tags/pcre-4.3/study.c

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

/*
This 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. See
the file Tech.Notes for some information on the internals.

Written by: Philip Hazel <ph10@cam.ac.uk>

           Copyright (c) 1997-2002 University of Cambridge

-----------------------------------------------------------------------------
Permission is granted to anyone to use this software for any purpose on any
computer system, and to redistribute it freely, subject to the following
restrictions:

1. This software is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

2. The origin of this software must not be misrepresented, either by
   explicit claim or by omission.

3. Altered versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

4. If PCRE is embedded in any software that is released under the GNU
   General Purpose Licence (GPL), then the terms of that licence shall
   supersede any condition above with which it is incompatible.
-----------------------------------------------------------------------------
*/


/* Include the internals header, which itself includes Standard C headers plus
the external pcre header. */

#include "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, 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;
      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++;

      case OP_CHARS:       /* Fall through */
      tcode++;

      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_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 the top-bit set is a potentially valid starter because it may start
      a character with a value > 255. (This is sub-optimal in that the
      character may be in the range 128-255, and those characters might be
      unwanted, but that's as far as we go for the moment.) */

      case OP_NCLASS:
      if (utf8) memset(start_bits+16, 0xff, 16);
      /* Fall through */

      case OP_CLASS:
        {
        tcode++;
        for (c = 0; c < 32; c++) start_bits[c] |= tcode[c];
        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_extra *
pcre_study(const pcre *external_re, int options, const char **errorptr)
{
uschar start_bits[32];
pcre_extra *extra;
pcre_study_data *study;
const real_pcre *re = (const real_pcre *)external_re;
uschar *code = (uschar *)re + sizeof(real_pcre) +
  (re->name_count * re->name_entry_size);
compile_data compile_block;

*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";
  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 which is passed around */

