode */
          {
          for (fi = min;; fi++)
            {
            RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
            if (rrc != MATCH_NOMATCH) RRETURN(rrc);
            if (fi >= max || eptr >= md->end_subject || fc == md->lcc[*eptr++])
              RRETURN(MATCH_NOMATCH);
            }
          }
        /* Control never gets here */
        }

      /* Maximize case */

      else
        {
        pp = eptr;

        /* Not UTF-8 mode */
          {
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || fc == md->lcc[*eptr]) break;
            eptr++;
            }
          while (eptr >= pp)
            {
            RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
            if (rrc != MATCH_NOMATCH) RRETURN(rrc);
            eptr--;
            }
          }

        RRETURN(MATCH_NOMATCH);
        }
      /* Control never gets here */
      }

    /* Caseful comparisons */

    else
      {
      /* Not UTF-8 mode */
        {
        for (i = 1; i <= min; i++)
          if (fc == *eptr++) RRETURN(MATCH_NOMATCH);
        }

      if (min == max) continue;

      if (minimize)
        {
        /* Not UTF-8 mode */
          {
          for (fi = min;; fi++)
            {
            RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
            if (rrc != MATCH_NOMATCH) RRETURN(rrc);
            if (fi >= max || eptr >= md->end_subject || fc == *eptr++)
              RRETURN(MATCH_NOMATCH);
            }
          }
        /* Control never gets here */
        }

      /* Maximize case */

      else
        {
        pp = eptr;

        /* Not UTF-8 mode */
          {
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || fc == *eptr) break;
            eptr++;
            }
          while (eptr >= pp)
            {
            RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
            if (rrc != MATCH_NOMATCH) RRETURN(rrc);
            eptr--;
            }
          }

        RRETURN(MATCH_NOMATCH);
        }
      }
    /* Control never gets here */

    /* Match a single character type repeatedly; several different opcodes
    share code. This is very similar to the code for single characters, but we
    repeat it in the interests of efficiency. */

    case OP_TYPEEXACT:
    min = max = GET2(ecode, 1);
    minimize = TRUE;
    ecode += 3;
    goto REPEATTYPE;

    case OP_TYPEUPTO:
    case OP_TYPEMINUPTO:
    min = 0;
    max = GET2(ecode, 1);
    minimize = *ecode == OP_TYPEMINUPTO;
    ecode += 3;
    goto REPEATTYPE;

    case OP_TYPESTAR:
    case OP_TYPEMINSTAR:
    case OP_TYPEPLUS:
    case OP_TYPEMINPLUS:
    case OP_TYPEQUERY:
    case OP_TYPEMINQUERY:
    c = *ecode++ - OP_TYPESTAR;
    minimize = (c & 1) != 0;
    min = rep_min[c];                 /* Pick up values from tables; */
    max = rep_max[c];                 /* zero for max => infinity */
    if (max == 0) max = INT_MAX;

    /* Common code for all repeated single character type matches. Note that
    in UTF-8 mode, '.' matches a character of any length, but for the other
    character types, the valid characters are all one-byte long. */

    REPEATTYPE:
    ctype = *ecode++;      /* Code for the character type */

    /* First, ensure the minimum number of matches are present. Use inline
    code for maximizing the speed, and do the type test once at the start
    (i.e. keep it out of the loop). Also we can test that there are at least
    the minimum number of bytes before we start. This isn't as effective in
    UTF-8 mode, but it does no harm. Separate the UTF-8 code completely as that
    is tidier. Also separate the UCP code, which can be the same for both UTF-8
    and single-bytes. */

    if (min > md->end_subject - eptr) RRETURN(MATCH_NOMATCH);
    if (min > 0)
      {
      /* Code for the non-UTF-8 case for minimum matching of operators other
      than OP_PROP and OP_NOTPROP. */

      switch(ctype)
        {
        case OP_ANY:
        if ((ims & PCRE_DOTALL) == 0)
          {
          for (i = 1; i <= min; i++)
            if (*eptr++ == NEWLINE) RRETURN(MATCH_NOMATCH);
          }
        else eptr += min;
        break;

        case OP_ANYBYTE:
        eptr += min;
        break;

