* Makefile.am, regcomp.c, regex.c, regex_internal.c, regex_internal.h,

regexec.c: Add new regex files from glibc 2.3.1.

1 files changed, 3225 insertions, 0 deletions

diff --git a/util/regexec.c b/util/regexec.c
new file mode 100644
index 000000000..d791edb36
--- /dev/null
+++ b/util/regexec.c
@@ -0,0 +1,3225 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <[email protected]>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <assert.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if defined HAVE_WCHAR_H || defined _LIBC
+# include <wchar.h>
+#endif /* HAVE_WCHAR_H || _LIBC */
+#if defined HAVE_WCTYPE_H || defined _LIBC
+# include <wctype.h>
+#endif /* HAVE_WCTYPE_H || _LIBC */
+
+#ifdef _LIBC
+# ifndef _RE_DEFINE_LOCALE_FUNCTIONS
+#  define _RE_DEFINE_LOCALE_FUNCTIONS 1
+#  include <locale/localeinfo.h>
+#  include <locale/elem-hash.h>
+#  include <locale/coll-lookup.h>
+# endif
+#endif
+
+#include "_regex.h" /* gnupg */
+#include "regex_internal.h"
+
+static reg_errcode_t match_ctx_init (re_match_context_t *cache, int eflags,
+				     re_string_t *input, int n);
+static void match_ctx_free (re_match_context_t *cache);
+static reg_errcode_t match_ctx_add_entry (re_match_context_t *cache, int node,
+                                          int str_idx, int from, int to);
+static void match_ctx_clear_flag (re_match_context_t *mctx);
+static void sift_ctx_init (re_sift_context_t *sctx, re_dfastate_t **sifted_sts,
+                           re_dfastate_t **limited_sts, int last_node,
+                           int last_str_idx, int check_subexp);
+static reg_errcode_t re_search_internal (const regex_t *preg,
+                                         const char *string, int length,
+                                         int start, int range, int stop,
+                                         size_t nmatch, regmatch_t pmatch[],
+                                         int eflags);
+static int re_search_2_stub (struct re_pattern_buffer *bufp,
+                             const char *string1, int length1,
+                             const char *string2, int length2,
+                             int start, int range, struct re_registers *regs,
+                             int stop, int ret_len);
+static int re_search_stub (struct re_pattern_buffer *bufp,
+                           const char *string, int length, int start,
+                           int range, int stop, struct re_registers *regs,
+                           int ret_len);
+static unsigned re_copy_regs (struct re_registers *regs, regmatch_t *pmatch,
+                              int nregs, int regs_allocated);
+static inline re_dfastate_t *acquire_init_state_context (reg_errcode_t *err,
+                                                         const regex_t *preg,
+                                                         const re_match_context_t *mctx,
+                                                         int idx);
+static int check_matching (const regex_t *preg, re_match_context_t *mctx,
+                           int fl_search, int fl_longest_match);
+static int check_halt_node_context (const re_dfa_t *dfa, int node,
+                                    unsigned int context);
+static int check_halt_state_context (const regex_t *preg,
+                                     const re_dfastate_t *state,
+                                     const re_match_context_t *mctx, int idx);
+static void update_regs (re_dfa_t *dfa, regmatch_t *pmatch, int cur_node,
+                         int cur_idx, int nmatch);
+static int proceed_next_node (const regex_t *preg, int nregs, regmatch_t *regs,
+                              const re_match_context_t *mctx,
+                              int *pidx, int node, re_node_set *eps_via_nodes,
+                              struct re_fail_stack_t *fs);
+static reg_errcode_t push_fail_stack (struct re_fail_stack_t *fs, 
+                                      int str_idx, int *dests, int nregs,
+                                      regmatch_t *regs,
+                                      re_node_set *eps_via_nodes);
+static int pop_fail_stack (struct re_fail_stack_t *fs, int *pidx, int nregs,
+                           regmatch_t *regs, re_node_set *eps_via_nodes);
+static reg_errcode_t set_regs (const regex_t *preg,
+                               const re_match_context_t *mctx,
+                               size_t nmatch, regmatch_t *pmatch,
+                               int fl_backtrack);
+#ifdef RE_ENABLE_I18N
+static int sift_states_iter_mb (const regex_t *preg,
+                                const re_match_context_t *mctx,
+                                re_sift_context_t *sctx,
+                                int node_idx, int str_idx, int max_str_idx);
+#endif /* RE_ENABLE_I18N */
+static reg_errcode_t sift_states_backward (const regex_t *preg,
+                                           re_match_context_t *mctx,
+                                           re_sift_context_t *sctx);
+static reg_errcode_t update_cur_sifted_state (const regex_t *preg,
+                                              re_match_context_t *mctx,
+                                              re_sift_context_t *sctx,
+                                              int str_idx,
+                                              re_node_set *dest_nodes);
+static reg_errcode_t add_epsilon_src_nodes (re_dfa_t *dfa,
+                                            re_node_set *dest_nodes,
+                                            const re_node_set *candidates);
+static reg_errcode_t sub_epsilon_src_nodes (re_dfa_t *dfa, int node,
+                                            re_node_set *dest_nodes,
+                                            const re_node_set *and_nodes);
+static int check_dst_limits (re_dfa_t *dfa, re_node_set *limits,
+                             re_match_context_t *mctx, int dst_node,
+                             int dst_idx, int src_node, int src_idx);
+static int check_dst_limits_calc_pos (re_dfa_t *dfa, re_match_context_t *mctx,
+                                      int limit, re_node_set *eclosures,
+                                      int subexp_idx, int node, int str_idx);
+static reg_errcode_t check_subexp_limits (re_dfa_t *dfa,
+                                          re_node_set *dest_nodes,
+                                          const re_node_set *candidates,
+                                          re_node_set *limits,
+                                          struct re_backref_cache_entry *bkref_ents,
+                                          int str_idx);
+static reg_errcode_t search_subexp (const regex_t *preg,
+                                    re_match_context_t *mctx,
+                                    re_sift_context_t *sctx, int str_idx,
+                                    re_node_set *dest_nodes);
+static reg_errcode_t sift_states_bkref (const regex_t *preg,
+                                        re_match_context_t *mctx,
+                                        re_sift_context_t *sctx,
+                                        int str_idx, re_node_set *dest_nodes);
+static reg_errcode_t clean_state_log_if_need (re_match_context_t *mctx,
+                                              int next_state_log_idx);
+static reg_errcode_t merge_state_array (re_dfa_t *dfa, re_dfastate_t **dst,
+                                        re_dfastate_t **src, int num);
+static re_dfastate_t *transit_state (reg_errcode_t *err, const regex_t *preg,
+                                     re_match_context_t *mctx,
+                                     re_dfastate_t *state, int fl_search);
+static re_dfastate_t *transit_state_sb (reg_errcode_t *err, const regex_t *preg,
+                                        re_dfastate_t *pstate,
+                                        int fl_search,
+                                        re_match_context_t *mctx);
+#ifdef RE_ENABLE_I18N
+static reg_errcode_t transit_state_mb (const regex_t *preg,
+                                       re_dfastate_t *pstate,
+                                       re_match_context_t *mctx);
+#endif /* RE_ENABLE_I18N */
+static reg_errcode_t transit_state_bkref (const regex_t *preg,
+                                          re_dfastate_t *pstate,
+                                          re_match_context_t *mctx);
+static reg_errcode_t transit_state_bkref_loop (const regex_t *preg,
+                                               re_node_set *nodes,
+                                               re_dfastate_t **work_state_log,
+                                               re_match_context_t *mctx);
+static re_dfastate_t **build_trtable (const regex_t *dfa,
+                                      const re_dfastate_t *state,
+                                      int fl_search);
+#ifdef RE_ENABLE_I18N
+static int check_node_accept_bytes (const regex_t *preg, int node_idx,
+                                    const re_string_t *input, int idx);
+# ifdef _LIBC
+static unsigned int find_collation_sequence_value (const unsigned char *mbs,
+                                                   size_t name_len);
+# endif /* _LIBC */
+#endif /* RE_ENABLE_I18N */
+static int group_nodes_into_DFAstates (const regex_t *dfa,
+                                       const re_dfastate_t *state,
+                                       re_node_set *states_node,
+                                       bitset *states_ch);
+static int check_node_accept (const regex_t *preg, const re_token_t *node,
+                              const re_match_context_t *mctx, int idx);
+static reg_errcode_t extend_buffers (re_match_context_t *mctx);
+
+/* Entry point for POSIX code.  */
+
+/* regexec searches for a given pattern, specified by PREG, in the
+   string STRING.
+
+   If NMATCH is zero or REG_NOSUB was set in the cflags argument to
+   `regcomp', we ignore PMATCH.  Otherwise, we assume PMATCH has at
+   least NMATCH elements, and we set them to the offsets of the
+   corresponding matched substrings.
+
+   EFLAGS specifies `execution flags' which affect matching: if
+   REG_NOTBOL is set, then ^ does not match at the beginning of the
+   string; if REG_NOTEOL is set, then $ does not match at the end.
+
+   We return 0 if we find a match and REG_NOMATCH if not.  */
+
+int
+regexec (preg, string, nmatch, pmatch, eflags)
+    const regex_t *__restrict preg;
+    const char *__restrict string;
+    size_t nmatch;
+    regmatch_t pmatch[];
+    int eflags;
+{
+  reg_errcode_t err;
+  int length = strlen (string);
+  if (preg->no_sub)
+    err = re_search_internal (preg, string, length, 0, length, length, 0,
+                              NULL, eflags);
+  else
+    err = re_search_internal (preg, string, length, 0, length, length, nmatch,
+                              pmatch, eflags);
+  return err != REG_NOERROR;
+}
+#ifdef _LIBC
+weak_alias (__regexec, regexec)
+#endif
+
+/* Entry points for GNU code.  */
+
+/* re_match, re_search, re_match_2, re_search_2
+
+   The former two functions operate on STRING with length LENGTH,
+   while the later two operate on concatenation of STRING1 and STRING2
+   with lengths LENGTH1 and LENGTH2, respectively.
+
+   re_match() matches the compiled pattern in BUFP against the string,
+   starting at index START.
+
+   re_search() first tries matching at index START, then it tries to match
+   starting from index START + 1, and so on.  The last start position tried
+   is START + RANGE.  (Thus RANGE = 0 forces re_search to operate the same
+   way as re_match().)
+
+   The parameter STOP of re_{match,search}_2 specifies that no match exceeding
+   the first STOP characters of the concatenation of the strings should be
+   concerned.
+
+   If REGS is not NULL, and BUFP->no_sub is not set, the offsets of the match
+   and all groups is stroed in REGS.  (For the "_2" variants, the offsets are
+   computed relative to the concatenation, not relative to the individual
+   strings.)
+
+   On success, re_match* functions return the length of the match, re_search*
+   return the position of the start of the match.  Return value -1 means no
+   match was found and -2 indicates an internal error.  */
+
+int
+re_match (bufp, string, length, start, regs)
+    struct re_pattern_buffer *bufp;
+    const char *string;
+    int length, start;
+    struct re_registers *regs;
+{
+  return re_search_stub (bufp, string, length, start, 0, length, regs, 1);
+}
+#ifdef _LIBC
+weak_alias (__re_match, re_match)
+#endif
+
+int
+re_search (bufp, string, length, start, range, regs)
+    struct re_pattern_buffer *bufp;
+    const char *string;
+    int length, start, range;
+    struct re_registers *regs;
+{
+  return re_search_stub (bufp, string, length, start, range, length, regs, 0);
+}
+#ifdef _LIBC
+weak_alias (__re_search, re_search)
+#endif
+
+int
+re_match_2 (bufp, string1, length1, string2, length2, start, regs, stop)
+    struct re_pattern_buffer *bufp;
+    const char *string1, *string2;
+    int length1, length2, start, stop;
+    struct re_registers *regs;
+{
+  return re_search_2_stub (bufp, string1, length1, string2, length2,
+                           start, 0, regs, stop, 1);
+}
+#ifdef _LIBC
+weak_alias (__re_match_2, re_match_2)
+#endif
+
+int
+re_search_2 (bufp, string1, length1, string2, length2, start, range, regs, stop)
+    struct re_pattern_buffer *bufp;
+    const char *string1, *string2;
+    int length1, length2, start, range, stop;
+    struct re_registers *regs;
+{
+  return re_search_2_stub (bufp, string1, length1, string2, length2,
+                           start, range, regs, stop, 0);
+}
+#ifdef _LIBC
+weak_alias (__re_search_2, re_search_2)
+#endif
+
+static int
+re_search_2_stub (bufp, string1, length1, string2, length2, start, range, regs,
+                  stop, ret_len)
+    struct re_pattern_buffer *bufp;
+    const char *string1, *string2;
+    int length1, length2, start, range, stop, ret_len;
+    struct re_registers *regs;
+{
+  const char *str;
+  int rval;
+  int len = length1 + length2;
+  int free_str = 0;
+
+  if (BE (length1 < 0 || length2 < 0 || stop < 0, 0))
+    return -2;
+
+  /* Concatenate the strings.  */
+  if (length2 > 0)
+    if (length1 > 0)
+      {
+        char *s = re_malloc (char, len);
+
+        if (BE (s == NULL, 0))
+          return -2;
+        memcpy (s, string1, length1);
+        memcpy (s + length1, string2, length2);
+        str = s;
+        free_str = 1;
+      }
+    else
+      str = string2;
+  else
+    str = string1;
+
+  rval = re_search_stub (bufp, str, len, start, range, stop, regs,
+                         ret_len);
+  if (free_str)
+      re_free ((char *) str);
+  return rval;
+}
+
+/* The parameters have the same meaning as those of re_search.
