moving functions for testing and evaluation and experiments to the test library, minimizing the internal library, renaming files according to which library they belong to

1 files changed, 3485 insertions, 0 deletions

diff --git a/src/regex/regex_internal.c b/src/regex/regex_internal.c
new file mode 100644
index 000000000..e66835134
--- /dev/null
+++ b/src/regex/regex_internal.c
@@ -0,0 +1,3485 @@
+/*
+     This file is part of GNUnet
+     (C) 2012 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet 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
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+/**
+ * @file src/regex/regex_internal.c
+ * @brief library to create Deterministic Finite Automatons (DFAs) from regular
+ * expressions (regexes).
+ * @author Maximilian Szengel
+ */
+#include "platform.h"
+#include "gnunet_util_lib.h"
+#include "gnunet_regex_service.h"
+#include "regex_internal_lib.h"
+#include "regex_internal.h"
+
+
+/**
+ * Set this to GNUNET_YES to enable state naming. Used to debug NFA->DFA
+ * creation. Disabled by default for better performance.
+ */
+#define REGEX_DEBUG_DFA GNUNET_NO
+
+/**
+ * Set of states using MDLL API.
+ */
+struct REGEX_ITERNAL_StateSet_MDLL
+{
+  /**
+   * MDLL of states.
+   */
+  struct REGEX_ITERNAL_State *head;
+
+  /**
+   * MDLL of states.
+   */
+  struct REGEX_ITERNAL_State *tail;
+
+  /**
+   * Length of the MDLL.
+   */
+  unsigned int len;
+};
+
+
+/**
+ * Append state to the given StateSet '
+ *
+ * @param set set to be modified
+ * @param state state to be appended
+ */
+static void
+state_set_append (struct REGEX_ITERNAL_StateSet *set,
+                  struct REGEX_ITERNAL_State *state)
+{
+  if (set->off == set->size)
+    GNUNET_array_grow (set->states, set->size, set->size * 2 + 4);
+  set->states[set->off++] = state;
+}
+
+
+/**
+ * Compare two strings for equality. If either is NULL they are not equal.
+ *
+ * @param str1 first string for comparison.
+ * @param str2 second string for comparison.
+ *
+ * @return 0 if the strings are the same or both NULL, 1 or -1 if not.
+ */
+static int
+nullstrcmp (const char *str1, const char *str2)
+{
+  if ((NULL == str1) != (NULL == str2))
+    return -1;
+  if ((NULL == str1) && (NULL == str2))
+    return 0;
+
+  return strcmp (str1, str2);
+}
+
+
+/**
+ * Adds a transition from one state to another on 'label'. Does not add
+ * duplicate states.
+ *
+ * @param ctx context
+ * @param from_state starting state for the transition
+ * @param label transition label
+ * @param to_state state to where the transition should point to
+ */
+static void
+state_add_transition (struct REGEX_ITERNAL_Context *ctx,
+                      struct REGEX_ITERNAL_State *from_state, const char *label,
+                      struct REGEX_ITERNAL_State *to_state)
+{
+  struct REGEX_ITERNAL_Transition *t;
+  struct REGEX_ITERNAL_Transition *oth;
+
+  if (NULL == from_state)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not create Transition.\n");
+    return;
+  }
+
+  /* Do not add duplicate state transitions */
+  for (t = from_state->transitions_head; NULL != t; t = t->next)
+  {
+    if (t->to_state == to_state && 0 == nullstrcmp (t->label, label) &&
+        t->from_state == from_state)
+      return;
+  }
+
+  /* sort transitions by label */
+  for (oth = from_state->transitions_head; NULL != oth; oth = oth->next)
+  {
+    if (0 < nullstrcmp (oth->label, label))
+      break;
+  }
+
+  t = GNUNET_malloc (sizeof (struct REGEX_ITERNAL_Transition));
+  if (NULL != ctx)
+    t->id = ctx->transition_id++;
+  if (NULL != label)
+    t->label = GNUNET_strdup (label);
+  else
+    t->label = NULL;
+  t->to_state = to_state;
+  t->from_state = from_state;
+
+  /* Add outgoing transition to 'from_state' */
+  from_state->transition_count++;
+  GNUNET_CONTAINER_DLL_insert_before (from_state->transitions_head,
+                                      from_state->transitions_tail, oth, t);
+}
+
+
+/**
+ * Remove a 'transition' from 'state'.
+ *
+ * @param state state from which the to-be-removed transition originates.
+ * @param transition transition that should be removed from state 'state'.
+ */
+static void
+state_remove_transition (struct REGEX_ITERNAL_State *state,
+                         struct REGEX_ITERNAL_Transition *transition)
+{
+  if (NULL == state || NULL == transition)
+    return;
+
+  if (transition->from_state != state)
+    return;
+
+  GNUNET_free_non_null (transition->label);
+
+  state->transition_count--;
+  GNUNET_CONTAINER_DLL_remove (state->transitions_head, state->transitions_tail,
+                               transition);
+
+  GNUNET_free (transition);
+}
+
+
+/**
+ * Compare two states. Used for sorting.
+ *
+ * @param a first state
+ * @param b second state
+ *
+ * @return an integer less than, equal to, or greater than zero
+ *         if the first argument is considered to be respectively
+ *         less than, equal to, or greater than the second.
+ */
+static int
+state_compare (const void *a, const void *b)
+{
+  struct REGEX_ITERNAL_State **s1 = (struct REGEX_ITERNAL_State **) a;
+  struct REGEX_ITERNAL_State **s2 = (struct REGEX_ITERNAL_State **) b;
+
+  return (*s1)->id - (*s2)->id;
+}
+
+
+/**
+ * Get all edges leaving state 's'.
+ *
+ * @param s state.
+ * @param edges all edges leaving 's', expected to be allocated and have enough
+ *        space for s->transitions_count elements.
+ *
+ * @return number of edges.
+ */
+static unsigned int
+state_get_edges (struct REGEX_ITERNAL_State *s, struct REGEX_ITERNAL_Edge *edges)
+{
+  struct REGEX_ITERNAL_Transition *t;
+  unsigned int count;
+
+  if (NULL == s)
+    return 0;
+
+  count = 0;
+
+  for (t = s->transitions_head; NULL != t; t = t->next)
+  {
+    if (NULL != t->to_state)
+    {
+      edges[count].label = t->label;
+      edges[count].destination = t->to_state->hash;
+      count++;
+    }
+  }
+  return count;
+}
+
+
+/**
+ * Compare to state sets by comparing the id's of the states that are contained
+ * in each set. Both sets are expected to be sorted by id!
+ *
+ * @param sset1 first state set
+ * @param sset2 second state set
+ * @return 0 if the sets are equal, otherwise non-zero
+ */
+static int
+state_set_compare (struct REGEX_ITERNAL_StateSet *sset1,
+                   struct REGEX_ITERNAL_StateSet *sset2)
+{
+  int result;
+  unsigned int i;
+
+  if (NULL == sset1 || NULL == sset2)
+    return 1;
+
+  result = sset1->off - sset2->off;
+  if (result < 0)
+    return -1;
+  if (result > 0)
+    return 1;
+  for (i = 0; i < sset1->off; i++)
+    if (0 != (result = state_compare (&sset1->states[i], &sset2->states[i])))
+      break;
+  return result;
+}
+
+
+/**
+ * Clears the given StateSet 'set'
+ *
+ * @param set set to be cleared
+ */
+static void
+state_set_clear (struct REGEX_ITERNAL_StateSet *set)
+{
+  GNUNET_array_grow (set->states, set->size, 0);
+  set->off = 0;
+}
+
+
+/**
+ * Clears an automaton fragment. Does not destroy the states inside the
+ * automaton.
+ *
+ * @param a automaton to be cleared
+ */
+static void
+automaton_fragment_clear (struct REGEX_ITERNAL_Automaton *a)
+{
+  if (NULL == a)
+    return;
+
+  a->start = NULL;
+  a->end = NULL;
+  a->states_head = NULL;
+  a->states_tail = NULL;
+  a->state_count = 0;
+  GNUNET_free (a);
+}
+
+
+/**
+ * Frees the memory used by State 's'
+ *
+ * @param s state that should be destroyed
+ */
+static void
+automaton_destroy_state (struct REGEX_ITERNAL_State *s)
+{
+  struct REGEX_ITERNAL_Transition *t;
+  struct REGEX_ITERNAL_Transition *next_t;
+
+  if (NULL == s)
+    return;
+
+  GNUNET_free_non_null (s->name);
+  GNUNET_free_non_null (s->proof);
+  state_set_clear (&s->nfa_set);
+  for (t = s->transitions_head; NULL != t; t = next_t)
+  {
+    next_t = t->next;
+    state_remove_transition (s, t);
+  }
+
+  GNUNET_free (s);
+}
+
+
+/**
+ * Remove a state from the given automaton 'a'. Always use this function when
+ * altering the states of an automaton. Will also remove all transitions leading
+ * to this state, before destroying it.
+ *
+ * @param a automaton
+ * @param s state to remove
+ */
+static void
+automaton_remove_state (struct REGEX_ITERNAL_Automaton *a,
+                        struct REGEX_ITERNAL_State *s)
+{
+  struct REGEX_ITERNAL_State *s_check;
+  struct REGEX_ITERNAL_Transition *t_check;
+  struct REGEX_ITERNAL_Transition *t_check_next;
+
+  if (NULL == a || NULL == s)
+    return;
+
+  /* remove all transitions leading to this state */
+  for (s_check = a->states_head; NULL != s_check; s_check = s_check->next)
+  {
+    for (t_check = s_check->transitions_head; NULL != t_check;
+         t_check = t_check_next)
+    {
+      t_check_next = t_check->next;
+      if (t_check->to_state == s)
+        state_remove_transition (s_check, t_check);
+    }
+  }
+
+  /* remove state */
+  GNUNET_CONTAINER_DLL_remove (a->states_head, a->states_tail, s);
+  a->state_count--;
+
+  automaton_destroy_state (s);
+}
+
+
+/**
+ * Merge two states into one. Will merge 's1' and 's2' into 's1' and destroy
+ * 's2'. 's1' will contain all (non-duplicate) outgoing transitions of 's2'.
+ *
+ * @param ctx context
+ * @param a automaton
+ * @param s1 first state
+ * @param s2 second state, will be destroyed
+ */
+static void
+automaton_merge_states (struct REGEX_ITERNAL_Context *ctx,
+                        struct REGEX_ITERNAL_Automaton *a,
+                        struct REGEX_ITERNAL_State *s1,
+                        struct REGEX_ITERNAL_State *s2)
+{
+  struct REGEX_ITERNAL_State *s_check;
+  struct REGEX_ITERNAL_Transition *t_check;
+  struct REGEX_ITERNAL_Transition *t;
+  struct REGEX_ITERNAL_Transition *t_next;
+  int is_dup;
+
+  if (s1 == s2)
+    return;
+
+  /* 1. Make all transitions pointing to s2 point to s1, unless this transition
+   * does not already exists, if it already exists remove transition. */
+  for (s_check = a->states_head; NULL != s_check; s_check = s_check->next)
+  {
+    for (t_check = s_check->transitions_head; NULL != t_check; t_check = t_next)
+    {
+      t_next = t_check->next;
+
+      if (s2 == t_check->to_state)
+      {
+        is_dup = GNUNET_NO;
+        for (t = t_check->from_state->transitions_head; NULL != t; t = t->next)
+        {
+          if (t->to_state == s1 && 0 == strcmp (t_check->label, t->label))
+            is_dup = GNUNET_YES;
+        }
+        if (GNUNET_NO == is_dup)
+          t_check->to_state = s1;
+        else
+          state_remove_transition (t_check->from_state, t_check);
+      }
+    }
+  }
+
+  /* 2. Add all transitions from s2 to sX to s1 */
+  for (t_check = s2->transitions_head; NULL != t_check; t_check = t_check->next)
+  {
+    if (t_check->to_state != s1)
+      state_add_transition (ctx, s1, t_check->label, t_check->to_state);
+  }
+
+  /* 3. Rename s1 to {s1,s2} */
+#if REGEX_DEBUG_DFA
+  char *new_name;
+
+  new_name = s1->name;
+  GNUNET_asprintf (&s1->name, "{%s,%s}", new_name, s2->name);
+  GNUNET_free (new_name);
+#endif
+
+  /* remove state */
+  GNUNET_CONTAINER_DLL_remove (a->states_head, a->states_tail, s2);
+  a->state_count--;
+  automaton_destroy_state (s2);
+}
+
+
+/**
+ * Add a state to the automaton 'a', always use this function to alter the
+ * states DLL of the automaton.
+ *
+ * @param a automaton to add the state to
+ * @param s state that should be added
+ */
+static void
+automaton_add_state (struct REGEX_ITERNAL_Automaton *a,
+                     struct REGEX_ITERNAL_State *s)
+{
+  GNUNET_CONTAINER_DLL_insert (a->states_head, a->states_tail, s);
+  a->state_count++;
+}
+
+
+/**
+ * Depth-first traversal (DFS) of all states that are reachable from state
+ * 's'. Performs 'action' on each visited state.
+ *
+ * @param s start state.
+ * @param marks an array of size a->state_count to remember which state was
+ *        already visited.
+ * @param count current count of the state.
+ * @param check function that is checked before advancing on each transition
+ *              in the DFS.
+ * @param check_cls closure for check.
+ * @param action action to be performed on each state.
+ * @param action_cls closure for action.
+ */
+static void
+automaton_state_traverse (struct REGEX_ITERNAL_State *s, int *marks,
+                          unsigned int *count,
+                          REGEX_ITERNAL_traverse_check check, void *check_cls,
+                          REGEX_ITERNAL_traverse_action action, void *action_cls)
+{
+  struct REGEX_ITERNAL_Transition *t;
+
+  if (GNUNET_YES == marks[s->traversal_id])
+    return;
+
+  marks[s->traversal_id] = GNUNET_YES;
+
+  if (NULL != action)
+    action (action_cls, *count, s);
+
+  (*count)++;
+
+  for (t = s->transitions_head; NULL != t; t = t->next)
+  {
+    if (NULL == check ||
+        (NULL != check && GNUNET_YES == check (check_cls, s, t)))
+    {
+      automaton_state_traverse (t->to_state, marks, count, check, check_cls,
+                                action, action_cls);
+    }
+  }
+}
+
+
+/**
+ * Traverses the given automaton using depth-first-search (DFS) from it's start
+ * state, visiting all reachable states and calling 'action' on each one of
+ * them.