        case OP_NOT_DIGIT:
        for (i = 1; i <= min; i++)
          if ((md->ctypes[*eptr++] & ctype_digit) != 0) RRETURN(MATCH_NOMATCH);
        break;

        case OP_DIGIT:
        for (i = 1; i <= min; i++)
          if ((md->ctypes[*eptr++] & ctype_digit) == 0) RRETURN(MATCH_NOMATCH);
        break;

        case OP_NOT_WHITESPACE:
        for (i = 1; i <= min; i++)
          if ((md->ctypes[*eptr++] & ctype_space) != 0) RRETURN(MATCH_NOMATCH);
        break;

        case OP_WHITESPACE:
        for (i = 1; i <= min; i++)
          if ((md->ctypes[*eptr++] & ctype_space) == 0) RRETURN(MATCH_NOMATCH);
        break;

        case OP_NOT_WORDCHAR:
        for (i = 1; i <= min; i++)
          if ((md->ctypes[*eptr++] & ctype_word) != 0)
            RRETURN(MATCH_NOMATCH);
        break;

        case OP_WORDCHAR:
        for (i = 1; i <= min; i++)
          if ((md->ctypes[*eptr++] & ctype_word) == 0)
            RRETURN(MATCH_NOMATCH);
        break;

        default:
        RRETURN(PCRE_ERROR_INTERNAL);
        }
      }

    /* If min = max, continue at the same level without recursing */

    if (min == max) continue;

    /* If minimizing, we have to test the rest of the pattern before each
    subsequent match. Again, separate the UTF-8 case for speed, and also
    separate the UCP cases. */

    if (minimize)
      {
      /* Not UTF-8 mode */
        {
        for (fi = min;; fi++)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          if (fi >= max || eptr >= md->end_subject) RRETURN(MATCH_NOMATCH);
          c = *eptr++;
          switch(ctype)
            {
            case OP_ANY:
            if ((ims & PCRE_DOTALL) == 0 && c == NEWLINE) RRETURN(MATCH_NOMATCH);
            break;

            case OP_ANYBYTE:
            break;

            case OP_NOT_DIGIT:
            if ((md->ctypes[c] & ctype_digit) != 0) RRETURN(MATCH_NOMATCH);
            break;

            case OP_DIGIT:
            if ((md->ctypes[c] & ctype_digit) == 0) RRETURN(MATCH_NOMATCH);
            break;

            case OP_NOT_WHITESPACE:
            if ((md->ctypes[c] & ctype_space) != 0) RRETURN(MATCH_NOMATCH);
            break;

            case OP_WHITESPACE:
            if  ((md->ctypes[c] & ctype_space) == 0) RRETURN(MATCH_NOMATCH);
            break;

            case OP_NOT_WORDCHAR:
            if ((md->ctypes[c] & ctype_word) != 0) RRETURN(MATCH_NOMATCH);
            break;

            case OP_WORDCHAR:
            if ((md->ctypes[c] & ctype_word) == 0) RRETURN(MATCH_NOMATCH);
            break;

            default:
            RRETURN(PCRE_ERROR_INTERNAL);
            }
          }
        }
      /* Control never gets here */
      }

    /* If maximizing it is worth using inline code for speed, doing the type
    test once at the start (i.e. keep it out of the loop). Again, keep the
    UTF-8 and UCP stuff separate. */

    else
      {
      pp = eptr;  /* Remember where we started */

      /* Not UTF-8 mode */
        {
        switch(ctype)
          {
          case OP_ANY:
          if ((ims & PCRE_DOTALL) == 0)
            {
            for (i = min; i < max; i++)
              {
              if (eptr >= md->end_subject || *eptr == NEWLINE) break;
              eptr++;
              }
            break;
            }
          /* For DOTALL case, fall through and treat as \C */

          case OP_ANYBYTE:
          c = max - min;
          if (c > md->end_subject - eptr) c = md->end_subject - eptr;
          eptr += c;
          break;

          case OP_NOT_DIGIT:
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || (md->ctypes[*eptr] & ctype_digit) != 0)
              break;
            eptr++;
            }
          break;

          case OP_DIGIT:
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || (md->ctypes[*eptr] & ctype_digit) == 0)
              break;
            eptr++;
            }
          break;

          case OP_NOT_WHITESPACE:
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || (md->ctypes[*eptr] & ctype_space) != 0)
              break;
            eptr++;
            }
          break;