+   Additional parameters:
+   If RET_LEN is nonzero the length of the match is returned (re_match style);
+   otherwise the position of the match is returned.  */
+
+static int
+re_search_stub (bufp, string, length, start, range, stop, regs, ret_len)
+    struct re_pattern_buffer *bufp;
+    const char *string;
+    int length, start, range, stop, ret_len;
+    struct re_registers *regs;
+{
+  reg_errcode_t result;
+  regmatch_t *pmatch;
+  int nregs, rval;
+  int eflags = 0;
+
+  /* Check for out-of-range.  */
+  if (BE (start < 0 || start > length, 0))
+    return -1;
+  if (BE (start + range > length, 0))
+    range = length - start;
+  else if (BE (start + range < 0, 0))
+    range = -start;
+
+  eflags |= (bufp->not_bol) ? REG_NOTBOL : 0;
+  eflags |= (bufp->not_eol) ? REG_NOTEOL : 0;
+
+  /* Compile fastmap if we haven't yet.  */
+  if (range > 0 && bufp->fastmap != NULL && !bufp->fastmap_accurate)
+    re_compile_fastmap (bufp);
+
+  if (BE (bufp->no_sub, 0))
+    regs = NULL;
+
+  /* We need at least 1 register.  */
+  if (regs == NULL)
+    nregs = 1;
+  else if (BE (bufp->regs_allocated == REGS_FIXED &&
+               regs->num_regs < bufp->re_nsub + 1, 0))
+    {
+      nregs = regs->num_regs;
+      if (BE (nregs < 1, 0))
+        {
+          /* Nothing can be copied to regs.  */
+          regs = NULL;
+          nregs = 1;
+        }
+    }
+  else
+    nregs = bufp->re_nsub + 1;
+  pmatch = re_malloc (regmatch_t, nregs);
+  if (BE (pmatch == NULL, 0))
+    return -2;
+
+  result = re_search_internal (bufp, string, length, start, range, stop,
+                               nregs, pmatch, eflags);
+
+  rval = 0;
+
+  /* I hope we needn't fill ther regs with -1's when no match was found.  */
+  if (result != REG_NOERROR)
+    rval = -1;
+  else if (regs != NULL)
+    {
+      /* If caller wants register contents data back, copy them.  */
+      bufp->regs_allocated = re_copy_regs (regs, pmatch, nregs,
+                                           bufp->regs_allocated);
+      if (BE (bufp->regs_allocated == REGS_UNALLOCATED, 0))
+        rval = -2;
+    }
+
+  if (BE (rval == 0, 1))
+    {
+      if (ret_len)
+        {
+          assert (pmatch[0].rm_so == start);
+          rval = pmatch[0].rm_eo - start;
+        }
+      else
+        rval = pmatch[0].rm_so;
+    }
+  re_free (pmatch);
+  return rval;
+}
+
+static unsigned
+re_copy_regs (regs, pmatch, nregs, regs_allocated)
+    struct re_registers *regs;
+    regmatch_t *pmatch;
+    int nregs, regs_allocated;
+{
+  int rval = REGS_REALLOCATE;
+  int i;
+  int need_regs = nregs + 1;
+  /* We need one extra element beyond `num_regs' for the `-1' marker GNU code
+     uses.  */
+
+  /* Have the register data arrays been allocated?  */
+  if (regs_allocated == REGS_UNALLOCATED)
+    { /* No.  So allocate them with malloc.  */
+      regs->start = re_malloc (regoff_t, need_regs);
+      if (BE (regs->start == NULL, 0))
+        return REGS_UNALLOCATED;
+      regs->end = re_malloc (regoff_t, need_regs);
+      if (BE (regs->end == NULL, 0))
+        {
+          re_free (regs->start);
+          return REGS_UNALLOCATED;
+        }
+      regs->num_regs = need_regs;
+    }
+  else if (regs_allocated == REGS_REALLOCATE)
+    { /* Yes.  If we need more elements than were already
+         allocated, reallocate them.  If we need fewer, just
+         leave it alone.  */
+      if (need_regs > regs->num_regs)
+        {
+          regs->start = re_realloc (regs->start, regoff_t, need_regs);
+          if (BE (regs->start == NULL, 0))
+            {
+              if (regs->end != NULL)
+                re_free (regs->end);
+              return REGS_UNALLOCATED;
+            }
+          regs->end = re_realloc (regs->end, regoff_t, need_regs);
+          if (BE (regs->end == NULL, 0))
+            {
+              re_free (regs->start);
+              return REGS_UNALLOCATED;
+            }
+          regs->num_regs = need_regs;
+        }
+    }
+  else
+    {
+      assert (regs_allocated == REGS_FIXED);
+      /* This function may not be called with REGS_FIXED and nregs too big.  */
+      assert (regs->num_regs >= nregs);
+      rval = REGS_FIXED;
+    }
+
+  /* Copy the regs.  */
+  for (i = 0; i < nregs; ++i)
+    {
+      regs->start[i] = pmatch[i].rm_so;
+      regs->end[i] = pmatch[i].rm_eo;
+    }
+  for ( ; i < regs->num_regs; ++i)
+    regs->start[i] = regs->end[i] = -1;
+
+  return rval;
+}
+
+/* Set REGS to hold NUM_REGS registers, storing them in STARTS and
+   ENDS.  Subsequent matches using PATTERN_BUFFER and REGS will use
+   this memory for recording register information.  STARTS and ENDS
+   must be allocated using the malloc library routine, and must each
+   be at least NUM_REGS * sizeof (regoff_t) bytes long.
+
+   If NUM_REGS == 0, then subsequent matches should allocate their own
+   register data.
+
+   Unless this function is called, the first search or match using
+   PATTERN_BUFFER will allocate its own register data, without
+   freeing the old data.  */
+
+void
+re_set_registers (bufp, regs, num_regs, starts, ends)
+    struct re_pattern_buffer *bufp;
+    struct re_registers *regs;
+    unsigned num_regs;
+    regoff_t *starts, *ends;
+{
+  if (num_regs)
+    {
+      bufp->regs_allocated = REGS_REALLOCATE;
+      regs->num_regs = num_regs;
+      regs->start = starts;
+      regs->end = ends;
+    }
+  else
+    {
+      bufp->regs_allocated = REGS_UNALLOCATED;
+      regs->num_regs = 0;
+      regs->start = regs->end = (regoff_t *) 0;
+    }
+}
+#ifdef _LIBC
+weak_alias (__re_set_registers, re_set_registers)
+#endif
+
+/* Entry points compatible with 4.2 BSD regex library.  We don't define
+   them unless specifically requested.  */
+
+#if defined _REGEX_RE_COMP || defined _LIBC
+int
+# ifdef _LIBC
+weak_function
+# endif
+re_exec (s)
+     const char *s;
+{
+  return 0 == regexec (&re_comp_buf, s, 0, NULL, 0);
+}
+#endif /* _REGEX_RE_COMP */
+
+static re_node_set empty_set;
+
+/* Internal entry point.  */
+
+/* Searches for a compiled pattern PREG in the string STRING, whose
+   length is LENGTH.  NMATCH, PMATCH, and EFLAGS have the same
+   mingings with regexec.  START, and RANGE have the same meanings
+   with re_search.
+   Return REG_NOERROR if we find a match, and REG_NOMATCH if not,
+   otherwise return the error code.
+   Note: We assume front end functions already check ranges.
+   (START + RANGE >= 0 && START + RANGE <= LENGTH)  */
+
+static reg_errcode_t
+re_search_internal (preg, string, length, start, range, stop, nmatch, pmatch,
+                    eflags)
+    const regex_t *preg;
+    const char *string;
+    int length, start, range, stop, eflags;
+    size_t nmatch;
+    regmatch_t pmatch[];
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  re_string_t input;
+  int left_lim, right_lim, incr;
+  int fl_longest_match, match_first, match_last = -1;
+  re_match_context_t mctx;
+  char *fastmap = ((preg->fastmap != NULL && preg->fastmap_accurate)
+                   ? preg->fastmap : NULL);
+
+  /* Check if the DFA haven't been compiled.  */
+  if (BE (preg->used == 0 || dfa->init_state == NULL
+          || dfa->init_state_word == NULL || dfa->init_state_nl == NULL
+          || dfa->init_state_begbuf == NULL, 0))
+    return REG_NOMATCH;
+
+  re_node_set_init_empty (&empty_set);
+
+  /* We must check the longest matching, if nmatch > 0.  */
+  fl_longest_match = (nmatch != 0);
+
+  err = re_string_allocate (&input, string, length, dfa->nodes_len + 1,
+                            preg->translate, preg->syntax & RE_ICASE);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+  input.stop = stop;
+
+  err = match_ctx_init (&mctx, eflags, &input, dfa->nbackref * 2);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+
+  /* We will log all the DFA states through which the dfa pass,
+     if nmatch > 1, or this dfa has "multibyte node", which is a
+     back-reference or a node which can accept multibyte character or
+     multi character collating element.  */
+  if (nmatch > 1 || dfa->has_mb_node)
+    {
+      mctx.state_log = re_malloc (re_dfastate_t *, dfa->nodes_len + 1);
+      if (BE (mctx.state_log == NULL, 0))
+        return REG_ESPACE;
+    }
+  else
+    mctx.state_log = NULL;
+
+#ifdef DEBUG
+  /* We assume front-end functions already check them.  */
+  assert (start + range >= 0 && start + range <= length);
+#endif
+
+  match_first = start;
+  input.tip_context = ((eflags & REG_NOTBOL) ? CONTEXT_BEGBUF
+                       : CONTEXT_NEWLINE | CONTEXT_BEGBUF);
+
+  /* Check incrementally whether of not the input string match.  */
+  incr = (range < 0) ? -1 : 1;
+  left_lim = (range < 0) ? start + range : start;
+  right_lim = (range < 0) ? start : start + range;
+
+  for (;;)
+    {
+      /* At first get the current byte from input string.  */
+      int ch;
+      if (MB_CUR_MAX > 1 && (preg->syntax & RE_ICASE || preg->translate))
+        {
+          /* In this case, we can't determin easily the current byte,
+             since it might be a component byte of a multibyte character.
+             Then we use the constructed buffer instead.  */
+          /* If MATCH_FIRST is out of the valid range, reconstruct the
+             buffers.  */
+          if (input.raw_mbs_idx + input.valid_len <= match_first)
+            re_string_reconstruct (&input, match_first, eflags,
+                                   preg->newline_anchor);
+          /* If MATCH_FIRST is out of the buffer, leave it as '\0'.
+             Note that MATCH_FIRST must not be smaller than 0.  */
+          ch = ((match_first >= length) ? 0
+                : re_string_byte_at (&input, match_first - input.raw_mbs_idx));
+        }
+      else
+        {
+          /* We apply translate/conversion manually, since it is trivial
+             in this case.  */
+          /* If MATCH_FIRST is out of the buffer, leave it as '\0'.
+             Note that MATCH_FIRST must not be smaller than 0.  */
+          ch = (match_first < length) ? (unsigned char)string[match_first] : 0;
+          /* Apply translation if we need.  */
+          ch = preg->translate ? preg->translate[ch] : ch;
+          /* In case of case insensitive mode, convert to upper case.  */
+          ch = ((preg->syntax & RE_ICASE) && islower (ch)) ? toupper (ch) : ch;
+        }
+
+      /* Eliminate inappropriate one by fastmap.  */
+      if (preg->can_be_null || fastmap == NULL || fastmap[ch])
+        {
+          /* Reconstruct the buffers so that the matcher can assume that
+             the matching starts from the begining of the buffer.  */
+          re_string_reconstruct (&input, match_first, eflags,
+                                 preg->newline_anchor);
+#ifdef RE_ENABLE_I18N
+          /* Eliminate it when it is a component of a multibyte character
+             and isn't the head of a multibyte character.  */
+          if (MB_CUR_MAX == 1 || re_string_first_byte (&input, 0))
+#endif
+            {
+              /* It seems to be appropriate one, then use the matcher.  */
+              /* We assume that the matching starts from 0.  */
+              mctx.state_log_top = mctx.nbkref_ents = mctx.max_mb_elem_len = 0;
+              match_last = check_matching (preg, &mctx, 0, fl_longest_match);
+              if (match_last != -1)
+                {
+                  if (BE (match_last == -2, 0))
+                    return REG_ESPACE;
+                  else
+                    break; /* We found a matching.  */
+                }
+            }
+        }
+      /* Update counter.  */
+      match_first += incr;
+      if (match_first < left_lim || right_lim < match_first)
+        break;
+    }
+
+  /* Set pmatch[] if we need.  */
+  if (match_last != -1 && nmatch > 0)
+    {
+      int reg_idx;
+
+      /* Initialize registers.  */
+      for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
+        pmatch[reg_idx].rm_so = pmatch[reg_idx].rm_eo = -1;
+
+      /* Set the points where matching start/end.  */
+      pmatch[0].rm_so = 0;
+      mctx.match_last = pmatch[0].rm_eo = match_last;
+
+      if (!preg->no_sub && nmatch > 1)
+        {
+          /* We need the ranges of all the subexpressions.  */
+          int halt_node;
+          re_dfastate_t **sifted_states;
+          re_dfastate_t **lim_states = NULL;
+          re_dfastate_t *pstate = mctx.state_log[match_last];
+          re_sift_context_t sctx;
+#ifdef DEBUG
+          assert (mctx.state_log != NULL);
+#endif
+          halt_node = check_halt_state_context (preg, pstate, &mctx,
+                                                match_last);
+          if (dfa->has_plural_match)
+            {
+              match_ctx_clear_flag (&mctx);
+              sifted_states = re_malloc (re_dfastate_t *, match_last + 1);
+              if (BE (sifted_states == NULL, 0))
+                return REG_ESPACE;
+              if (dfa->nbackref)
+                {
+                  lim_states = calloc (sizeof (re_dfastate_t *),
+                                       match_last + 1);
+                  if (BE (lim_states == NULL, 0))
+                    return REG_ESPACE;
+                }
+              sift_ctx_init (&sctx, sifted_states, lim_states, halt_node,
+                             mctx.match_last, 0);
+              err = sift_states_backward (preg, &mctx, &sctx);
+              if (BE (err != REG_NOERROR, 0))
+                return err;
+              if (lim_states != NULL)
+                {
+                  err = merge_state_array (dfa, sifted_states, lim_states,
+                                           match_last + 1);
+                  if (BE (err != REG_NOERROR, 0))
+                    return err;
+                  re_free (lim_states);
+                }
+              re_node_set_free (&sctx.limits);
+              re_free (mctx.state_log);
+              mctx.state_log = sifted_states;
+            }
+          mctx.last_node = halt_node;
+          err = set_regs (preg, &mctx, nmatch, pmatch,
+                          dfa->has_plural_match && dfa->nbackref > 0);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+        }
+
+      /* At last, add the offset to the each registers, since we slided
+         the buffers so that We can assume that the matching starts from 0.  */
+      for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
+        if (pmatch[reg_idx].rm_so != -1)
+          {
+            pmatch[reg_idx].rm_so += match_first;
+            pmatch[reg_idx].rm_eo += match_first;
+          }
+    }
+
+  re_free (mctx.state_log);
+  if (dfa->nbackref)
+    match_ctx_free (&mctx);
+  re_string_destruct (&input);
+
+  return (match_last == -1) ? REG_NOMATCH : REG_NOERROR;
+}
+
+/* Acquire an initial state and return it.