+ *
+ * @param a automaton to be traversed.
+ * @param start start state, pass a->start or NULL to traverse the whole automaton.
+ * @param check function that is checked before advancing on each transition
+ *              in the DFS.
+ * @param check_cls closure for check.
+ * @param action action to be performed on each state.
+ * @param action_cls closure for action
+ */
+void
+REGEX_ITERNAL_automaton_traverse (const struct REGEX_ITERNAL_Automaton *a,
+                                 struct REGEX_ITERNAL_State *start,
+                                 REGEX_ITERNAL_traverse_check check,
+                                 void *check_cls,
+                                 REGEX_ITERNAL_traverse_action action,
+                                 void *action_cls)
+{
+  unsigned int count;
+  struct REGEX_ITERNAL_State *s;
+
+  if (NULL == a || 0 == a->state_count)
+    return;
+
+  int marks[a->state_count];
+
+  for (count = 0, s = a->states_head; NULL != s && count < a->state_count;
+       s = s->next, count++)
+  {
+    s->traversal_id = count;
+    marks[s->traversal_id] = GNUNET_NO;
+  }
+
+  count = 0;
+
+  if (NULL == start)
+    s = a->start;
+  else
+    s = start;
+
+  automaton_state_traverse (s, marks, &count, check, check_cls, action,
+                            action_cls);
+}
+
+
+/**
+ * String container for faster string operations.
+ */
+struct StringBuffer
+{
+  /**
+   * Buffer holding the string (may start in the middle!);
+   * NOT 0-terminated!
+   */
+  char *sbuf;
+
+  /**
+   * Allocated buffer.
+   */
+  char *abuf;
+  
+  /**
+   * Length of the string in the buffer.
+   */
+  size_t slen;
+
+  /**
+   * Number of bytes allocated for 'sbuf'
+   */
+  unsigned int blen;
+
+  /**
+   * Buffer currently represents "NULL" (not the empty string!)
+   */
+  int16_t null_flag;
+
+  /**
+   * If this entry is part of the last/current generation array,
+   * this flag is GNUNET_YES if the last and current generation are
+   * identical (and thus copying is unnecessary if the value didn't
+   * change).  This is used in an optimization that improves
+   * performance by about 1% --- if we use int16_t here.  With just
+   * "int" for both flags, performance drops (on my system) significantly,
+   * most likely due to increased cache misses. 
+   */
+  int16_t synced;
+  
+};
+
+
+/**
+ * Compare two strings for equality. If either is NULL they are not equal.
+ *
+ * @param s1 first string for comparison.
+ * @param s2 second string for comparison.
+ *
+ * @return 0 if the strings are the same or both NULL, 1 or -1 if not.
+ */
+static int
+sb_nullstrcmp (const struct StringBuffer *s1,
+               const struct StringBuffer *s2)
+{
+  if ( (GNUNET_YES == s1->null_flag) &&
+       (GNUNET_YES == s2->null_flag) )
+    return 0;
+  if ( (GNUNET_YES == s1->null_flag) ||
+       (GNUNET_YES == s2->null_flag) )
+    return -1;
+  if (s1->slen != s2->slen)
+    return -1;
+  return memcmp (s1->sbuf, s2->sbuf, s1->slen);
+}
+               
+
+/**
+ * Compare two strings for equality. 
+ *
+ * @param s1 first string for comparison.
+ * @param s2 second string for comparison.
+ *
+ * @return 0 if the strings are the same, 1 or -1 if not.
+ */
+static int
+sb_strcmp (const struct StringBuffer *s1,
+           const struct StringBuffer *s2)
+{
+  if (s1->slen != s2->slen)
+    return -1;
+  return memcmp (s1->sbuf, s2->sbuf, s1->slen);
+}
+         
+
+/**
+ * Reallocate the buffer of 'ret' to fit 'nlen' characters;
+ * move the existing string to the beginning of the new buffer.
+ *
+ * @param ret current buffer, to be updated
+ * @param nlen target length for the buffer, must be at least ret->slen
+ */
+static void
+sb_realloc (struct StringBuffer *ret,
+            size_t nlen)
+{
+  char *old;
+
+  GNUNET_assert (nlen >= ret->slen);
+  old = ret->abuf;
+  ret->abuf = GNUNET_malloc (nlen);
+  ret->blen = nlen;
+  memcpy (ret->abuf,
+          ret->sbuf,
+          ret->slen);
+  ret->sbuf = ret->abuf;
+  GNUNET_free_non_null (old);
+}
+  
+
+/**
+ * Append a string.
+ *
+ * @param ret where to write the result
+ * @param sarg string to append
+ */
+static void
+sb_append (struct StringBuffer *ret,
+           const struct StringBuffer *sarg)
+{
+  if (GNUNET_YES == ret->null_flag)
+    ret->slen = 0;
+  ret->null_flag = GNUNET_NO;
+  if (ret->blen < sarg->slen + ret->slen)
+    sb_realloc (ret, ret->blen + sarg->slen + 128);
+  memcpy (&ret->sbuf[ret->slen],
+          sarg->sbuf,
+          sarg->slen);
+  ret->slen += sarg->slen;
+}
+           
+
+/**
+ * Append a C string.
+ *
+ * @param ret where to write the result
+ * @param cstr string to append
+ */
+static void
+sb_append_cstr (struct StringBuffer *ret,
+                const char *cstr)
+{
+  size_t cstr_len = strlen (cstr);
+
+  if (GNUNET_YES == ret->null_flag)
+    ret->slen = 0;
+  ret->null_flag = GNUNET_NO;
+  if (ret->blen < cstr_len + ret->slen)
+    sb_realloc (ret, ret->blen + cstr_len + 128);
+  memcpy (&ret->sbuf[ret->slen],
+          cstr,
+          cstr_len);
+  ret->slen += cstr_len;
+}
+           
+
+/**
+ * Wrap a string buffer, that is, set ret to the format string
+ * which contains an "%s" which is to be replaced with the original
+ * content of 'ret'.  Note that optimizing this function is not
+ * really worth it, it is rarely called.
+ *
+ * @param ret where to write the result and take the input for %.*s from
+ * @param format format string, fprintf-style, with exactly one "%.*s"
+ * @param extra_chars how long will the result be, in addition to 'sarg' length
+ */
+static void
+sb_wrap (struct StringBuffer *ret,
+         const char *format,
+         size_t extra_chars)
+{
+  char *temp;
+
+  if (GNUNET_YES == ret->null_flag)
+    ret->slen = 0;
+  ret->null_flag = GNUNET_NO;
+  temp = GNUNET_malloc (ret->slen + extra_chars + 1);
+  GNUNET_snprintf (temp,
+                   ret->slen + extra_chars + 1,
+                   format,
+                   (int) ret->slen,
+                   ret->sbuf);
+  GNUNET_free_non_null (ret->abuf);
+  ret->abuf = temp;
+  ret->sbuf = temp;
+  ret->blen = ret->slen + extra_chars + 1;
+  ret->slen = ret->slen + extra_chars;
+}
+
+
+/**
+ * Format a string buffer.    Note that optimizing this function is not
+ * really worth it, it is rarely called.
+ *
+ * @param ret where to write the result
+ * @param format format string, fprintf-style, with exactly one "%.*s"
+ * @param extra_chars how long will the result be, in addition to 'sarg' length
+ * @param sarg string to print into the format
+ */
+static void
+sb_printf1 (struct StringBuffer *ret,
+            const char *format,
+            size_t extra_chars,
+            const struct StringBuffer *sarg)
+{
+  if (ret->blen < sarg->slen + extra_chars + 1)
+    sb_realloc (ret,
+                sarg->slen + extra_chars + 1);
+  ret->null_flag = GNUNET_NO;
+  ret->sbuf = ret->abuf;
+  ret->slen = sarg->slen + extra_chars;
+  GNUNET_snprintf (ret->sbuf,
+                   ret->blen,
+                   format,
+                   (int) sarg->slen,
+                   sarg->sbuf);
+}
+
+
+/**
+ * Format a string buffer.
+ *
+ * @param ret where to write the result
+ * @param format format string, fprintf-style, with exactly two "%.*s"
+ * @param extra_chars how long will the result be, in addition to 'sarg1/2' length
+ * @param sarg1 first string to print into the format
+ * @param sarg2 second string to print into the format
+ */
+static void
+sb_printf2 (struct StringBuffer *ret,
+            const char *format,
+            size_t extra_chars,
+            const struct StringBuffer *sarg1,
+            const struct StringBuffer *sarg2)
+{
+  if (ret->blen < sarg1->slen + sarg2->slen + extra_chars + 1)
+    sb_realloc (ret,
+                sarg1->slen + sarg2->slen + extra_chars + 1);
+  ret->null_flag = GNUNET_NO;
+  ret->slen = sarg1->slen + sarg2->slen + extra_chars;
+  ret->sbuf = ret->abuf;
+  GNUNET_snprintf (ret->sbuf,
+                   ret->blen,
+                   format,
+                   (int) sarg1->slen,
+                   sarg1->sbuf,
+                   (int) sarg2->slen,
+                   sarg2->sbuf);
+}
+
+
+/**
+ * Format a string buffer.     Note that optimizing this function is not
+ * really worth it, it is rarely called.
+ *
+ * @param ret where to write the result
+ * @param format format string, fprintf-style, with exactly three "%.*s"
+ * @param extra_chars how long will the result be, in addition to 'sarg1/2/3' length
+ * @param sarg1 first string to print into the format
+ * @param sarg2 second string to print into the format
+ * @param sarg3 third string to print into the format
+ */
+static void
+sb_printf3 (struct StringBuffer *ret,
+            const char *format,
+            size_t extra_chars,
+            const struct StringBuffer *sarg1,
+            const struct StringBuffer *sarg2,
+            const struct StringBuffer *sarg3)
+{
+  if (ret->blen < sarg1->slen + sarg2->slen + sarg3->slen + extra_chars + 1)
+    sb_realloc (ret,
+                sarg1->slen + sarg2->slen + sarg3->slen + extra_chars + 1);
+  ret->null_flag = GNUNET_NO;
+  ret->slen = sarg1->slen + sarg2->slen + sarg3->slen + extra_chars;
+  ret->sbuf = ret->abuf;
+  GNUNET_snprintf (ret->sbuf,
+                   ret->blen,
+                   format,
+                   (int) sarg1->slen,
+                   sarg1->sbuf,
+                   (int) sarg2->slen,
+                   sarg2->sbuf,
+                   (int) sarg3->slen,
+                   sarg3->sbuf);
+}
+
+
+/**
+ * Free resources of the given string buffer.
+ *
+ * @param sb buffer to free (actual pointer is not freed, as they
+ *        should not be individually allocated)
+ */
+static void
+sb_free (struct StringBuffer *sb)
+{
+  GNUNET_array_grow (sb->abuf,
+                     sb->blen,
+                     0);
+  sb->slen = 0;
+  sb->sbuf = NULL;
+  sb->null_flag= GNUNET_YES;
+}
+
+
+/**
+ * Copy the given string buffer from 'in' to 'out'.
+ *
+ * @param in input string
+ * @param out output string
+ */
+static void
+sb_strdup (struct StringBuffer *out,
+           const struct StringBuffer *in)
+           
+{
+  out->null_flag = in->null_flag;
+  if (GNUNET_YES == out->null_flag)
+    return;
+  if (out->blen < in->slen)
+  {
+    GNUNET_array_grow (out->abuf,
+                       out->blen,
+                       in->slen);
+  }
+  out->sbuf = out->abuf;
+  out->slen = in->slen;
+  memcpy (out->sbuf, in->sbuf, out->slen);
+}
+
+
+/**
+ * Copy the given string buffer from 'in' to 'out'.
+ *
+ * @param cstr input string
+ * @param out output string
+ */
+static void
+sb_strdup_cstr (struct StringBuffer *out,
+                const char *cstr)
+{
+  if (NULL == cstr)
+  {
+    out->null_flag = GNUNET_YES;
+    return;
+  }
+  out->null_flag = GNUNET_NO;
+  out->slen = strlen (cstr);
+  if (out->blen < out->slen)
+  {
+    GNUNET_array_grow (out->abuf,
+                       out->blen,
+                       out->slen);
+  }
+  out->sbuf = out->abuf;
+  memcpy (out->sbuf, cstr, out->slen);
+}
+
+
+/**
+ * Check if the given string 'str' needs parentheses around it when
+ * using it to generate a regex.
+ *
+ * @param str string
+ *
+ * @return GNUNET_YES if parentheses are needed, GNUNET_NO otherwise
+ */
+static int
+needs_parentheses (const struct StringBuffer *str)
+{
+  size_t slen;
+  const char *op;
+  const char *cl;
+  const char *pos;
+  const char *end;
+  unsigned int cnt;
+
+  if ((GNUNET_YES == str->null_flag) || ((slen = str->slen) < 2))
+    return GNUNET_NO;
+  pos = str->sbuf;
+  if ('(' != pos[0])
+    return GNUNET_YES;
+  end = str->sbuf + slen;
+  cnt = 1;
+  pos++;
+  while (cnt > 0)
+  {
+    cl = memchr (pos, ')', end - pos);
+    if (NULL == cl)
+    {
+      GNUNET_break (0);
+      return GNUNET_YES;
+    }
+    /* while '(' before ')', count opening parens */
+    while ( (NULL != (op = memchr (pos, '(', end - pos)))  &&
+            (op < cl) ) 
+    {
+      cnt++;
+      pos = op + 1;
+    }
+    /* got ')' first */
+    cnt--;
+    pos = cl + 1;
+  }
+  return (*pos == '\0') ? GNUNET_NO : GNUNET_YES;
+}
+
+
+/**
+ * Remove parentheses surrounding string 'str'.
+ * Example: "(a)" becomes "a", "(a|b)|(a|c)" stays the same.
+ * You need to GNUNET_free the returned string.