          case OP_WHITESPACE:
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || (md->ctypes[*eptr] & ctype_space) == 0)
              break;
            eptr++;
            }
          break;

          case OP_NOT_WORDCHAR:
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || (md->ctypes[*eptr] & ctype_word) != 0)
              break;
            eptr++;
            }
          break;

          case OP_WORDCHAR:
          for (i = min; i < max; i++)
            {
            if (eptr >= md->end_subject || (md->ctypes[*eptr] & ctype_word) == 0)
              break;
            eptr++;
            }
          break;

          default:
          RRETURN(PCRE_ERROR_INTERNAL);
          }

        /* eptr is now past the end of the maximum run */

        while (eptr >= pp)
          {
          RMATCH(rrc, eptr, ecode, offset_top, md, ims, eptrb, 0);
          eptr--;
          if (rrc != MATCH_NOMATCH) RRETURN(rrc);
          }
        }

      /* Get here if we can't make it match with any permitted repetitions */

      RRETURN(MATCH_NOMATCH);
      }
    /* Control never gets here */

    /* There's been some horrible disaster. Since all codes > OP_BRA are
    for capturing brackets, and there shouldn't be any gaps between 0 and
    OP_BRA, arrival here can only mean there is something seriously wrong
    in the code above or the OP_xxx definitions. */

    default:
    DPRINTF(("Unknown opcode %d\n", *ecode));
    RRETURN(PCRE_ERROR_UNKNOWN_NODE);
    }

  /* Do not stick any code in here without much thought; it is assumed
  that "continue" in the code above comes out to here to repeat the main
  loop. */

  }             /* End of main loop */
/* Control never reaches here */
}


/***************************************************************************
****************************************************************************
                   RECURSION IN THE match() FUNCTION

Undefine all the macros that were defined above to handle this. */

#ifdef NO_RECURSE
#undef eptr
#undef ecode
#undef offset_top
#undef ims
#undef eptrb
#undef flags

#undef callpat
#undef charptr
#undef data
#undef next
#undef pp
#undef prev
#undef saved_eptr

#undef new_recursive

#undef cur_is_word
#undef condition
#undef minimize
#undef prev_is_word

#undef original_ims

#undef ctype
#undef length
#undef max
#undef min
#undef number
#undef offset
#undef op
#undef save_capture_last
#undef save_offset1
#undef save_offset2
#undef save_offset3
#undef stacksave

#undef newptrb

#endif

/* These two are defined as macros in both cases */

#undef fc
#undef fi

/***************************************************************************
***************************************************************************/


/*************************************************
*         Execute a Regular Expression           *
*************************************************/

/* This function applies a compiled re to a subject string and picks out
portions of the string if it matches. Two elements in the vector are set for
each substring: the offsets to the start and end of the substring.

Arguments:
  argument_re     points to the compiled expression
  extra_data      points to extra data or is NULL
  subject         points to the subject string
  length          length of subject string (may contain binary zeros)
  start_offset    where to start in the subject string
  options         option bits
  offsets         points to a vector of ints to be filled in with offsets
  offsetcount     the number of elements in the vector

Returns:          > 0 => success; value is the number of elements filled in
                  = 0 => success, but offsets is not big enough
                   -1 => failed to match
                 < -1 => some kind of unexpected problem
*/

EXPORT int
pcre_exec(const pcre *argument_re, const pcre_extra *extra_data,
  const char *subject, int length, int start_offset, int options, int *offsets,
  int offsetcount)
{
int rc, resetcount, ocount;
int first_byte = -1;
int req_byte = -1;
int req_byte2 = -1;
unsigned long int ims = 0;
BOOL using_temporary_offsets = FALSE;
BOOL anchored;
BOOL startline;
BOOL firstline;
BOOL first_byte_caseless = FALSE;
BOOL req_byte_caseless = FALSE;
match_data match_block;
const uschar *tables;
const uschar *start_bits = NULL;
const uschar *start_match = (const uschar *)subject + start_offset;
const uschar *end_subject;
const uschar *req_byte_ptr = start_match - 1;

pcre_study_data internal_study;
const pcre_study_data *study;

real_pcre internal_re;
const real_pcre *external_re = (const real_pcre *)argument_re;
const real_pcre *re = external_re;