+   We must select appropriate initial state depending on the context,
+   since initial states may have constraints like "\<", "^", etc..  */
+
+static inline re_dfastate_t *
+acquire_init_state_context (err, preg, mctx, idx)
+     reg_errcode_t *err;
+     const regex_t *preg;
+     const re_match_context_t *mctx;
+     int idx;
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+
+  *err = REG_NOERROR;
+  if (dfa->init_state->has_constraint)
+    {
+      unsigned int context;
+      context =  re_string_context_at (mctx->input, idx - 1, mctx->eflags,
+                                       preg->newline_anchor);
+      if (IS_WORD_CONTEXT (context))
+        return dfa->init_state_word;
+      else if (IS_ORDINARY_CONTEXT (context))
+        return dfa->init_state;
+      else if (IS_BEGBUF_CONTEXT (context) && IS_NEWLINE_CONTEXT (context))
+        return dfa->init_state_begbuf;
+      else if (IS_NEWLINE_CONTEXT (context))
+        return dfa->init_state_nl;
+      else if (IS_BEGBUF_CONTEXT (context))
+        {
+          /* It is relatively rare case, then calculate on demand.  */
+          return  re_acquire_state_context (err, dfa,
+                                            dfa->init_state->entrance_nodes,
+                                            context);
+        }
+      else
+        /* Must not happen?  */
+        return dfa->init_state;
+    }
+  else
+    return dfa->init_state;
+}
+
+/* Check whether the regular expression match input string INPUT or not,
+   and return the index where the matching end, return -1 if not match,
+   or return -2 in case of an error.
+   FL_SEARCH means we must search where the matching starts,
+   FL_LONGEST_MATCH means we want the POSIX longest matching.
+   Note that the matcher assume that the maching starts from the current
+   index of the buffer.  */
+
+static int
+check_matching (preg, mctx, fl_search, fl_longest_match)
+    const regex_t *preg;
+    re_match_context_t *mctx;
+    int fl_search, fl_longest_match;
+{
+  reg_errcode_t err;
+  int match = 0;
+  int match_last = -1;
+  int cur_str_idx = re_string_cur_idx (mctx->input);
+  re_dfastate_t *cur_state;
+
+  cur_state = acquire_init_state_context (&err, preg, mctx, cur_str_idx);
+  /* An initial state must not be NULL(invalid state).  */
+  if (BE (cur_state == NULL, 0))
+    return -2;
+  if (mctx->state_log != NULL)
+    mctx->state_log[cur_str_idx] = cur_state;
+
+  if (cur_state->has_backref)
+    {
+      int i;
+      re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+      for (i = 0; i < cur_state->nodes.nelem; ++i)
+        {
+          re_token_type_t type;
+          int node = cur_state->nodes.elems[i];
+          int entity = (dfa->nodes[node].type != OP_CONTEXT_NODE ? node
+                        : dfa->nodes[node].opr.ctx_info->entity);
+          type = dfa->nodes[entity].type;
+          if (type == OP_BACK_REF)
+            {
+              int clexp_idx;
+              for (clexp_idx = 0; clexp_idx < cur_state->nodes.nelem;
+                   ++clexp_idx)
+                {
+                  re_token_t *clexp_node;
+                  clexp_node = dfa->nodes + cur_state->nodes.elems[clexp_idx];
+                  if (clexp_node->type == OP_CLOSE_SUBEXP
+                      && clexp_node->opr.idx + 1== dfa->nodes[entity].opr.idx)
+                    {
+                      err = match_ctx_add_entry (mctx, node, 0, 0, 0);
+                      if (BE (err != REG_NOERROR, 0))
+                        return -2;
+                      break;
+                    }
+                }
+            }
+        }
+    }
+
+  /* If the RE accepts NULL string.  */
+  if (cur_state->halt)
+    {
+      if (!cur_state->has_constraint
+          || check_halt_state_context (preg, cur_state, mctx, cur_str_idx))
+        {
+          if (!fl_longest_match)
+            return cur_str_idx;
+          else
+            {
+              match_last = cur_str_idx;
+              match = 1;
+            }
+        }
+    }
+
+  while (!re_string_eoi (mctx->input))
+    {
+      cur_state = transit_state (&err, preg, mctx, cur_state,
+                                 fl_search && !match);
+      if (cur_state == NULL) /* Reached at the invalid state or an error.  */
+        {
+          cur_str_idx = re_string_cur_idx (mctx->input);
+          if (BE (err != REG_NOERROR, 0))
+            return -2;
+          if (fl_search && !match)
+            {
+              /* Restart from initial state, since we are searching
+                 the point from where matching start.  */
+#ifdef RE_ENABLE_I18N
+              if (MB_CUR_MAX == 1
+                  || re_string_first_byte (mctx->input, cur_str_idx))
+#endif /* RE_ENABLE_I18N */
+                cur_state = acquire_init_state_context (&err, preg, mctx,
+                                                        cur_str_idx);
+              if (BE (cur_state == NULL && err != REG_NOERROR, 0))
+                return -2;
+              if (mctx->state_log != NULL)
+                mctx->state_log[cur_str_idx] = cur_state;
+            }
+          else if (!fl_longest_match && match)
+            break;
+          else /* (fl_longest_match && match) || (!fl_search && !match)  */
+            {
+              if (mctx->state_log == NULL)
+                break;
+              else
+                {
+                  int max = mctx->state_log_top;
+                  for (; cur_str_idx <= max; ++cur_str_idx)
+                    if (mctx->state_log[cur_str_idx] != NULL)
+                      break;
+                  if (cur_str_idx > max)
+                    break;
+                }
+            }
+        }
+
+      if (cur_state != NULL && cur_state->halt)
+        {
+          /* Reached at a halt state.
+             Check the halt state can satisfy the current context.  */
+          if (!cur_state->has_constraint
+              || check_halt_state_context (preg, cur_state, mctx,
+                                           re_string_cur_idx (mctx->input)))
+            {
+              /* We found an appropriate halt state.  */
+              match_last = re_string_cur_idx (mctx->input);
+              match = 1;
+              if (!fl_longest_match)
+                break;
+            }
+        }
+   }
+  return match_last;
+}
+
+/* Check NODE match the current context.  */
+
+static int check_halt_node_context (dfa, node, context)
+    const re_dfa_t *dfa;
+    int node;
+    unsigned int context;
+{
+  int entity;
+  re_token_type_t type = dfa->nodes[node].type;
+  if (type == END_OF_RE)
+    return 1;
+  if (type != OP_CONTEXT_NODE)
+    return 0;
+  entity = dfa->nodes[node].opr.ctx_info->entity;
+  if (dfa->nodes[entity].type != END_OF_RE
+      || NOT_SATISFY_NEXT_CONSTRAINT (dfa->nodes[node].constraint, context))
+    return 0;
+  return 1;
+}
+
+/* Check the halt state STATE match the current context.
+   Return 0 if not match, if the node, STATE has, is a halt node and
+   match the context, return the node.  */
+
+static int
+check_halt_state_context (preg, state, mctx, idx)
+    const regex_t *preg;
+    const re_dfastate_t *state;
+    const re_match_context_t *mctx;
+    int idx;
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  int i;
+  unsigned int context;
+#ifdef DEBUG
+  assert (state->halt);
+#endif
+  context = re_string_context_at (mctx->input, idx, mctx->eflags,
+                                  preg->newline_anchor);
+  for (i = 0; i < state->nodes.nelem; ++i)
+    if (check_halt_node_context (dfa, state->nodes.elems[i], context))
+      return state->nodes.elems[i];
+  return 0;
+}
+
+/* Compute the next node to which "NFA" transit from NODE("NFA" is a NFA
+   corresponding to the DFA).
+   Return the destination node, and update EPS_VIA_NODES, return -1 in case
+   of errors.  */
+
+static int
+proceed_next_node (preg, nregs, regs, mctx, pidx, node, eps_via_nodes, fs)
+    const regex_t *preg;
+    regmatch_t *regs;
+    const re_match_context_t *mctx;
+    int nregs, *pidx, node;
+    re_node_set *eps_via_nodes;
+    struct re_fail_stack_t *fs;
+{
+  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  int i, err, dest_node, cur_entity;
+  dest_node = -1;
+  cur_entity = ((dfa->nodes[node].type == OP_CONTEXT_NODE)
+                ? dfa->nodes[node].opr.ctx_info->entity : node);
+  if (IS_EPSILON_NODE (dfa->nodes[node].type))
+    {
+      int ndest, dest_nodes[2], dest_entities[2];
+      err = re_node_set_insert (eps_via_nodes, node);
+      if (BE (err < 0, 0))
+        return -1;
+      /* Pick up valid destinations.  */
+      for (ndest = 0, i = 0; i < mctx->state_log[*pidx]->nodes.nelem; ++i)
+        {
+          int candidate = mctx->state_log[*pidx]->nodes.elems[i];
+          int entity;
+          entity = ((dfa->nodes[candidate].type == OP_CONTEXT_NODE)
+                    ? dfa->nodes[candidate].opr.ctx_info->entity : candidate);
+          if (!re_node_set_contains (dfa->edests + node, entity))
+            continue;
+          dest_nodes[0] = (ndest == 0) ? candidate : dest_nodes[0];
+          dest_entities[0] = (ndest == 0) ? entity : dest_entities[0];
+          dest_nodes[1] = (ndest == 1) ? candidate : dest_nodes[1];
+          dest_entities[1] = (ndest == 1) ? entity : dest_entities[1];
+          ++ndest;
+        }
+      if (ndest <= 1)
+        return ndest == 0 ? -1 : (ndest == 1 ? dest_nodes[0] : 0);
+      if (dest_entities[0] > dest_entities[1])
+        {
+          int swap_work = dest_nodes[0];
+          dest_nodes[0] = dest_nodes[1];
+          dest_nodes[1] = swap_work;
+        }
+      /* In order to avoid infinite loop like "(a*)*".  */
+      if (re_node_set_contains (eps_via_nodes, dest_nodes[0]))
+        return dest_nodes[1];
+      if (fs != NULL)
+        push_fail_stack (fs, *pidx, dest_nodes, nregs, regs, eps_via_nodes);
+      return dest_nodes[0];
+    }
+  else
+    {
+      int naccepted = 0, entity = node;
+      re_token_type_t type = dfa->nodes[node].type;
+      if (type == OP_CONTEXT_NODE)
+        {
+          entity = dfa->nodes[node].opr.ctx_info->entity;
+          type = dfa->nodes[entity].type;
+        }
+
+#ifdef RE_ENABLE_I18N
+      if (ACCEPT_MB_NODE (type))
+        naccepted = check_node_accept_bytes (preg, entity, mctx->input, *pidx);
+      else
+#endif /* RE_ENABLE_I18N */
+      if (type == OP_BACK_REF)
+        {
+          int subexp_idx = dfa->nodes[entity].opr.idx;
+          naccepted = regs[subexp_idx].rm_eo - regs[subexp_idx].rm_so;
+          if (fs != NULL)
+            {
+              if (regs[subexp_idx].rm_so == -1 || regs[subexp_idx].rm_eo == -1)
+                return -1;
+              else if (naccepted)
+                {
+                  char *buf = re_string_get_buffer (mctx->input);
+                  if (strncmp (buf + regs[subexp_idx].rm_so, buf + *pidx,
+                               naccepted) != 0)
+                    return -1;
+                }
+            }
+
+          if (naccepted == 0)
+            {
+              err = re_node_set_insert (eps_via_nodes, node);
+              if (BE (err < 0, 0))
+                return -2;
+              dest_node = dfa->nexts[node];
+              if (re_node_set_contains (&mctx->state_log[*pidx]->nodes,
+                                        dest_node))
+                return dest_node;
+              for (i = 0; i < mctx->state_log[*pidx]->nodes.nelem; ++i)
+                {
+                  dest_node = mctx->state_log[*pidx]->nodes.elems[i];
+                  if ((dfa->nodes[dest_node].type == OP_CONTEXT_NODE
+                       && (dfa->nexts[node]
+                           == dfa->nodes[dest_node].opr.ctx_info->entity)))
+                    return dest_node;
+                }
+            }
+        }
+
+      if (naccepted != 0
+          || check_node_accept (preg, dfa->nodes + node, mctx, *pidx))
+        {
+          dest_node = dfa->nexts[node];
+          *pidx = (naccepted == 0) ? *pidx + 1 : *pidx + naccepted;
+          if (fs && (*pidx > mctx->match_last || mctx->state_log[*pidx] == NULL
+                     || !re_node_set_contains (&mctx->state_log[*pidx]->nodes,
+                                               dest_node)))
+            return -1;
+          re_node_set_empty (eps_via_nodes);
+          return dest_node;
+        }
+    }
+  return -1;
+}
+
+static reg_errcode_t
+push_fail_stack (fs, str_idx, dests, nregs, regs, eps_via_nodes)
+     struct re_fail_stack_t *fs;
+     int str_idx, *dests, nregs;
+     regmatch_t *regs;
+     re_node_set *eps_via_nodes;
+{
+  reg_errcode_t err;
+  int num = fs->num++;
+  if (fs->num == fs->alloc)
+    {
+      fs->alloc *= 2;
+      fs->stack = realloc (fs->stack, (sizeof (struct re_fail_stack_ent_t)
+                                       * fs->alloc));
+      if (fs->stack == NULL)
+        return REG_ESPACE;
+    }
+  fs->stack[num].idx = str_idx;
+  fs->stack[num].node = dests[1];
+  fs->stack[num].regs = re_malloc (regmatch_t, nregs);
+  memcpy (fs->stack[num].regs, regs, sizeof (regmatch_t) * nregs);
+  err = re_node_set_init_copy (&fs->stack[num].eps_via_nodes, eps_via_nodes);
+  return err;
+}
+ 
+static int
+pop_fail_stack (fs, pidx, nregs, regs, eps_via_nodes)
+     struct re_fail_stack_t *fs;
+     int *pidx, nregs;
+     regmatch_t *regs;
+     re_node_set *eps_via_nodes;
+{
+  int num = --fs->num;
+  assert (num >= 0);
+ *pidx = fs->stack[num].idx;
+  memcpy (regs, fs->stack[num].regs, sizeof (regmatch_t) * nregs);
+  re_node_set_free (eps_via_nodes);
+  *eps_via_nodes = fs->stack[num].eps_via_nodes;
+  return fs->stack[num].node;
+}
+
+/* Set the positions where the subexpressions are starts/ends to registers
+   PMATCH.