compile_block.lcc = re->tables + lcc_offset;
compile_block.fcc = re->tables + fcc_offset;
compile_block.cbits = re->tables + cbits_offset;
compile_block.ctypes = re->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 study.c */
1	/*************************************************
2	* Perl-Compatible Regular Expressions *
3	*************************************************/
4
5	/*
6	This is a library of functions to support regular expressions whose syntax
7	and semantics are as close as possible to those of the Perl 5 language. See
8	the file Tech.Notes for some information on the internals.
9
10	Written by: Philip Hazel <ph10@cam.ac.uk>
11
12	Copyright (c) 1997-2002 University of Cambridge
13
14	-----------------------------------------------------------------------------
15	Permission is granted to anyone to use this software for any purpose on any
16	computer system, and to redistribute it freely, subject to the following
17	restrictions:
18
19	1. This software is distributed in the hope that it will be useful,
20	but WITHOUT ANY WARRANTY; without even the implied warranty of
21	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
22
23	2. The origin of this software must not be misrepresented, either by
24	explicit claim or by omission.
25
26	3. Altered versions must be plainly marked as such, and must not be
27	misrepresented as being the original software.
28
29	4. If PCRE is embedded in any software that is released under the GNU
30	General Purpose Licence (GPL), then the terms of that licence shall
31	supersede any condition above with which it is incompatible.
32	-----------------------------------------------------------------------------
33	*/
34
35
36	/* Include the internals header, which itself includes Standard C headers plus
37	the external pcre header. */
38
39	#include "internal.h"
40
41
42
43	/*************************************************
44	* Set a bit and maybe its alternate case *
45	*************************************************/
46
47	/* Given a character, set its bit in the table, and also the bit for the other
48	version of a letter if we are caseless.
49
50	Arguments:
51	start_bits points to the bit map
52	c is the character
53	caseless the caseless flag
54	cd the block with char table pointers
55
56	Returns: nothing
57	*/
58
59	static void
60	set_bit(uschar start_bits, int c, BOOL caseless, compile_data cd)
61	{
62	start_bits[c/8] \|= (1 << (c&7));
63	if (caseless && (cd->ctypes[c] & ctype_letter) != 0)
64	start_bits[cd->fcc[c]/8] \|= (1 << (cd->fcc[c]&7));
65	}
66
67
68
69	/*************************************************
70	* Create bitmap of starting chars *
71	*************************************************/
72
73	/* This function scans a compiled unanchored expression and attempts to build a
74	bitmap of the set of initial characters. If it can't, it returns FALSE. As time
75	goes by, we may be able to get more clever at doing this.
76
77	Arguments:
78	code points to an expression
79	start_bits points to a 32-byte table, initialized to 0
80	caseless the current state of the caseless flag
81	utf8 TRUE if in UTF-8 mode
82	cd the block with char table pointers
83
84	Returns: TRUE if table built, FALSE otherwise
85	*/
86
87	static BOOL
88	set_start_bits(const uschar code, uschar start_bits, BOOL caseless,
89	BOOL utf8, compile_data *cd)
90	{
91	register int c;
92
93	/* This next statement and the later reference to dummy are here in order to
94	trick the optimizer of the IBM C compiler for OS/2 into generating correct
95	code. Apparently IBM isn't going to fix the problem, and we would rather not
96	disable optimization (in this module it actually makes a big difference, and
97	the pcre module can use all the optimization it can get). */
98
99	volatile int dummy;
100
101	do
102	{
103	const uschar *tcode = code + 1 + LINK_SIZE;
104	BOOL try_next = TRUE;
105
106	while (try_next)
107	{
108	/* If a branch starts with a bracket or a positive lookahead assertion,
109	recurse to set bits from within them. That's all for this branch. */
110
111	if ((int)tcode >= OP_BRA \|\| tcode == OP_ASSERT)
112	{
113	if (!set_start_bits(tcode, start_bits, caseless, utf8, cd))
114	return FALSE;
115	try_next = FALSE;
116	}
117
118	else switch(*tcode)
119	{