/* Plausibility checks */

if ((options & ~PUBLIC_EXEC_OPTIONS) != 0) return PCRE_ERROR_BADOPTION;
if (re == NULL || subject == NULL ||
   (offsets == NULL && offsetcount > 0)) return PCRE_ERROR_NULL;
if (offsetcount < 0) return PCRE_ERROR_BADCOUNT;

/* Fish out the optional data from the extra_data structure, first setting
the default values. */

study = NULL;
match_block.match_limit = MATCH_LIMIT;
match_block.callout_data = NULL;

/* The table pointer is always in native byte order. */

tables = external_re->tables;

if (extra_data != NULL)
  {
  register unsigned int flags = extra_data->flags;
  if ((flags & PCRE_EXTRA_STUDY_DATA) != 0)
    study = (const pcre_study_data *)extra_data->study_data;
  if ((flags & PCRE_EXTRA_MATCH_LIMIT) != 0)
    match_block.match_limit = extra_data->match_limit;
  if ((flags & PCRE_EXTRA_CALLOUT_DATA) != 0)
    match_block.callout_data = extra_data->callout_data;
  if ((flags & PCRE_EXTRA_TABLES) != 0) tables = extra_data->tables;
  }

/* If the exec call supplied NULL for tables, use the inbuilt ones. This
is a feature that makes it possible to save compiled regex and re-use them
in other programs later. */

if (tables == NULL) tables = _pcre_default_tables;

/* Check that the first field in the block is the magic number. If it is not,
test for a regex that was compiled on a host of opposite endianness. If this is
the case, flipped values are put in internal_re and internal_study if there was
study data too. */

if (re->magic_number != MAGIC_NUMBER)
  {
  re = _pcre_try_flipped(re, &internal_re, study, &internal_study);
  if (re == NULL) return PCRE_ERROR_BADMAGIC;
  if (study != NULL) study = &internal_study;
  }

/* Set up other data */

anchored = ((re->options | options) & PCRE_ANCHORED) != 0;
startline = (re->options & PCRE_STARTLINE) != 0;
firstline = (re->options & PCRE_FIRSTLINE) != 0;

/* The code starts after the real_pcre block and the capture name table. */

match_block.start_code = (const uschar *)external_re + re->name_table_offset +
  re->name_count * re->name_entry_size;

match_block.start_subject = (const uschar *)subject;
match_block.start_offset = start_offset;
match_block.end_subject = match_block.start_subject + length;
end_subject = match_block.end_subject;

match_block.endonly = (re->options & PCRE_DOLLAR_ENDONLY) != 0;
match_block.utf8 = (re->options & PCRE_UTF8) != 0;

match_block.notbol = (options & PCRE_NOTBOL) != 0;
match_block.noteol = (options & PCRE_NOTEOL) != 0;
match_block.notempty = (options & PCRE_NOTEMPTY) != 0;
match_block.partial = (options & PCRE_PARTIAL) != 0;
match_block.hitend = FALSE;

match_block.recursive = NULL;                   /* No recursion at top level */

match_block.lcc = tables + lcc_offset;
match_block.ctypes = tables + ctypes_offset;

/* Partial matching is supported only for a restricted set of regexes at the
moment. */

if (match_block.partial && (re->options & PCRE_NOPARTIAL) != 0)
  return PCRE_ERROR_BADPARTIAL;

/* The ims options can vary during the matching as a result of the presence
of (?ims) items in the pattern. They are kept in a local variable so that
restoring at the exit of a group is easy. */

ims = re->options & (PCRE_CASELESS|PCRE_MULTILINE|PCRE_DOTALL);

/* If the expression has got more back references than the offsets supplied can
hold, we get a temporary chunk of working store to use during the matching.
Otherwise, we can use the vector supplied, rounding down its size to a multiple
of 3. */

ocount = offsetcount - (offsetcount % 3);

if (re->top_backref > 0 && re->top_backref >= ocount/3)
  {
  ocount = re->top_backref * 3 + 3;
  match_block.offset_vector = (int *)(pcre_malloc)(ocount * sizeof(int));
  if (match_block.offset_vector == NULL) return PCRE_ERROR_NOMEMORY;
  using_temporary_offsets = TRUE;
  DPRINTF(("Got memory to hold back references\n"));
  }
else match_block.offset_vector = offsets;

match_block.offset_end = ocount;
match_block.offset_max = (2*ocount)/3;
match_block.offset_overflow = FALSE;
match_block.capture_last = -1;