+   Note: We assume that pmatch[0] is already set, and
+   pmatch[i].rm_so == pmatch[i].rm_eo == -1 (i > 1).  */
+
+static reg_errcode_t
+set_regs (preg, mctx, nmatch, pmatch, fl_backtrack)
+     const regex_t *preg;
+     const re_match_context_t *mctx;
+     size_t nmatch;
+     regmatch_t *pmatch;
+     int fl_backtrack;
+{
+  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  int idx, cur_node, real_nmatch;
+  re_node_set eps_via_nodes;
+  struct re_fail_stack_t *fs;
+  struct re_fail_stack_t fs_body = {0, 2, NULL};
+#ifdef DEBUG
+  assert (nmatch > 1);
+  assert (mctx->state_log != NULL);
+#endif
+  if (fl_backtrack)
+    {
+      fs = &fs_body;
+      fs->stack = re_malloc (struct re_fail_stack_ent_t, fs->alloc);
+    }
+  else
+    fs = NULL;
+  cur_node = dfa->init_node;
+  real_nmatch = (nmatch <= preg->re_nsub) ? nmatch : preg->re_nsub + 1;
+  re_node_set_init_empty (&eps_via_nodes);
+  for (idx = pmatch[0].rm_so; idx <= pmatch[0].rm_eo ;)
+    {
+      update_regs (dfa, pmatch, cur_node, idx, real_nmatch);
+      if (idx == pmatch[0].rm_eo && cur_node == mctx->last_node)
+        {
+          int reg_idx;
+          if (fs)
+            {
+              for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
+                if (pmatch[reg_idx].rm_so > -1 && pmatch[reg_idx].rm_eo == -1)
+                  break;
+              if (reg_idx == nmatch)
+                return REG_NOERROR;
+              cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
+                                         &eps_via_nodes);
+            }
+          else
+            return REG_NOERROR;
+        }
+
+      /* Proceed to next node.  */
+      cur_node = proceed_next_node (preg, nmatch, pmatch, mctx, &idx, cur_node,
+                                    &eps_via_nodes, fs);
+
+      if (BE (cur_node < 0, 0))
+        {
+          if (cur_node == -2)
+            return REG_ESPACE;
+          if (fs)
+            cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
+                                       &eps_via_nodes);
+          else
+            return REG_NOMATCH;
+        }
+    }
+  re_node_set_free (&eps_via_nodes);
+  return REG_NOERROR;
+}
+
+static void
+update_regs (dfa, pmatch, cur_node, cur_idx, nmatch)
+     re_dfa_t *dfa;
+     regmatch_t *pmatch;
+     int cur_node, cur_idx, nmatch;
+{
+  int type = dfa->nodes[cur_node].type;
+  int reg_num;
+  if (type != OP_OPEN_SUBEXP && type != OP_CLOSE_SUBEXP)
+    return;
+  reg_num = dfa->nodes[cur_node].opr.idx + 1;
+  if (reg_num >= nmatch)
+    return;
+  if (type == OP_OPEN_SUBEXP)
+    {
+      /* We are at the first node of this sub expression.  */
+      pmatch[reg_num].rm_so = cur_idx;
+      pmatch[reg_num].rm_eo = -1;
+    }
+  else if (type == OP_CLOSE_SUBEXP)
+    /* We are at the first node of this sub expression.  */
+    pmatch[reg_num].rm_eo = cur_idx;
+}
+
+#define NUMBER_OF_STATE 1
+
+/* This function checks the STATE_LOG from the SCTX->last_str_idx to 0
+   and sift the nodes in each states according to the following rules.
+   Updated state_log will be wrote to STATE_LOG.
+
+   Rules: We throw away the Node `a' in the STATE_LOG[STR_IDX] if...
+     1. When STR_IDX == MATCH_LAST(the last index in the state_log):
+        If `a' isn't the LAST_NODE and `a' can't epsilon transit to
+        the LAST_NODE, we throw away the node `a'.
+     2. When 0 <= STR_IDX < MATCH_LAST and `a' accepts
+        string `s' and transit to `b':
+        i. If 'b' isn't in the STATE_LOG[STR_IDX+strlen('s')], we throw
+           away the node `a'.
+        ii. If 'b' is in the STATE_LOG[STR_IDX+strlen('s')] but 'b' is
+            throwed away, we throw away the node `a'.
+     3. When 0 <= STR_IDX < n and 'a' epsilon transit to 'b':
+        i. If 'b' isn't in the STATE_LOG[STR_IDX], we throw away the
+           node `a'.
+        ii. If 'b' is in the STATE_LOG[STR_IDX] but 'b' is throwed away,
+            we throw away the node `a'.  */
+
+#define STATE_NODE_CONTAINS(state,node) \
+  ((state) != NULL && re_node_set_contains (&(state)->nodes, node))
+
+static reg_errcode_t
+sift_states_backward (preg, mctx, sctx)
+     const regex_t *preg;
+     re_match_context_t *mctx;
+     re_sift_context_t *sctx;
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  int null_cnt = 0;
+  int str_idx = sctx->last_str_idx;
+  re_node_set cur_dest;
+  re_node_set *cur_src; /* Points the state_log[str_idx]->nodes  */
+
+#ifdef DEBUG
+  assert (mctx->state_log != NULL && mctx->state_log[str_idx] != NULL);
+#endif
+  cur_src = &mctx->state_log[str_idx]->nodes;
+
+  /* Build sifted state_log[str_idx].  It has the nodes which can epsilon
+     transit to the last_node and the last_node itself.  */
+  err = re_node_set_init_1 (&cur_dest, sctx->last_node);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+  err = update_cur_sifted_state (preg, mctx, sctx, str_idx, &cur_dest);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+
+  /* Then check each states in the state_log.  */
+  while (str_idx > 0)
+    {
+      int i, ret;
+      /* Update counters.  */
+      null_cnt = (sctx->sifted_states[str_idx] == NULL) ? null_cnt + 1 : 0;
+      if (null_cnt > mctx->max_mb_elem_len)
+        {
+          memset (sctx->sifted_states, '\0',
+                  sizeof (re_dfastate_t *) * str_idx);
+          return REG_NOERROR;
+        }
+      re_node_set_empty (&cur_dest);
+      --str_idx;
+      cur_src = ((mctx->state_log[str_idx] == NULL) ? &empty_set
+                 : &mctx->state_log[str_idx]->nodes);
+
+      /* Then build the next sifted state.
+         We build the next sifted state on `cur_dest', and update
+         `sifted_states[str_idx]' with `cur_dest'.
+         Note:
+         `cur_dest' is the sifted state from `state_log[str_idx + 1]'.
+         `cur_src' points the node_set of the old `state_log[str_idx]'.  */
+      for (i = 0; i < cur_src->nelem; i++)
+        {
+          int prev_node = cur_src->elems[i];
+          int entity = prev_node;
+          int naccepted = 0;
+          re_token_type_t type = dfa->nodes[prev_node].type;
+
+          if (IS_EPSILON_NODE(type))
+            continue;
+          if (type == OP_CONTEXT_NODE)
+            {
+              entity = dfa->nodes[prev_node].opr.ctx_info->entity;
+              type = dfa->nodes[entity].type;
+            }
+#ifdef RE_ENABLE_I18N
+          /* If the node may accept `multi byte'.  */
+          if (ACCEPT_MB_NODE (type))
+            naccepted = sift_states_iter_mb (preg, mctx, sctx, entity, str_idx,
+                                             sctx->last_str_idx);
+
+#endif /* RE_ENABLE_I18N */
+          /* We don't check backreferences here.
+             See update_cur_sifted_state().  */
+
+          if (!naccepted
+              && check_node_accept (preg, dfa->nodes + prev_node, mctx,
+                                    str_idx)
+              && STATE_NODE_CONTAINS (sctx->sifted_states[str_idx + 1],
+                                      dfa->nexts[prev_node]))
+            naccepted = 1;
+
+          if (naccepted == 0)
+            continue;
+
+          if (sctx->limits.nelem)
+            {
+              int to_idx = str_idx + naccepted;
+              if (check_dst_limits (dfa, &sctx->limits, mctx,
+                                    dfa->nexts[prev_node], to_idx,
+                                    prev_node, str_idx))
+                continue;
+            }
+          ret = re_node_set_insert (&cur_dest, prev_node);
+          if (BE (ret == -1, 0))
+            return err;
+        }
+
+      /* Add all the nodes which satisfy the following conditions:
+         - It can epsilon transit to a node in CUR_DEST.
+         - It is in CUR_SRC.
+         And update state_log.  */
+      err = update_cur_sifted_state (preg, mctx, sctx, str_idx, &cur_dest);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
+
+  re_node_set_free (&cur_dest);
+  return REG_NOERROR;
+}
+
+/* Helper functions.  */
+
+static inline reg_errcode_t
+clean_state_log_if_need (mctx, next_state_log_idx)
+    re_match_context_t *mctx;
+    int next_state_log_idx;
+{
+  int top = mctx->state_log_top;
+
+  if (next_state_log_idx >= mctx->input->bufs_len
+      || (next_state_log_idx >= mctx->input->valid_len
+          && mctx->input->valid_len < mctx->input->len))
+    {
+      reg_errcode_t err;
+      err = extend_buffers (mctx);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
+
+  if (top < next_state_log_idx)
+    {
+      memset (mctx->state_log + top + 1, '\0',
+              sizeof (re_dfastate_t *) * (next_state_log_idx - top));
+      mctx->state_log_top = next_state_log_idx;
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t merge_state_array (dfa, dst, src, num)
+     re_dfa_t *dfa;
+     re_dfastate_t **dst;
+     re_dfastate_t **src;
+     int num;
+{
+  int st_idx;
+  reg_errcode_t err;
+  for (st_idx = 0; st_idx < num; ++st_idx)
+    {
+      if (dst[st_idx] == NULL)
+        dst[st_idx] = src[st_idx];
+      else if (src[st_idx] != NULL)
+        {
+          re_node_set merged_set;
+          err = re_node_set_init_union (&merged_set, &dst[st_idx]->nodes,
+                                        &src[st_idx]->nodes);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          dst[st_idx] = re_acquire_state (&err, dfa, &merged_set);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          re_node_set_free (&merged_set);
+        }
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+update_cur_sifted_state (preg, mctx, sctx, str_idx, dest_nodes)
+     const regex_t *preg;
+     re_match_context_t *mctx;
+     re_sift_context_t *sctx;
+     int str_idx;
+     re_node_set *dest_nodes;
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  const re_node_set *candidates;
+  candidates = ((mctx->state_log[str_idx] == NULL) ? &empty_set
+                : &mctx->state_log[str_idx]->nodes);
+
+  /* At first, add the nodes which can epsilon transit to a node in
+     DEST_NODE.  */
+  err = add_epsilon_src_nodes (dfa, dest_nodes, candidates);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+
+  /* Then, check the limitations in the current sift_context.  */
+  if (sctx->limits.nelem)
+    {
+      err = check_subexp_limits (dfa, dest_nodes, candidates, &sctx->limits,
+                                 mctx->bkref_ents, str_idx);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
+
+  /* Update state_log.  */
+  sctx->sifted_states[str_idx] = re_acquire_state (&err, dfa, dest_nodes);
+  if (BE (sctx->sifted_states[str_idx] == NULL && err != REG_NOERROR, 0))
+    return err;
+
+  /* If we are searching for the subexpression candidates.
+     Note that we were from transit_state_bkref_loop() in this case.  */
+  if (sctx->check_subexp)
+    {
+      err = search_subexp (preg, mctx, sctx, str_idx, dest_nodes);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
+
+  if ((mctx->state_log[str_idx] != NULL
+       && mctx->state_log[str_idx]->has_backref))
+    {
+      err = sift_states_bkref (preg, mctx, sctx, str_idx, dest_nodes);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+add_epsilon_src_nodes (dfa, dest_nodes, candidates)
+     re_dfa_t *dfa;
+     re_node_set *dest_nodes;
+     const re_node_set *candidates;
+{
+  reg_errcode_t err;
+  int src_idx;
+  re_node_set src_copy;
+
+  err = re_node_set_init_copy (&src_copy, dest_nodes);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+  for (src_idx = 0; src_idx < src_copy.nelem; ++src_idx)
+    {
+      err = re_node_set_add_intersect (dest_nodes, candidates,
+                                       dfa->inveclosures
+                                       + src_copy.elems[src_idx]);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
+  re_node_set_free (&src_copy);
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+sub_epsilon_src_nodes (dfa, node, dest_nodes, candidates)
+     re_dfa_t *dfa;
+     int node;
+     re_node_set *dest_nodes;
+     const re_node_set *candidates;
+{
+    int ecl_idx;
+    reg_errcode_t err;
+    re_node_set *inv_eclosure = dfa->inveclosures + node;
+    re_node_set except_nodes;
+    re_node_set_init_empty (&except_nodes);
+    for (ecl_idx = 0; ecl_idx < inv_eclosure->nelem; ++ecl_idx)
+      {
+        int cur_node = inv_eclosure->elems[ecl_idx];
+        if (cur_node == node)
+          continue;
+        if (dfa->edests[cur_node].nelem)
+          {
+            int edst1 = dfa->edests[cur_node].elems[0];
+            int edst2 = ((dfa->edests[cur_node].nelem > 1)
+                         ? dfa->edests[cur_node].elems[1] : -1);
+            if ((!re_node_set_contains (inv_eclosure, edst1)
+                 && re_node_set_contains (dest_nodes, edst1))
+                || (edst2 > 0
+                    && !re_node_set_contains (inv_eclosure, edst2)
+                    && re_node_set_contains (dest_nodes, edst2)))
+              {
+                err = re_node_set_add_intersect (&except_nodes, candidates,
+                                                 dfa->inveclosures + cur_node);
+                if (BE (err != REG_NOERROR, 0))
+                  return err;
+              }
+          }
+      }
+    for (ecl_idx = 0; ecl_idx < inv_eclosure->nelem; ++ecl_idx)
+      {
+        int cur_node = inv_eclosure->elems[ecl_idx];
+        if (!re_node_set_contains (&except_nodes, cur_node))
+          {
+            int idx = re_node_set_contains (dest_nodes, cur_node) - 1;
+            re_node_set_remove_at (dest_nodes, idx);
+          }
+      }
+    re_node_set_free (&except_nodes);
+    return REG_NOERROR;
+}
+
+static int
+check_dst_limits (dfa, limits, mctx, dst_node, dst_idx, src_node, src_idx)
+     re_dfa_t *dfa;
+     re_node_set *limits;
+     re_match_context_t *mctx;
+     int dst_node, dst_idx, src_node, src_idx;
+{
+  int lim_idx, src_pos, dst_pos;
+
+  for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
+    {
+      int bkref, subexp_idx/*, node_idx, cls_node*/;
+      struct re_backref_cache_entry *ent;
+      ent = mctx->bkref_ents + limits->elems[lim_idx];
+      bkref = (dfa->nodes[ent->node].type == OP_CONTEXT_NODE
+               ? dfa->nodes[ent->node].opr.ctx_info->entity : ent->node);
+      subexp_idx = dfa->nodes[bkref].opr.idx - 1;
+
+      dst_pos = check_dst_limits_calc_pos (dfa, mctx, limits->elems[lim_idx],
+                                           dfa->eclosures + dst_node,
+                                           subexp_idx, dst_node, dst_idx);
+      src_pos = check_dst_limits_calc_pos (dfa, mctx, limits->elems[lim_idx],
+                                           dfa->eclosures + src_node,
+                                           subexp_idx, src_node, src_idx);
+
+      /* In case of:
+         <src> <dst> ( <subexp> )
+         ( <subexp> ) <src> <dst>
+         ( <subexp1> <src> <subexp2> <dst> <subexp3> )  */
+      if (src_pos == dst_pos)
+        continue; /* This is unrelated limitation.  */
+      else
+        return 1;
+    }
+  return 0;
+}
+
+static int
+check_dst_limits_calc_pos (dfa, mctx, limit, eclosures, subexp_idx, node,
+                           str_idx)
+     re_dfa_t *dfa;
+     re_match_context_t *mctx;
+     re_node_set *eclosures;
+     int limit, subexp_idx, node, str_idx;
+{
+  struct re_backref_cache_entry *lim = mctx->bkref_ents + limit;
+  int pos = (str_idx < lim->subexp_from ? -1
+             : (lim->subexp_to < str_idx ? 1 : 0));
+  if (pos == 0
+      && (str_idx == lim->subexp_from || str_idx == lim->subexp_to))
+    {
+      int node_idx;
+      for (node_idx = 0; node_idx < eclosures->nelem; ++node_idx)
+        {
+          int node = eclosures->elems[node_idx];
+          int entity = node;
+          re_token_type_t type= dfa->nodes[node].type;
+          if (type == OP_CONTEXT_NODE)
+            {
+              entity = dfa->nodes[node].opr.ctx_info->entity;
+              type = dfa->nodes[entity].type;
+            }
+          if (type == OP_BACK_REF)
+            {
+              int bi;
+              for (bi = 0; bi < mctx->nbkref_ents; ++bi)
+                {
+                  struct re_backref_cache_entry *ent = mctx->bkref_ents + bi;
+                  if (ent->node == node && ent->subexp_from == ent->subexp_to
+                      && ent->str_idx == str_idx)
+                    {
+                      int cpos, dst;
+                      dst = dfa->nexts[node];
+                      cpos = check_dst_limits_calc_pos (dfa, mctx, limit,
+                                                        dfa->eclosures + dst,
+                                                        subexp_idx, dst,
+                                                        str_idx);
+                      if ((str_idx == lim->subexp_from && cpos == -1)
+                          || (str_idx == lim->subexp_to && cpos == 0))
+                        return cpos;
+                    }
+                }
+            }
+          if (type == OP_OPEN_SUBEXP && subexp_idx == dfa->nodes[node].opr.idx
+              && str_idx == lim->subexp_from)
+            {
+              pos = -1;
+              break;
+            }
+          if (type == OP_CLOSE_SUBEXP && subexp_idx == dfa->nodes[node].opr.idx
+              && str_idx == lim->subexp_to)
+            break;
+        }
