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

*      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) 1997-2008 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 the external function pcre_study(), along with local

supporting functions. */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "pcre_internal.h"

/* Returns from set_start_bits() */

enum { SSB_FAIL, SSB_DONE, SSB_CONTINUE };

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

*      Set a bit and maybe its alternate case    *

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

/* Given a character, set its bit in the table, and also the bit for the other

version of a letter if we are caseless.

Arguments:

  start_bits    points to the bit map

  c             is the character

  caseless      the caseless flag

  cd            the block with char table pointers

Returns:        nothing

*/

static void

set_bit(uschar *start_bits, unsigned int c, BOOL caseless, compile_data *cd)

{

start_bits[c/8] |= (1 << (c&7));

if (caseless && (cd->ctypes[c] & ctype_letter) != 0)

  start_bits[cd->fcc[c]/8] |= (1 << (cd->fcc[c]&7));

}

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

*          Create bitmap of starting bytes       *

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

/* This function scans a compiled unanchored expression recursively and

attempts to build a bitmap of the set of possible starting bytes. As time goes

by, we may be able to get more clever at doing this. The SSB_CONTINUE return is

useful for parenthesized groups in patterns such as (a*)b where the group

provides some optional starting bytes but scanning must continue at the outer

level to find at least one mandatory byte. At the outermost level, this

function fails unless the result is SSB_DONE.

Arguments:

  code         points to an expression

  start_bits   points to a 32-byte table, initialized to 0

  caseless     the current state of the caseless flag

  utf8         TRUE if in UTF-8 mode

  cd           the block with char table pointers

Returns:       SSB_FAIL     => Failed to find any starting bytes

               SSB_DONE     => Found mandatory starting bytes

               SSB_CONTINUE => Found optional starting bytes

*/

static int

set_start_bits(const uschar *code, uschar *start_bits, BOOL caseless,

  BOOL utf8, compile_data *cd)

{

register int c;

int yield = SSB_DONE;

#if 0

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

/* The following comment and code was inserted in January 1999. In May 2006,

when it was observed to cause compiler warnings about unused values, I took it

out again. If anybody is still using OS/2, they will have to put it back

manually. */

/* This next statement and the later reference to dummy are here in order to

trick the optimizer of the IBM C compiler for OS/2 into generating correct

code. Apparently IBM isn't going to fix the problem, and we would rather not

disable optimization (in this module it actually makes a big difference, and

the pcre module can use all the optimization it can get). */

volatile int dummy;

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

#endif

do

  {

  const uschar *tcode = code + (((int)*code == OP_CBRA)? 3:1) + LINK_SIZE;

  BOOL try_next = TRUE;

  while (try_next)    /* Loop for items in this branch */

    {

    int rc;

    switch(*tcode)

      {

      /* Fail if we reach something we don't understand */

      default:

      return SSB_FAIL;

      /* If we hit a bracket or a positive lookahead assertion, recurse to set

      bits from within the subpattern. If it can't find anything, we have to

      give up. If it finds some mandatory character(s), we are done for this

      branch. Otherwise, carry on scanning after the subpattern. */

      case OP_BRA:

      case OP_SBRA:

      case OP_CBRA:

      case OP_SCBRA:

      case OP_ONCE:

      case OP_ASSERT:

      rc = set_start_bits(tcode, start_bits, caseless, utf8, cd);

      if (rc == SSB_FAIL) return SSB_FAIL;

      if (rc == SSB_DONE) try_next = FALSE; else

        {

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

        tcode += 1 + LINK_SIZE;

        }

      break;

      /* If we hit ALT or KET, it means we haven't found anything mandatory in

      this branch, though we might have found something optional. For ALT, we

      continue with the next alternative, but we have to arrange that the final

      result from subpattern is SSB_CONTINUE rather than SSB_DONE. For KET,

      return SSB_CONTINUE: if this is the top level, that indicates failure,

      but after a nested subpattern, it causes scanning to continue. */

      case OP_ALT:

      yield = SSB_CONTINUE;

      try_next = FALSE;

      break;

      case OP_KET:

      case OP_KETRMAX:

      case OP_KETRMIN:

      return SSB_CONTINUE;

      /* Skip over callout */

      case OP_CALLOUT:

      tcode += 2 + 2*LINK_SIZE;

      break;

      /* Skip over lookbehind and negative lookahead assertions */

      case OP_ASSERT_NOT:

      case OP_ASSERTBACK:

      case OP_ASSERTBACK_NOT:

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

      tcode += 1 + LINK_SIZE;

      break;

      /* Skip over an option setting, changing the caseless flag */

      case OP_OPT:

      caseless = (tcode[1] & PCRE_CASELESS) != 0;

      tcode += 2;

      break;