+ *
+ * @param str string, modified to contain a
+ * @return string without surrounding parentheses, string 'str' if no preceding
+ *         epsilon could be found, NULL if 'str' was NULL
+ */
+static void
+remove_parentheses (struct StringBuffer *str)
+{
+  size_t slen;
+  const char *pos;
+  const char *end;
+  const char *sbuf;
+  const char *op;
+  const char *cp;
+  unsigned int cnt;
+
+  if (0)
+    return;
+  sbuf = str->sbuf;
+  if ( (GNUNET_YES == str->null_flag) || 
+       (1 >=  (slen = str->slen)) ||
+       ('(' != str->sbuf[0]) ||
+       (')' != str->sbuf[slen - 1]) )
+    return;
+  cnt = 0;
+  pos = &sbuf[1];
+  end = &sbuf[slen - 1];
+  op = memchr (pos, '(', end - pos);
+  cp = memchr (pos, ')', end - pos);
+  while (NULL != cp) 
+  {
+    while ( (NULL != op) &&
+            (op < cp) )
+    {
+      cnt++;
+      pos = op + 1;
+      op = memchr (pos, '(', end - pos);
+    }
+    while ( (NULL != cp) &&
+            ( (NULL == op) ||
+              (cp < op) ) )
+    {
+      if (0 == cnt)
+        return; /* can't strip parens */
+      cnt--;
+      pos = cp + 1;
+      cp = memchr (pos, ')', end - pos);
+    }
+  }
+  if (0 != cnt)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  str->sbuf++;
+  str->slen -= 2;  
+}
+
+
+/**
+ * Check if the string 'str' starts with an epsilon (empty string).
+ * Example: "(|a)" is starting with an epsilon.
+ *
+ * @param str string to test
+ *
+ * @return 0 if str has no epsilon, 1 if str starts with '(|' and ends with ')'
+ */
+static int
+has_epsilon (const struct StringBuffer *str)
+{
+  return 
+    (GNUNET_YES != str->null_flag) && 
+    (0 < str->slen) &&
+    ('(' == str->sbuf[0]) && 
+    ('|' == str->sbuf[1]) &&
+    (')' == str->sbuf[str->slen - 1]);
+}
+
+
+/**
+ * Remove an epsilon from the string str. Where epsilon is an empty string
+ * Example: str = "(|a|b|c)", result: "a|b|c"
+ * The returned string needs to be freed.
+ *
+ * @param str original string
+ * @param ret where to return string without preceding epsilon, string 'str' if no preceding
+ *         epsilon could be found, NULL if 'str' was NULL
+ */
+static void
+remove_epsilon (const struct StringBuffer *str,
+                struct StringBuffer *ret)
+{
+  if (GNUNET_YES == str->null_flag)
+  {
+    ret->null_flag = GNUNET_YES;
+    return;
+  }  
+  if ( (str->slen > 1) && 
+       ('(' == str->sbuf[0]) &&
+       ('|' == str->sbuf[1]) &&
+       (')' == str->sbuf[str->slen - 1]) )
+  {
+    /* remove epsilon */
+    if (ret->blen < str->slen - 3)
+    {
+      GNUNET_array_grow (ret->abuf,
+                         ret->blen,
+                         str->slen - 3);
+    }
+    ret->sbuf = ret->abuf;
+    ret->slen = str->slen - 3;
+    memcpy (ret->sbuf, &str->sbuf[2], ret->slen);
+    return;
+  }
+  sb_strdup (ret, str);
+}
+
+
+/**
+ * Compare n bytes of 'str1' and 'str2'
+ *
+ * @param str1 first string to compare
+ * @param str2 second string for comparison
+ * @param n number of bytes to compare
+ *
+ * @return -1 if any of the strings is NULL, 0 if equal, non 0 otherwise
+ */
+static int
+sb_strncmp (const struct StringBuffer *str1, 
+            const struct StringBuffer *str2, size_t n)
+{
+  size_t max;
+  
+  if ( (str1->slen != str2->slen) &&
+       ( (str1->slen < n) ||
+         (str2->slen < n) ) )
+    return -1;
+  max = GNUNET_MAX (str1->slen, str2->slen);
+  if (max > n)
+    max = n;
+  return memcmp (str1->sbuf, str2->sbuf, max);
+}
+
+
+/**
+ * Compare n bytes of 'str1' and 'str2'
+ *
+ * @param str1 first string to compare
+ * @param str2 second C string for comparison
+ * @param n number of bytes to compare (and length of str2)
+ *
+ * @return -1 if any of the strings is NULL, 0 if equal, non 0 otherwise
+ */
+static int
+sb_strncmp_cstr (const struct StringBuffer *str1, 
+                 const char *str2, size_t n)
+{
+  if (str1->slen < n) 
+    return -1;
+  return memcmp (str1->sbuf, str2, n);
+}
+
+
+/**
+ * Initialize string buffer for storing strings of up to n 
+ * characters.
+ *
+ * @param sb buffer to initialize
+ * @param n desired target length
+ */
+static void
+sb_init (struct StringBuffer *sb,
+         size_t n)
+{
+  sb->null_flag = GNUNET_NO;
+  sb->abuf = sb->sbuf = (0 == n) ? NULL : GNUNET_malloc (n);
+  sb->blen = n;
+  sb->slen = 0;
+}
+
+
+/**
+ * Compare 'str1', starting from position 'k',  with whole 'str2'
+ *
+ * @param str1 first string to compare, starting from position 'k'
+ * @param str2 second string for comparison
+ * @param k starting position in 'str1'
+ *
+ * @return -1 if any of the strings is NULL, 0 if equal, non 0 otherwise
+ */
+static int
+sb_strkcmp (const struct StringBuffer *str1, 
+            const struct StringBuffer *str2, size_t k)
+{
+  if ( (GNUNET_YES == str1->null_flag) ||
+       (GNUNET_YES == str2->null_flag) ||
+       (k > str1->slen) ||
+       (str1->slen - k != str2->slen) )
+    return -1;
+  return memcmp (&str1->sbuf[k], str2->sbuf, str2->slen);
+}
+
+
+/**
+ * Helper function used as 'action' in 'REGEX_ITERNAL_automaton_traverse'
+ * function to create the depth-first numbering of the states.
+ *
+ * @param cls states array.
+ * @param count current state counter.
+ * @param s current state.
+ */
+static void
+number_states (void *cls, const unsigned int count,
+               struct REGEX_ITERNAL_State *s)
+{
+  struct REGEX_ITERNAL_State **states = cls;
+
+  s->dfs_id = count;
+  if (NULL != states)
+    states[count] = s;
+}
+
+
+
+#define PRIS(a) \
+  ((GNUNET_YES == a.null_flag) ? 6 : (int) a.slen), \
+  ((GNUNET_YES == a.null_flag) ? "(null)" : a.sbuf)
+
+
+/**
+ * Construct the regular expression given the inductive step,
+ * $R^{(k)}_{ij} = R^{(k-1)}_{ij} | R^{(k-1)}_{ik} ( R^{(k-1)}_{kk} )^*
+ * R^{(k-1)}_{kj}, and simplify the resulting expression saved in R_cur_ij.
+ *
+ * @param R_last_ij value of  $R^{(k-1)_{ij}.
+ * @param R_last_ik value of  $R^{(k-1)_{ik}.
+ * @param R_last_kk value of  $R^{(k-1)_{kk}.
+ * @param R_last_kj value of  $R^{(k-1)_{kj}.
+ * @param R_cur_ij result for this inductive step is saved in R_cur_ij, R_cur_ij
+ *                 is expected to be NULL when called!
+ * @param R_cur_l optimization -- kept between iterations to avoid realloc
+ * @param R_cur_r optimization -- kept between iterations to avoid realloc
+ */
+static void
+automaton_create_proofs_simplify (const struct StringBuffer *R_last_ij, 
+                                  const struct StringBuffer *R_last_ik,
+                                  const struct StringBuffer *R_last_kk,
+                                  const struct StringBuffer *R_last_kj,
+                                  struct StringBuffer *R_cur_ij,
+                                  struct StringBuffer *R_cur_l,
+                                  struct StringBuffer *R_cur_r)
+{
+  struct StringBuffer R_temp_ij;
+  struct StringBuffer R_temp_ik;
+  struct StringBuffer R_temp_kj;
+  struct StringBuffer R_temp_kk;
+  int eps_check;
+  int ij_ik_cmp;
+  int ij_kj_cmp;
+  int ik_kk_cmp;
+  int kk_kj_cmp;
+  int clean_ik_kk_cmp;
+  int clean_kk_kj_cmp;
+  size_t length;
+  size_t length_l;
+  size_t length_r;
+
+  /*
+   * $R^{(k)}_{ij} = R^{(k-1)}_{ij} | R^{(k-1)}_{ik} ( R^{(k-1)}_{kk} )^* R^{(k-1)}_{kj}
+   * R_last == R^{(k-1)}, R_cur == R^{(k)}
+   * R_cur_ij = R_cur_l | R_cur_r
+   * R_cur_l == R^{(k-1)}_{ij}
+   * R_cur_r == R^{(k-1)}_{ik} ( R^{(k-1)}_{kk} )^* R^{(k-1)}_{kj}
+   */
+
+  if ( (GNUNET_YES == R_last_ij->null_flag) && 
+       ( (GNUNET_YES == R_last_ik->null_flag) || 
+         (GNUNET_YES == R_last_kj->null_flag)))
+  {
+    /* R^{(k)}_{ij} = N | N */
+    R_cur_ij->null_flag = GNUNET_YES;
+    R_cur_ij->synced = GNUNET_NO;
+    return;
+  }
+
+  if ( (GNUNET_YES == R_last_ik->null_flag) || 
+       (GNUNET_YES == R_last_kj->null_flag) )
+  {
+    /*  R^{(k)}_{ij} = R^{(k-1)}_{ij} | N */
+    if (GNUNET_YES == R_last_ij->synced)
+    {
+      R_cur_ij->synced = GNUNET_YES;      
+      R_cur_ij->null_flag = GNUNET_NO;
+      return;
+    }
+    R_cur_ij->synced = GNUNET_YES;
+    sb_strdup (R_cur_ij, R_last_ij);
+    return;
+  }
+  R_cur_ij->synced = GNUNET_NO;
+
+  /* $R^{(k)}_{ij} = N | R^{(k-1)}_{ik} ( R^{(k-1)}_{kk} )^* R^{(k-1)}_{kj} OR
+   * $R^{(k)}_{ij} = R^{(k-1)}_{ij} | R^{(k-1)}_{ik} ( R^{(k-1)}_{kk} )^* R^{(k-1)}_{kj} */
+
+  R_cur_r->null_flag = GNUNET_YES; 
+  R_cur_r->slen = 0; 
+  R_cur_l->null_flag = GNUNET_YES; 
+  R_cur_l->slen = 0; 
+
+  /* cache results from strcmp, we might need these many times */
+  ij_kj_cmp = sb_nullstrcmp (R_last_ij, R_last_kj);
+  ij_ik_cmp = sb_nullstrcmp (R_last_ij, R_last_ik);
+  ik_kk_cmp = sb_nullstrcmp (R_last_ik, R_last_kk);
+  kk_kj_cmp = sb_nullstrcmp (R_last_kk, R_last_kj);
+
+  /* Assign R_temp_(ik|kk|kj) to R_last[][] and remove epsilon as well
+   * as parentheses, so we can better compare the contents */
+
+  memset (&R_temp_ij, 0, sizeof (struct StringBuffer));
+  memset (&R_temp_ik, 0, sizeof (struct StringBuffer));
+  memset (&R_temp_kk, 0, sizeof (struct StringBuffer));
+  memset (&R_temp_kj, 0, sizeof (struct StringBuffer));
+  remove_epsilon (R_last_ik, &R_temp_ik);
+  remove_epsilon (R_last_kk, &R_temp_kk);
+  remove_epsilon (R_last_kj, &R_temp_kj);
+  remove_parentheses (&R_temp_ik);
+  remove_parentheses (&R_temp_kk);
+  remove_parentheses (&R_temp_kj);
+  clean_ik_kk_cmp = sb_nullstrcmp (R_last_ik, &R_temp_kk);
+  clean_kk_kj_cmp = sb_nullstrcmp (&R_temp_kk, R_last_kj);
+
+  /* construct R_cur_l (and, if necessary R_cur_r) */
+  if (GNUNET_YES != R_last_ij->null_flag)
+  {
+    /* Assign R_temp_ij to R_last_ij and remove epsilon as well
+     * as parentheses, so we can better compare the contents */
+    remove_epsilon (R_last_ij, &R_temp_ij);
+    remove_parentheses (&R_temp_ij);
+
+    if ( (0 == sb_strcmp (&R_temp_ij, &R_temp_ik)) && 
+         (0 == sb_strcmp (&R_temp_ik, &R_temp_kk)) && 
+         (0 == sb_strcmp (&R_temp_kk, &R_temp_kj)) )
+    {
+      if (0 == R_temp_ij.slen)
+      {
+        R_cur_r->null_flag = GNUNET_NO;
+      }
+      else if ((0 == sb_strncmp_cstr (R_last_ij, "(|", 2)) ||
+               (0 == sb_strncmp_cstr (R_last_ik, "(|", 2) &&
+                0 == sb_strncmp_cstr (R_last_kj, "(|", 2)))
+      {
+        /*
+         * a|(e|a)a*(e|a) = a*
+         * a|(e|a)(e|a)*(e|a) = a*
+         * (e|a)|aa*a = a*
+         * (e|a)|aa*(e|a) = a*
+         * (e|a)|(e|a)a*a = a*
+         * (e|a)|(e|a)a*(e|a) = a*
+         * (e|a)|(e|a)(e|a)*(e|a) = a*
+         */
+        if (GNUNET_YES == needs_parentheses (&R_temp_ij))
+          sb_printf1 (R_cur_r, "(%.*s)*", 3, &R_temp_ij);
+        else
+          sb_printf1 (R_cur_r, "%.*s*", 1, &R_temp_ij);
+      }
+      else
+      {
+        /*
+         * a|aa*a = a+
+         * a|(e|a)a*a = a+
+         * a|aa*(e|a) = a+
+         * a|(e|a)(e|a)*a = a+
+         * a|a(e|a)*(e|a) = a+
+         */
+        if (GNUNET_YES == needs_parentheses (&R_temp_ij))
+          sb_printf1 (R_cur_r, "(%.*s)+", 3, &R_temp_ij);
+        else
+          sb_printf1 (R_cur_r, "%.*s+", 1, &R_temp_ij);
+      }
+    }
+    else if ( (0 == ij_ik_cmp) && (0 == clean_kk_kj_cmp) && (0 != clean_ik_kk_cmp) )
+    {
+      /* a|ab*b = ab* */
+      if (0 == R_last_kk->slen)
+        sb_strdup (R_cur_r, R_last_ij);
+      else if (GNUNET_YES == needs_parentheses (&R_temp_kk))
+        sb_printf2 (R_cur_r, "%.*s(%.*s)*", 3, R_last_ij, &R_temp_kk);
+      else
+        sb_printf2 (R_cur_r, "%.*s%.*s*", 1, R_last_ij, R_last_kk);
+      R_cur_l->null_flag = GNUNET_YES;
+    }
+    else if ( (0 == ij_kj_cmp) && (0 == clean_ik_kk_cmp) && (0 != clean_kk_kj_cmp))
+    {
+      /* a|bb*a = b*a */
+      if (R_last_kk->slen < 1)
+      {
+        sb_strdup (R_cur_r, R_last_kj);
+      }
+      else if (GNUNET_YES == needs_parentheses (&R_temp_kk))
+        sb_printf2 (R_cur_r, "(%.*s)*%.*s", 3, &R_temp_kk, R_last_kj);
+      else
+        sb_printf2 (R_cur_r, "%.*s*%.*s", 1, &R_temp_kk, R_last_kj);
+
+      R_cur_l->null_flag = GNUNET_YES;
+    }
+    else if ( (0 == ij_ik_cmp) && (0 == kk_kj_cmp) && (! has_epsilon (R_last_ij)) &&