+      if (node_idx == eclosures->nelem && str_idx == lim->subexp_to)
+        pos = 1;
+    }
+  return pos;
+}
+
+/* Check the limitations of sub expressions LIMITS, and remove the nodes
+   which are against limitations from DEST_NODES. */
+
+static reg_errcode_t
+check_subexp_limits (dfa, dest_nodes, candidates, limits, bkref_ents, str_idx)
+     re_dfa_t *dfa;
+     re_node_set *dest_nodes;
+     const re_node_set *candidates;
+     re_node_set *limits;
+     struct re_backref_cache_entry *bkref_ents;
+     int str_idx;
+{
+  reg_errcode_t err;
+  int node_idx, lim_idx;
+
+  for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
+    {
+      int bkref, subexp_idx;
+      struct re_backref_cache_entry *ent;
+      ent = bkref_ents + limits->elems[lim_idx];
+
+      if (str_idx <= ent->subexp_from || ent->str_idx < str_idx)
+        continue; /* This is unrelated limitation.  */
+
+      bkref = (dfa->nodes[ent->node].type == OP_CONTEXT_NODE
+               ? dfa->nodes[ent->node].opr.ctx_info->entity : ent->node);
+      subexp_idx = dfa->nodes[bkref].opr.idx - 1;
+
+      if (ent->subexp_to == str_idx)
+        {
+          int ops_node = -1;
+          int cls_node = -1;
+          for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+            {
+              int node = dest_nodes->elems[node_idx];
+              re_token_type_t type= dfa->nodes[node].type;
+              if (type == OP_OPEN_SUBEXP
+                  && subexp_idx == dfa->nodes[node].opr.idx)
+                ops_node = node;
+              else if (type == OP_CLOSE_SUBEXP
+                       && subexp_idx == dfa->nodes[node].opr.idx)
+                cls_node = node;
+            }
+
+          /* Check the limitation of the open subexpression.  */
+          /* Note that (ent->subexp_to = str_idx != ent->subexp_from).  */
+          if (ops_node >= 0)
+            {
+              err = sub_epsilon_src_nodes(dfa, ops_node, dest_nodes,
+                                          candidates);
+              if (BE (err != REG_NOERROR, 0))
+                return err;
+            }
+          /* Check the limitation of the close subexpression.  */
+          for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+            {
+              int node = dest_nodes->elems[node_idx];
+              if (!re_node_set_contains (dfa->inveclosures + node, cls_node)
+                  && !re_node_set_contains (dfa->eclosures + node, cls_node))
+                {
+                  /* It is against this limitation.
+                     Remove it form the current sifted state.  */
+                  err = sub_epsilon_src_nodes(dfa, node, dest_nodes,
+                                              candidates);
+                  if (BE (err != REG_NOERROR, 0))
+                    return err;
+                  --node_idx;
+                }
+            }
+        }
+      else /* (ent->subexp_to != str_idx)  */
+        {
+          for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+            {
+              int node = dest_nodes->elems[node_idx];
+              re_token_type_t type= dfa->nodes[node].type;
+              if (type == OP_CLOSE_SUBEXP || type == OP_OPEN_SUBEXP)
+                {
+                  if (subexp_idx != dfa->nodes[node].opr.idx)
+                    continue;
+                  if ((type == OP_CLOSE_SUBEXP && ent->subexp_to != str_idx)
+                      || (type == OP_OPEN_SUBEXP))
+                    {
+                      /* It is against this limitation.
+                         Remove it form the current sifted state.  */
+                      err = sub_epsilon_src_nodes(dfa, node, dest_nodes,
+                                                  candidates);
+                      if (BE (err != REG_NOERROR, 0))
+                        return err;
+                    }
+                }
+            }
+        }
+    }
+  return REG_NOERROR;
+}
+
+/* Search for the top (in case of sctx->check_subexp < 0) or the
+   bottom (in case of sctx->check_subexp > 0) of the subexpressions
+   which the backreference sctx->cur_bkref can match.  */
+
+static reg_errcode_t
+search_subexp (preg, mctx, sctx, str_idx, dest_nodes)
+     const regex_t *preg;
+     re_match_context_t *mctx;
+     re_sift_context_t *sctx;
+     int str_idx;
+     re_node_set *dest_nodes;
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  re_sift_context_t local_sctx;
+  int node_idx, node=0; /* gnupg */
+  const re_node_set *candidates;
+  re_dfastate_t **lim_states = NULL;
+  candidates = ((mctx->state_log[str_idx] == NULL) ? &empty_set
+                : &mctx->state_log[str_idx]->nodes);
+  local_sctx.sifted_states = NULL; /* Mark that it hasn't been initialized.  */
+
+  for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+    {
+      re_token_type_t type;
+      int entity;
+      node = dest_nodes->elems[node_idx];
+      type = dfa->nodes[node].type;
+      entity = (type != OP_CONTEXT_NODE ? node
+                : dfa->nodes[node].opr.ctx_info->entity);
+      type = (type != OP_CONTEXT_NODE ? type : dfa->nodes[entity].type);
+
+      if (type == OP_CLOSE_SUBEXP
+          && sctx->check_subexp == dfa->nodes[node].opr.idx + 1)
+        {
+          re_dfastate_t *cur_state;
+          /* Found the bottom of the subexpression, then search for the
+             top of it.  */
+          if (local_sctx.sifted_states == NULL)
+            {
+              /* It hasn't been initialized yet, initialize it now.  */
+              local_sctx = *sctx;
+              err = re_node_set_init_copy (&local_sctx.limits, &sctx->limits);
+              if (BE (err != REG_NOERROR, 0))
+                return err;
+            }
+          local_sctx.check_subexp = -sctx->check_subexp;
+          local_sctx.limited_states = sctx->limited_states;
+          local_sctx.last_node = node;
+          local_sctx.last_str_idx = local_sctx.cls_subexp_idx = str_idx;
+          cur_state = local_sctx.sifted_states[str_idx];
+          err = sift_states_backward (preg, mctx, &local_sctx);
+          local_sctx.sifted_states[str_idx] = cur_state;
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          /* There must not 2 same node in a node set.  */
+          break;
+        }
+      else if (type == OP_OPEN_SUBEXP
+               && -sctx->check_subexp == dfa->nodes[node].opr.idx + 1)
+        {
+          /* Found the top of the subexpression, check that the
+             backreference can match the input string.  */
+          char *buf;
+          int dest_str_idx;
+          int bkref_str_idx = re_string_cur_idx (mctx->input);
+          int subexp_len = sctx->cls_subexp_idx - str_idx;
+          if (subexp_len < 0 || bkref_str_idx + subexp_len > mctx->input->len)
+            break;
+
+          if (bkref_str_idx + subexp_len > mctx->input->valid_len
+              && mctx->input->valid_len < mctx->input->len)
+            {
+              reg_errcode_t err;
+              err = extend_buffers (mctx);
+              if (BE (err != REG_NOERROR, 0))
+                return err;
+            }
+          buf = (char *) re_string_get_buffer (mctx->input);
+          if (strncmp (buf + str_idx, buf + bkref_str_idx, subexp_len) != 0)
+            break;
+
+          if (sctx->limits.nelem && str_idx > 0)
+            {
+              re_dfastate_t *cur_state = sctx->sifted_states[str_idx];
+              if (lim_states == NULL)
+                {
+                  lim_states = re_malloc (re_dfastate_t *, str_idx + 1);
+                }
+              if (local_sctx.sifted_states == NULL)
+                {
+                  /* It hasn't been initialized yet, initialize it now.  */
+                  local_sctx = *sctx;
+                  if (BE (lim_states == NULL, 0))
+                    return REG_ESPACE;
+                  err = re_node_set_init_copy (&local_sctx.limits,
+                                               &sctx->limits);
+                  if (BE (err != REG_NOERROR, 0))
+                    return err;
+                }
+              local_sctx.check_subexp = 0;
+              local_sctx.last_node = node;
+              local_sctx.last_str_idx = str_idx;
+              local_sctx.limited_states = lim_states;
+              memset (lim_states, '\0',
+                      sizeof (re_dfastate_t*) * (str_idx + 1));
+              err = sift_states_backward (preg, mctx, &local_sctx);
+              if (BE (err != REG_NOERROR, 0))
+                return err;
+              if (local_sctx.sifted_states[0] == NULL
+                  && local_sctx.limited_states[0] == NULL)
+                {
+                  sctx->sifted_states[str_idx] = cur_state;
+                  break;
+                }
+              sctx->sifted_states[str_idx] = cur_state;
+            }
+          /* Successfully matched, add a new cache entry.  */
+          dest_str_idx = bkref_str_idx + subexp_len;
+          err = match_ctx_add_entry (mctx, sctx->cur_bkref, bkref_str_idx,
+                                     str_idx, sctx->cls_subexp_idx);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          err = clean_state_log_if_need (mctx, dest_str_idx);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          break;
+        }
+    }
+
+  /* Remove the top/bottom of the sub expression we processed.  */
+  if (node_idx < dest_nodes->nelem)
+    {
+      err = sub_epsilon_src_nodes(dfa, node, dest_nodes, candidates);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+      /* Update state_log.  */
+      sctx->sifted_states[str_idx] = re_acquire_state (&err, dfa, dest_nodes);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
+
+  if (local_sctx.sifted_states != NULL)
+    re_node_set_free (&local_sctx.limits);
+  if (lim_states != NULL)
+    re_free (lim_states);
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+sift_states_bkref (preg, mctx, sctx, str_idx, dest_nodes)
+     const regex_t *preg;
+     re_match_context_t *mctx;
+     re_sift_context_t *sctx;
+     int str_idx;
+     re_node_set *dest_nodes;
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  int node_idx, node;
+  re_sift_context_t local_sctx;
+  const re_node_set *candidates;
+  candidates = ((mctx->state_log[str_idx] == NULL) ? &empty_set
+                : &mctx->state_log[str_idx]->nodes);
+  local_sctx.sifted_states = NULL; /* Mark that it hasn't been initialized.  */
+
+  for (node_idx = 0; node_idx < candidates->nelem; ++node_idx)
+    {
+      int entity;
+      int cur_bkref_idx = re_string_cur_idx (mctx->input);
+      re_token_type_t type;
+      node = candidates->elems[node_idx];
+      type = dfa->nodes[node].type;
+      entity = (type != OP_CONTEXT_NODE ? node
+                : dfa->nodes[node].opr.ctx_info->entity);
+      type = (type != OP_CONTEXT_NODE ? type : dfa->nodes[entity].type);
+      if (node == sctx->cur_bkref && str_idx == cur_bkref_idx)
+        continue;
+      /* Avoid infinite loop for the REs like "()\1+".  */
+      if (node == sctx->last_node && str_idx == sctx->last_str_idx)
+        continue;
+      if (type == OP_BACK_REF)
+        {
+          int enabled_idx;
+          for (enabled_idx = 0; enabled_idx < mctx->nbkref_ents; ++enabled_idx)
+            {
+              int disabled_idx, subexp_len, to_idx;
+              struct re_backref_cache_entry *entry;
+              entry = mctx->bkref_ents + enabled_idx;
+              subexp_len = entry->subexp_to - entry->subexp_from;
+              to_idx = str_idx + subexp_len;
+
+              if (entry->node != node || entry->str_idx != str_idx
+                  || to_idx > sctx->last_str_idx
+                  || sctx->sifted_states[to_idx] == NULL)
+                continue;
+              if (!STATE_NODE_CONTAINS (sctx->sifted_states[to_idx],
+                                        dfa->nexts[node]))
+                {
+                  int dst_idx;
+                  re_node_set *dsts = &sctx->sifted_states[to_idx]->nodes;
+                  for (dst_idx = 0; dst_idx < dsts->nelem; ++dst_idx)
+                    {
+                      int dst_node = dsts->elems[dst_idx];
+                      if (dfa->nodes[dst_node].type == OP_CONTEXT_NODE
+                          && (dfa->nodes[dst_node].opr.ctx_info->entity
+                              == dfa->nexts[node]))
+                        break;
+                    }
+                  if (dst_idx == dsts->nelem)
+                    continue;
+                }
+
+              if (check_dst_limits (dfa, &sctx->limits, mctx, node,
+                                    str_idx, dfa->nexts[node], to_idx))
+                continue;
+              if (sctx->check_subexp == dfa->nodes[entity].opr.idx)
+                {
+                  char *buf;
+                  buf = (char *) re_string_get_buffer (mctx->input);
+                  if (strncmp (buf + entry->subexp_from,
+                               buf + cur_bkref_idx, subexp_len) != 0)
+                    continue;
+                  err = match_ctx_add_entry (mctx, sctx->cur_bkref,
+                                             cur_bkref_idx, entry->subexp_from,
+                                             entry->subexp_to);
+                  if (BE (err != REG_NOERROR, 0))
+                    return err;
+                  err = clean_state_log_if_need (mctx, cur_bkref_idx
+                                                 + subexp_len);
+                  if (BE (err != REG_NOERROR, 0))
+                    return err;
+                }
+              else
+                {
+                  re_dfastate_t *cur_state;
+                  entry->flag = 0;
+                  for (disabled_idx = enabled_idx + 1;
+                       disabled_idx < mctx->nbkref_ents; ++disabled_idx)
+                    {
+                      struct re_backref_cache_entry *entry2;
+                      entry2 = mctx->bkref_ents + disabled_idx;
+                      if (entry2->node != node || entry2->str_idx != str_idx)
+                        continue;
+                      entry2->flag = 1;
+                    }
+
+                  if (local_sctx.sifted_states == NULL)
+                    {
+                      local_sctx = *sctx;
+                      err = re_node_set_init_copy (&local_sctx.limits,
+                                                   &sctx->limits);
+                      if (BE (err != REG_NOERROR, 0))
+                        return err;
+                    }
+                  local_sctx.last_node = node;
+                  local_sctx.last_str_idx = str_idx;
+                  err = re_node_set_insert (&local_sctx.limits, enabled_idx);
+                  if (BE (err < 0, 0))
+                    return REG_ESPACE;
+                  cur_state = local_sctx.sifted_states[str_idx];
+                  err = sift_states_backward (preg, mctx, &local_sctx);
+                  if (BE (err != REG_NOERROR, 0))
+                    return err;
+                  if (sctx->limited_states != NULL)
+                    {
+                      err = merge_state_array (dfa, sctx->limited_states,
+                                               local_sctx.sifted_states,
+                                               str_idx + 1);
+                      if (BE (err != REG_NOERROR, 0))
+                        return err;
+                    }
+                  local_sctx.sifted_states[str_idx] = cur_state;
+                  re_node_set_remove_at (&local_sctx.limits,
+                                         local_sctx.limits.nelem - 1);
+                  entry->flag = 1;
+                }
+            }
+          for (enabled_idx = 0; enabled_idx < mctx->nbkref_ents; ++enabled_idx)
+            {
+              struct re_backref_cache_entry *entry;
+              entry = mctx->bkref_ents + enabled_idx;
+              if (entry->node == node && entry->str_idx == str_idx)
+                entry->flag = 0;
+            }
+        }
+    }
+  if (local_sctx.sifted_states != NULL)
+    {
+      re_node_set_free (&local_sctx.limits);
+    }
+
+  return REG_NOERROR;
+}
+
+
+#ifdef RE_ENABLE_I18N
+static int
+sift_states_iter_mb (preg, mctx, sctx, node_idx, str_idx, max_str_idx)
+    const regex_t *preg;
+    const re_match_context_t *mctx;
+    re_sift_context_t *sctx;
+    int node_idx, str_idx, max_str_idx;
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  int naccepted;
+  /* Check the node can accept `multi byte'.  */
+  naccepted = check_node_accept_bytes (preg, node_idx, mctx->input, str_idx);
+  if (naccepted > 0 && str_idx + naccepted <= max_str_idx &&
+      !STATE_NODE_CONTAINS (sctx->sifted_states[str_idx + naccepted],
+                            dfa->nexts[node_idx]))
+    /* The node can't accept the `multi byte', or the
+       destination was already throwed away, then the node
+       could't accept the current input `multi byte'.   */
+    naccepted = 0;
+  /* Otherwise, it is sure that the node could accept
+     `naccepted' bytes input.  */
+  return naccepted;
+}
+#endif /* RE_ENABLE_I18N */
+
+
+/* Functions for state transition.  */
+
+/* Return the next state to which the current state STATE will transit by
+   accepting the current input byte, and update STATE_LOG if necessary.
