Imported Upstream version 0.9.3upstream/0.9.3

1 files changed, 2252 insertions, 0 deletions

diff --git a/src/regex/regex.c b/src/regex/regex.c
new file mode 100644
index 0000000..5244c26
--- /dev/null
+++ b/src/regex/regex.c
@@ -0,0 +1,2252 @@
+/*
+     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.c
+ * @brief library to create automatons from regular expressions
+ * @author Maximilian Szengel
+ */
+#include "platform.h"
+#include "gnunet_container_lib.h"
+#include "gnunet_crypto_lib.h"
+#include "gnunet_regex_lib.h"
+#include "regex.h"
+
+#define initial_bits 10
+
+/**
+ * Context that contains an id counter for states and transitions as well as a
+ * DLL of automatons used as a stack for NFA construction.
+ */
+struct GNUNET_REGEX_Context
+{
+  /**
+   * Unique state id.
+   */
+  unsigned int state_id;
+
+  /**
+   * Unique transition id.
+   */
+  unsigned int transition_id;
+
+  /**
+   * Unique SCC (Strongly Connected Component) id.
+   */
+  unsigned int scc_id;
+
+  /**
+   * DLL of GNUNET_REGEX_Automaton's used as a stack.
+   */
+  struct GNUNET_REGEX_Automaton *stack_head;
+
+  /**
+   * DLL of GNUNET_REGEX_Automaton's used as a stack.
+   */
+  struct GNUNET_REGEX_Automaton *stack_tail;
+};
+
+/**
+ * Type of an automaton.
+ */
+enum GNUNET_REGEX_automaton_type
+{
+  NFA,
+  DFA
+};
+
+/**
+ * Automaton representation.
+ */
+struct GNUNET_REGEX_Automaton
+{
+  /**
+   * This is a linked list.
+   */
+  struct GNUNET_REGEX_Automaton *prev;
+
+  /**
+   * This is a linked list.
+   */
+  struct GNUNET_REGEX_Automaton *next;
+
+  /**
+   * First state of the automaton. This is mainly used for constructing an NFA,
+   * where each NFA itself consists of one or more NFAs linked together.
+   */
+  struct GNUNET_REGEX_State *start;
+
+  /**
+   * End state of the automaton.
+   */
+  struct GNUNET_REGEX_State *end;
+
+  /**
+   * Number of states in the automaton.
+   */
+  unsigned int state_count;
+
+  /**
+   * DLL of states.
+   */
+  struct GNUNET_REGEX_State *states_head;
+
+  /**
+   * DLL of states
+   */
+  struct GNUNET_REGEX_State *states_tail;
+
+  /**
+   * Type of the automaton.
+   */
+  enum GNUNET_REGEX_automaton_type type;
+};
+
+/**
+ * A state. Can be used in DFA and NFA automatons.
+ */
+struct GNUNET_REGEX_State
+{
+  /**
+   * This is a linked list.
+   */
+  struct GNUNET_REGEX_State *prev;
+
+  /**
+   * This is a linked list.
+   */
+  struct GNUNET_REGEX_State *next;
+
+  /**
+   * Unique state id.
+   */
+  unsigned int id;
+
+  /**
+   * If this is an accepting state or not.
+   */
+  int accepting;
+
+  /**
+   * Marking of the state. This is used for marking all visited states when
+   * traversing all states of an automaton and for cases where the state id
+   * cannot be used (dfa minimization).
+   */
+  int marked;
+
+  /**
+   * Marking the state as contained. This is used for checking, if the state is
+   * contained in a set in constant time
+   */
+  int contained;
+
+  /**
+   * Marking the state as part of an SCC (Strongly Connected Component).  All
+   * states with the same scc_id are part of the same SCC. scc_id is 0, if state
+   * is not a part of any SCC.
+   */
+  unsigned int scc_id;
+
+  /**
+   * Used for SCC detection.
+   */
+  int index;
+
+  /**
+   * Used for SCC detection.
+   */
+  int lowlink;
+
+  /**
+   * Human readable name of the automaton. Used for debugging and graph
+   * creation.
+   */
+  char *name;
+
+  /**
+   * Hash of the state.
+   */
+  GNUNET_HashCode hash;
+
+  /**
+   * Proof for this state.
+   */
+  char *proof;
+
+  /**
+   * Number of transitions from this state to other states.
+   */
+  unsigned int transition_count;
+
+  /**
+   * DLL of transitions.
+   */
+  struct Transition *transitions_head;
+
+  /**
+   * DLL of transitions.
+   */
+  struct Transition *transitions_tail;
+
+  /**
+   * Set of states on which this state is based on. Used when creating a DFA out
+   * of several NFA states.
+   */
+  struct GNUNET_REGEX_StateSet *nfa_set;
+};
+
+/**
+ * Transition between two states. Each state can have 0-n transitions.  If label
+ * is 0, this is considered to be an epsilon transition.
+ */
+struct Transition
+{
+  /**
+   * This is a linked list.
+   */
+  struct Transition *prev;
+
+  /**
+   * This is a linked list.
+   */
+  struct Transition *next;
+
+  /**
+   * Unique id of this transition.
+   */
+  unsigned int id;
+
+  /**
+   * Label for this transition. This is basically the edge label for the graph.
+   */
+  char label;
+
+  /**
+   * State to which this transition leads.
+   */
+  struct GNUNET_REGEX_State *to_state;
+
+  /**
+   * State from which this transition origins.
+   */
+  struct GNUNET_REGEX_State *from_state;
+
+  /**
+   * Mark this transition. For example when reversing the automaton.
+   */
+  int mark;
+};
+
+/**
+ * Set of states.
+ */
+struct GNUNET_REGEX_StateSet
+{
+  /**
+   * Array of states.
+   */
+  struct GNUNET_REGEX_State **states;
+
+  /**
+   * Length of the 'states' array.