/* Compute the minimum number of offsets that we need to reset each time. Doing
this makes a huge difference to execution time when there aren't many brackets
in the pattern. */

resetcount = 2 + re->top_bracket * 2;
if (resetcount > offsetcount) resetcount = ocount;

/* Reset the working variable associated with each extraction. These should
never be used unless previously set, but they get saved and restored, and so we
initialize them to avoid reading uninitialized locations. */

if (match_block.offset_vector != NULL)
  {
  register int *iptr = match_block.offset_vector + ocount;
  register int *iend = iptr - resetcount/2 + 1;
  while (--iptr >= iend) *iptr = -1;
  }

/* Set up the first character to match, if available. The first_byte value is
never set for an anchored regular expression, but the anchoring may be forced
at run time, so we have to test for anchoring. The first char may be unset for
an unanchored pattern, of course. If there's no first char and the pattern was
studied, there may be a bitmap of possible first characters. */

if (!anchored)
  {
  if ((re->options & PCRE_FIRSTSET) != 0)
    {
    first_byte = re->first_byte & 255;
    if ((first_byte_caseless = ((re->first_byte & REQ_CASELESS) != 0)) == TRUE)
      first_byte = match_block.lcc[first_byte];
    }
  else
    if (!startline && study != NULL &&
      (study->options & PCRE_STUDY_MAPPED) != 0)
        start_bits = study->start_bits;
  }

/* For anchored or unanchored matches, there may be a "last known required
character" set. */

if ((re->options & PCRE_REQCHSET) != 0)
  {
  req_byte = re->req_byte & 255;
  req_byte_caseless = (re->req_byte & REQ_CASELESS) != 0;
  req_byte2 = (tables + fcc_offset)[req_byte];  /* case flipped */
  }

/* Loop for handling unanchored repeated matching attempts; for anchored regexs
the loop runs just once. */

do
  {
  const uschar *save_end_subject = end_subject;

  /* Reset the maximum number of extractions we might see. */

  if (match_block.offset_vector != NULL)
    {
    register int *iptr = match_block.offset_vector;
    register int *iend = iptr + resetcount;
    while (iptr < iend) *iptr++ = -1;
    }

  /* Advance to a unique first char if possible. If firstline is TRUE, the
  start of the match is constrained to the first line of a multiline string.
  Implement this by temporarily adjusting end_subject so that we stop scanning
  at a newline. If the match fails at the newline, later code breaks this loop.
  */

  if (firstline)
    {
    const uschar *t = start_match;
    while (t < save_end_subject && *t != '\n') t++;
    end_subject = t;
    }

  /* Now test for a unique first byte */

  if (first_byte >= 0)
    {
    if (first_byte_caseless)
      while (start_match < end_subject &&
             match_block.lcc[*start_match] != first_byte)
        start_match++;
    else
      while (start_match < end_subject && *start_match != first_byte)
        start_match++;
    }

  /* Or to just after \n for a multiline match if possible */

  else if (startline)
    {
    if (start_match > match_block.start_subject + start_offset)
      {
      while (start_match < end_subject && start_match[-1] != NEWLINE)
        start_match++;
      }
    }

  /* Or to a non-unique first char after study */

  else if (start_bits != NULL)
    {
    while (start_match < end_subject)
      {
      register unsigned int c = *start_match;
      if ((start_bits[c/8] & (1 << (c&7))) == 0) start_match++; else break;
      }
    }

  /* Restore fudged end_subject */

  end_subject = save_end_subject;

#ifdef DEBUG  /* Sigh. Some compilers never learn. */
  printf(">>>> Match against: ");
  pchars(start_match, end_subject - start_match, TRUE, &match_block);
  printf("\n");
#endif

  /* If req_byte is set, we know that that character must appear in the subject
  for the match to succeed. If the first character is set, req_byte must be
  later in the subject; otherwise the test starts at the match point. This
  optimization can save a huge amount of backtracking in patterns with nested
  unlimited repeats that aren't going to match. Writing separate code for
  cased/caseless versions makes it go faster, as does using an autoincrement
  and backing off on a match.