+   If STATE can accept a multibyte char/collating element/back reference
+   update the destination of STATE_LOG.  */
+
+static re_dfastate_t *
+transit_state (err, preg, mctx, state, fl_search)
+     reg_errcode_t *err;
+     const regex_t *preg;
+     re_match_context_t *mctx;
+     re_dfastate_t *state;
+     int fl_search;
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  re_dfastate_t **trtable, *next_state;
+  unsigned char ch;
+
+  if (re_string_cur_idx (mctx->input) + 1 >= mctx->input->bufs_len
+      || (re_string_cur_idx (mctx->input) + 1 >= mctx->input->valid_len
+          && mctx->input->valid_len < mctx->input->len))
+    {
+      *err = extend_buffers (mctx);
+      if (BE (*err != REG_NOERROR, 0))
+        return NULL;
+    }
+
+  *err = REG_NOERROR;
+  if (state == NULL)
+    {
+      next_state = state;
+      re_string_skip_bytes (mctx->input, 1);
+    }
+  else
+    {
+#ifdef RE_ENABLE_I18N
+      /* If the current state can accept multibyte.  */
+      if (state->accept_mb)
+        {
+          *err = transit_state_mb (preg, state, mctx);
+          if (BE (*err != REG_NOERROR, 0))
+            return NULL;
+        }
+#endif /* RE_ENABLE_I18N */
+
+      /* Then decide the next state with the single byte.  */
+      if (1)
+        {
+          /* Use transition table  */
+          ch = re_string_fetch_byte (mctx->input);
+          trtable = fl_search ? state->trtable_search : state->trtable;
+          if (trtable == NULL)
+            {
+              trtable = build_trtable (preg, state, fl_search);
+              if (fl_search)
+                state->trtable_search = trtable;
+              else
+                state->trtable = trtable;
+            }
+          next_state = trtable[ch];
+        }
+      else
+        {
+          /* don't use transition table  */
+          next_state = transit_state_sb (err, preg, state, fl_search, mctx);
+          if (BE (next_state == NULL && err != REG_NOERROR, 0))
+            return NULL;
+        }
+    }
+
+  /* Update the state_log if we need.  */
+  if (mctx->state_log != NULL)
+    {
+      int cur_idx = re_string_cur_idx (mctx->input);
+      if (cur_idx > mctx->state_log_top)
+        {
+          mctx->state_log[cur_idx] = next_state;
+          mctx->state_log_top = cur_idx;
+        }
+      else if (mctx->state_log[cur_idx] == 0)
+        {
+          mctx->state_log[cur_idx] = next_state;
+        }
+      else
+        {
+          re_dfastate_t *pstate;
+          unsigned int context;
+          re_node_set next_nodes, *log_nodes, *table_nodes = NULL;
+          /* If (state_log[cur_idx] != 0), it implies that cur_idx is
+             the destination of a multibyte char/collating element/
+             back reference.  Then the next state is the union set of
+             these destinations and the results of the transition table.  */
+          pstate = mctx->state_log[cur_idx];
+          log_nodes = pstate->entrance_nodes;
+          if (next_state != NULL)
+            {
+              table_nodes = next_state->entrance_nodes;
+              *err = re_node_set_init_union (&next_nodes, table_nodes,
+                                             log_nodes);
+              if (BE (*err != REG_NOERROR, 0))
+                return NULL;
+            }
+          else
+            next_nodes = *log_nodes;
+          /* Note: We already add the nodes of the initial state,
+                   then we don't need to add them here.  */
+
+          context = re_string_context_at (mctx->input,
+                                          re_string_cur_idx (mctx->input) - 1,
+                                          mctx->eflags, preg->newline_anchor);
+          next_state = mctx->state_log[cur_idx]
+            = re_acquire_state_context (err, dfa, &next_nodes, context);
+          /* We don't need to check errors here, since the return value of
+             this function is next_state and ERR is already set.  */
+
+          if (table_nodes != NULL)
+            re_node_set_free (&next_nodes);
+        }
+      /* If the next state has back references.  */
+      if (next_state != NULL && next_state->has_backref)
+        {
+          *err = transit_state_bkref (preg, next_state, mctx);
+          if (BE (*err != REG_NOERROR, 0))
+            return NULL;
+          next_state = mctx->state_log[cur_idx];
+        }
+    }
+  return next_state;
+}
+
+/* Helper functions for transit_state.  */
+
+/* Return the next state to which the current state STATE will transit by
+   accepting the current input byte.  */
+
+static re_dfastate_t *
+transit_state_sb (err, preg, state, fl_search, mctx)
+     reg_errcode_t *err;
+     const regex_t *preg;
+     re_dfastate_t *state;
+     int fl_search;
+     re_match_context_t *mctx;
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  re_node_set next_nodes;
+  re_dfastate_t *next_state;
+  int node_cnt, cur_str_idx = re_string_cur_idx (mctx->input);
+  unsigned int context;
+
+  *err = re_node_set_alloc (&next_nodes, state->nodes.nelem + 1);
+  if (BE (*err != REG_NOERROR, 0))
+    return NULL;
+  for (node_cnt = 0; node_cnt < state->nodes.nelem; ++node_cnt)
+    {
+      int cur_node = state->nodes.elems[node_cnt];
+      if (check_node_accept (preg, dfa->nodes + cur_node, mctx, cur_str_idx))
+        {
+          *err = re_node_set_merge (&next_nodes,
+                                    dfa->eclosures + dfa->nexts[cur_node]);
+          if (BE (*err != REG_NOERROR, 0))
+            return NULL;
+        }
+    }
+  if (fl_search)
+    {
+#ifdef RE_ENABLE_I18N
+      int not_initial = 0;
+      if (MB_CUR_MAX > 1)
+        for (node_cnt = 0; node_cnt < next_nodes.nelem; ++node_cnt)
+          if (dfa->nodes[next_nodes.elems[node_cnt]].type == CHARACTER)
+            {
+              not_initial = dfa->nodes[next_nodes.elems[node_cnt]].mb_partial;
+              break;
+            }
+      if (!not_initial)
+#endif
+        {
+          *err = re_node_set_merge (&next_nodes,
+                                    dfa->init_state->entrance_nodes);
+          if (BE (*err != REG_NOERROR, 0))
+            return NULL;
+        }
+    }
+  context = re_string_context_at (mctx->input, cur_str_idx, mctx->eflags,
+                                  preg->newline_anchor);
+  next_state = re_acquire_state_context (err, dfa, &next_nodes, context);
+  /* We don't need to check errors here, since the return value of
+     this function is next_state and ERR is already set.  */
+
+  re_node_set_free (&next_nodes);
+  re_string_skip_bytes (mctx->input, 1);
+  return next_state;
+}
+
+#ifdef RE_ENABLE_I18N
+static reg_errcode_t
+transit_state_mb (preg, pstate, mctx)
+    const regex_t *preg;
+    re_dfastate_t *pstate;
+    re_match_context_t *mctx;
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  int i;
+
+  for (i = 0; i < pstate->nodes.nelem; ++i)
+    {
+      re_node_set dest_nodes, *new_nodes;
+      int cur_node_idx = pstate->nodes.elems[i];
+      int naccepted = 0, dest_idx;
+      unsigned int context;
+      re_dfastate_t *dest_state;
+
+      if (dfa->nodes[cur_node_idx].type == OP_CONTEXT_NODE)
+        {
+          context = re_string_context_at (mctx->input,
+                                          re_string_cur_idx (mctx->input),
+                                          mctx->eflags, preg->newline_anchor);
+          if (NOT_SATISFY_NEXT_CONSTRAINT (dfa->nodes[cur_node_idx].constraint,
+                                        context))
+            continue;
+          cur_node_idx = dfa->nodes[cur_node_idx].opr.ctx_info->entity;
+        }
+
+      /* How many bytes the node can accepts?  */
+      if (ACCEPT_MB_NODE (dfa->nodes[cur_node_idx].type))
+        naccepted = check_node_accept_bytes (preg, cur_node_idx, mctx->input,
+                                             re_string_cur_idx (mctx->input));
+      if (naccepted == 0)
+        continue;
+
+      /* The node can accepts `naccepted' bytes.  */
+      dest_idx = re_string_cur_idx (mctx->input) + naccepted;
+      mctx->max_mb_elem_len = ((mctx->max_mb_elem_len < naccepted) ? naccepted
+                               : mctx->max_mb_elem_len);
+      err = clean_state_log_if_need (mctx, dest_idx);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+#ifdef DEBUG
+      assert (dfa->nexts[cur_node_idx] != -1);
+#endif
+      /* `cur_node_idx' may point the entity of the OP_CONTEXT_NODE,
+         then we use pstate->nodes.elems[i] instead.  */
+      new_nodes = dfa->eclosures + dfa->nexts[pstate->nodes.elems[i]];
+
+      dest_state = mctx->state_log[dest_idx];
+      if (dest_state == NULL)
+        dest_nodes = *new_nodes;
+      else
+        {
+          err = re_node_set_init_union (&dest_nodes,
+                                        dest_state->entrance_nodes, new_nodes);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+        }
+      context = re_string_context_at (mctx->input, dest_idx - 1, mctx->eflags,
+                                      preg->newline_anchor);
+      mctx->state_log[dest_idx]
+        = re_acquire_state_context (&err, dfa, &dest_nodes, context);
+      if (BE (mctx->state_log[dest_idx] == NULL && err != REG_NOERROR, 0))
+        return err;
+      if (dest_state != NULL)
+        re_node_set_free (&dest_nodes);
+    }
+  return REG_NOERROR;
+}
+#endif /* RE_ENABLE_I18N */
+
+static reg_errcode_t
+transit_state_bkref (preg, pstate, mctx)
+    const regex_t *preg;
+    re_dfastate_t *pstate;
+    re_match_context_t *mctx;
+{
+  reg_errcode_t err;
+  re_dfastate_t **work_state_log;
+
+  work_state_log = re_malloc (re_dfastate_t *,
+                              re_string_cur_idx (mctx->input) + 1);
+  if (BE (work_state_log == NULL, 0))
+    return REG_ESPACE;
+
+  err = transit_state_bkref_loop (preg, &pstate->nodes, work_state_log, mctx);
+  re_free (work_state_log);
+  return err;
+}
+
+/* Caller must allocate `work_state_log'.  */
+
+static reg_errcode_t
+transit_state_bkref_loop (preg, nodes, work_state_log, mctx)
+    const regex_t *preg;
+    re_node_set *nodes;
+    re_dfastate_t **work_state_log;
+    re_match_context_t *mctx;
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  int i;
+  regmatch_t *cur_regs = re_malloc (regmatch_t, preg->re_nsub + 1);
+  int cur_str_idx = re_string_cur_idx (mctx->input);
+  if (BE (cur_regs == NULL, 0))
+    return REG_ESPACE;
+
+  for (i = 0; i < nodes->nelem; ++i)
+    {
+      int dest_str_idx, subexp_idx, prev_nelem, bkc_idx;
+      int node_idx = nodes->elems[i];
+      unsigned int context;
+      re_token_t *node = dfa->nodes + node_idx;
+      re_node_set *new_dest_nodes;
+      re_sift_context_t sctx;
+
+      /* Check whether `node' is a backreference or not.  */
+      if (node->type == OP_BACK_REF)
+        subexp_idx = node->opr.idx;
+      else if (node->type == OP_CONTEXT_NODE &&
+               dfa->nodes[node->opr.ctx_info->entity].type == OP_BACK_REF)
+        {
+          context = re_string_context_at (mctx->input, cur_str_idx,
+                                          mctx->eflags, preg->newline_anchor);
+          if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
+            continue;
+          subexp_idx = dfa->nodes[node->opr.ctx_info->entity].opr.idx;
+        }
+      else
+        continue;
+
+      /* `node' is a backreference.
