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

*      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 the external function pcre_study(), along with local

supporting functions. */

#include "pcre_internal.h"

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

*      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 chars       *

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

/* This function scans a compiled unanchored expression and attempts to build a

bitmap of the set of initial characters. If it can't, it returns FALSE. As time

goes by, we may be able to get more clever at doing this.

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:       TRUE if table built, FALSE otherwise

*/

static BOOL

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

  BOOL utf8, compile_data *cd)

{

register int c;

/* 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;

do

  {

  const uschar *tcode = code + 1 + LINK_SIZE;

  BOOL try_next = TRUE;

  while (try_next)

    {

    /* If a branch starts with a bracket or a positive lookahead assertion,

    recurse to set bits from within them. That's all for this branch. */

    if ((int)*tcode >= OP_BRA || *tcode == OP_ASSERT)

      {

      if (!set_start_bits(tcode, start_bits, caseless, utf8, cd))

        return FALSE;

      try_next = FALSE;

      }

    else switch(*tcode)

      {

      default:

      return FALSE;

      /* Skip over callout */

      case OP_CALLOUT:

      tcode += 2 + 2*LINK_SIZE;

      break;

      /* Skip over extended extraction bracket number */

      case OP_BRANUMBER:

      tcode += 3;

      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))

        return FALSE;

      dummy = 1;

      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_QUERY:

      case OP_MINQUERY:

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

      tcode += 2;

#ifdef SUPPORT_UTF8

      if (utf8) while ((*tcode & 0xc0) == 0x80) tcode++;

#endif

      break;

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

      case OP_UPTO:

      case OP_MINUPTO:

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

      tcode += 4;

#ifdef SUPPORT_UTF8

      if (utf8) while ((*tcode & 0xc0) == 0x80) tcode++;

#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:

      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;

      case OP_NOT_WHITESPACE:

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

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

      try_next = FALSE;

      break;

      case OP_WHITESPACE:

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

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

      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:

      tcode += 2;               /* Fall through */

      case OP_TYPESTAR:

      case OP_TYPEMINSTAR:

      case OP_TYPEQUERY:

      case OP_TYPEMINQUERY:

      switch(tcode[1])

        {

        case OP_ANY:

        return FALSE;

        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;

        case OP_NOT_WHITESPACE:

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

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

        break;

        case OP_WHITESPACE:

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

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

        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:

      if (utf8)

        {

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

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

        }

      /* 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. */

        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

          {

          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 TRUE;

}

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

*          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_EXPORT pcre_extra *

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;

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

uschar *code;

compile_data compile_block;

*errorptr = NULL;

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

  {

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

  return NULL;

  }

code = (uschar *)re + re->name_table_offset +

  (re->name_count * re->name_entry_size);

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

  {

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

  return NULL;

  }

/* For an anchored pattern, or an unanchored pattern that has a first char, or

a multiline pattern that matches only at "line starts", no further processing

at present. */

if ((re->options & (PCRE_ANCHORED|PCRE_FIRSTSET|PCRE_STARTLINE)) != 0)

  return NULL;

/* Set the character tables in the block that is passed around */

tables = re->tables;

if (tables == NULL)

  (void)pcre_fullinfo(external_re, NULL, PCRE_INFO_DEFAULT_TABLES,

  (void *)(&tables));

compile_block.lcc = tables + lcc_offset;

compile_block.fcc = tables + fcc_offset;

compile_block.cbits = tables + cbits_offset;

compile_block.ctypes = tables + ctypes_offset;

/* See if we can find a fixed set of initial characters for the pattern. */

memset(start_bits, 0, 32 * sizeof(uschar));

if (!set_start_bits(code, start_bits, (re->options & PCRE_CASELESS) != 0,

  (re->options & PCRE_UTF8) != 0, &compile_block)) return NULL;

/* Get a pcre_extra block and a pcre_study_data block. The study data is put in

the latter, which is pointed to by the former, which may also get additional

data set later by the calling program. At the moment, the size of

pcre_study_data is fixed. We nevertheless save it in a field for returning via

the pcre_fullinfo() function so that if it becomes variable in the future, we

don't have to change that code. */

extra = (pcre_extra *)(pcre_malloc)

  (sizeof(pcre_extra) + sizeof(pcre_study_data));

if (extra == NULL)

  {

  *errorptr = "failed to get memory";

  return NULL;

  }

study = (pcre_study_data *)((char *)extra + sizeof(pcre_extra));

extra->flags = PCRE_EXTRA_STUDY_DATA;

extra->study_data = study;

study->size = sizeof(pcre_study_data);

study->options = PCRE_STUDY_MAPPED;

memcpy(study->start_bits, start_bits, sizeof(start_bits));

return extra;

}

/* End of pcre_study.c */