  HOWEVER: when the subject string is very, very long, searching to its end can
  take a long time, and give bad performance on quite ordinary patterns. This
  showed up when somebody was matching /^C/ on a 32-megabyte string... so we
  don't do this when the string is sufficiently long.

  ALSO: this processing is disabled when partial matching is requested.
  */

  if (req_byte >= 0 &&
      end_subject - start_match < REQ_BYTE_MAX &&
      !match_block.partial)
    {
    register const uschar *p = start_match + ((first_byte >= 0)? 1 : 0);

    /* We don't need to repeat the search if we haven't yet reached the
    place we found it at last time. */

    if (p > req_byte_ptr)
      {
      if (req_byte_caseless)
        {
        while (p < end_subject)
          {
          register int pp = *p++;
          if (pp == req_byte || pp == req_byte2) { p--; break; }
          }
        }
      else
        {
        while (p < end_subject)
          {
          if (*p++ == req_byte) { p--; break; }
          }
        }

      /* If we can't find the required character, break the matching loop */

      if (p >= end_subject) break;

      /* If we have found the required character, save the point where we
      found it, so that we don't search again next time round the loop if
      the start hasn't passed this character yet. */

      req_byte_ptr = p;
      }
    }

  /* When a match occurs, substrings will be set for all internal extractions;
  we just need to set up the whole thing as substring 0 before returning. If
  there were too many extractions, set the return code to zero. In the case
  where we had to get some local store to hold offsets for backreferences, copy
  those back references that we can. In this case there need not be overflow
  if certain parts of the pattern were not used. */

  match_block.start_match = start_match;
  match_block.match_call_count = 0;

  rc = match(start_match, match_block.start_code, 2, &match_block, ims, NULL,
    match_isgroup);

  /* When the result is no match, if the subject's first character was a
  newline and the PCRE_FIRSTLINE option is set, break (which will return
  PCRE_ERROR_NOMATCH). The option requests that a match occur before the first
  newline in the subject. Otherwise, advance the pointer to the next character
  and continue - but the continuation will actually happen only when the
  pattern is not anchored. */

  if (rc == MATCH_NOMATCH)
    {
    if (firstline && *start_match == NEWLINE) break;
    start_match++;
    continue;
    }

  if (rc != MATCH_MATCH)
    {
    DPRINTF((">>>> error: returning %d\n", rc));
    return rc;
    }

  /* We have a match! Copy the offset information from temporary store if
  necessary */

  if (using_temporary_offsets)
    {
    if (offsetcount >= 4)
      {
      memcpy(offsets + 2, match_block.offset_vector + 2,
        (offsetcount - 2) * sizeof(int));
      DPRINTF(("Copied offsets from temporary memory\n"));
      }
    if (match_block.end_offset_top > offsetcount)
      match_block.offset_overflow = TRUE;

    DPRINTF(("Freeing temporary memory\n"));
    (pcre_free)(match_block.offset_vector);
    }

  rc = match_block.offset_overflow? 0 : match_block.end_offset_top/2;

  if (offsetcount < 2) rc = 0; else
    {
    offsets[0] = start_match - match_block.start_subject;
    offsets[1] = match_block.end_match_ptr - match_block.start_subject;
    }

  DPRINTF((">>>> returning %d\n", rc));
  return rc;
  }

/* This "while" is the end of the "do" above */

while (!anchored && start_match <= end_subject);

if (using_temporary_offsets)
  {
  DPRINTF(("Freeing temporary memory\n"));
  (pcre_free)(match_block.offset_vector);
  }

if (match_block.partial && match_block.hitend)
  {
  DPRINTF((">>>> returning PCRE_ERROR_PARTIAL\n"));
  return PCRE_ERROR_PARTIAL;
  }
else
  {
  DPRINTF((">>>> returning PCRE_ERROR_NOMATCH\n"));
  return PCRE_ERROR_NOMATCH;
  }
}

/* End of pcre_exec.c */
Revision:	59
Committed:	Mon Oct 3 15:11:57 2005 UTC (20 years, 10 months ago) by adx
Content type:	text/x-csrc
File size:	80471 byte(s)
Log Message:	- move non-irc related sources to /libio - todo: make it independent of the rest of code