+         Check the substring which the substring matched.  */
+      sift_ctx_init (&sctx, work_state_log, NULL, node_idx, cur_str_idx,
+                     subexp_idx);
+      sctx.cur_bkref = node_idx;
+      match_ctx_clear_flag (mctx);
+      err = sift_states_backward (preg, mctx, &sctx);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+
+      /* And add the epsilon closures (which is `new_dest_nodes') of
+         the backreference to appropriate state_log.  */
+#ifdef DEBUG
+      assert (dfa->nexts[node_idx] != -1);
+#endif
+      for (bkc_idx = 0; bkc_idx < mctx->nbkref_ents; ++bkc_idx)
+        {
+          int subexp_len;
+          re_dfastate_t *dest_state;
+          struct re_backref_cache_entry *bkref_ent;
+          bkref_ent = mctx->bkref_ents + bkc_idx;
+          if (bkref_ent->node != node_idx || bkref_ent->str_idx != cur_str_idx)
+            continue;
+          subexp_len = bkref_ent->subexp_to - bkref_ent->subexp_from;
+          new_dest_nodes = ((node->type == OP_CONTEXT_NODE && subexp_len == 0)
+                            ? dfa->nodes[node_idx].opr.ctx_info->bkref_eclosure
+                            : dfa->eclosures + dfa->nexts[node_idx]);
+          dest_str_idx = (cur_str_idx + bkref_ent->subexp_to
+                          - bkref_ent->subexp_from);
+          context = (IS_WORD_CHAR (re_string_byte_at (mctx->input,
+                                                      dest_str_idx - 1))
+                     ? CONTEXT_WORD : 0);
+          dest_state = mctx->state_log[dest_str_idx];
+          prev_nelem = ((mctx->state_log[cur_str_idx] == NULL) ? 0
+                        : mctx->state_log[cur_str_idx]->nodes.nelem);
+          /* Add `new_dest_node' to state_log.  */
+          if (dest_state == NULL)
+            {
+              mctx->state_log[dest_str_idx]
+                = re_acquire_state_context (&err, dfa, new_dest_nodes,
+                                            context);
+              if (BE (mctx->state_log[dest_str_idx] == NULL
+                      && err != REG_NOERROR, 0))
+                return err;
+            }
+          else
+            {
+              re_node_set dest_nodes;
+              err = re_node_set_init_union (&dest_nodes,
+                                            dest_state->entrance_nodes,
+                                            new_dest_nodes);
+              if (BE (err != REG_NOERROR, 0))
+                return err;
+              mctx->state_log[dest_str_idx]
+                = re_acquire_state_context (&err, dfa, &dest_nodes, context);
+              if (BE (mctx->state_log[dest_str_idx] == NULL
+                      && err != REG_NOERROR, 0))
+                return err;
+              re_node_set_free (&dest_nodes);
+            }
+          /* We need to check recursively if the backreference can epsilon
+             transit.  */
+          if (subexp_len == 0
+              && mctx->state_log[cur_str_idx]->nodes.nelem > prev_nelem)
+            {
+              err = transit_state_bkref_loop (preg, new_dest_nodes,
+                                              work_state_log, mctx);
+              if (BE (err != REG_NOERROR, 0))
+                return err;
+            }
+        }
+    }
+  re_free (cur_regs);
+  return REG_NOERROR;
+}
+
+/* Build transition table for the state.
+   Return the new table if succeeded, otherwise return NULL.  */
+
+static re_dfastate_t **
+build_trtable (preg, state, fl_search)
+    const regex_t *preg;
+    const re_dfastate_t *state;
+    int fl_search;
+{
+  reg_errcode_t err;
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  int i, j, k, ch;
+  int ndests; /* Number of the destination states from `state'.  */
+  re_dfastate_t **trtable, **dest_states, **dest_states_word, **dest_states_nl;
+  re_node_set follows, *dests_node;
+  bitset *dests_ch;
+  bitset acceptable;
+
+  /* We build DFA states which corresponds to the destination nodes
+     from `state'.  `dests_node[i]' represents the nodes which i-th
+     destination state contains, and `dests_ch[i]' represents the
+     characters which i-th destination state accepts.  */
+  dests_node = re_malloc (re_node_set, SBC_MAX);
+  dests_ch = re_malloc (bitset, SBC_MAX);
+
+  /* Initialize transiton table.  */
+  trtable = (re_dfastate_t **) calloc (sizeof (re_dfastate_t *), SBC_MAX);
+  if (BE (dests_node == NULL || dests_ch == NULL || trtable == NULL, 0))
+    return NULL;
+
+  /* At first, group all nodes belonging to `state' into several
+     destinations.  */
+  ndests = group_nodes_into_DFAstates (preg, state, dests_node, dests_ch);
+  if (BE (ndests <= 0, 0))
+    {
+      re_free (dests_node);
+      re_free (dests_ch);
+      /* Return NULL in case of an error, trtable otherwise.  */
+      return (ndests < 0) ? NULL : trtable;
+    }
+
+  dest_states = re_malloc (re_dfastate_t *, ndests);
+  dest_states_word = re_malloc (re_dfastate_t *, ndests);
+  dest_states_nl = re_malloc (re_dfastate_t *, ndests);
+  bitset_empty (acceptable);
+
+  err = re_node_set_alloc (&follows, ndests + 1);
+  if (BE (dest_states == NULL || dest_states_word == NULL
+          || dest_states_nl == NULL || err != REG_NOERROR, 0))
+    return NULL;
+
+  /* Then build the states for all destinations.  */
+  for (i = 0; i < ndests; ++i)
+    {
+      int next_node;
+      re_node_set_empty (&follows);
+      /* Merge the follows of this destination states.  */
+      for (j = 0; j < dests_node[i].nelem; ++j)
+        {
+          next_node = dfa->nexts[dests_node[i].elems[j]];
+          if (next_node != -1)
+            {
+              err = re_node_set_merge (&follows, dfa->eclosures + next_node);
+              if (BE (err != REG_NOERROR, 0))
+                return NULL;
+            }
+        }
+      /* If search flag is set, merge the initial state.  */
+      if (fl_search)
+        {
+#ifdef RE_ENABLE_I18N
+          int not_initial = 0;
+          for (j = 0; j < follows.nelem; ++j)
+            if (dfa->nodes[follows.elems[j]].type == CHARACTER)
+              {
+                not_initial = dfa->nodes[follows.elems[j]].mb_partial;
+                break;
+              }
+          if (!not_initial)
+#endif
+            {
+              err = re_node_set_merge (&follows,
+                                       dfa->init_state->entrance_nodes);
+              if (BE (err != REG_NOERROR, 0))
+                return NULL;
+            }
+        }
+      dest_states[i] = re_acquire_state_context (&err, dfa, &follows, 0);
+      if (BE (dest_states[i] == NULL && err != REG_NOERROR, 0))
+        return NULL;
+      /* If the new state has context constraint,
+         build appropriate states for these contexts.  */
+      if (dest_states[i]->has_constraint)
+        {
+          dest_states_word[i] = re_acquire_state_context (&err, dfa, &follows,
+                                                          CONTEXT_WORD);
+          if (BE (dest_states_word[i] == NULL && err != REG_NOERROR, 0))
+            return NULL;
+          dest_states_nl[i] = re_acquire_state_context (&err, dfa, &follows,
+                                                        CONTEXT_NEWLINE);
+          if (BE (dest_states_nl[i] == NULL && err != REG_NOERROR, 0))
+            return NULL;
+        }
+      else
+        {
+          dest_states_word[i] = dest_states[i];
+          dest_states_nl[i] = dest_states[i];
+        }
+      bitset_merge (acceptable, dests_ch[i]);
+    }
+
+  /* Update the transition table.  */
+  /* For all characters ch...:  */
+  for (i = 0, ch = 0; i < BITSET_UINTS; ++i)
+    for (j = 0; j < UINT_BITS; ++j, ++ch)
+      if ((acceptable[i] >> j) & 1)
+        {
+          /* The current state accepts the character ch.  */
+          if (IS_WORD_CHAR (ch))
+            {
+              for (k = 0; k < ndests; ++k)
+                if ((dests_ch[k][i] >> j) & 1)
+                  {
+                    /* k-th destination accepts the word character ch.  */
+                    trtable[ch] = dest_states_word[k];
+                    /* There must be only one destination which accepts
+                       character ch.  See group_nodes_into_DFAstates.  */
+                    break;
+                  }
+            }
+          else /* not WORD_CHAR */
+            {
+              for (k = 0; k < ndests; ++k)
+                if ((dests_ch[k][i] >> j) & 1)
+                  {
+                    /* k-th destination accepts the non-word character ch.  */
+                    trtable[ch] = dest_states[k];
+                    /* There must be only one destination which accepts
+                       character ch.  See group_nodes_into_DFAstates.  */
+                    break;
+                  }
+            }
+        }
+  /* new line */
+  if (bitset_contain (acceptable, NEWLINE_CHAR))
+    {
+      /* The current state accepts newline character.  */
+      for (k = 0; k < ndests; ++k)
+        if (bitset_contain (dests_ch[k], NEWLINE_CHAR))
+          {
+            /* k-th destination accepts newline character.  */
+            trtable[NEWLINE_CHAR] = dest_states_nl[k];
+            /* There must be only one destination which accepts
+               newline.  See group_nodes_into_DFAstates.  */
+            break;
+          }
+    }
+
+  re_free (dest_states_nl);
+  re_free (dest_states_word);
+  re_free (dest_states);
+
+  re_node_set_free (&follows);
+  for (i = 0; i < ndests; ++i)
+    re_node_set_free (dests_node + i);
+
+  re_free (dests_ch);
+  re_free (dests_node);
+
+  return trtable;
+}
+
+/* Group all nodes belonging to STATE into several destinations.
+   Then for all destinations, set the nodes belonging to the destination
+   to DESTS_NODE[i] and set the characters accepted by the destination
+   to DEST_CH[i].  This function return the number of destinations.  */
+
+static int
+group_nodes_into_DFAstates (preg, state, dests_node, dests_ch)
+    const regex_t *preg;
+    const re_dfastate_t *state;
+    re_node_set *dests_node;
+    bitset *dests_ch;
+{
+  reg_errcode_t err;
+  const re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  int i, j, k;
+  int ndests; /* Number of the destinations from `state'.  */
+  bitset accepts; /* Characters a node can accept.  */
+  const re_node_set *cur_nodes = &state->nodes;
+  bitset_empty (accepts);
+  ndests = 0;
+
+  /* For all the nodes belonging to `state',  */
+  for (i = 0; i < cur_nodes->nelem; ++i)
+    {
+      unsigned int constraint = 0;
+      re_token_t *node = &dfa->nodes[cur_nodes->elems[i]];
+      re_token_type_t type = node->type;
+
+      if (type == OP_CONTEXT_NODE)
+        {
+          constraint = node->constraint;
+          node = dfa->nodes + node->opr.ctx_info->entity;
+          type = node->type;
+        }
+
+      /* Enumerate all single byte character this node can accept.  */
+      if (type == CHARACTER)
+        bitset_set (accepts, node->opr.c);
+      else if (type == SIMPLE_BRACKET)
+        {
+          bitset_merge (accepts, node->opr.sbcset);
+        }
+      else if (type == OP_PERIOD)
+        {
+          bitset_set_all (accepts);
+          if (!(preg->syntax & RE_DOT_NEWLINE))
+            bitset_clear (accepts, '\n');
+          if (preg->syntax & RE_DOT_NOT_NULL)
+            bitset_clear (accepts, '\0');
+        }
+      else
+        continue;
+
+      /* Check the `accepts' and sift the characters which are not
+         match it the context.  */
+      if (constraint)
+        {
+          if (constraint & NEXT_WORD_CONSTRAINT)
+            for (j = 0; j < BITSET_UINTS; ++j)
+              accepts[j] &= dfa->word_char[j];
+          else if (constraint & NEXT_NOTWORD_CONSTRAINT)
+            for (j = 0; j < BITSET_UINTS; ++j)
+              accepts[j] &= ~dfa->word_char[j];
+          else if (constraint & NEXT_NEWLINE_CONSTRAINT)
+            {
+              int accepts_newline = bitset_contain (accepts, NEWLINE_CHAR);
+              bitset_empty (accepts);
+              if (accepts_newline)
+                bitset_set (accepts, NEWLINE_CHAR);
+              else
+                continue;
+            }
+        }
+
+      /* Then divide `accepts' into DFA states, or create a new
+         state.  */
+      for (j = 0; j < ndests; ++j)
+        {
+          bitset intersec; /* Intersection sets, see below.  */
+          bitset remains;
+          /* Flags, see below.  */
+          int has_intersec, not_subset, not_consumed;
+
+          /* Optimization, skip if this state doesn't accept the character.  */
+          if (type == CHARACTER && !bitset_contain (dests_ch[j], node->opr.c))
+            continue;
+
+          /* Enumerate the intersection set of this state and `accepts'.  */
+          has_intersec = 0;
+          for (k = 0; k < BITSET_UINTS; ++k)
+            has_intersec |= intersec[k] = accepts[k] & dests_ch[j][k];
+          /* And skip if the intersection set is empty.  */
+          if (!has_intersec)
+            continue;
+
+          /* Then check if this state is a subset of `accepts'.  */
+          not_subset = not_consumed = 0;
+          for (k = 0; k < BITSET_UINTS; ++k)
+            {
+              not_subset |= remains[k] = ~accepts[k] & dests_ch[j][k];
+              not_consumed |= accepts[k] = accepts[k] & ~dests_ch[j][k];
+            }
+
+          /* If this state isn't a subset of `accepts', create a
+             new group state, which has the `remains'. */
+          if (not_subset)
+            {
+              bitset_copy (dests_ch[ndests], remains);
+              bitset_copy (dests_ch[j], intersec);
+              err = re_node_set_init_copy (dests_node + ndests, &dests_node[j]);
+              if (BE (err != REG_NOERROR, 0))
+                return -1;
+              ++ndests;
+            }
+
+          /* Put the position in the current group. */
+          err = re_node_set_insert (&dests_node[j], cur_nodes->elems[i]);
+          if (BE (err < 0, 0))
+            return -1;
+
+          /* If all characters are consumed, go to next node. */
+          if (!not_consumed)
+            break;
+        }
+      /* Some characters remain, create a new group. */
+      if (j == ndests)
+        {
+          bitset_copy (dests_ch[ndests], accepts);
+          err = re_node_set_init_1 (dests_node + ndests, cur_nodes->elems[i]);
+          if (BE (err != REG_NOERROR, 0))
+            return -1;
+          ++ndests;
+          bitset_empty (accepts);
+        }
+    }
+  return ndests;
+}
+
+#ifdef RE_ENABLE_I18N
+/* Check how many bytes the node `dfa->nodes[node_idx]' accepts.