+              has_epsilon (R_last_kk))
+    {
+      /* a|a(e|b)*(e|b) = a|ab* = a|a|ab|abb|abbb|... = ab* */
+      if (needs_parentheses (&R_temp_kk))
+        sb_printf2 (R_cur_r, "%.*s(%.*s)*", 3, R_last_ij, &R_temp_kk);
+      else
+        sb_printf2 (R_cur_r, "%.*s%.*s*", 1, R_last_ij, &R_temp_kk);
+      R_cur_l->null_flag = GNUNET_YES;
+    }
+    else if ( (0 == ij_kj_cmp) && (0 == ik_kk_cmp) && (! has_epsilon (R_last_ij)) &&
+             has_epsilon (R_last_kk))
+    {
+      /* a|(e|b)(e|b)*a = a|b*a = a|a|ba|bba|bbba|...  = b*a */
+      if (needs_parentheses (&R_temp_kk))
+        sb_printf2 (R_cur_r, "(%.*s)*%.*s", 3, &R_temp_kk, R_last_ij);
+      else
+        sb_printf2 (R_cur_r, "%.*s*%.*s", 1, &R_temp_kk, R_last_ij);
+      R_cur_l->null_flag = GNUNET_YES;
+    }
+    else
+    {
+      sb_strdup (R_cur_l, R_last_ij);
+      remove_parentheses (R_cur_l);
+    }
+  }
+  else
+  {
+    /* we have no left side */
+    R_cur_l->null_flag = GNUNET_YES;
+  }
+
+  /* construct R_cur_r, if not already constructed */
+  if (GNUNET_YES == R_cur_r->null_flag)
+  {
+    length = R_temp_kk.slen - R_last_ik->slen;
+
+    /* a(ba)*bx = (ab)+x */
+    if ( (length > 0) && 
+         (GNUNET_YES != R_last_kk->null_flag) &&
+         (0 < R_last_kk->slen) &&
+         (GNUNET_YES != R_last_kj->null_flag) && 
+         (0 < R_last_kj->slen) &&
+         (GNUNET_YES != R_last_ik->null_flag) &&
+         (0 < R_last_ik->slen) &&
+         (0 == sb_strkcmp (&R_temp_kk, R_last_ik, length)) &&
+         (0 == sb_strncmp (&R_temp_kk, R_last_kj, length)) )
+    { 
+      struct StringBuffer temp_a;
+      struct StringBuffer temp_b;
+
+      sb_init (&temp_a, length);
+      sb_init (&temp_b, R_last_kj->slen - length);
+
+      length_l = length;
+      temp_a.sbuf = temp_a.abuf;
+      memcpy (temp_a.sbuf, R_last_kj->sbuf, length_l);
+      temp_a.slen = length_l;
+
+      length_r = R_last_kj->slen - length;
+      temp_b.sbuf = temp_b.abuf;
+      memcpy (temp_b.sbuf, &R_last_kj->sbuf[length], length_r);
+      temp_b.slen = length_r;
+
+      /* e|(ab)+ = (ab)* */
+      if ( (GNUNET_YES != R_cur_l->null_flag) &&
+           (0 == R_cur_l->slen) &&
+           (0 == temp_b.slen) )
+      {
+        sb_printf2 (R_cur_r, "(%.*s%.*s)*", 3, R_last_ik, &temp_a);
+        sb_free (R_cur_l);
+        R_cur_l->null_flag = GNUNET_YES;
+      }
+      else
+      {
+        sb_printf3 (R_cur_r, "(%.*s%.*s)+%.*s", 3, R_last_ik, &temp_a, &temp_b);
+      }
+      sb_free (&temp_a);
+      sb_free (&temp_b);
+    }
+    else if (0 == sb_strcmp (&R_temp_ik, &R_temp_kk) &&
+             0 == sb_strcmp (&R_temp_kk, &R_temp_kj))
+    {
+      /*
+       * (e|a)a*(e|a) = a*
+       * (e|a)(e|a)*(e|a) = a*
+       */
+      if (has_epsilon (R_last_ik) && has_epsilon (R_last_kj))
+      {
+        if (needs_parentheses (&R_temp_kk))
+          sb_printf1 (R_cur_r, "(%.*s)*", 3, &R_temp_kk);
+        else
+          sb_printf1 (R_cur_r, "%.*s*", 1, &R_temp_kk);
+      }
+      /* aa*a = a+a */
+      else if ( (0 == clean_ik_kk_cmp) && 
+                (0 == clean_kk_kj_cmp) &&
+                (! has_epsilon (R_last_ik)) )
+      {
+        if (needs_parentheses (&R_temp_kk))
+          sb_printf2 (R_cur_r, "(%.*s)+%.*s", 3, &R_temp_kk, &R_temp_kk);
+        else
+          sb_printf2 (R_cur_r, "%.*s+%.*s", 1, &R_temp_kk, &R_temp_kk);
+      }
+      /*
+       * (e|a)a*a = a+
+       * aa*(e|a) = a+
+       * a(e|a)*(e|a) = a+
+       * (e|a)a*a = a+
+       */
+      else
+      {
+        eps_check =
+          (has_epsilon (R_last_ik) + has_epsilon (R_last_kk) +
+           has_epsilon (R_last_kj));
+
+        if (1 == eps_check)
+        {
+          if (needs_parentheses (&R_temp_kk))
+            sb_printf1 (R_cur_r, "(%.*s)+", 3, &R_temp_kk);
+          else
+            sb_printf1 (R_cur_r, "%.*s+", 1, &R_temp_kk);
+        }
+      }
+    }
+    /*
+     * aa*b = a+b
+     * (e|a)(e|a)*b = a*b
+     */
+    else if (0 == sb_strcmp (&R_temp_ik, &R_temp_kk))
+    {
+      if (has_epsilon (R_last_ik))
+      {
+        if (needs_parentheses (&R_temp_kk))
+          sb_printf2 (R_cur_r, "(%.*s)*%.*s", 3, &R_temp_kk, R_last_kj);
+        else
+          sb_printf2 (R_cur_r, "%.*s*%.*s", 1, &R_temp_kk, R_last_kj);
+      }
+      else
+      {
+        if (needs_parentheses (&R_temp_kk))
+          sb_printf2 (R_cur_r, "(%.*s)+%.*s", 3, &R_temp_kk, R_last_kj);
+        else
+          sb_printf2 (R_cur_r, "%.*s+%.*s", 1, &R_temp_kk, R_last_kj);
+      }
+    }
+    /*
+     * ba*a = ba+
+     * b(e|a)*(e|a) = ba*
+     */
+    else if (0 == sb_strcmp (&R_temp_kk, &R_temp_kj))
+    {
+      if (has_epsilon (R_last_kj))
+      {
+        if (needs_parentheses (&R_temp_kk))
+          sb_printf2 (R_cur_r, "%.*s(%.*s)*", 3, R_last_ik, &R_temp_kk);
+        else
+          sb_printf2 (R_cur_r, "%.*s%.*s*", 1, R_last_ik, &R_temp_kk);
+      }
+      else
+      {
+        if (needs_parentheses (&R_temp_kk))
+          sb_printf2 (R_cur_r, "(%.*s)+%.*s", 3, R_last_ik, &R_temp_kk);
+        else
+          sb_printf2 (R_cur_r, "%.*s+%.*s", 1, R_last_ik, &R_temp_kk);
+      }
+    }
+    else
+    {
+      if (0 < R_temp_kk.slen)
+      {
+        if (needs_parentheses (&R_temp_kk))
+        {
+          sb_printf3 (R_cur_r, "%.*s(%.*s)*%.*s", 3, R_last_ik, &R_temp_kk,
+                      R_last_kj);
+        }
+        else
+        {
+          sb_printf3 (R_cur_r, "%.*s%.*s*%.*s", 1, R_last_ik, &R_temp_kk,
+                      R_last_kj);
+        }
+      }
+      else
+      {
+        sb_printf2 (R_cur_r, "%.*s%.*s", 0, R_last_ik, R_last_kj);
+      }
+    }
+  }
+  sb_free (&R_temp_ij);
+  sb_free (&R_temp_ik);
+  sb_free (&R_temp_kk);
+  sb_free (&R_temp_kj);
+
+  if ( (GNUNET_YES == R_cur_l->null_flag) && 
+       (GNUNET_YES == R_cur_r->null_flag) )
+  {
+    R_cur_ij->null_flag = GNUNET_YES;
+    return;
+  }
+
+  if ( (GNUNET_YES != R_cur_l->null_flag) &&
+       (GNUNET_YES == R_cur_r->null_flag) )
+  {
+    struct StringBuffer tmp;
+
+    tmp = *R_cur_ij;
+    *R_cur_ij = *R_cur_l;
+    *R_cur_l = tmp;
+    return;
+  }
+
+  if ( (GNUNET_YES == R_cur_l->null_flag) &&
+       (GNUNET_YES != R_cur_r->null_flag) )
+  {
+    struct StringBuffer tmp;
+
+    tmp = *R_cur_ij;
+    *R_cur_ij = *R_cur_r;
+    *R_cur_r = tmp;
+    return;
+  }
+
+  if (0 == sb_nullstrcmp (R_cur_l, R_cur_r))
+  {
+    struct StringBuffer tmp;
+
+    tmp = *R_cur_ij;
+    *R_cur_ij = *R_cur_l;
+    *R_cur_l = tmp;
+    return;
+  }
+  sb_printf2 (R_cur_ij, "(%.*s|%.*s)", 3, R_cur_l, R_cur_r);
+}
+
+
+/**
+ * Create proofs for all states in the given automaton. Implementation of the
+ * algorithm descriped in chapter 3.2.1 of "Automata Theory, Languages, and
+ * Computation 3rd Edition" by Hopcroft, Motwani and Ullman.
+ *
+ * Each state in the automaton gets assigned 'proof' and 'hash' (hash of the
+ * proof) fields. The starting state will only have a valid proof/hash if it has
+ * any incoming transitions.
+ *
+ * @param a automaton for which to assign proofs and hashes, must not be NULL
+ */
+static int
+automaton_create_proofs (struct REGEX_ITERNAL_Automaton *a)
+{
+  unsigned int n = a->state_count;
+  struct REGEX_ITERNAL_State *states[n];
+  struct StringBuffer *R_last;
+  struct StringBuffer *R_cur;
+  struct StringBuffer R_cur_r;
+  struct StringBuffer R_cur_l;
+  struct StringBuffer *R_swap;
+  struct REGEX_ITERNAL_Transition *t;
+  struct StringBuffer complete_regex;
+  unsigned int i;
+  unsigned int j;
+  unsigned int k;
+
+  R_last = GNUNET_malloc_large (sizeof (struct StringBuffer) * n * n);
+  R_cur = GNUNET_malloc_large (sizeof (struct StringBuffer) * n * n);
+  if ( (NULL == R_last) ||
+       (NULL == R_cur) )
+  {
+    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "malloc");
+    GNUNET_free_non_null (R_cur);
+    GNUNET_free_non_null (R_last);
+    return GNUNET_SYSERR;
+  }
+
+  /* create depth-first numbering of the states, initializes 'state' */
+  REGEX_ITERNAL_automaton_traverse (a, a->start, NULL, NULL, &number_states,
+                                   states);
+
+  for (i = 0; i < n; i++)
+    GNUNET_assert (NULL != states[i]);
+  for (i = 0; i < n; i++)
+    for (j = 0; j < n; j++)
+      R_last[i *n + j].null_flag = GNUNET_YES;
+
+  /* Compute regular expressions of length "1" between each pair of states */
+  for (i = 0; i < n; i++)
+  {
+    for (t = states[i]->transitions_head; NULL != t; t = t->next)
+    {
+      j = t->to_state->dfs_id;
+      if (GNUNET_YES == R_last[i * n + j].null_flag)
+      {
+        sb_strdup_cstr (&R_last[i * n + j], t->label);
+      }
+      else
+      {
+        sb_append_cstr (&R_last[i * n + j], "|");
+        sb_append_cstr (&R_last[i * n + j], t->label);
+      }
+    }
+    /* add self-loop: i is reachable from i via epsilon-transition */
+    if (GNUNET_YES == R_last[i * n + i].null_flag)
+    {
+      R_last[i * n + i].slen = 0;
+      R_last[i * n + i].null_flag = GNUNET_NO;
+    }
+    else
+    {
+      sb_wrap (&R_last[i * n + i], "(|%.*s)", 3);
+    }
+  }
+  for (i = 0; i < n; i++)
+    for (j = 0; j < n; j++)
+      if (needs_parentheses (&R_last[i * n + j]))
+        sb_wrap (&R_last[i * n + j], "(%.*s)", 2);  
+  /* Compute regular expressions of length "k" between each pair of states per
+   * induction */
+  memset (&R_cur_l, 0, sizeof (struct StringBuffer));
+  memset (&R_cur_r, 0, sizeof (struct StringBuffer));
+  for (k = 0; k < n; k++)
+  {
+    for (i = 0; i < n; i++)
+    {
+      for (j = 0; j < n; j++)
+      {
+        /* Basis for the recursion:
+         * $R^{(k)}_{ij} = R^{(k-1)}_{ij} | R^{(k-1)}_{ik} ( R^{(k-1)}_{kk} )^* R^{(k-1)}_{kj}
+         * R_last == R^{(k-1)}, R_cur == R^{(k)}
+         */
+
+        /* Create R_cur[i][j] and simplify the expression */
+        automaton_create_proofs_simplify (&R_last[i * n + j], &R_last[i * n + k],
+                                          &R_last[k * n + k], &R_last[k * n + j],
+                                          &R_cur[i * n + j],
+                                          &R_cur_l, &R_cur_r);
+      }
+    }
+    /* set R_last = R_cur */
+    R_swap = R_last;
+    R_last = R_cur;
+    R_cur = R_swap;
+    /* clear 'R_cur' for next iteration */
+    for (i = 0; i < n; i++)
+      for (j = 0; j < n; j++)
+        R_cur[i * n + j].null_flag = GNUNET_YES;
+  }
+  sb_free (&R_cur_l);
+  sb_free (&R_cur_r);
+  /* assign proofs and hashes */
+  for (i = 0; i < n; i++)
+  {
+    if (GNUNET_YES != R_last[a->start->dfs_id * n + i].null_flag)
+    {
+      states[i]->proof = GNUNET_strndup (R_last[a->start->dfs_id * n + i].sbuf,
+                                         R_last[a->start->dfs_id * n + i].slen);
+      GNUNET_CRYPTO_hash (states[i]->proof, strlen (states[i]->proof),
+                          &states[i]->hash);
+    }
+  }
+
+  /* complete regex for whole DFA: union of all pairs (start state/accepting
+   * state(s)). */
+  sb_init (&complete_regex, 16 * n);
+  for (i = 0; i < n; i++)
+  {
+    if (states[i]->accepting)
+    {
+      if ( (0 == complete_regex.slen) &&
+           (0 < R_last[a->start->dfs_id * n + i].slen) )
+      {
+        sb_append (&complete_regex, 
+                   &R_last[a->start->dfs_id * n + i]);
+      }
+      else if ( (GNUNET_YES != R_last[a->start->dfs_id * n + i].null_flag) &&
+                (0 < R_last[a->start->dfs_id * n + i].slen) )
+      {
+        sb_append_cstr (&complete_regex, "|");
+        sb_append (&complete_regex, 
+                   &R_last[a->start->dfs_id * n + i]);
+      }
+    }
+  }
+  a->canonical_regex = GNUNET_strndup (complete_regex.sbuf, complete_regex.slen);
+
+  /* cleanup */
+  sb_free (&complete_regex);
+  for (i = 0; i < n; i++)  
+    for (j = 0; j < n; j++)
+    {
+      sb_free (&R_cur[i * n + j]);  
+      sb_free (&R_last[i * n + j]);  
+    }
+  GNUNET_free (R_cur);
+  GNUNET_free (R_last);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Creates a new DFA state based on a set of NFA states. Needs to be freed using
+ * automaton_destroy_state.