      /* BRAZERO does the bracket, but carries on. */

      case OP_BRAZERO:

      case OP_BRAMINZERO:

      if (set_start_bits(++tcode, start_bits, caseless, utf8, cd) == SSB_FAIL)

        return SSB_FAIL;

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

      See the comment at the head of this function concerning the next line,

      which was an old fudge for the benefit of OS/2.

      dummy = 1;

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

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

      tcode += 1 + LINK_SIZE;

      break;

      /* SKIPZERO skips the bracket. */

      case OP_SKIPZERO:

      tcode++;

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

      tcode += 1 + LINK_SIZE;

      break;

      /* Single-char * or ? sets the bit and tries the next item */

      case OP_STAR:

      case OP_MINSTAR:

      case OP_POSSTAR:

      case OP_QUERY:

      case OP_MINQUERY:

      case OP_POSQUERY:

      set_bit(start_bits, tcode[1], caseless, cd);

      tcode += 2;

#ifdef SUPPORT_UTF8

      if (utf8 && tcode[-1] >= 0xc0)

        tcode += _pcre_utf8_table4[tcode[-1] & 0x3f];

#endif

      break;

      /* Single-char upto sets the bit and tries the next */

      case OP_UPTO:

      case OP_MINUPTO:

      case OP_POSUPTO:

      set_bit(start_bits, tcode[3], caseless, cd);

      tcode += 4;

#ifdef SUPPORT_UTF8

      if (utf8 && tcode[-1] >= 0xc0)

        tcode += _pcre_utf8_table4[tcode[-1] & 0x3f];

#endif

      break;

      /* At least one single char sets the bit and stops */

      case OP_EXACT:       /* Fall through */

      tcode += 2;

      case OP_CHAR:

      case OP_CHARNC:

      case OP_PLUS:

      case OP_MINPLUS:

      case OP_POSPLUS:

      set_bit(start_bits, tcode[1], caseless, cd);

      try_next = FALSE;

      break;

      /* Single character type sets the bits and stops */

      case OP_NOT_DIGIT:

      for (c = 0; c < 32; c++)

        start_bits[c] |= ~cd->cbits[c+cbit_digit];

      try_next = FALSE;

      break;

      case OP_DIGIT:

      for (c = 0; c < 32; c++)

        start_bits[c] |= cd->cbits[c+cbit_digit];

      try_next = FALSE;

      break;

      /* The cbit_space table has vertical tab as whitespace; we have to

      discard it. */

      case OP_NOT_WHITESPACE:

      for (c = 0; c < 32; c++)

        {

        int d = cd->cbits[c+cbit_space];

        if (c == 1) d &= ~0x08;

        start_bits[c] |= ~d;

        }

      try_next = FALSE;

      break;

      /* The cbit_space table has vertical tab as whitespace; we have to

      discard it. */

      case OP_WHITESPACE:

      for (c = 0; c < 32; c++)

        {

        int d = cd->cbits[c+cbit_space];

        if (c == 1) d &= ~0x08;

        start_bits[c] |= d;

        }

      try_next = FALSE;

      break;

      case OP_NOT_WORDCHAR:

      for (c = 0; c < 32; c++)

        start_bits[c] |= ~cd->cbits[c+cbit_word];

      try_next = FALSE;

      break;

      case OP_WORDCHAR:

      for (c = 0; c < 32; c++)

        start_bits[c] |= cd->cbits[c+cbit_word];

      try_next = FALSE;

      break;

      /* One or more character type fudges the pointer and restarts, knowing

      it will hit a single character type and stop there. */

      case OP_TYPEPLUS:

      case OP_TYPEMINPLUS:

      tcode++;

      break;

      case OP_TYPEEXACT:

      tcode += 3;

      break;

      /* Zero or more repeats of character types set the bits and then

      try again. */

      case OP_TYPEUPTO:

      case OP_TYPEMINUPTO:

      case OP_TYPEPOSUPTO:

      tcode += 2;               /* Fall through */

      case OP_TYPESTAR:

      case OP_TYPEMINSTAR:

      case OP_TYPEPOSSTAR:

      case OP_TYPEQUERY:

      case OP_TYPEMINQUERY:

      case OP_TYPEPOSQUERY:

      switch(tcode[1])

        {

        case OP_ANY:

        case OP_ALLANY:

        return SSB_FAIL;

        case OP_NOT_DIGIT:

        for (c = 0; c < 32; c++)

          start_bits[c] |= ~cd->cbits[c+cbit_digit];

        break;

        case OP_DIGIT:

        for (c = 0; c < 32; c++)

          start_bits[c] |= cd->cbits[c+cbit_digit];

        break;