+   Return the number of the bytes the node accepts.
+   STR_IDX is the current index of the input string.
+
+   This function handles the nodes which can accept one character, or
+   one collating element like '.', '[a-z]', opposite to the other nodes
+   can only accept one byte.  */
+
+static int
+check_node_accept_bytes (preg, node_idx, input, str_idx)
+    const regex_t *preg;
+    int node_idx, str_idx;
+    const re_string_t *input;
+{
+  const re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  const re_token_t *node = dfa->nodes + node_idx;
+  int elem_len = re_string_elem_size_at (input, str_idx);
+  int char_len = re_string_char_size_at (input, str_idx);
+  int i;
+# ifdef _LIBC
+  int j;
+  uint32_t nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
+# endif /* _LIBC */
+  if (elem_len <= 1 && char_len <= 1)
+    return 0;
+  if (node->type == OP_PERIOD)
+    {
+      /* '.' accepts any one character except the following two cases.  */
+      if ((!(preg->syntax & RE_DOT_NEWLINE) &&
+           re_string_byte_at (input, str_idx) == '\n') ||
+          ((preg->syntax & RE_DOT_NOT_NULL) &&
+           re_string_byte_at (input, str_idx) == '\0'))
+        return 0;
+      return char_len;
+    }
+  else if (node->type == COMPLEX_BRACKET)
+    {
+      const re_charset_t *cset = node->opr.mbcset;
+# ifdef _LIBC
+      const unsigned char *pin = re_string_get_buffer (input) + str_idx;
+# endif /* _LIBC */
+      int match_len = 0;
+      wchar_t wc = ((cset->nranges || cset->nchar_classes || cset->nmbchars)
+                    ? re_string_wchar_at (input, str_idx) : 0);
+
+      /* match with multibyte character?  */
+      for (i = 0; i < cset->nmbchars; ++i)
+        if (wc == cset->mbchars[i])
+          {
+            match_len = char_len;
+            goto check_node_accept_bytes_match;
+          }
+      /* match with character_class?  */
+      for (i = 0; i < cset->nchar_classes; ++i)
+        {
+          wctype_t wt = cset->char_classes[i];
+          if (__iswctype (wc, wt))
+            {
+              match_len = char_len;
+              goto check_node_accept_bytes_match;
+            }
+        }
+
+# ifdef _LIBC
+      if (nrules != 0)
+        {
+          unsigned int in_collseq = 0;
+          const int32_t *table, *indirect;
+          const unsigned char *weights, *extra;
+          const char *collseqwc;
+          int32_t idx;
+          /* This #include defines a local function!  */
+#  include <locale/weight.h>
+
+          /* match with collating_symbol?  */
+          if (cset->ncoll_syms)
+            extra = (const unsigned char *)
+              _NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB);
+          for (i = 0; i < cset->ncoll_syms; ++i)
+            {
+              const unsigned char *coll_sym = extra + cset->coll_syms[i];
+              /* Compare the length of input collating element and
+                 the length of current collating element.  */
+              if (*coll_sym != elem_len)
+                continue;
+              /* Compare each bytes.  */
+              for (j = 0; j < *coll_sym; j++)
+                if (pin[j] != coll_sym[1 + j])
+                  break;
+              if (j == *coll_sym)
+                {
+                  /* Match if every bytes is equal.  */
+                  match_len = j;
+                  goto check_node_accept_bytes_match;
+                }
+            }
+
+          if (cset->nranges)
+            {
+              if (elem_len <= char_len)
+                {
+                  collseqwc = _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQWC);
+                  in_collseq = collseq_table_lookup (collseqwc, wc);
+                }
+              else
+                in_collseq = find_collation_sequence_value (pin, elem_len);
+            }
+          /* match with range expression?  */
+          for (i = 0; i < cset->nranges; ++i)
+            if (cset->range_starts[i] <= in_collseq
+                && in_collseq <= cset->range_ends[i])
+              {
+                match_len = elem_len;
+                goto check_node_accept_bytes_match;
+              }
+
+          /* match with equivalence_class?  */
+          if (cset->nequiv_classes)
+            {
+              const unsigned char *cp = pin;
+              table = (const int32_t *)
+                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_TABLEMB);
+              weights = (const unsigned char *)
+                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_WEIGHTMB);
+              extra = (const unsigned char *)
+                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_EXTRAMB);
+              indirect = (const int32_t *)
+                _NL_CURRENT (LC_COLLATE, _NL_COLLATE_INDIRECTMB);
+              idx = findidx (&cp);
+              if (idx > 0)
+                for (i = 0; i < cset->nequiv_classes; ++i)
+                  {
+                    int32_t equiv_class_idx = cset->equiv_classes[i];
+                    size_t weight_len = weights[idx];
+                    if (weight_len == weights[equiv_class_idx])
+                      {
+                        int cnt = 0;
+                        while (cnt <= weight_len
+                               && (weights[equiv_class_idx + 1 + cnt]
+                                   == weights[idx + 1 + cnt]))
+                          ++cnt;
+                        if (cnt > weight_len)
+                          {
+                            match_len = elem_len;
+                            goto check_node_accept_bytes_match;
+                          }
+                      }
+                  }
+            }
+        }
+      else
+# endif /* _LIBC */
+        {
+          /* match with range expression?  */
+#if __GNUC__ >= 2
+          wchar_t cmp_buf[] = {L'\0', L'\0', wc, L'\0', L'\0', L'\0'};
+#else
+          wchar_t cmp_buf[] = {L'\0', L'\0', L'\0', L'\0', L'\0', L'\0'};
+          cmp_buf[2] = wc;
+#endif
+          for (i = 0; i < cset->nranges; ++i)
+            {
+              cmp_buf[0] = cset->range_starts[i];
+              cmp_buf[4] = cset->range_ends[i];
+              if (wcscoll (cmp_buf, cmp_buf + 2) <= 0
+                  && wcscoll (cmp_buf + 2, cmp_buf + 4) <= 0)
+                {
+                  match_len = char_len;
+                  goto check_node_accept_bytes_match;
+                }
+            }
+        }
+    check_node_accept_bytes_match:
+      if (!cset->non_match)
+        return match_len;
+      else
+        {
+          if (match_len > 0)
+            return 0;
+          else
+            return (elem_len > char_len) ? elem_len : char_len;
+        }
+    }
+  return 0;
+}
+
+# ifdef _LIBC
+static unsigned int
+find_collation_sequence_value (mbs, mbs_len)
+    const unsigned char *mbs;
+    size_t mbs_len;
+{
+  uint32_t nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
+  if (nrules == 0)
+    {
+      if (mbs_len == 1)
+        {
+          /* No valid character.  Match it as a single byte character.  */
+          const unsigned char *collseq = (const unsigned char *)
+            _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQMB);
+          return collseq[mbs[0]];
+        }
+      return UINT_MAX;
+    }
+  else
+    {
+      int32_t idx;
+      const unsigned char *extra = (const unsigned char *)
+        _NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB);
+
+      for (idx = 0; ;)
+        {
+          int mbs_cnt, found = 0;
+          int32_t elem_mbs_len;
+          /* Skip the name of collating element name.  */
+          idx = idx + extra[idx] + 1;
+          elem_mbs_len = extra[idx++];
+          if (mbs_len == elem_mbs_len)
+            {
+              for (mbs_cnt = 0; mbs_cnt < elem_mbs_len; ++mbs_cnt)
+                if (extra[idx + mbs_cnt] != mbs[mbs_cnt])
+                  break;
+              if (mbs_cnt == elem_mbs_len)
+                /* Found the entry.  */
+                found = 1;
+            }
+          /* Skip the byte sequence of the collating element.  */
+          idx += elem_mbs_len;
+          /* Adjust for the alignment.  */
+          idx = (idx + 3) & ~3;
+          /* Skip the collation sequence value.  */
+          idx += sizeof (uint32_t);
+          /* Skip the wide char sequence of the collating element.  */
+          idx = idx + sizeof (uint32_t) * (extra[idx] + 1);
+          /* If we found the entry, return the sequence value.  */
+          if (found)
+            return *(uint32_t *) (extra + idx);
+          /* Skip the collation sequence value.  */
+          idx += sizeof (uint32_t);
+        }
+    }
+}
+# endif /* _LIBC */
+#endif /* RE_ENABLE_I18N */
+
+/* Check whether the node accepts the byte which is IDX-th
+   byte of the INPUT.  */
+
+static int
+check_node_accept (preg, node, mctx, idx)
+    const regex_t *preg;
+    const re_token_t *node;
+    const re_match_context_t *mctx;
+    int idx;
+{
+  const re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  const re_token_t *cur_node;
+  unsigned char ch;
+  if (node->type == OP_CONTEXT_NODE)
+    {
+      /* The node has constraints.  Check whether the current context
+         satisfies the constraints.  */
+      unsigned int context = re_string_context_at (mctx->input, idx,
+                                                   mctx->eflags,
+                                                   preg->newline_anchor);
+      if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
+        return 0;
+      cur_node = dfa->nodes + node->opr.ctx_info->entity;
+    }
+  else
+    cur_node = node;
+
+  ch = re_string_byte_at (mctx->input, idx);
+  if (cur_node->type == CHARACTER)
+    return cur_node->opr.c == ch;
+  else if (cur_node->type == SIMPLE_BRACKET)
+    return bitset_contain (cur_node->opr.sbcset, ch);
+  else if (cur_node->type == OP_PERIOD)
+    return !((ch == '\n' && !(preg->syntax & RE_DOT_NEWLINE))
+             || (ch == '\0' && (preg->syntax & RE_DOT_NOT_NULL)));
+  else
+    return 0;
+}
+
+/* Extend the buffers, if the buffers have run out.  */
+
+static reg_errcode_t
+extend_buffers (mctx)
+     re_match_context_t *mctx;
+{
+  reg_errcode_t ret;
+  re_string_t *pstr = mctx->input;
+
+  /* Double the lengthes of the buffers.  */
+  ret = re_string_realloc_buffers (pstr, pstr->bufs_len * 2);
+  if (BE (ret != REG_NOERROR, 0))
+    return ret;
+
+  if (mctx->state_log != NULL)
+    {
+      /* And double the length of state_log.  */
+      mctx->state_log = re_realloc (mctx->state_log, re_dfastate_t *,
+                                    pstr->bufs_len * 2);
+      if (BE (mctx->state_log == NULL, 0))
+        return REG_ESPACE;
+    }
+
+  /* Then reconstruct the buffers.  */
+  if (pstr->icase)
+    {
+#ifdef RE_ENABLE_I18N
+      if (MB_CUR_MAX > 1)
+        build_wcs_upper_buffer (pstr);
+      else
+#endif /* RE_ENABLE_I18N  */
+        build_upper_buffer (pstr);
+    }
+  else
+    {
+#ifdef RE_ENABLE_I18N
+      if (MB_CUR_MAX > 1)
+        build_wcs_buffer (pstr);
+      else
+#endif /* RE_ENABLE_I18N  */
+        {
+          if (pstr->trans != NULL)
+            re_string_translate_buffer (pstr);
+          else
+            pstr->valid_len = pstr->bufs_len;
+        }
+    }
+  return REG_NOERROR;
+}
+
+
+/* Functions for matching context.  */
+
+static reg_errcode_t
+match_ctx_init (mctx, eflags, input, n)
+    re_match_context_t *mctx;
+    int eflags, n;
+    re_string_t *input;
+{
+  mctx->eflags = eflags;
+  mctx->input = input;
+  mctx->match_last = -1;
+  if (n > 0)
+    {
+      mctx->bkref_ents = re_malloc (struct re_backref_cache_entry, n);
+      if (BE (mctx->bkref_ents == NULL, 0))
+        return REG_ESPACE;
+    }
+  else
+    mctx->bkref_ents = NULL;
+  mctx->nbkref_ents = 0;
+  mctx->abkref_ents = n;
+  mctx->max_mb_elem_len = 0;
+  return REG_NOERROR;
+}
+
+static void
+match_ctx_free (mctx)
+    re_match_context_t *mctx;
+{
+  re_free (mctx->bkref_ents);
+}
+
+/* Add a new backreference entry to the cache.  */
+
+static reg_errcode_t
+match_ctx_add_entry (mctx, node, str_idx, from, to)
+    re_match_context_t *mctx;
+    int node, str_idx, from, to;
+{
+  if (mctx->nbkref_ents >= mctx->abkref_ents)
+    {
+      mctx->bkref_ents = re_realloc (mctx->bkref_ents,
+                                     struct re_backref_cache_entry,
+                                     mctx->abkref_ents * 2);
+      if (BE (mctx->bkref_ents == NULL, 0))
+        return REG_ESPACE;
+      memset (mctx->bkref_ents + mctx->nbkref_ents, '\0',
+             sizeof (struct re_backref_cache_entry) * mctx->abkref_ents);
+      mctx->abkref_ents *= 2;
+    }
+  mctx->bkref_ents[mctx->nbkref_ents].node = node;
+  mctx->bkref_ents[mctx->nbkref_ents].str_idx = str_idx;
+  mctx->bkref_ents[mctx->nbkref_ents].subexp_from = from;
+  mctx->bkref_ents[mctx->nbkref_ents].subexp_to = to;
+  mctx->bkref_ents[mctx->nbkref_ents++].flag = 0;
+  if (mctx->max_mb_elem_len < to - from)
+    mctx->max_mb_elem_len = to - from;
+  return REG_NOERROR;
+}
+
+static void
+match_ctx_clear_flag (mctx)
+     re_match_context_t *mctx;
+{
+  int i;
+  for (i = 0; i < mctx->nbkref_ents; ++i)
+    {
+      mctx->bkref_ents[i].flag = 0;
+    }
+}
+
+static void
+sift_ctx_init (sctx, sifted_sts, limited_sts, last_node, last_str_idx,
+               check_subexp)
+    re_sift_context_t *sctx;
+    re_dfastate_t **sifted_sts, **limited_sts;
+    int last_node, last_str_idx, check_subexp;
+{
+  sctx->sifted_states = sifted_sts;
+  sctx->limited_states = limited_sts;
+  sctx->last_node = last_node;
+  sctx->last_str_idx = last_str_idx;
+  sctx->check_subexp = check_subexp;
+  re_node_set_init_empty (&sctx->limits);
+}