+   */
+  unsigned int len;
+};
+
+/*
+ * Debug helper functions
+ */
+void
+debug_print_transitions (struct GNUNET_REGEX_State *);
+
+void
+debug_print_state (struct GNUNET_REGEX_State *s)
+{
+  char *proof;
+
+  if (NULL == s->proof)
+    proof = "NULL";
+  else
+    proof = s->proof;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "State %i: %s marked: %i accepting: %i scc_id: %i transitions: %i proof: %s\n",
+              s->id, s->name, s->marked, s->accepting, s->scc_id,
+              s->transition_count, proof);
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Transitions:\n");
+  debug_print_transitions (s);
+}
+
+void
+debug_print_states (struct GNUNET_REGEX_Automaton *a)
+{
+  struct GNUNET_REGEX_State *s;
+
+  for (s = a->states_head; NULL != s; s = s->next)
+    debug_print_state (s);
+}
+
+void
+debug_print_transition (struct Transition *t)
+{
+  char *to_state;
+  char *from_state;
+  char label;
+
+  if (NULL == t)
+    return;
+
+  if (0 == t->label)
+    label = '0';
+  else
+    label = t->label;
+
+  if (NULL == t->to_state)
+    to_state = "NULL";
+  else
+    to_state = t->to_state->name;
+
+  if (NULL == t->from_state)
+    from_state = "NULL";
+  else
+    from_state = t->from_state->name;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Transition %i: From %s on %c to %s\n",
+              t->id, from_state, label, to_state);
+}
+
+void
+debug_print_transitions (struct GNUNET_REGEX_State *s)
+{
+  struct Transition *t;
+
+  for (t = s->transitions_head; NULL != t; t = t->next)
+    debug_print_transition (t);
+}
+
+/**
+ * Recursive function doing DFS with 'v' as a start, detecting all SCCs inside
+ * the subgraph reachable from 'v'. Used with scc_tarjan function to detect all
+ * SCCs inside an automaton.
+ *
+ * @param ctx context
+ * @param v start vertex
+ * @param index current index
+ * @param stack stack for saving all SCCs
+ * @param stack_size current size of the stack
+ */
+static void
+scc_tarjan_strongconnect (struct GNUNET_REGEX_Context *ctx,
+                          struct GNUNET_REGEX_State *v, int *index,
+                          struct GNUNET_REGEX_State **stack,
+                          unsigned int *stack_size)
+{
+  struct GNUNET_REGEX_State *w;
+  struct Transition *t;
+
+  v->index = *index;
+  v->lowlink = *index;
+  (*index)++;
+  stack[(*stack_size)++] = v;
+  v->contained = 1;
+
+  for (t = v->transitions_head; NULL != t; t = t->next)
+  {
+    w = t->to_state;
+    if (NULL != w && w->index < 0)
+    {
+      scc_tarjan_strongconnect (ctx, w, index, stack, stack_size);
+      v->lowlink = (v->lowlink > w->lowlink) ? w->lowlink : v->lowlink;
+    }
+    else if (0 != w->contained)
+      v->lowlink = (v->lowlink > w->index) ? w->index : v->lowlink;
+  }
+
+  if (v->lowlink == v->index)
+  {
+    w = stack[--(*stack_size)];
+    w->contained = 0;
+
+    if (v != w)
+    {
+      ctx->scc_id++;
+      while (v != w)
+      {
+        w->scc_id = ctx->scc_id;
+        w = stack[--(*stack_size)];
+        w->contained = 0;
+      }
+      w->scc_id = ctx->scc_id;
+    }
+  }
+}
+
+/**
+ * Detect all SCCs (Strongly Connected Components) inside the given automaton.
+ * SCCs will be marked using the scc_id on each state.
+ *
+ * @param ctx context
+ * @param a automaton
+ */
+static void
+scc_tarjan (struct GNUNET_REGEX_Context *ctx, struct GNUNET_REGEX_Automaton *a)
+{
+  int index;
+  struct GNUNET_REGEX_State *v;
+  struct GNUNET_REGEX_State *stack[a->state_count];
+  unsigned int stack_size;
+
+  for (v = a->states_head; NULL != v; v = v->next)
+  {
+    v->contained = 0;
+    v->index = -1;
+    v->lowlink = -1;
+  }
+
+  stack_size = 0;
+  index = 0;
+
+  for (v = a->states_head; NULL != v; v = v->next)
+  {
+    if (v->index < 0)
+      scc_tarjan_strongconnect (ctx, v, &index, stack, &stack_size);
+  }
+}
+
+/**
+ * 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 GNUNET_REGEX_Context *ctx,
+                      struct GNUNET_REGEX_State *from_state, const char label,
+                      struct GNUNET_REGEX_State *to_state)
+{
+  int is_dup;
+  struct Transition *t;
+
+  if (NULL == from_state)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not create Transition.\n");
+    return;
+  }
+
+  // Do not add duplicate state transitions
+  is_dup = GNUNET_NO;
+  for (t = from_state->transitions_head; NULL != t; t = t->next)
+  {
+    if (t->to_state == to_state && t->label == label &&
+        t->from_state == from_state)
+    {
+      is_dup = GNUNET_YES;
+      break;
+    }
+  }
+
+  if (is_dup)
+    return;
+
+  t = GNUNET_malloc (sizeof (struct Transition));
+  t->id = ctx->transition_id++;
+  t->label = label;
+  t->to_state = to_state;
+  t->from_state = from_state;
+
+  // Add outgoing transition to 'from_state'
+  from_state->transition_count++;
+  GNUNET_CONTAINER_DLL_insert (from_state->transitions_head,
+                               from_state->transitions_tail, t);
+}
+
+/**
+ * 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 GNUNET_REGEX_State **s1;
+  struct GNUNET_REGEX_State **s2;
+
+  s1 = (struct GNUNET_REGEX_State **) a;
+  s2 = (struct GNUNET_REGEX_State **) b;
+
+  return (*s1)->id - (*s2)->id;
+}
+
+/**
+ * Get all edges leaving state 's'.
+ *
+ * @param s state.
+ * @param edges all edges leaving 's'.
+ *
+ * @return number of edges.