        /* The cbit_space table has vertical tab as whitespace; we have to

        discard it. */

        case OP_NOT_WHITESPACE:

        for (c = 0; c < 32; c++)

          {

          int d = cd->cbits[c+cbit_space];

          if (c == 1) d &= ~0x08;

          start_bits[c] |= ~d;

          }

        break;

        /* The cbit_space table has vertical tab as whitespace; we have to

        discard it. */

        case OP_WHITESPACE:

        for (c = 0; c < 32; c++)

          {

          int d = cd->cbits[c+cbit_space];

          if (c == 1) d &= ~0x08;

          start_bits[c] |= d;

          }

        break;

        case OP_NOT_WORDCHAR:

        for (c = 0; c < 32; c++)

          start_bits[c] |= ~cd->cbits[c+cbit_word];

        break;

        case OP_WORDCHAR:

        for (c = 0; c < 32; c++)

          start_bits[c] |= cd->cbits[c+cbit_word];

        break;

        }

      tcode += 2;

      break;

      /* Character class where all the information is in a bit map: set the

      bits and either carry on or not, according to the repeat count. If it was

      a negative class, and we are operating with UTF-8 characters, any byte

      with a value >= 0xc4 is a potentially valid starter because it starts a

      character with a value > 255. */

      case OP_NCLASS:

#ifdef SUPPORT_UTF8

      if (utf8)

        {

        start_bits[24] |= 0xf0;              /* Bits for 0xc4 - 0xc8 */

        memset(start_bits+25, 0xff, 7);      /* Bits for 0xc9 - 0xff */

        }

#endif

      /* Fall through */

      case OP_CLASS:

        {

        tcode++;

        /* In UTF-8 mode, the bits in a bit map correspond to character

        values, not to byte values. However, the bit map we are constructing is

        for byte values. So we have to do a conversion for characters whose

        value is > 127. In fact, there are only two possible starting bytes for

        characters in the range 128 - 255. */

#ifdef SUPPORT_UTF8

        if (utf8)

          {

          for (c = 0; c < 16; c++) start_bits[c] |= tcode[c];

          for (c = 128; c < 256; c++)

            {

            if ((tcode[c/8] && (1 << (c&7))) != 0)

              {

              int d = (c >> 6) | 0xc0;            /* Set bit for this starter */

              start_bits[d/8] |= (1 << (d&7));    /* and then skip on to the */

              c = (c & 0xc0) + 0x40 - 1;          /* next relevant character. */

              }

            }

          }

        /* In non-UTF-8 mode, the two bit maps are completely compatible. */

        else

#endif

          {

          for (c = 0; c < 32; c++) start_bits[c] |= tcode[c];

          }

        /* Advance past the bit map, and act on what follows */

        tcode += 32;

        switch (*tcode)

          {

          case OP_CRSTAR:

          case OP_CRMINSTAR:

          case OP_CRQUERY:

          case OP_CRMINQUERY:

          tcode++;

          break;

          case OP_CRRANGE:

          case OP_CRMINRANGE:

          if (((tcode[1] << 8) + tcode[2]) == 0) tcode += 5;

            else try_next = FALSE;

          break;

          default:

          try_next = FALSE;

          break;

          }

        }

      break; /* End of bitmap class handling */

      }      /* End of switch */

    }        /* End of try_next loop */

  code += GET(code, 1);   /* Advance to next branch */

  }

while (*code == OP_ALT);

return yield;

}

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

*          Study a compiled expression           *

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

/* This function is handed a compiled expression that it must study to produce

information that will speed up the matching. It returns a pcre_extra block

which then gets handed back to pcre_exec().

Arguments:

  re        points to the compiled expression

  options   contains option bits

  errorptr  points to where to place error messages;

            set NULL unless error

Returns:    pointer to a pcre_extra block, with study_data filled in and the

              appropriate flag set;

            NULL on error or if no optimization possible

*/

PCRE_EXP_DEFN pcre_extra * PCRE_CALL_CONVENTION

pcre_study(const pcre *external_re, int options, const char **errorptr)

{

uschar start_bits[32];

pcre_extra *extra;

pcre_study_data *study;

const uschar *tables;

uschar *code;

compile_data compile_block;

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

*errorptr = NULL;

if (re == NULL || re->magic_number != MAGIC_NUMBER)

  {

  *errorptr = "argument is not a compiled regular expression";

  return NULL;

  }

if ((options & ~PUBLIC_STUDY_OPTIONS) != 0)

  {

  *errorptr = "unknown or incorrect option bit(s) set";