120	default:
121	return FALSE;
122
123	/* Skip over callout */
124
125	case OP_CALLOUT:
126	tcode += 2;
127	break;
128
129	/* Skip over extended extraction bracket number */
130
131	case OP_BRANUMBER:
132	tcode += 3;
133	break;
134
135	/* Skip over lookbehind and negative lookahead assertions */
136
137	case OP_ASSERT_NOT:
138	case OP_ASSERTBACK:
139	case OP_ASSERTBACK_NOT:
140	do tcode += GET(tcode, 1); while (*tcode == OP_ALT);
141	tcode += 1+LINK_SIZE;
142	break;
143
144	/* Skip over an option setting, changing the caseless flag */
145
146	case OP_OPT:
147	caseless = (tcode[1] & PCRE_CASELESS) != 0;
148	tcode += 2;
149	break;
150
151	/* BRAZERO does the bracket, but carries on. */
152
153	case OP_BRAZERO:
154	case OP_BRAMINZERO:
155	if (!set_start_bits(++tcode, start_bits, caseless, utf8, cd))
156	return FALSE;
157	dummy = 1;
158	do tcode += GET(tcode,1); while (*tcode == OP_ALT);
159	tcode += 1+LINK_SIZE;
160	break;
161
162	/* Single-char * or ? sets the bit and tries the next item */
163
164	case OP_STAR:
165	case OP_MINSTAR:
166	case OP_QUERY:
167	case OP_MINQUERY:
168	set_bit(start_bits, tcode[1], caseless, cd);
169	tcode += 2;
170	#ifdef SUPPORT_UTF8
171	if (utf8) while ((*tcode & 0xc0) == 0x80) tcode++;
172	#endif
173	break;
174
175	/* Single-char upto sets the bit and tries the next */
176
177	case OP_UPTO:
178	case OP_MINUPTO:
179	set_bit(start_bits, tcode[3], caseless, cd);
180	tcode += 4;
181	#ifdef SUPPORT_UTF8
182	if (utf8) while ((*tcode & 0xc0) == 0x80) tcode++;
183	#endif
184	break;
185
186	/* At least one single char sets the bit and stops */
187
188	case OP_EXACT: /* Fall through */
189	tcode++;
190
191	case OP_CHARS: /* Fall through */
192	tcode++;
193
194	case OP_PLUS:
195	case OP_MINPLUS:
196	set_bit(start_bits, tcode[1], caseless, cd);
197	try_next = FALSE;
198	break;
199
200	/* Single character type sets the bits and stops */
201
202	case OP_NOT_DIGIT:
203	for (c = 0; c < 32; c++)
204	start_bits[c] \|= ~cd->cbits[c+cbit_digit];
205	try_next = FALSE;
206	break;
207
208	case OP_DIGIT:
209	for (c = 0; c < 32; c++)
210	start_bits[c] \|= cd->cbits[c+cbit_digit];
211	try_next = FALSE;
212	break;
213
214	case OP_NOT_WHITESPACE:
215	for (c = 0; c < 32; c++)
216	start_bits[c] \|= ~cd->cbits[c+cbit_space];
217	try_next = FALSE;
218	break;
219
220	case OP_WHITESPACE:
221	for (c = 0; c < 32; c++)
222	start_bits[c] \|= cd->cbits[c+cbit_space];
223	try_next = FALSE;
224	break;
225
226	case OP_NOT_WORDCHAR:
227	for (c = 0; c < 32; c++)
228	start_bits[c] \|= ~cd->cbits[c+cbit_word];
229	try_next = FALSE;
230	break;
231
232	case OP_WORDCHAR:
233	for (c = 0; c < 32; c++)
234	start_bits[c] \|= cd->cbits[c+cbit_word];
235	try_next = FALSE;
236	break;
237
238	/* One or more character type fudges the pointer and restarts, knowing
239	it will hit a single character type and stop there. */
240
241	case OP_TYPEPLUS:
242	case OP_TYPEMINPLUS:
243	tcode++;
244	break;
245
246	case OP_TYPEEXACT:
247	tcode += 3;
248	break;
249
250	/* Zero or more repeats of character types set the bits and then
251	try again. */
252
253	case OP_TYPEUPTO:
254	case OP_TYPEMINUPTO:
255	tcode += 2; /* Fall through */
256
257	case OP_TYPESTAR:
258	case OP_TYPEMINSTAR:
259	case OP_TYPEQUERY:
260	case OP_TYPEMINQUERY:
261	switch(tcode[1])
262	{
263	case OP_NOT_DIGIT:
264	for (c = 0; c < 32; c++)
265	start_bits[c] \|= ~cd->cbits[c+cbit_digit];
266	break;
267
268	case OP_DIGIT:
269	for (c = 0; c < 32; c++)
270	start_bits[c] \|= cd->cbits[c+cbit_digit];
271	break;
272
273	case OP_NOT_WHITESPACE:
274	for (c = 0; c < 32; c++)
275	start_bits[c] \|= ~cd->cbits[c+cbit_space];
276	break;
277
278	case OP_WHITESPACE:
279	for (c = 0; c < 32; c++)
280	start_bits[c] \|= cd->cbits[c+cbit_space];
281	break;
282
283	case OP_NOT_WORDCHAR:
284	for (c = 0; c < 32; c++)
285	start_bits[c] \|= ~cd->cbits[c+cbit_word];
286	break;
287
288	case OP_WORDCHAR:
289	for (c = 0; c < 32; c++)
290	start_bits[c] \|= cd->cbits[c+cbit_word];
291	break;
292	}
293
294	tcode += 2;
295	break;
296
297	/* Character class where all the information is in a bit map: set the
298	bits and either carry on or not, according to the repeat count. If it was
299	a negative class, and we are operating with UTF-8 characters, any byte