+ */
+static unsigned int
+state_get_edges (struct GNUNET_REGEX_State *s, struct GNUNET_REGEX_Edge *edges)
+{
+  struct 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 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_set_compare (struct GNUNET_REGEX_StateSet *sset1,
+                   struct GNUNET_REGEX_StateSet *sset2)
+{
+  int result;
+  int i;
+
+  if (NULL == sset1 || NULL == sset2)
+    return 1;
+
+  result = sset1->len - sset2->len;
+
+  for (i = 0; i < sset1->len; i++)
+  {
+    if (0 != result)
+      break;
+
+    result = state_compare (&sset1->states[i], &sset2->states[i]);
+  }
+  return result;
+}
+
+/**
+ * Clears the given StateSet 'set'
+ *
+ * @param set set to be cleared
+ */
+static void
+state_set_clear (struct GNUNET_REGEX_StateSet *set)
+{
+  if (NULL != set)
+  {
+    if (NULL != set->states)
+      GNUNET_free (set->states);
+    GNUNET_free (set);
+  }
+}
+
+/**
+ * Clears an automaton fragment. Does not destroy the states inside the
+ * automaton.
+ *
+ * @param a automaton to be cleared
+ */
+static void
+automaton_fragment_clear (struct GNUNET_REGEX_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 GNUNET_REGEX_State *s)
+{
+  struct Transition *t;
+  struct Transition *next_t;
+
+  if (NULL == s)
+    return;
+
+  if (NULL != s->name)
+    GNUNET_free (s->name);
+
+  if (NULL != s->proof)
+    GNUNET_free (s->proof);
+
+  for (t = s->transitions_head; NULL != t; t = next_t)
+  {
+    next_t = t->next;
+    GNUNET_CONTAINER_DLL_remove (s->transitions_head, s->transitions_tail, t);
+    GNUNET_free (t);
+  }
+
+  state_set_clear (s->nfa_set);
+
+  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 GNUNET_REGEX_Automaton *a,
+                        struct GNUNET_REGEX_State *s)
+{
+  struct GNUNET_REGEX_State *ss;
+  struct GNUNET_REGEX_State *s_check;
+  struct Transition *t_check;
+
+  if (NULL == a || NULL == s)
+    return;
+
+  // remove state
+  ss = s;
+  GNUNET_CONTAINER_DLL_remove (a->states_head, a->states_tail, s);
+  a->state_count--;
+
+  // 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)
+    {
+      if (t_check->to_state == ss)
+      {
+        GNUNET_CONTAINER_DLL_remove (s_check->transitions_head,
+                                     s_check->transitions_tail, t_check);
+        s_check->transition_count--;
+      }
+    }
+  }
+
+  automaton_destroy_state (ss);
+}
+
+/**
+ * Merge two states into one. Will merge 's1' and 's2' into 's1' and destroy
+ * 's2'.
+ *
+ * @param ctx context
+ * @param a automaton
+ * @param s1 first state
+ * @param s2 second state, will be destroyed
+ */
+static void
+automaton_merge_states (struct GNUNET_REGEX_Context *ctx,
+                        struct GNUNET_REGEX_Automaton *a,
+                        struct GNUNET_REGEX_State *s1,
+                        struct GNUNET_REGEX_State *s2)
+{
+  struct GNUNET_REGEX_State *s_check;
+  struct Transition *t_check;
+  char *new_name;
+
+  GNUNET_assert (NULL != ctx && NULL != a && NULL != s1 && NULL != s2);
+
+  if (s1 == s2)
+    return;
+
+  // 1. Make all transitions pointing to s2 point to s1
+  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)
+    {
+      if (s2 == t_check->to_state)
+        t_check->to_state = s1;
+    }
+  }
+
+  // 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}
+  new_name = GNUNET_strdup (s1->name);
+  if (NULL != s1->name)
+  {
+    GNUNET_free (s1->name);
+    s1->name = NULL;
+  }
+  GNUNET_asprintf (&s1->name, "{%s,%s}", new_name, s2->name);
+  GNUNET_free (new_name);
+
+  // 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 GNUNET_REGEX_Automaton *a,
+                     struct GNUNET_REGEX_State *s)
+{
+  GNUNET_CONTAINER_DLL_insert (a->states_head, a->states_tail, s);
+  a->state_count++;
+}
+
+/**
+ * Function that is called with each state, when traversing an automaton.
+ *
+ * @param cls closure
+ * @param s state
+ */
+typedef void (*GNUNET_REGEX_traverse_action) (void *cls,
+                                              struct GNUNET_REGEX_State * s);
+
+/**
+ * Traverses all states that are reachable from state 's'. Expects the states to
+ * be unmarked (s->marked == GNUNET_NO). Performs 'action' on each visited
+ * state.
+ *
+ * @param cls closure.
+ * @param s start state.
+ * @param action action to be performed on each state.
+ */
+static void
+automaton_state_traverse (void *cls, struct GNUNET_REGEX_State *s,
+                          GNUNET_REGEX_traverse_action action)
+{
+  struct Transition *t;
+
+  if (GNUNET_NO == s->marked)
+  {
+    s->marked = GNUNET_YES;
+
+    if (action > 0)
+      action (cls, s);
+
+    for (t = s->transitions_head; NULL != t; t = t->next)
+      automaton_state_traverse (cls, t->to_state, action);
+  }
+}
+
+/**
+ * Traverses the given automaton from it's start state, visiting all reachable
+ * states and calling 'action' on each one of them.
+ *
+ * @param cls closure.
+ * @param a automaton.
+ * @param action action to be performed on each state.
+ */
+static void
+automaton_traverse (void *cls, struct GNUNET_REGEX_Automaton *a,
+                    GNUNET_REGEX_traverse_action action)
+{
+  struct GNUNET_REGEX_State *s;
+
+  for (s = a->states_head; NULL != s; s = s->next)
+    s->marked = GNUNET_NO;
+
+  automaton_state_traverse (cls, a->start, action);
+}
+
+/**
+ * Reverses all transitions of the given automaton.
+ *
+ * @param a automaton.
+ */
+static void
+automaton_reverse (struct GNUNET_REGEX_Automaton *a)
+{
+  struct GNUNET_REGEX_State *s;
+  struct Transition *t;
+  struct Transition *t_next;
+  struct GNUNET_REGEX_State *s_swp;
+
+  for (s = a->states_head; NULL != s; s = s->next)
+    for (t = s->transitions_head; NULL != t; t = t->next)
+      t->mark = GNUNET_NO;
+
+  for (s = a->states_head; NULL != s; s = s->next)
+  {
+    for (t = s->transitions_head; NULL != t; t = t_next)
+    {
+      t_next = t->next;
+
+      if (GNUNET_YES == t->mark || t->from_state == t->to_state)
+        continue;
+
+      t->mark = GNUNET_YES;
+
+      GNUNET_CONTAINER_DLL_remove (t->from_state->transitions_head,
+                                   t->from_state->transitions_tail, t);
+      t->from_state->transition_count--;
+      GNUNET_CONTAINER_DLL_insert (t->to_state->transitions_head,
+                                   t->to_state->transitions_tail, t);
+      t->to_state->transition_count++;
+
+      s_swp = t->from_state;
+      t->from_state = t->to_state;
+      t->to_state = s_swp;
+    }
+  }
+}
+
+/**
+ * Create proof for the given state.