+ *
+ * @param ctx context
+ * @param nfa_states set of NFA states on which the DFA should be based on
+ *
+ * @return new DFA state
+ */
+static struct REGEX_ITERNAL_State *
+dfa_state_create (struct REGEX_ITERNAL_Context *ctx,
+                  struct REGEX_ITERNAL_StateSet *nfa_states)
+{
+  struct REGEX_ITERNAL_State *s;
+  char *pos;
+  size_t len;
+  struct REGEX_ITERNAL_State *cstate;
+  struct REGEX_ITERNAL_Transition *ctran;
+  unsigned int i;
+
+  s = GNUNET_malloc (sizeof (struct REGEX_ITERNAL_State));
+  s->id = ctx->state_id++;
+  s->index = -1;
+  s->lowlink = -1;
+
+  if (NULL == nfa_states)
+  {
+    GNUNET_asprintf (&s->name, "s%i", s->id);
+    return s;
+  }
+
+  s->nfa_set = *nfa_states;
+
+  if (nfa_states->off < 1)
+    return s;
+
+  /* Create a name based on 'nfa_states' */
+  len = nfa_states->off * 14 + 4;
+  s->name = GNUNET_malloc (len);
+  strcat (s->name, "{");
+  pos = s->name + 1;
+
+  for (i = 0; i < nfa_states->off; i++)
+  {
+    cstate = nfa_states->states[i];
+    GNUNET_snprintf (pos, pos - s->name + len,
+                     "%i,", cstate->id);
+    pos += strlen (pos);
+
+    /* Add a transition for each distinct label to NULL state */
+    for (ctran = cstate->transitions_head; NULL != ctran; ctran = ctran->next)    
+      if (NULL != ctran->label)
+        state_add_transition (ctx, s, ctran->label, NULL);    
+
+    /* If the nfa_states contain an accepting state, the new dfa state is also
+     * accepting. */
+    if (cstate->accepting)
+      s->accepting = 1;
+  }  
+  pos[-1] = '}';
+  s->name = GNUNET_realloc (s->name, strlen (s->name) + 1);
+
+  memset (nfa_states, 0, sizeof (struct REGEX_ITERNAL_StateSet));
+  return s;
+}
+
+
+/**
+ * Move from the given state 's' to the next state on transition 'str'. Consumes
+ * as much of the given 'str' as possible (usefull for strided DFAs). On return
+ * 's' will point to the next state, and the length of the substring used for
+ * this transition will be returned. If no transition possible 0 is returned and
+ * 's' points to NULL.
+ *
+ * @param s starting state, will point to the next state or NULL (if no
+ * transition possible)
+ * @param str edge label to follow (will match longest common prefix)
+ *
+ * @return length of the substring comsumed from 'str'
+ */
+static unsigned int
+dfa_move (struct REGEX_ITERNAL_State **s, const char *str)
+{
+  struct REGEX_ITERNAL_Transition *t;
+  struct REGEX_ITERNAL_State *new_s;
+  unsigned int len;
+  unsigned int max_len;
+
+  if (NULL == s)
+    return 0;
+
+  new_s = NULL;
+  max_len = 0;
+  for (t = (*s)->transitions_head; NULL != t; t = t->next)
+  {
+    len = strlen (t->label);
+
+    if (0 == strncmp (t->label, str, len))
+    {
+      if (len >= max_len)
+      {
+        max_len = len;
+        new_s = t->to_state;
+      }
+    }
+  }
+
+  *s = new_s;
+  return max_len;
+}
+
+
+/**
+ * Set the given state 'marked' to GNUNET_YES. Used by the
+ * 'dfa_remove_unreachable_states' function to detect unreachable states in the
+ * automaton.
+ *
+ * @param cls closure, not used.
+ * @param count count, not used.
+ * @param s state where the marked attribute will be set to GNUNET_YES.
+ */
+static void
+mark_states (void *cls, const unsigned int count, struct REGEX_ITERNAL_State *s)
+{
+  s->marked = GNUNET_YES;
+}
+
+
+/**
+ * Remove all unreachable states from DFA 'a'. Unreachable states are those
+ * states that are not reachable from the starting state.
+ *
+ * @param a DFA automaton
+ */
+static void
+dfa_remove_unreachable_states (struct REGEX_ITERNAL_Automaton *a)
+{
+  struct REGEX_ITERNAL_State *s;
+  struct REGEX_ITERNAL_State *s_next;
+
+  /* 1. unmark all states */
+  for (s = a->states_head; NULL != s; s = s->next)
+    s->marked = GNUNET_NO;
+
+  /* 2. traverse dfa from start state and mark all visited states */
+  REGEX_ITERNAL_automaton_traverse (a, a->start, NULL, NULL, &mark_states, NULL);
+
+  /* 3. delete all states that were not visited */
+  for (s = a->states_head; NULL != s; s = s_next)
+  {
+    s_next = s->next;
+    if (GNUNET_NO == s->marked)
+      automaton_remove_state (a, s);
+  }
+}
+
+
+/**
+ * Remove all dead states from the DFA 'a'. Dead states are those states that do
+ * not transition to any other state but themselves.
+ *
+ * @param a DFA automaton
+ */
+static void
+dfa_remove_dead_states (struct REGEX_ITERNAL_Automaton *a)
+{
+  struct REGEX_ITERNAL_State *s;
+  struct REGEX_ITERNAL_State *s_next;
+  struct REGEX_ITERNAL_Transition *t;
+  int dead;
+
+  GNUNET_assert (DFA == a->type);
+
+  for (s = a->states_head; NULL != s; s = s_next)
+  {
+    s_next = s->next;
+
+    if (s->accepting)
+      continue;
+
+    dead = 1;
+    for (t = s->transitions_head; NULL != t; t = t->next)
+    {
+      if (NULL != t->to_state && t->to_state != s)
+      {
+        dead = 0;
+        break;
+      }
+    }
+
+    if (0 == dead)
+      continue;
+
+    /* state s is dead, remove it */
+    automaton_remove_state (a, s);
+  }
+}
+
+
+/**
+ * Merge all non distinguishable states in the DFA 'a'
+ *
+ * @param ctx context
+ * @param a DFA automaton
+ * @return GNUNET_OK on success
+ */
+static int
+dfa_merge_nondistinguishable_states (struct REGEX_ITERNAL_Context *ctx,
+                                     struct REGEX_ITERNAL_Automaton *a)
+{
+  uint32_t *table;
+  struct REGEX_ITERNAL_State *s1;
+  struct REGEX_ITERNAL_State *s2;
+  struct REGEX_ITERNAL_Transition *t1;
+  struct REGEX_ITERNAL_Transition *t2;
+  struct REGEX_ITERNAL_State *s1_next;
+  struct REGEX_ITERNAL_State *s2_next;
+  int change;
+  unsigned int num_equal_edges;
+  unsigned int i;
+  unsigned int state_cnt;
+  unsigned long long idx;
+  unsigned long long idx1;
+
+  if ( (NULL == a) || (0 == a->state_count) )
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Could not merge nondistinguishable states, automaton was NULL.\n");
+    return GNUNET_SYSERR;
+  }
+
+  state_cnt = a->state_count;
+  table = GNUNET_malloc_large ((sizeof (uint32_t) * state_cnt * state_cnt / 32)  + sizeof (uint32_t));
+  if (NULL == table)
+  {
+    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "malloc");
+    return GNUNET_SYSERR;
+  }
+
+  for (i = 0, s1 = a->states_head; NULL != s1; s1 = s1->next)
+    s1->marked = i++;
+
+  /* Mark all pairs of accepting/!accepting states */
+  for (s1 = a->states_head; NULL != s1; s1 = s1->next)
+    for (s2 = a->states_head; NULL != s2; s2 = s2->next)
+      if ( (s1->accepting && !s2->accepting) ||
+           (!s1->accepting && s2->accepting) )
+      {
+        idx = s1->marked * state_cnt + s2->marked;
+        table[idx / 32] |= (1 << (idx % 32));
+      }
+
+  /* Find all equal states */
+  change = 1;
+  while (0 != change)
+  {
+    change = 0;
+    for (s1 = a->states_head; NULL != s1; s1 = s1->next)
+    {
+      for (s2 = a->states_head; NULL != s2 && s1 != s2; s2 = s2->next)
+      {
+        idx = s1->marked * state_cnt + s2->marked;
+        if (0 != (table[idx / 32] & (1 << (idx % 32))))
+          continue;
+        num_equal_edges = 0;
+        for (t1 = s1->transitions_head; NULL != t1; t1 = t1->next)
+        {
+          for (t2 = s2->transitions_head; NULL != t2; t2 = t2->next)
+          {
+            if (0 == strcmp (t1->label, t2->label))
+            {
+              num_equal_edges++;
+              /* same edge, but targets definitively different, so we're different
+                 as well */
+              if (t1->to_state->marked > t2->to_state->marked)
+                idx1 = t1->to_state->marked * state_cnt + t2->to_state->marked;
+              else
+                idx1 = t2->to_state->marked * state_cnt + t1->to_state->marked;
+              if (0 != (table[idx1 / 32] & (1 << (idx1 % 32))))
+              {
+                table[idx / 32] |= (1 << (idx % 32));
+                change = 1; /* changed a marker, need to run again */
+              }
+            }
+          }
+        }
+        if ( (num_equal_edges != s1->transition_count) ||
+             (num_equal_edges != s2->transition_count) )
+        {
+          /* Make sure ALL edges of possible equal states are the same */
+          table[idx / 32] |= (1 << (idx % 32));
+          change = 1;  /* changed a marker, need to run again */
+        }
+      }
+    }
+  }
+
+  /* Merge states that are equal */
+  for (s1 = a->states_head; NULL != s1; s1 = s1_next)
+  {
+    s1_next = s1->next;
+    for (s2 = a->states_head; NULL != s2 && s1 != s2; s2 = s2_next)
+    {
+      s2_next = s2->next;
+      idx = s1->marked * state_cnt + s2->marked;
+      if (0 == (table[idx / 32] & (1 << (idx % 32))))
+        automaton_merge_states (ctx, a, s1, s2);
+    }
+  }
+
+  GNUNET_free (table);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Minimize the given DFA 'a' by removing all unreachable states, removing all
+ * dead states and merging all non distinguishable states
+ *
+ * @param ctx context
+ * @param a DFA automaton
+ * @return GNUNET_OK on success
+ */
+static int
+dfa_minimize (struct REGEX_ITERNAL_Context *ctx,
+              struct REGEX_ITERNAL_Automaton *a)
+{
+  if (NULL == a)
+    return GNUNET_SYSERR;
+
+  GNUNET_assert (DFA == a->type);
+
+  /* 1. remove unreachable states */
+  dfa_remove_unreachable_states (a);
+
+  /* 2. remove dead states */
+  dfa_remove_dead_states (a);
+
+  /* 3. Merge nondistinguishable states */
+  if (GNUNET_OK != dfa_merge_nondistinguishable_states (ctx, a))
+    return GNUNET_SYSERR;
+  return GNUNET_OK;
+}
+
+
+/**
+ * Context for adding strided transitions to a DFA.
+ */
+struct REGEX_ITERNAL_Strided_Context
+{
+  /**
+   * Length of the strides.
+   */
+  const unsigned int stride;
+
+  /**
+   * Strided transitions DLL. New strided transitions will be stored in this DLL
+   * and afterwards added to the DFA.
+   */
+  struct REGEX_ITERNAL_Transition *transitions_head;
+
+  /**
+   * Strided transitions DLL.