300	with the top-bit set is a potentially valid starter because it may start
301	a character with a value > 255. (This is sub-optimal in that the
302	character may be in the range 128-255, and those characters might be
303	unwanted, but that's as far as we go for the moment.) */
304
305	case OP_NCLASS:
306	if (utf8) memset(start_bits+16, 0xff, 16);
307	/* Fall through */
308
309	case OP_CLASS:
310	{
311	tcode++;
312	for (c = 0; c < 32; c++) start_bits[c] \|= tcode[c];
313	tcode += 32;
314	switch (*tcode)
315	{
316	case OP_CRSTAR:
317	case OP_CRMINSTAR:
318	case OP_CRQUERY:
319	case OP_CRMINQUERY:
320	tcode++;
321	break;
322
323	case OP_CRRANGE:
324	case OP_CRMINRANGE:
325	if (((tcode[1] << 8) + tcode[2]) == 0) tcode += 5;
326	else try_next = FALSE;
327	break;
328
329	default:
330	try_next = FALSE;
331	break;
332	}
333	}
334	break; /* End of bitmap class handling */
335
336	} /* End of switch */
337	} /* End of try_next loop */
338
339	code += GET(code, 1); /* Advance to next branch */
340	}
341	while (*code == OP_ALT);
342	return TRUE;
343	}
344
345
346
347	/*************************************************
348	* Study a compiled expression *
349	*************************************************/
350
351	/* This function is handed a compiled expression that it must study to produce
352	information that will speed up the matching. It returns a pcre_extra block
353	which then gets handed back to pcre_exec().
354
355	Arguments:
356	re points to the compiled expression
357	options contains option bits
358	errorptr points to where to place error messages;
359	set NULL unless error
360
361	Returns: pointer to a pcre_extra block, with study_data filled in and the
362	appropriate flag set;
363	NULL on error or if no optimization possible
364	*/
365
366	pcre_extra *
367	pcre_study(const pcre external_re, int options, const char *errorptr)
368	{
369	uschar start_bits[32];
370	pcre_extra *extra;
371	pcre_study_data *study;
372	const real_pcre re = (const real_pcre )external_re;
373	uschar code = (uschar )re + sizeof(real_pcre) +
374	(re->name_count * re->name_entry_size);
375	compile_data compile_block;
376
377	*errorptr = NULL;
378
379	if (re == NULL \|\| re->magic_number != MAGIC_NUMBER)
380	{
381	*errorptr = "argument is not a compiled regular expression";
382	return NULL;
383	}
384
385	if ((options & ~PUBLIC_STUDY_OPTIONS) != 0)
386	{
387	*errorptr = "unknown or incorrect option bit(s) set";
388	return NULL;
389	}
390
391	/* For an anchored pattern, or an unanchored pattern that has a first char, or
392	a multiline pattern that matches only at "line starts", no further processing
393	at present. */
394
395	if ((re->options & (PCRE_ANCHORED\|PCRE_FIRSTSET\|PCRE_STARTLINE)) != 0)
396	return NULL;
397
398	/* Set the character tables in the block which is passed around */
399
400	compile_block.lcc = re->tables + lcc_offset;
401	compile_block.fcc = re->tables + fcc_offset;
402	compile_block.cbits = re->tables + cbits_offset;
403	compile_block.ctypes = re->tables + ctypes_offset;
404
405	/* See if we can find a fixed set of initial characters for the pattern. */
406
407	memset(start_bits, 0, 32 * sizeof(uschar));
408	if (!set_start_bits(code, start_bits, (re->options & PCRE_CASELESS) != 0,
409	(re->options & PCRE_UTF8) != 0, &compile_block)) return NULL;
410
411	/* Get a pcre_extra block and a pcre_study_data block. The study data is put in
412	the latter, which is pointed to by the former, which may also get additional
413	data set later by the calling program. At the moment, the size of
414	pcre_study_data is fixed. We nevertheless save it in a field for returning via
415	the pcre_fullinfo() function so that if it becomes variable in the future, we
416	don't have to change that code. */
417
418	extra = (pcre_extra *)(pcre_malloc)
419	(sizeof(pcre_extra) + sizeof(pcre_study_data));
420
421	if (extra == NULL)
422	{
423	*errorptr = "failed to get memory";
424	return NULL;
425	}
426
427	study = (pcre_study_data )((char )extra + sizeof(pcre_extra));
428	extra->flags = PCRE_EXTRA_STUDY_DATA;
429	extra->study_data = study;
430
431	study->size = sizeof(pcre_study_data);
432	study->options = PCRE_STUDY_MAPPED;
433	memcpy(study->start_bits, start_bits, sizeof(start_bits));
434
435	return extra;
436	}
437
438	/* End of study.c */