+ *
+ * @param cls closure.
+ * @param s state.
+ */
+static void
+automaton_create_proofs_step (void *cls, struct GNUNET_REGEX_State *s)
+{
+  struct Transition *t;
+  int i;
+  char *tmp;
+
+  for (i = 0, t = s->transitions_head; NULL != t; t = t->next, i++)
+  {
+    if (t->to_state == s)
+      GNUNET_asprintf (&tmp, "%c*", t->label);
+    else if (i != s->transition_count - 1)
+      GNUNET_asprintf (&tmp, "%c|", t->label);
+    else
+      GNUNET_asprintf (&tmp, "%c", t->label);
+
+    if (NULL != s->proof)
+      s->proof =
+          GNUNET_realloc (s->proof, strlen (s->proof) + strlen (tmp) + 1);
+    else
+      s->proof = GNUNET_malloc (strlen (tmp) + 1);
+    strcat (s->proof, tmp);
+    GNUNET_free (tmp);
+  }
+}
+
+/**
+ * Create proofs for all states in the given automaton.
+ *
+ * @param a automaton.
+ */
+static void
+automaton_create_proofs (struct GNUNET_REGEX_Automaton *a)
+{
+  struct GNUNET_REGEX_State *s;
+
+  automaton_reverse (a);
+
+  for (s = a->states_head; NULL != s; s = s->next)
+    automaton_create_proofs_step (NULL, s);
+
+  automaton_reverse (a);
+}
+
+/**
+ * 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 GNUNET_REGEX_State *
+dfa_state_create (struct GNUNET_REGEX_Context *ctx,
+                  struct GNUNET_REGEX_StateSet *nfa_states)
+{
+  struct GNUNET_REGEX_State *s;
+  char *name;
+  int len = 0;
+  struct GNUNET_REGEX_State *cstate;
+  struct Transition *ctran;
+  int insert = 1;
+  struct Transition *t;
+  int i;
+
+  s = GNUNET_malloc (sizeof (struct GNUNET_REGEX_State));
+  s->id = ctx->state_id++;
+  s->accepting = 0;
+  s->marked = 0;
+  s->name = NULL;
+  s->scc_id = 0;
+  s->index = -1;
+  s->lowlink = -1;
+  s->contained = 0;
+  s->proof = NULL;
+
+  if (NULL == nfa_states)
+  {
+    GNUNET_asprintf (&s->name, "s%i", s->id);
+    return s;
+  }
+
+  s->nfa_set = nfa_states;
+
+  if (nfa_states->len < 1)
+    return s;
+
+  // Create a name based on 'sset'
+  s->name = GNUNET_malloc (sizeof (char) * 2);
+  strcat (s->name, "{");
+  name = NULL;
+
+  for (i = 0; i < nfa_states->len; i++)
+  {
+    cstate = nfa_states->states[i];
+    GNUNET_asprintf (&name, "%i,", cstate->id);
+
+    if (NULL != name)
+    {
+      len = strlen (s->name) + strlen (name) + 1;
+      s->name = GNUNET_realloc (s->name, len);
+      strcat (s->name, name);
+      GNUNET_free (name);
+      name = NULL;
+    }
+
+    // Add a transition for each distinct label to NULL state
+    for (ctran = cstate->transitions_head; NULL != ctran; ctran = ctran->next)
+    {
+      if (0 != ctran->label)
+      {
+        insert = 1;
+
+        for (t = s->transitions_head; NULL != t; t = t->next)
+        {
+          if (t->label == ctran->label)
+          {
+            insert = 0;
+            break;
+          }
+        }
+
+        if (insert)
+          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;
+  }
+
+  s->name[strlen (s->name) - 1] = '}';
+
+  return s;
+}
+
+/**
+ * Move from the given state 's' to the next state on transition 'label'
+ *
+ * @param s starting state
+ * @param label edge label to follow
+ *
+ * @return new state or NULL, if transition on label not possible
+ */
+static struct GNUNET_REGEX_State *
+dfa_move (struct GNUNET_REGEX_State *s, const char label)
+{
+  struct Transition *t;
+  struct GNUNET_REGEX_State *new_s;
+
+  if (NULL == s)
+    return NULL;
+
+  new_s = NULL;
+
+  for (t = s->transitions_head; NULL != t; t = t->next)
+  {
+    if (label == t->label)
+    {
+      new_s = t->to_state;
+      break;
+    }
+  }
+
+  return new_s;
+}
+
+/**
+ * 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 GNUNET_REGEX_Automaton *a)
+{
+  struct GNUNET_REGEX_State *s;
+  struct GNUNET_REGEX_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
+  automaton_traverse (NULL, a, 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 themselfes.