+   */
+  struct REGEX_ITERNAL_Transition *transitions_tail;
+};
+
+
+/**
+ * Recursive helper function to add strides to a DFA.
+ *
+ * @param cls context, contains stride length and strided transitions DLL.
+ * @param depth current depth of the depth-first traversal of the graph.
+ * @param label current label, string that contains all labels on the path from
+ *        'start' to 's'.
+ * @param start start state for the depth-first traversal of the graph.
+ * @param s current state in the depth-first traversal
+ */
+void
+dfa_add_multi_strides_helper (void *cls, const unsigned int depth, char *label,
+                              struct REGEX_ITERNAL_State *start,
+                              struct REGEX_ITERNAL_State *s)
+{
+  struct REGEX_ITERNAL_Strided_Context *ctx = cls;
+  struct REGEX_ITERNAL_Transition *t;
+  char *new_label;
+
+  if (depth == ctx->stride)
+  {
+    t = GNUNET_malloc (sizeof (struct REGEX_ITERNAL_Transition));
+    t->label = GNUNET_strdup (label);
+    t->to_state = s;
+    t->from_state = start;
+    GNUNET_CONTAINER_DLL_insert (ctx->transitions_head, ctx->transitions_tail,
+                                 t);
+  }
+  else
+  {
+    for (t = s->transitions_head; NULL != t; t = t->next)
+    {
+      /* Do not consider self-loops, because it end's up in too many
+       * transitions */
+      if (t->to_state == t->from_state)
+        continue;
+
+      if (NULL != label)
+      {
+        GNUNET_asprintf (&new_label, "%s%s", label, t->label);
+      }
+      else
+        new_label = GNUNET_strdup (t->label);
+
+      dfa_add_multi_strides_helper (cls, (depth + 1), new_label, start,
+                                    t->to_state);
+    }
+  }
+  GNUNET_free_non_null (label);
+}
+
+
+/**
+ * Function called for each state in the DFA. Starts a traversal of depth set in
+ * context starting from state 's'.
+ *
+ * @param cls context.
+ * @param count not used.
+ * @param s current state.
+ */
+void
+dfa_add_multi_strides (void *cls, const unsigned int count,
+                       struct REGEX_ITERNAL_State *s)
+{
+  dfa_add_multi_strides_helper (cls, 0, NULL, s, s);
+}
+
+
+/**
+ * Adds multi-strided transitions to the given 'dfa'.
+ *
+ * @param regex_ctx regex context needed to add transitions to the automaton.
+ * @param dfa DFA to which the multi strided transitions should be added.
+ * @param stride_len length of the strides.
+ */
+void
+REGEX_ITERNAL_dfa_add_multi_strides (struct REGEX_ITERNAL_Context *regex_ctx,
+                                    struct REGEX_ITERNAL_Automaton *dfa,
+                                    const unsigned int stride_len)
+{
+  struct REGEX_ITERNAL_Strided_Context ctx = { stride_len, NULL, NULL };
+  struct REGEX_ITERNAL_Transition *t;
+  struct REGEX_ITERNAL_Transition *t_next;
+
+  if (1 > stride_len || GNUNET_YES == dfa->is_multistrided)
+    return;
+
+  /* Compute the new transitions of given stride_len */
+  REGEX_ITERNAL_automaton_traverse (dfa, dfa->start, NULL, NULL,
+                                   &dfa_add_multi_strides, &ctx);
+
+  /* Add all the new transitions to the automaton. */
+  for (t = ctx.transitions_head; NULL != t; t = t_next)
+  {
+    t_next = t->next;
+    state_add_transition (regex_ctx, t->from_state, t->label, t->to_state);
+    GNUNET_CONTAINER_DLL_remove (ctx.transitions_head, ctx.transitions_tail, t);
+    GNUNET_free_non_null (t->label);
+    GNUNET_free (t);
+  }
+
+  /* Mark this automaton as multistrided */
+  dfa->is_multistrided = GNUNET_YES;
+}
+
+/**
+ * Recursive Helper function for DFA path compression. Does DFS on the DFA graph
+ * and adds new transitions to the given transitions DLL and marks states that
+ * should be removed by setting state->contained to GNUNET_YES.
+ *
+ * @param dfa DFA for which the paths should be compressed.
+ * @param start starting state for linear path search.
+ * @param cur current state in the recursive DFS.
+ * @param label current label (string of traversed labels).
+ * @param max_len maximal path compression length.
+ * @param transitions_head transitions DLL.
+ * @param transitions_tail transitions DLL.
+ */
+void
+dfa_compress_paths_helper (struct REGEX_ITERNAL_Automaton *dfa,
+                           struct REGEX_ITERNAL_State *start,
+                           struct REGEX_ITERNAL_State *cur, char *label,
+                           unsigned int max_len,
+                           struct REGEX_ITERNAL_Transition **transitions_head,
+                           struct REGEX_ITERNAL_Transition **transitions_tail)
+{
+  struct REGEX_ITERNAL_Transition *t;
+  char *new_label;
+
+
+  if (NULL != label &&
+      ((cur->incoming_transition_count > 1 || GNUNET_YES == cur->accepting ||
+        GNUNET_YES == cur->marked) || (start != dfa->start && max_len > 0 &&
+                                       max_len == strlen (label)) ||
+       (start == dfa->start && GNUNET_REGEX_INITIAL_BYTES == strlen (label))))
+  {
+    t = GNUNET_malloc (sizeof (struct REGEX_ITERNAL_Transition));
+    t->label = GNUNET_strdup (label);
+    t->to_state = cur;
+    t->from_state = start;
+    GNUNET_CONTAINER_DLL_insert (*transitions_head, *transitions_tail, t);
+
+    if (GNUNET_NO == cur->marked)
+    {
+      dfa_compress_paths_helper (dfa, cur, cur, NULL, max_len, transitions_head,
+                                 transitions_tail);
+    }
+    return;
+  }
+  else if (cur != start)
+    cur->contained = GNUNET_YES;
+
+  if (GNUNET_YES == cur->marked && cur != start)
+    return;
+
+  cur->marked = GNUNET_YES;
+
+
+  for (t = cur->transitions_head; NULL != t; t = t->next)
+  {
+    if (NULL != label)
+      GNUNET_asprintf (&new_label, "%s%s", label, t->label);
+    else
+      new_label = GNUNET_strdup (t->label);
+
+    if (t->to_state != cur)
+    {
+      dfa_compress_paths_helper (dfa, start, t->to_state, new_label, max_len,
+                                 transitions_head, transitions_tail);
+    }
+    GNUNET_free (new_label);
+  }
+}
+
+
+/**
+ * Compress paths in the given 'dfa'. Linear paths like 0->1->2->3 will be
+ * compressed to 0->3 by combining transitions.
+ *
+ * @param regex_ctx context for adding new transitions.
+ * @param dfa DFA representation, will directly modify the given DFA.
+ * @param max_len maximal length of the compressed paths.
+ */
+static void
+dfa_compress_paths (struct REGEX_ITERNAL_Context *regex_ctx,
+                    struct REGEX_ITERNAL_Automaton *dfa, unsigned int max_len)
+{
+  struct REGEX_ITERNAL_State *s;
+  struct REGEX_ITERNAL_State *s_next;
+  struct REGEX_ITERNAL_Transition *t;
+  struct REGEX_ITERNAL_Transition *t_next;
+  struct REGEX_ITERNAL_Transition *transitions_head = NULL;
+  struct REGEX_ITERNAL_Transition *transitions_tail = NULL;
+
+  if (NULL == dfa)
+    return;
+
+  /* Count the incoming transitions on each state. */
+  for (s = dfa->states_head; NULL != s; s = s->next)
+  {
+    for (t = s->transitions_head; NULL != t; t = t->next)
+    {
+      if (NULL != t->to_state)
+        t->to_state->incoming_transition_count++;
+    }
+  }
+
+  /* Unmark all states. */
+  for (s = dfa->states_head; NULL != s; s = s->next)
+  {
+    s->marked = GNUNET_NO;
+    s->contained = GNUNET_NO;
+  }
+
+  /* Add strides and mark states that can be deleted. */
+  dfa_compress_paths_helper (dfa, dfa->start, dfa->start, NULL, max_len,
+                             &transitions_head, &transitions_tail);
+
+  /* Add all the new transitions to the automaton. */
+  for (t = transitions_head; NULL != t; t = t_next)
+  {
+    t_next = t->next;
+    state_add_transition (regex_ctx, t->from_state, t->label, t->to_state);
+    GNUNET_CONTAINER_DLL_remove (transitions_head, transitions_tail, t);
+    GNUNET_free_non_null (t->label);
+    GNUNET_free (t);
+  }
+
+  /* Remove marked states (including their incoming and outgoing transitions). */
+  for (s = dfa->states_head; NULL != s; s = s_next)
+  {
+    s_next = s->next;
+    if (GNUNET_YES == s->contained)
+      automaton_remove_state (dfa, s);
+  }
+}
+
+
+/**
+ * Creates a new NFA fragment. Needs to be cleared using
+ * automaton_fragment_clear.
+ *
+ * @param start starting state
+ * @param end end state
+ *
+ * @return new NFA fragment
+ */
+static struct REGEX_ITERNAL_Automaton *
+nfa_fragment_create (struct REGEX_ITERNAL_State *start,
+                     struct REGEX_ITERNAL_State *end)
+{
+  struct REGEX_ITERNAL_Automaton *n;
+
+  n = GNUNET_malloc (sizeof (struct REGEX_ITERNAL_Automaton));
+
+  n->type = NFA;
+  n->start = NULL;
+  n->end = NULL;
+  n->state_count = 0;
+
+  if (NULL == start || NULL == end)
+    return n;
+
+  automaton_add_state (n, end);
+  automaton_add_state (n, start);
+
+  n->state_count = 2;
+
+  n->start = start;
+  n->end = end;
+
+  return n;
+}
+
+
+/**
+ * Adds a list of states to the given automaton 'n'.
+ *
+ * @param n automaton to which the states should be added
+ * @param states_head head of the DLL of states
+ * @param states_tail tail of the DLL of states
+ */
+static void
+nfa_add_states (struct REGEX_ITERNAL_Automaton *n,
+                struct REGEX_ITERNAL_State *states_head,
+                struct REGEX_ITERNAL_State *states_tail)
+{
+  struct REGEX_ITERNAL_State *s;
+
+  if (NULL == n || NULL == states_head)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not add states\n");
+    return;
+  }
+
+  if (NULL == n->states_head)
+  {
+    n->states_head = states_head;
+    n->states_tail = states_tail;
+    return;
+  }
+
+  if (NULL != states_head)
+  {
+    n->states_tail->next = states_head;
+    n->states_tail = states_tail;
+  }
+
+  for (s = states_head; NULL != s; s = s->next)
+    n->state_count++;
+}
+
+
+/**
+ * Creates a new NFA state. Needs to be freed using automaton_destroy_state.
+ *
+ * @param ctx context
+ * @param accepting is it an accepting state or not
+ *
+ * @return new NFA state
+ */
+static struct REGEX_ITERNAL_State *
+nfa_state_create (struct REGEX_ITERNAL_Context *ctx, int accepting)
+{
+  struct REGEX_ITERNAL_State *s;
+
+  s = GNUNET_malloc (sizeof (struct REGEX_ITERNAL_State));
+  s->id = ctx->state_id++;
+  s->accepting = accepting;
+  s->marked = GNUNET_NO;
+  s->contained = 0;
+  s->index = -1;
+  s->lowlink = -1;
+  s->scc_id = 0;
+  s->name = NULL;
+  GNUNET_asprintf (&s->name, "s%i", s->id);
+
+  return s;
+}
+
+
+/**
+ * Calculates the closure set for the given set of states.