+ *
+ * @param a DFA automaton
+ */
+static void
+dfa_remove_dead_states (struct GNUNET_REGEX_Automaton *a)
+{
+  struct GNUNET_REGEX_State *s;
+  struct Transition *t;
+  int dead;
+
+  GNUNET_assert (DFA == a->type);
+
+  for (s = a->states_head; NULL != s; s = 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
+ */
+static void
+dfa_merge_nondistinguishable_states (struct GNUNET_REGEX_Context *ctx,
+                                     struct GNUNET_REGEX_Automaton *a)
+{
+  int i;
+  int table[a->state_count][a->state_count];
+  struct GNUNET_REGEX_State *s1;
+  struct GNUNET_REGEX_State *s2;
+  struct Transition *t1;
+  struct Transition *t2;
+  struct GNUNET_REGEX_State *s1_next;
+  struct GNUNET_REGEX_State *s2_next;
+  int change;
+  int num_equal_edges;
+
+  for (i = 0, s1 = a->states_head; i < a->state_count && NULL != s1;
+       i++, 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)
+    {
+      table[s1->marked][s2->marked] = 0;
+
+      if ((s1->accepting && !s2->accepting) ||
+          (!s1->accepting && s2->accepting))
+      {
+        table[s1->marked][s2->marked] = 1;
+      }
+    }
+  }
+
+  // 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)
+      {
+        if (0 != table[s1->marked][s2->marked])
+          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 (t1->label == t2->label)
+            {
+              num_equal_edges++;
+              if (0 != table[t1->to_state->marked][t2->to_state->marked] ||
+                  0 != table[t2->to_state->marked][t1->to_state->marked])
+              {
+                table[s1->marked][s2->marked] = t1->label != 0 ? t1->label : 1;
+                change = 1;
+              }
+            }
+          }
+        }
+        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[s1->marked][s2->marked] = -2;
+        }
+      }
+    }
+  }
+
+  // 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;
+      if (table[s1->marked][s2->marked] == 0)
+        automaton_merge_states (ctx, a, s1, s2);
+    }
+  }
+}
+
+/**
+ * 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
+ */
+static void
+dfa_minimize (struct GNUNET_REGEX_Context *ctx,
+              struct GNUNET_REGEX_Automaton *a)
+{
+  if (NULL == a)
+    return;
+
+  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
+  dfa_merge_nondistinguishable_states (ctx, a);
+}
+
+/**
+ * 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 GNUNET_REGEX_Automaton *
+nfa_fragment_create (struct GNUNET_REGEX_State *start,
+                     struct GNUNET_REGEX_State *end)
+{
+  struct GNUNET_REGEX_Automaton *n;
+
+  n = GNUNET_malloc (sizeof (struct GNUNET_REGEX_Automaton));
+
+  n->type = NFA;
+  n->start = NULL;
+  n->end = NULL;
+
+  if (NULL == start && NULL == end)
+    return n;
+
+  automaton_add_state (n, end);
+  automaton_add_state (n, start);
+
+  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 GNUNET_REGEX_Automaton *n,
+                struct GNUNET_REGEX_State *states_head,
+                struct GNUNET_REGEX_State *states_tail)
+{
+  struct GNUNET_REGEX_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 GNUNET_REGEX_State *
+nfa_state_create (struct GNUNET_REGEX_Context *ctx, int accepting)
+{
+  struct GNUNET_REGEX_State *s;
+
+  s = GNUNET_malloc (sizeof (struct GNUNET_REGEX_State));
+  s->id = ctx->state_id++;
+  s->accepting = accepting;
+  s->marked = 0;
+  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 NFA closure set for the given state.
+ *
+ * @param nfa the NFA containing 's'
+ * @param s starting point state
+ * @param label transitioning label on which to base the closure on,
+ *                pass 0 for epsilon transition
+ *
+ * @return sorted nfa closure on 'label' (epsilon closure if 'label' is 0)
+ */
+static struct GNUNET_REGEX_StateSet *
+nfa_closure_create (struct GNUNET_REGEX_Automaton *nfa,
+                    struct GNUNET_REGEX_State *s, const char label)
+{
+  struct GNUNET_REGEX_StateSet *cls;
+  struct GNUNET_REGEX_StateSet *cls_check;
+  struct GNUNET_REGEX_State *clsstate;
+  struct GNUNET_REGEX_State *currentstate;
+  struct Transition *ctran;
+
+  if (NULL == s)
+    return NULL;
+
+  cls = GNUNET_malloc (sizeof (struct GNUNET_REGEX_StateSet));
+  cls_check = GNUNET_malloc (sizeof (struct GNUNET_REGEX_StateSet));
+
+  for (clsstate = nfa->states_head; NULL != clsstate; clsstate = clsstate->next)
+    clsstate->contained = 0;
+
+  // Add start state to closure only for epsilon closure
+  if (0 == label)
+    GNUNET_array_append (cls->states, cls->len, s);
+
+  GNUNET_array_append (cls_check->states, cls_check->len, s);
+  while (cls_check->len > 0)
+  {
+    currentstate = cls_check->states[cls_check->len - 1];
+    GNUNET_array_grow (cls_check->states, cls_check->len, cls_check->len - 1);
+
+    for (ctran = currentstate->transitions_head; NULL != ctran;
+         ctran = ctran->next)
+    {
+      if (NULL != ctran->to_state && label == ctran->label)
+      {
+        clsstate = ctran->to_state;
+
+        if (NULL != clsstate && 0 == clsstate->contained)
+        {
+          GNUNET_array_append (cls->states, cls->len, clsstate);
+          GNUNET_array_append (cls_check->states, cls_check->len, clsstate);
+          clsstate->contained = 1;
+        }
+      }
+    }
+  }
+  GNUNET_assert (0 == cls_check->len);
+  GNUNET_free (cls_check);
+
+  if (cls->len > 1)
+    qsort (cls->states, cls->len, sizeof (struct GNUNET_REGEX_State *),
+           state_compare);
+
+  return cls;
+}
+
+/**
+ * Calculates the closure set for the given set of states.