+ *
+ * @param ret set to sorted nfa closure on 'label' (epsilon closure if 'label' is NULL)
+ * @param nfa the NFA containing 's'
+ * @param states list of states on which to base the closure on
+ * @param label transitioning label for which to base the closure on,
+ *                pass NULL for epsilon transition
+ */
+static void
+nfa_closure_set_create (struct REGEX_ITERNAL_StateSet *ret,
+                        struct REGEX_ITERNAL_Automaton *nfa,
+                        struct REGEX_ITERNAL_StateSet *states, const char *label)
+{
+  struct REGEX_ITERNAL_State *s;
+  unsigned int i;
+  struct REGEX_ITERNAL_StateSet_MDLL cls_stack;
+  struct REGEX_ITERNAL_State *clsstate;
+  struct REGEX_ITERNAL_State *currentstate;
+  struct REGEX_ITERNAL_Transition *ctran;
+
+  memset (ret, 0, sizeof (struct REGEX_ITERNAL_StateSet));
+  if (NULL == states)
+    return;
+
+  for (i = 0; i < states->off; i++)
+  {
+    s = states->states[i];
+
+    /* Add start state to closure only for epsilon closure */
+    if (NULL == label)
+      state_set_append (ret, s);
+    
+    /* initialize work stack */
+    cls_stack.head = NULL;
+    cls_stack.tail = NULL;
+    GNUNET_CONTAINER_MDLL_insert (ST, cls_stack.head, cls_stack.tail, s);
+    cls_stack.len = 1;
+
+    while (NULL != (currentstate = cls_stack.tail))
+    {
+      GNUNET_CONTAINER_MDLL_remove (ST, cls_stack.head, cls_stack.tail,
+                                    currentstate);
+      cls_stack.len--;      
+      for (ctran = currentstate->transitions_head; NULL != ctran;
+           ctran = ctran->next)
+      {
+        if (NULL == (clsstate = ctran->to_state))
+          continue;
+        if (0 != clsstate->contained)
+          continue;
+        if (0 != nullstrcmp (label, ctran->label))
+          continue;
+        state_set_append (ret, clsstate);
+        GNUNET_CONTAINER_MDLL_insert_tail (ST, cls_stack.head, cls_stack.tail,
+                                           clsstate);
+        cls_stack.len++;
+        clsstate->contained = 1;
+      }    
+    }
+  }
+  for (i = 0; i < ret->off; i++)
+    ret->states[i]->contained = 0;
+
+  if (ret->off > 1)
+    qsort (ret->states, ret->off, sizeof (struct REGEX_ITERNAL_State *),
+           &state_compare);
+}
+
+
+/**
+ * Pops two NFA fragments (a, b) from the stack and concatenates them (ab)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_concatenation (struct REGEX_ITERNAL_Context *ctx)
+{
+  struct REGEX_ITERNAL_Automaton *a;
+  struct REGEX_ITERNAL_Automaton *b;
+  struct REGEX_ITERNAL_Automaton *new_nfa;
+
+  b = ctx->stack_tail;
+  GNUNET_assert (NULL != b);
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, b);
+  a = ctx->stack_tail;
+  GNUNET_assert (NULL != a);
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  state_add_transition (ctx, a->end, NULL, b->start);
+  a->end->accepting = 0;
+  b->end->accepting = 1;
+
+  new_nfa = nfa_fragment_create (NULL, NULL);
+  nfa_add_states (new_nfa, a->states_head, a->states_tail);
+  nfa_add_states (new_nfa, b->states_head, b->states_tail);
+  new_nfa->start = a->start;
+  new_nfa->end = b->end;
+  new_nfa->state_count += a->state_count + b->state_count;
+  automaton_fragment_clear (a);
+  automaton_fragment_clear (b);
+
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, new_nfa);
+}
+
+
+/**
+ * Pops a NFA fragment from the stack (a) and adds a new fragment (a*)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_star_op (struct REGEX_ITERNAL_Context *ctx)
+{
+  struct REGEX_ITERNAL_Automaton *a;
+  struct REGEX_ITERNAL_Automaton *new_nfa;
+  struct REGEX_ITERNAL_State *start;
+  struct REGEX_ITERNAL_State *end;
+
+  a = ctx->stack_tail;
+
+  if (NULL == a)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "nfa_add_star_op failed, because there was no element on the stack");
+    return;
+  }
+
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  start = nfa_state_create (ctx, 0);
+  end = nfa_state_create (ctx, 1);
+
+  state_add_transition (ctx, start, NULL, a->start);
+  state_add_transition (ctx, start, NULL, end);
+  state_add_transition (ctx, a->end, NULL, a->start);
+  state_add_transition (ctx, a->end, NULL, end);
+
+  a->end->accepting = 0;
+  end->accepting = 1;
+
+  new_nfa = nfa_fragment_create (start, end);
+  nfa_add_states (new_nfa, a->states_head, a->states_tail);
+  automaton_fragment_clear (a);
+
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, new_nfa);
+}
+
+
+/**
+ * Pops an NFA fragment (a) from the stack and adds a new fragment (a+)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_plus_op (struct REGEX_ITERNAL_Context *ctx)
+{
+  struct REGEX_ITERNAL_Automaton *a;
+
+  a = ctx->stack_tail;
+
+  if (NULL == a)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "nfa_add_plus_op failed, because there was no element on the stack");
+    return;
+  }
+
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  state_add_transition (ctx, a->end, NULL, a->start);
+
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, a);
+}
+
+
+/**
+ * Pops an NFA fragment (a) from the stack and adds a new fragment (a?)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_question_op (struct REGEX_ITERNAL_Context *ctx)
+{
+  struct REGEX_ITERNAL_Automaton *a;
+  struct REGEX_ITERNAL_Automaton *new_nfa;
+  struct REGEX_ITERNAL_State *start;
+  struct REGEX_ITERNAL_State *end;
+
+  a = ctx->stack_tail;
+
+  if (NULL == a)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "nfa_add_question_op failed, because there was no element on the stack");
+    return;
+  }
+
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  start = nfa_state_create (ctx, 0);
+  end = nfa_state_create (ctx, 1);
+
+  state_add_transition (ctx, start, NULL, a->start);
+  state_add_transition (ctx, start, NULL, end);
+  state_add_transition (ctx, a->end, NULL, end);
+
+  a->end->accepting = 0;
+
+  new_nfa = nfa_fragment_create (start, end);
+  nfa_add_states (new_nfa, a->states_head, a->states_tail);
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, new_nfa);
+  automaton_fragment_clear (a);
+}
+
+
+/**
+ * Pops two NFA fragments (a, b) from the stack and adds a new NFA fragment that
+ * alternates between a and b (a|b)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_alternation (struct REGEX_ITERNAL_Context *ctx)
+{
+  struct REGEX_ITERNAL_Automaton *a;
+  struct REGEX_ITERNAL_Automaton *b;
+  struct REGEX_ITERNAL_Automaton *new_nfa;
+  struct REGEX_ITERNAL_State *start;
+  struct REGEX_ITERNAL_State *end;
+
+  b = ctx->stack_tail;
+  GNUNET_assert (NULL != b);
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, b);
+  a = ctx->stack_tail;
+  GNUNET_assert (NULL != a);
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  start = nfa_state_create (ctx, 0);
+  end = nfa_state_create (ctx, 1);
+  state_add_transition (ctx, start, NULL, a->start);
+  state_add_transition (ctx, start, NULL, b->start);
+
+  state_add_transition (ctx, a->end, NULL, end);
+  state_add_transition (ctx, b->end, NULL, end);
+
+  a->end->accepting = 0;
+  b->end->accepting = 0;
+  end->accepting = 1;
+
+  new_nfa = nfa_fragment_create (start, end);
+  nfa_add_states (new_nfa, a->states_head, a->states_tail);
+  nfa_add_states (new_nfa, b->states_head, b->states_tail);
+  automaton_fragment_clear (a);
+  automaton_fragment_clear (b);
+
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, new_nfa);
+}
+
+
+/**
+ * Adds a new nfa fragment to the stack
+ *
+ * @param ctx context
+ * @param label label for nfa transition
+ */
+static void
+nfa_add_label (struct REGEX_ITERNAL_Context *ctx, const char *label)
+{
+  struct REGEX_ITERNAL_Automaton *n;
+  struct REGEX_ITERNAL_State *start;
+  struct REGEX_ITERNAL_State *end;
+
+  GNUNET_assert (NULL != ctx);
+
+  start = nfa_state_create (ctx, 0);
+  end = nfa_state_create (ctx, 1);
+  state_add_transition (ctx, start, label, end);
+  n = nfa_fragment_create (start, end);
+  GNUNET_assert (NULL != n);
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, n);
+}
+
+
+/**
+ * Initialize a new context
+ *
+ * @param ctx context
+ */
+static void
+REGEX_ITERNAL_context_init (struct REGEX_ITERNAL_Context *ctx)
+{
+  if (NULL == ctx)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Context was NULL!");
+    return;
+  }
+  ctx->state_id = 0;
+  ctx->transition_id = 0;
+  ctx->stack_head = NULL;
+  ctx->stack_tail = NULL;
+}
+
+
+/**
+ * Construct an NFA by parsing the regex string of length 'len'.
+ *
+ * @param regex regular expression string
+ * @param len length of the string
+ *
+ * @return NFA, needs to be freed using REGEX_ITERNAL_destroy_automaton
+ */
+struct REGEX_ITERNAL_Automaton *
+REGEX_ITERNAL_construct_nfa (const char *regex, const size_t len)
+{
+  struct REGEX_ITERNAL_Context ctx;
+  struct REGEX_ITERNAL_Automaton *nfa;
+  const char *regexp;
+  char curlabel[2];
+  char *error_msg;
+  unsigned int count;
+  unsigned int altcount;
+  unsigned int atomcount;
+  unsigned int poff;
+  unsigned int psize;
+  struct
+  {
+    int altcount;
+    int atomcount;
+  }     *p;
+
+  if (NULL == regex || 0 == strlen (regex) || 0 == len)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Could not parse regex. Empty regex string provided.\n");
+
+    return NULL;
+  }
+  REGEX_ITERNAL_context_init (&ctx);
+
+  regexp = regex;
+  curlabel[1] = '\0';
+  p = NULL;
+  error_msg = NULL;
+  altcount = 0;
+  atomcount = 0;
+  poff = 0;
+  psize = 0;
+
+  for (count = 0; count < len && *regexp; count++, regexp++)
+  {
+    switch (*regexp)
+    {
+    case '(':
+      if (atomcount > 1)
+      {
+        --atomcount;
+        nfa_add_concatenation (&ctx);
+      }
+      if (poff == psize)
+        GNUNET_array_grow (p, psize, psize * 2 + 4);
+      p[poff].altcount = altcount;
+      p[poff].atomcount = atomcount;
+      poff++;
+      altcount = 0;
+      atomcount = 0;
+      break;
+    case '|':
+      if (0 == atomcount)
+      {
+        error_msg = "Cannot append '|' to nothing";
+        goto error;
+      }
+      while (--atomcount > 0)
+        nfa_add_concatenation (&ctx);
+      altcount++;
+      break;
+    case ')':
+      if (0 == poff)
+      {
+        error_msg = "Missing opening '('";
+        goto error;
+      }
+      if (0 == atomcount)
+      {
+        /* Ignore this: "()" */
+        poff--;
+        altcount = p[poff].altcount;
+        atomcount = p[poff].atomcount;
+        break;
+      }
+      while (--atomcount > 0)
+        nfa_add_concatenation (&ctx);
+      for (; altcount > 0; altcount--)
+        nfa_add_alternation (&ctx);
+      poff--;
+      altcount = p[poff].altcount;
+      atomcount = p[poff].atomcount;
+      atomcount++;
+      break;
+    case '*':
+      if (atomcount == 0)
+      {
+        error_msg = "Cannot append '*' to nothing";
+        goto error;
+      }
+      nfa_add_star_op (&ctx);
+      break;
+    case '+':
+      if (atomcount == 0)
+      {
+        error_msg = "Cannot append '+' to nothing";
+        goto error;
+      }
+      nfa_add_plus_op (&ctx);
+      break;
+    case '?':
+      if (atomcount == 0)
+      {
+        error_msg = "Cannot append '?' to nothing";
+        goto error;
+      }
+      nfa_add_question_op (&ctx);
+      break;
+    default:
+      if (atomcount > 1)
+      {
+        --atomcount;
+        nfa_add_concatenation (&ctx);
+      }
+      curlabel[0] = *regexp;
+      nfa_add_label (&ctx, curlabel);
+      atomcount++;
+      break;
+    }
+  }
+  if (0 != poff)
+  {
+    error_msg = "Unbalanced parenthesis";
+    goto error;
+  }
+  while (--atomcount > 0)
+    nfa_add_concatenation (&ctx);
+  for (; altcount > 0; altcount--)
+    nfa_add_alternation (&ctx);
+
+  GNUNET_array_grow (p, psize, 0);
+
+  nfa = ctx.stack_tail;
+  GNUNET_CONTAINER_DLL_remove (ctx.stack_head, ctx.stack_tail, nfa);
+
+  if (NULL != ctx.stack_head)
+  {
+    error_msg = "Creating the NFA failed. NFA stack was not empty!";
+    goto error;
+  }
+
+  /* Remember the regex that was used to generate this NFA */
+  nfa->regex = GNUNET_strdup (regex);
+
+  /* create depth-first numbering of the states for pretty printing */
+  REGEX_ITERNAL_automaton_traverse (nfa, NULL, NULL, NULL, &number_states, NULL);
+
+  /* No multistriding added so far */
+  nfa->is_multistrided = GNUNET_NO;
+
+  return nfa;
+
+error:
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not parse regex: `%s'\n", regex);
+  if (NULL != error_msg)
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "%s\n", error_msg);
+
+  GNUNET_free_non_null (p);
+
+  while (NULL != (nfa = ctx.stack_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (ctx.stack_head, ctx.stack_tail, nfa);
+    REGEX_ITERNAL_automaton_destroy (nfa);
+  }
+
+  return NULL;
+}
+
+
+/**
+ * Create DFA states based on given 'nfa' and starting with 'dfa_state'.
+ *
+ * @param ctx context.
+ * @param nfa NFA automaton.
+ * @param dfa DFA automaton.
+ * @param dfa_state current dfa state, pass epsilon closure of first nfa state
+ *                  for starting.
+ */
+static void
+construct_dfa_states (struct REGEX_ITERNAL_Context *ctx,
+                      struct REGEX_ITERNAL_Automaton *nfa,
+                      struct REGEX_ITERNAL_Automaton *dfa,
+                      struct REGEX_ITERNAL_State *dfa_state)
+{
+  struct REGEX_ITERNAL_Transition *ctran;
+  struct REGEX_ITERNAL_State *new_dfa_state;
+  struct REGEX_ITERNAL_State *state_contains;
+  struct REGEX_ITERNAL_State *state_iter;
+  struct REGEX_ITERNAL_StateSet tmp;
+  struct REGEX_ITERNAL_StateSet nfa_set;
+
+  for (ctran = dfa_state->transitions_head; NULL != ctran; ctran = ctran->next)
+  {
+    if (NULL == ctran->label || NULL != ctran->to_state)
+      continue;
+
+    nfa_closure_set_create (&tmp, nfa, &dfa_state->nfa_set, ctran->label);
+    nfa_closure_set_create (&nfa_set, nfa, &tmp, NULL);
+    state_set_clear (&tmp);
+
+    state_contains = NULL;
+    for (state_iter = dfa->states_head; NULL != state_iter;
+         state_iter = state_iter->next)
+    {
+      if (0 == state_set_compare (&state_iter->nfa_set, &nfa_set))
+      {
+        state_contains = state_iter;
+        break;
+      }
+    }
+    if (NULL == state_contains)
+    {
+      new_dfa_state = dfa_state_create (ctx, &nfa_set);
+      automaton_add_state (dfa, new_dfa_state);
+      ctran->to_state = new_dfa_state;
+      construct_dfa_states (ctx, nfa, dfa, new_dfa_state);
+    }
+    else
+    {
+      ctran->to_state = state_contains;
+      state_set_clear (&nfa_set);
+    }
+  }
+}
+
+
+/**
+ * Construct DFA for the given 'regex' of length 'len'.
+ *
+ * Path compression means, that for example a DFA o -> a -> b -> c -> o will be
+ * compressed to o -> abc -> o. Note that this parameter influences the
+ * non-determinism of states of the resulting NFA in the DHT (number of outgoing
+ * edges with the same label). For example for an application that stores IPv4
+ * addresses as bitstrings it could make sense to limit the path compression to
+ * 4 or 8.
+ *
+ * @param regex regular expression string.
+ * @param len length of the regular expression.
+ * @param max_path_len limit the path compression length to the
+ *        given value. If set to 1, no path compression is applied. Set to 0 for
+ *        maximal possible path compression (generally not desireable).
+ * @return DFA, needs to be freed using REGEX_ITERNAL_automaton_destroy.