+ *
+ * @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 0 for epsilon transition
+ *
+ * @return sorted nfa closure on 'label' (epsilon closure if 'label' is 0)
+ */
+static struct GNUNET_REGEX_StateSet *
+nfa_closure_set_create (struct GNUNET_REGEX_Automaton *nfa,
+                        struct GNUNET_REGEX_StateSet *states, const char label)
+{
+  struct GNUNET_REGEX_State *s;
+  struct GNUNET_REGEX_StateSet *sset;
+  struct GNUNET_REGEX_StateSet *cls;
+  int i;
+  int j;
+  int k;
+  int contains;
+
+  if (NULL == states)
+    return NULL;
+
+  cls = GNUNET_malloc (sizeof (struct GNUNET_REGEX_StateSet));
+
+  for (i = 0; i < states->len; i++)
+  {
+    s = states->states[i];
+    sset = nfa_closure_create (nfa, s, label);
+
+    for (j = 0; j < sset->len; j++)
+    {
+      contains = 0;
+      for (k = 0; k < cls->len; k++)
+      {
+        if (sset->states[j]->id == cls->states[k]->id)
+        {
+          contains = 1;
+          break;
+        }
+      }
+      if (!contains)
+        GNUNET_array_append (cls->states, cls->len, sset->states[j]);
+    }
+    state_set_clear (sset);
+  }
+
+  if (cls->len > 1)
+    qsort (cls->states, cls->len, sizeof (struct GNUNET_REGEX_State *),
+           state_compare);
+
+  return cls;
+}
+
+/**
+ * Pops two NFA fragments (a, b) from the stack and concatenates them (ab)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_concatenation (struct GNUNET_REGEX_Context *ctx)
+{
+  struct GNUNET_REGEX_Automaton *a;
+  struct GNUNET_REGEX_Automaton *b;
+  struct GNUNET_REGEX_Automaton *new;
+
+  b = ctx->stack_tail;
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, b);
+  a = ctx->stack_tail;
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  state_add_transition (ctx, a->end, 0, b->start);
+  a->end->accepting = 0;
+  b->end->accepting = 1;
+
+  new = nfa_fragment_create (NULL, NULL);
+  nfa_add_states (new, a->states_head, a->states_tail);
+  nfa_add_states (new, b->states_head, b->states_tail);
+  new->start = a->start;
+  new->end = b->end;
+  automaton_fragment_clear (a);
+  automaton_fragment_clear (b);
+
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, new);
+}
+
+/**
+ * Pops a NFA fragment from the stack (a) and adds a new fragment (a*)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_star_op (struct GNUNET_REGEX_Context *ctx)
+{
+  struct GNUNET_REGEX_Automaton *a;
+  struct GNUNET_REGEX_Automaton *new;
+  struct GNUNET_REGEX_State *start;
+  struct GNUNET_REGEX_State *end;
+
+  a = ctx->stack_tail;
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  if (NULL == a)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "nfa_add_star_op failed, because there was no element on the stack");
+    return;
+  }
+
+  start = nfa_state_create (ctx, 0);
+  end = nfa_state_create (ctx, 1);
+
+  state_add_transition (ctx, start, 0, a->start);
+  state_add_transition (ctx, start, 0, end);
+  state_add_transition (ctx, a->end, 0, a->start);
+  state_add_transition (ctx, a->end, 0, end);
+
+  a->end->accepting = 0;
+  end->accepting = 1;
+
+  new = nfa_fragment_create (start, end);
+  nfa_add_states (new, a->states_head, a->states_tail);
+  automaton_fragment_clear (a);
+
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, new);
+}
+
+/**
+ * Pops an NFA fragment (a) from the stack and adds a new fragment (a+)
+ *
+ * @param ctx context
+ */
+static void
+nfa_add_plus_op (struct GNUNET_REGEX_Context *ctx)
+{
+  struct GNUNET_REGEX_Automaton *a;
+
+  a = ctx->stack_tail;
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  state_add_transition (ctx, a->end, 0, 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 GNUNET_REGEX_Context *ctx)
+{
+  struct GNUNET_REGEX_Automaton *a;
+  struct GNUNET_REGEX_Automaton *new;
+  struct GNUNET_REGEX_State *start;
+  struct GNUNET_REGEX_State *end;
+
+  a = ctx->stack_tail;
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, a);
+
+  if (NULL == a)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "nfa_add_question_op failed, because there was no element on the stack");
+    return;
+  }
+
+  start = nfa_state_create (ctx, 0);
+  end = nfa_state_create (ctx, 1);
+
+  state_add_transition (ctx, start, 0, a->start);
+  state_add_transition (ctx, start, 0, end);
+  state_add_transition (ctx, a->end, 0, end);
+
+  a->end->accepting = 0;
+
+  new = nfa_fragment_create (start, end);
+  nfa_add_states (new, a->states_head, a->states_tail);
+  automaton_fragment_clear (a);
+
+  GNUNET_CONTAINER_DLL_insert_tail (ctx->stack_head, ctx->stack_tail, new);
+}
+
+/**
+ * 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 GNUNET_REGEX_Context *ctx)
+{
+  struct GNUNET_REGEX_Automaton *a;
+  struct GNUNET_REGEX_Automaton *b;
+  struct GNUNET_REGEX_Automaton *new;
+  struct GNUNET_REGEX_State *start;
+  struct GNUNET_REGEX_State *end;
+
+  b = ctx->stack_tail;
+  GNUNET_CONTAINER_DLL_remove (ctx->stack_head, ctx->stack_tail, b);
+  a = ctx->stack_tail;
+  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, 0, a->start);
+  state_add_transition (ctx, start, 0, b->start);
+
+  state_add_transition (ctx, a->end, 0, end);
+  state_add_transition (ctx, b->end, 0, end);
+
+  a->end->accepting = 0;
+  b->end->accepting = 0;
+  end->accepting = 1;
+
+  new = nfa_fragment_create (start, end);
+  nfa_add_states (new, a->states_head, a->states_tail);
+  nfa_add_states (new, 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);
+}
+
+/**
+ * Adds a new nfa fragment to the stack
+ *
+ * @param ctx context
+ * @param lit label for nfa transition
+ */
+static void
+nfa_add_label (struct GNUNET_REGEX_Context *ctx, const char lit)
+{
+  struct GNUNET_REGEX_Automaton *n;
+  struct GNUNET_REGEX_State *start;
+  struct GNUNET_REGEX_State *end;
+
+  GNUNET_assert (NULL != ctx);
+
+  start = nfa_state_create (ctx, 0);
+  end = nfa_state_create (ctx, 1);
+  state_add_transition (ctx, start, lit, 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
+GNUNET_REGEX_context_init (struct GNUNET_REGEX_Context *ctx)
+{
+  if (NULL == ctx)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Context was NULL!");
+    return;
+  }
+  ctx->state_id = 0;
+  ctx->transition_id = 0;
+  ctx->scc_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 GNUNET_REGEX_destroy_automaton
+ */
+struct GNUNET_REGEX_Automaton *
+GNUNET_REGEX_construct_nfa (const char *regex, const size_t len)
+{
+  struct GNUNET_REGEX_Context ctx;
+  struct GNUNET_REGEX_Automaton *nfa;
+  const char *regexp;
+  char *error_msg;
+  unsigned int count;
+  unsigned int altcount;
+  unsigned int atomcount;
+  unsigned int pcount;
+  struct
+  {
+    int altcount;
+    int atomcount;
+  }     *p;
+
+  GNUNET_REGEX_context_init (&ctx);
+
+  regexp = regex;
+  p = NULL;
+  error_msg = NULL;
+  altcount = 0;
+  atomcount = 0;
+  pcount = 0;
+
+  for (count = 0; count < len && *regexp; count++, regexp++)
+  {
+    switch (*regexp)
+    {
+    case '(':
+      if (atomcount > 1)
+      {
+        --atomcount;
+        nfa_add_concatenation (&ctx);
+      }
+      GNUNET_array_grow (p, pcount, pcount + 1);
+      p[pcount - 1].altcount = altcount;
+      p[pcount - 1].atomcount = atomcount;
+      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 == pcount)
+      {
+        error_msg = "Missing opening '('";
+        goto error;
+      }
+      if (0 == atomcount)
+      {
+        // Ignore this: "()"
+        pcount--;
+        altcount = p[pcount].altcount;
+        atomcount = p[pcount].atomcount;
+        break;
+      }
+      while (--atomcount > 0)
+        nfa_add_concatenation (&ctx);
+      for (; altcount > 0; altcount--)
+        nfa_add_alternation (&ctx);
+      pcount--;
+      altcount = p[pcount].altcount;
+      atomcount = p[pcount].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;
+    case 92:                   /* escape: \ */
+      regexp++;
+      count++;
+    default:
+      if (atomcount > 1)
+      {
+        --atomcount;
+        nfa_add_concatenation (&ctx);
+      }
+      nfa_add_label (&ctx, *regexp);
+      atomcount++;
+      break;
+    }
+  }
+  if (0 != pcount)
+  {
+    error_msg = "Unbalanced parenthesis";
+    goto error;
+  }
+  while (--atomcount > 0)
+    nfa_add_concatenation (&ctx);
+  for (; altcount > 0; altcount--)
+    nfa_add_alternation (&ctx);
+
+  if (NULL != p)
+    GNUNET_free (p);
+
+  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;
+  }
+
+  return nfa;
+
+error:
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not parse regex\n");
+  if (NULL != error_msg)
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "%s\n", error_msg);
+  if (NULL != p)
+    GNUNET_free (p);
+  while (NULL != ctx.stack_tail)
+  {
+    GNUNET_REGEX_automaton_destroy (ctx.stack_tail);
+    GNUNET_CONTAINER_DLL_remove (ctx.stack_head, ctx.stack_tail,
+                                 ctx.stack_tail);
+  }
+  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 GNUNET_REGEX_Context *ctx,
+                      struct GNUNET_REGEX_Automaton *nfa,
+                      struct GNUNET_REGEX_Automaton *dfa,
+                      struct GNUNET_REGEX_State *dfa_state)
+{
+  struct Transition *ctran;
+  struct GNUNET_REGEX_State *state_iter;
+  struct GNUNET_REGEX_State *new_dfa_state;
+  struct GNUNET_REGEX_State *state_contains;
+  struct GNUNET_REGEX_StateSet *tmp;
+  struct GNUNET_REGEX_StateSet *nfa_set;
+
+  for (ctran = dfa_state->transitions_head; NULL != ctran; ctran = ctran->next)
+  {
+    if (0 == ctran->label || NULL != ctran->to_state)
+      continue;
+
+    tmp = nfa_closure_set_create (nfa, dfa_state->nfa_set, ctran->label);
+    nfa_set = nfa_closure_set_create (nfa, tmp, 0);
+    state_set_clear (tmp);
+    new_dfa_state = dfa_state_create (ctx, nfa_set);
+    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, new_dfa_state->nfa_set))
+        state_contains = state_iter;
+    }
+
+    if (NULL == state_contains)
+    {
+      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;
+      automaton_destroy_state (new_dfa_state);
+    }
+  }
+}
+
+/**
+ * Construct DFA for the given 'regex' of length 'len'
+ *
+ * @param regex regular expression string
+ * @param len length of the regular expression
+ *
+ * @return DFA, needs to be freed using GNUNET_REGEX_destroy_automaton
+ */
+struct GNUNET_REGEX_Automaton *
+GNUNET_REGEX_construct_dfa (const char *regex, const size_t len)
+{
+  struct GNUNET_REGEX_Context ctx;
+  struct GNUNET_REGEX_Automaton *dfa;
+  struct GNUNET_REGEX_Automaton *nfa;
+  struct GNUNET_REGEX_StateSet *nfa_set;
+
+  GNUNET_REGEX_context_init (&ctx);
+
+  // Create NFA
+  nfa = GNUNET_REGEX_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 GNUNET_REGEX_Automaton));
+  dfa->type = DFA;
+
+  // Create DFA start state from epsilon closure
+  nfa_set = nfa_closure_create (nfa, nfa->start, 0);
+  dfa->start = dfa_state_create (&ctx, nfa_set);
+  automaton_add_state (dfa, dfa->start);
+
+  construct_dfa_states (&ctx, nfa, dfa, dfa->start);
+
+  GNUNET_REGEX_automaton_destroy (nfa);
+
+  // Minimize DFA
+  dfa_minimize (&ctx, dfa);
+
+  // Calculate SCCs
+  scc_tarjan (&ctx, dfa);
+
+  // Create proofs for all states
+  automaton_create_proofs (dfa);
+
+  return dfa;
+}
+
+/**
+ * Free the memory allocated by constructing the GNUNET_REGEX_Automaton data
+ * structure.