+ */
+struct REGEX_ITERNAL_Automaton *
+REGEX_ITERNAL_construct_dfa (const char *regex, const size_t len,
+                            unsigned int max_path_len)
+{
+  struct REGEX_ITERNAL_Context ctx;
+  struct REGEX_ITERNAL_Automaton *dfa;
+  struct REGEX_ITERNAL_Automaton *nfa;
+  struct REGEX_ITERNAL_StateSet nfa_start_eps_cls;
+  struct REGEX_ITERNAL_StateSet singleton_set;
+
+  REGEX_ITERNAL_context_init (&ctx);
+
+  /* Create NFA */
+  // fprintf (stderr, "N");
+  nfa = REGEX_ITERNAL_construct_nfa (regex, len);
+
+  if (NULL == nfa)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Could not create DFA, because NFA creation failed\n");
+    return NULL;
+  }
+
+  dfa = GNUNET_malloc (sizeof (struct REGEX_ITERNAL_Automaton));
+  dfa->type = DFA;
+  dfa->regex = GNUNET_strdup (regex);
+
+  /* Create DFA start state from epsilon closure */
+  memset (&singleton_set, 0, sizeof (struct REGEX_ITERNAL_StateSet));
+  state_set_append (&singleton_set, nfa->start);
+  nfa_closure_set_create (&nfa_start_eps_cls, nfa, &singleton_set, NULL);
+  state_set_clear (&singleton_set);
+  dfa->start = dfa_state_create (&ctx, &nfa_start_eps_cls);
+  automaton_add_state (dfa, dfa->start);
+
+  // fprintf (stderr, "D");
+  construct_dfa_states (&ctx, nfa, dfa, dfa->start);
+  REGEX_ITERNAL_automaton_destroy (nfa);
+
+  /* Minimize DFA */
+  // fprintf (stderr, "M");
+  if (GNUNET_OK != dfa_minimize (&ctx, dfa))
+  {
+    REGEX_ITERNAL_automaton_destroy (dfa);
+    return NULL;
+  }
+
+  /* Create proofs and hashes for all states */
+  if (GNUNET_OK != automaton_create_proofs (dfa))
+  {
+    REGEX_ITERNAL_automaton_destroy (dfa);
+    return NULL;
+  }
+
+  /* Compress linear DFA paths */
+  if (1 != max_path_len)
+    dfa_compress_paths (&ctx, dfa, max_path_len);
+
+  return dfa;
+}
+
+
+/**
+ * Free the memory allocated by constructing the REGEX_ITERNAL_Automaton data
+ * structure.
+ *
+ * @param a automaton to be destroyed
+ */
+void
+REGEX_ITERNAL_automaton_destroy (struct REGEX_ITERNAL_Automaton *a)
+{
+  struct REGEX_ITERNAL_State *s;
+  struct REGEX_ITERNAL_State *next_state;
+
+  if (NULL == a)
+    return;
+
+  GNUNET_free_non_null (a->regex);
+  GNUNET_free_non_null (a->canonical_regex);
+
+  for (s = a->states_head; NULL != s; s = next_state)
+  {
+    next_state = s->next;
+    GNUNET_CONTAINER_DLL_remove (a->states_head, a->states_tail, s);
+    automaton_destroy_state (s);
+  }
+
+  GNUNET_free (a);
+}
+
+
+/**
+ * Evaluates the given string using the given DFA automaton
+ *
+ * @param a automaton, type must be DFA
+ * @param string string that should be evaluated
+ *
+ * @return 0 if string matches, non 0 otherwise
+ */
+static int
+evaluate_dfa (struct REGEX_ITERNAL_Automaton *a, const char *string)
+{
+  const char *strp;
+  struct REGEX_ITERNAL_State *s;
+  unsigned int step_len;
+
+  if (DFA != a->type)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Tried to evaluate DFA, but NFA automaton given");
+    return -1;
+  }
+
+  s = a->start;
+
+  /* If the string is empty but the starting state is accepting, we accept. */
+  if ((NULL == string || 0 == strlen (string)) && s->accepting)
+    return 0;
+
+  for (strp = string; NULL != strp && *strp; strp += step_len)
+  {
+    step_len = dfa_move (&s, strp);
+
+    if (NULL == s)
+      break;
+  }
+
+  if (NULL != s && s->accepting)
+    return 0;
+
+  return 1;
+}
+
+
+/**
+ * Evaluates the given string using the given NFA automaton
+ *
+ * @param a automaton, type must be NFA
+ * @param string string that should be evaluated
+ *
+ * @return 0 if string matches, non 0 otherwise
+ */
+static int
+evaluate_nfa (struct REGEX_ITERNAL_Automaton *a, const char *string)
+{
+  const char *strp;
+  char str[2];
+  struct REGEX_ITERNAL_State *s;
+  struct REGEX_ITERNAL_StateSet sset;
+  struct REGEX_ITERNAL_StateSet new_sset;
+  struct REGEX_ITERNAL_StateSet singleton_set;
+  unsigned int i;
+  int result;
+
+  if (NFA != a->type)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Tried to evaluate NFA, but DFA automaton given");
+    return -1;
+  }
+
+  /* If the string is empty but the starting state is accepting, we accept. */
+  if ((NULL == string || 0 == strlen (string)) && a->start->accepting)
+    return 0;
+
+  result = 1;
+  memset (&singleton_set, 0, sizeof (struct REGEX_ITERNAL_StateSet));
+  state_set_append (&singleton_set, a->start);
+  nfa_closure_set_create (&sset, a, &singleton_set, NULL);
+  state_set_clear (&singleton_set);
+
+  str[1] = '\0';
+  for (strp = string; NULL != strp && *strp; strp++)
+  {
+    str[0] = *strp;
+    nfa_closure_set_create (&new_sset, a, &sset, str);
+    state_set_clear (&sset);
+    nfa_closure_set_create (&sset, a, &new_sset, 0);
+    state_set_clear (&new_sset);
+  }
+
+  for (i = 0; i < sset.off; i++)
+  {
+    s = sset.states[i];
+    if ( (NULL != s) && (s->accepting) )
+    {
+      result = 0;
+      break;
+    }
+  }
+
+  state_set_clear (&sset);
+  return result;
+}
+
+
+/**
+ * Evaluates the given 'string' against the given compiled regex
+ *
+ * @param a automaton
+ * @param string string to check
+ *
+ * @return 0 if string matches, non 0 otherwise
+ */
+int
+REGEX_ITERNAL_eval (struct REGEX_ITERNAL_Automaton *a, const char *string)
+{
+  int result;
+
+  switch (a->type)
+  {
+  case DFA:
+    result = evaluate_dfa (a, string);
+    break;
+  case NFA:
+    result = evaluate_nfa (a, string);
+    break;
+  default:
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Evaluating regex failed, automaton has no type!\n");
+    result = GNUNET_SYSERR;
+    break;
+  }
+
+  return result;
+}
+
+
+/**
+ * Get the canonical regex of the given automaton.
+ * When constructing the automaton a proof is computed for each state,
+ * consisting of the regular expression leading to this state. A complete
+ * regex for the automaton can be computed by combining these proofs.
+ * As of now this function is only useful for testing.
+ *
+ * @param a automaton for which the canonical regex should be returned.
+ *
+ * @return
+ */
+const char *
+REGEX_ITERNAL_get_canonical_regex (struct REGEX_ITERNAL_Automaton *a)
+{
+  if (NULL == a)
+    return NULL;
+
+  return a->canonical_regex;
+}
+
+
+/**
+ * Get the number of transitions that are contained in the given automaton.
+ *
+ * @param a automaton for which the number of transitions should be returned.
+ *
+ * @return number of transitions in the given automaton.
+ */
+unsigned int
+REGEX_ITERNAL_get_transition_count (struct REGEX_ITERNAL_Automaton *a)
+{
+  unsigned int t_count;
+  struct REGEX_ITERNAL_State *s;
+
+  if (NULL == a)
+    return 0;
+
+  t_count = 0;
+  for (s = a->states_head; NULL != s; s = s->next)
+    t_count += s->transition_count;
+
+  return t_count;
+}
+
+
+/**
+ * Get the first key for the given 'input_string'. This hashes the first x bits
+ * of the 'input_string'.
+ *
+ * @param input_string string.
+ * @param string_len length of the 'input_string'.
+ * @param key pointer to where to write the hash code.
+ *
+ * @return number of bits of 'input_string' that have been consumed
+ *         to construct the key
+ */
+size_t
+REGEX_ITERNAL_get_first_key (const char *input_string, size_t string_len,
+                            struct GNUNET_HashCode * key)
+{
+  unsigned int size;
+
+  size =
+      string_len <
+      GNUNET_REGEX_INITIAL_BYTES ? string_len : GNUNET_REGEX_INITIAL_BYTES;
+
+  if (NULL == input_string)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Given input string was NULL!\n");
+    return 0;
+  }
+
+  GNUNET_CRYPTO_hash (input_string, size, key);
+
+  return size;
+}
+
+
+/**
+ * Check if the given 'proof' matches the given 'key'.
+ *
+ * @param proof partial regex of a state.
+ * @param key hash of a state.
+ *
+ * @return GNUNET_OK if the proof is valid for the given key.
+ */
+int
+REGEX_ITERNAL_check_proof (const char *proof, const struct GNUNET_HashCode *key)
+{
+  struct GNUNET_HashCode key_check;
+
+  if (NULL == proof || NULL == key)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Proof check failed, was NULL.\n");
+    return GNUNET_NO;
+  }
+
+  GNUNET_CRYPTO_hash (proof, strlen (proof), &key_check);
+  return (0 ==
+          GNUNET_CRYPTO_hash_cmp (key, &key_check)) ? GNUNET_OK : GNUNET_NO;
+}
+
+
+/**
+ * Recursive function that calls the iterator for each synthetic start state.
+ *
+ * @param min_len minimum length of the path in the graph.
+ * @param max_len maximum length of the path in the graph.
+ * @param consumed_string string consumed by traversing the graph till this state.
+ * @param state current state of the automaton.
+ * @param iterator iterator function called for each edge.
+ * @param iterator_cls closure for the iterator function.
+ */
+static void
+iterate_initial_edge (const unsigned int min_len, const unsigned int max_len,
+                      char *consumed_string, struct REGEX_ITERNAL_State *state,
+                      REGEX_ITERNAL_KeyIterator iterator, void *iterator_cls)
+{
+  unsigned int i;
+  char *temp;
+  struct REGEX_ITERNAL_Transition *t;
+  unsigned int num_edges = state->transition_count;
+  struct REGEX_ITERNAL_Edge edges[num_edges];
+  struct REGEX_ITERNAL_Edge edge[1];
+  struct GNUNET_HashCode hash;
+  struct GNUNET_HashCode hash_new;
+
+  unsigned int cur_len;
+
+  if (NULL != consumed_string)
+    cur_len = strlen (consumed_string);
+  else
+    cur_len = 0;
+
+  if ((cur_len >= min_len || GNUNET_YES == state->accepting) && cur_len > 0 &&
+      NULL != consumed_string)
+  {
+    if (cur_len <= max_len)
+    {
+      if (state->proof != NULL && 0 != strcmp (consumed_string, state->proof))
+      {
+        for (i = 0, t = state->transitions_head; NULL != t && i < num_edges;
+             t = t->next, i++)
+        {
+          edges[i].label = t->label;
+          edges[i].destination = t->to_state->hash;
+        }
+        GNUNET_CRYPTO_hash (consumed_string, strlen (consumed_string), &hash);
+        iterator (iterator_cls, &hash, consumed_string, state->accepting,
+                  num_edges, edges);
+      }
+
+      if (GNUNET_YES == state->accepting && cur_len > 1 &&
+          state->transition_count < 1 && cur_len < max_len)
+      {
+        /* Special case for regex consisting of just a string that is shorter than
+         * max_len */
+        edge[0].label = &consumed_string[cur_len - 1];
+        edge[0].destination = state->hash;
+        temp = GNUNET_strdup (consumed_string);
+        temp[cur_len - 1] = '\0';
+        GNUNET_CRYPTO_hash (temp, cur_len - 1, &hash_new);
+        iterator (iterator_cls, &hash_new, temp, GNUNET_NO, 1, edge);
+        GNUNET_free (temp);
+      }
+    }
+    else if (max_len < cur_len)
+    {
+      /* Case where the concatenated labels are longer than max_len, then split. */
+      edge[0].label = &consumed_string[max_len];
+      edge[0].destination = state->hash;
+      temp = GNUNET_strdup (consumed_string);
+      temp[max_len] = '\0';
+      GNUNET_CRYPTO_hash (temp, max_len, &hash);
+      iterator (iterator_cls, &hash, temp, GNUNET_NO, 1, edge);
+      GNUNET_free (temp);
+    }
+  }
+
+  if (cur_len < max_len)
+  {
+    for (t = state->transitions_head; NULL != t; t = t->next)
+    {
+      if (NULL != consumed_string)
+        GNUNET_asprintf (&temp, "%s%s", consumed_string, t->label);
+      else
+        GNUNET_asprintf (&temp, "%s", t->label);
+
+      iterate_initial_edge (min_len, max_len, temp, t->to_state, iterator,
+                            iterator_cls);
+      GNUNET_free (temp);
+    }
+  }
+}
+
+
+/**
+ * Iterate over all edges starting from start state of automaton 'a'. Calling
+ * iterator for each edge.
+ *
+ * @param a automaton.
+ * @param iterator iterator called for each edge.
+ * @param iterator_cls closure.
+ */
+void
+REGEX_ITERNAL_iterate_all_edges (struct REGEX_ITERNAL_Automaton *a,
+                                REGEX_ITERNAL_KeyIterator iterator,
+                                void *iterator_cls)
+{
+  struct REGEX_ITERNAL_State *s;
+
+  for (s = a->states_head; NULL != s; s = s->next)
+  {
+    struct REGEX_ITERNAL_Edge edges[s->transition_count];
+    unsigned int num_edges;
+
+    num_edges = state_get_edges (s, edges);
+
+    if ((NULL != s->proof && 0 < strlen (s->proof)) || s->accepting)
+      iterator (iterator_cls, &s->hash, s->proof, s->accepting, num_edges,
+                edges);
+
+    s->marked = GNUNET_NO;
+  }
+
+  iterate_initial_edge (GNUNET_REGEX_INITIAL_BYTES, GNUNET_REGEX_INITIAL_BYTES,
+                        NULL, a->start, iterator, iterator_cls);
+}
+
+
+
+
+/* end of regex.c */