+ *
+ * @param a automaton to be destroyed
+ */
+void
+GNUNET_REGEX_automaton_destroy (struct GNUNET_REGEX_Automaton *a)
+{
+  struct GNUNET_REGEX_State *s;
+  struct GNUNET_REGEX_State *next_state;
+
+  if (NULL == a)
+    return;
+
+  for (s = a->states_head; NULL != s;)
+  {
+    next_state = s->next;
+    automaton_destroy_state (s);
+    s = next_state;
+  }
+
+  GNUNET_free (a);
+}
+
+/**
+ * Save the given automaton as a GraphViz dot file
+ *
+ * @param a the automaton to be saved
+ * @param filename where to save the file
+ */
+void
+GNUNET_REGEX_automaton_save_graph (struct GNUNET_REGEX_Automaton *a,
+                                   const char *filename)
+{
+  struct GNUNET_REGEX_State *s;
+  struct Transition *ctran;
+  char *s_acc = NULL;
+  char *s_tran = NULL;
+  char *start;
+  char *end;
+  FILE *p;
+
+  if (NULL == a)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not print NFA, was NULL!");
+    return;
+  }
+
+  if (NULL == filename || strlen (filename) < 1)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "No Filename given!");
+    return;
+  }
+
+  p = fopen (filename, "w");
+
+  if (NULL == p)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not open file for writing: %s",
+                filename);
+    return;
+  }
+
+  start = "digraph G {\nrankdir=LR\n";
+  fwrite (start, strlen (start), 1, p);
+
+  for (s = a->states_head; NULL != s; s = s->next)
+  {
+    if (s->accepting)
+    {
+      GNUNET_asprintf (&s_acc,
+                       "\"%s\" [shape=doublecircle, color=\"0.%i 0.8 0.95\"];\n",
+                       s->name, s->scc_id);
+    }
+    else
+    {
+      GNUNET_asprintf (&s_acc, "\"%s\" [color=\"0.%i 0.8 0.95\"];\n", s->name,
+                       s->scc_id);
+    }
+
+    if (NULL == s_acc)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not print state %s\n",
+                  s->name);
+      return;
+    }
+    fwrite (s_acc, strlen (s_acc), 1, p);
+    GNUNET_free (s_acc);
+    s_acc = NULL;
+
+    for (ctran = s->transitions_head; NULL != ctran; ctran = ctran->next)
+    {
+      if (NULL == ctran->to_state)
+      {
+        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                    "Transition from State %i has has no state for transitioning\n",
+                    s->id);
+        continue;
+      }
+
+      if (ctran->label == 0)
+      {
+        GNUNET_asprintf (&s_tran,
+                         "\"%s\" -> \"%s\" [label = \"epsilon\", color=\"0.%i 0.8 0.95\"];\n",
+                         s->name, ctran->to_state->name, s->scc_id);
+      }
+      else
+      {
+        GNUNET_asprintf (&s_tran,
+                         "\"%s\" -> \"%s\" [label = \"%c\", color=\"0.%i 0.8 0.95\"];\n",
+                         s->name, ctran->to_state->name, ctran->label,
+                         s->scc_id);
+      }
+
+      if (NULL == s_tran)
+      {
+        GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Could not print state %s\n",
+                    s->name);
+        return;
+      }
+
+      fwrite (s_tran, strlen (s_tran), 1, p);
+      GNUNET_free (s_tran);
+      s_tran = NULL;
+    }
+  }
+
+  end = "\n}\n";
+  fwrite (end, strlen (end), 1, p);
+  fclose (p);
+}
+
+/**
+ * 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 GNUNET_REGEX_Automaton *a, const char *string)
+{
+  const char *strp;
+  struct GNUNET_REGEX_State *s;
+
+  if (DFA != a->type)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Tried to evaluate DFA, but NFA automaton given");
+    return -1;
+  }
+
+  s = a->start;
+
+  for (strp = string; NULL != strp && *strp; strp++)
+  {
+    s = 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 GNUNET_REGEX_Automaton *a, const char *string)
+{
+  const char *strp;
+  struct GNUNET_REGEX_State *s;
+  struct GNUNET_REGEX_StateSet *sset;
+  struct GNUNET_REGEX_StateSet *new_sset;
+  int i;
+  int result;
+
+  if (NFA != a->type)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Tried to evaluate NFA, but DFA automaton given");
+    return -1;
+  }
+
+  result = 1;
+  strp = string;
+  sset = nfa_closure_create (a, a->start, 0);
+
+  for (strp = string; NULL != strp && *strp; strp++)
+  {
+    new_sset = nfa_closure_set_create (a, sset, *strp);
+    state_set_clear (sset);
+    sset = nfa_closure_set_create (a, new_sset, 0);
+    state_set_clear (new_sset);
+  }
+
+  for (i = 0; i < sset->len; 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
+GNUNET_REGEX_eval (struct GNUNET_REGEX_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 first key for the given 'input_string'. This hashes the first x bits
+ * of the 'input_strings'.
+ *
+ * @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
+ */
+unsigned int
+GNUNET_REGEX_get_first_key (const char *input_string, unsigned int string_len,
+                            GNUNET_HashCode * key)
+{
+  unsigned int size;
+
+  size = string_len < initial_bits ? string_len : initial_bits;
+
+  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
+ * @param key hash
+ *
+ * @return GNUNET_OK if the proof is valid for the given key
+ */
+int
+GNUNET_REGEX_check_proof (const char *proof, const GNUNET_HashCode * key)
+{
+  return GNUNET_OK;
+}
+
+/**
+ * Iterate over all edges helper function starting from state 's', calling
+ * iterator on for each edge.
+ *
+ * @param s state.
+ * @param iterator iterator function called for each edge.
+ * @param iterator_cls closure.
+ */
+static void
+iterate_edge (struct GNUNET_REGEX_State *s, GNUNET_REGEX_KeyIterator iterator,
+              void *iterator_cls)
+{
+  struct Transition *t;
+  struct GNUNET_REGEX_Edge edges[s->transition_count];
+  unsigned int num_edges;
+
+  if (GNUNET_YES != s->marked)
+  {
+    s->marked = GNUNET_YES;
+
+    num_edges = state_get_edges (s, edges);
+
+    iterator (iterator_cls, &s->hash, s->proof, s->accepting, num_edges, edges);
+
+    for (t = s->transitions_head; NULL != t; t = t->next)
+      iterate_edge (t->to_state, iterator, iterator_cls);
+  }
+}
+
+/**
+ * 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
+GNUNET_REGEX_iterate_all_edges (struct GNUNET_REGEX_Automaton *a,
+                                GNUNET_REGEX_KeyIterator iterator,
+                                void *iterator_cls)
+{
+  struct GNUNET_REGEX_State *s;
+
+  for (s = a->states_head; NULL != s; s = s->next)
+    s->marked = GNUNET_NO;
+
+  iterate_edge (a->start, iterator, iterator_cls);
+}