+ {
+ is_dup = GNUNET_NO;
+ for (t = t_check->from_state->transitions_head; NULL != t; t = t->next)
+ {
+ if (t->to_state == s1 && 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}
+ new_name = s1->name;
+ 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++;
+}
+
+
+/**
+ * Depth-first traversal of 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 s start state.
+ * @param count current count of the state.
+ * @param action action to be performed on each state.
+ * @param action_cls closure for action
+ */
+static void
+automaton_state_traverse (struct GNUNET_REGEX_State *s, unsigned int *count,
+ GNUNET_REGEX_traverse_action action, void *action_cls)
+{
+ struct GNUNET_REGEX_Transition *t;
+
+ if (GNUNET_NO != s->marked)
+ return;
+ s->marked = GNUNET_YES;
+ if (NULL != action)
+ action (action_cls, *count, s);
+ (*count)++;
+ for (t = s->transitions_head; NULL != t; t = t->next)
+ automaton_state_traverse (t->to_state, count, action, action_cls);
+}
+
+
+/**
+ * Traverses the given automaton from it's start state, visiting all reachable
+ * states and calling 'action' on each one of them.
+ *
+ * @param a automaton.
+ * @param action action to be performed on each state.
+ * @param action_cls closure for action
+ */
+void
+GNUNET_REGEX_automaton_traverse (struct GNUNET_REGEX_Automaton *a,
+ GNUNET_REGEX_traverse_action action,
+ void *action_cls)
+{
+ unsigned int count;
+ struct GNUNET_REGEX_State *s;
+
+ for (s = a->states_head; NULL != s; s = s->next)
+ s->marked = GNUNET_NO;
+ count = 0;
+ automaton_state_traverse (a->start, &count, action, action_cls);
+}
+
+
+/**
+ * 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 char *str)
+{
+ size_t slen;
+ const char *op;
+ const char *cl;
+ const char *pos;
+ unsigned int cnt;
+
+ if ((NULL == str) || ((slen = strlen (str)) < 2))
+ return GNUNET_NO;
+
+ if ('(' != str[0])
+ return GNUNET_YES;
+ cnt = 1;
+ pos = &str[1];
+ while (cnt > 0)
+ {
+ cl = strchr (pos, ')');
+ if (NULL == cl)
+ {
+ GNUNET_break (0);
+ return GNUNET_YES;
+ }
+ op = strchr (pos, '(');
+ if ((NULL != op) && (op < cl))
+ {
+ cnt++;
+ pos = op + 1;
+ continue;
+ }
+ /* 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, free'd or re-used by this function, can be NULL
+ *
+ * @return string without surrounding parentheses, string 'str' if no preceding
+ * epsilon could be found, NULL if 'str' was NULL
+ */
+static char *
+remove_parentheses (char *str)
+{
+ size_t slen;
+ const char *pos;
+
+ if ((NULL == str) || ('(' != str[0]) ||
+ (str[(slen = strlen (str)) - 1] != ')'))
+ return str;
+
+ pos = strchr (&str[1], ')');
+ if (pos == &str[slen - 1])
+ {
+ memmove (str, &str[1], slen - 2);
+ str[slen - 2] = '\0';
+ }
+ return str;
+}
+
+
+/**
+ * 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 char *str)
+{
+ return (NULL != str) && ('(' == str[0]) && ('|' == str[1]) &&
+ (')' == str[strlen (str) - 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 string
+ *
+ * @return string without preceding epsilon, string 'str' if no preceding epsilon
+ * could be found, NULL if 'str' was NULL
+ */
+static char *
+remove_epsilon (const char *str)
+{
+ size_t len;
+
+ if (NULL == str)
+ return NULL;
+ if (('(' == str[0]) && ('|' == str[1]))
+ {
+ len = strlen (str);
+ if (')' == str[len - 1])
+ return GNUNET_strndup (&str[2], len - 3);
+ }
+ return GNUNET_strdup (str);
+}
+
+
+/**
+ * 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
+strkcmp (const char *str1, const char *str2, size_t k)
+{
+ if ((NULL == str1) || (NULL == str2) || (strlen (str1) < k))
+ return -1;
+ return strcmp (&str1[k], str2);
+}
+
+
+/**
+ * Compare two strings for equality. If either is NULL (or if both are
+ * 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, 1 or -1 if not
+ */
+static int
+nullstrcmp (const char *str1, const char *str2)
+{
+ if ((NULL == str1) || (NULL == str2))
+ return -1;
+ return strcmp (str1, str2);
+}
+
+
+/**
+ * Helper function used as 'action' in 'GNUNET_REGEX_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, unsigned int count, struct GNUNET_REGEX_State *s)
+{
+ struct GNUNET_REGEX_State **states = cls;
+
+ s->proof_id = count;
+ if (NULL != states)
+ states[count] = s;
+}
+
+
+/**
+ * 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!
+ */
+static void
+automaton_create_proofs_simplify (char *R_last_ij, char *R_last_ik,
+ char *R_last_kk, char *R_last_kj,
+ char **R_cur_ij)
+{
+ char *R_cur_l;
+ char *R_cur_r;
+ char *temp_a;
+ char *temp_b;
+ char *R_temp_ij;
+ char *R_temp_ik;
+ char *R_temp_kj;
+ char *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;
+ unsigned int cnt;
+
+ size_t length;
+ size_t length_l;
+ size_t length_r;
+
+ GNUNET_assert (NULL == *R_cur_ij && NULL != R_cur_ij);
+
+ // $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 ((NULL == R_last_ij) && ((NULL == R_last_ik) || (NULL == R_last_kk) || /* technically cannot happen, but looks saner */
+ (NULL == R_last_kj)))
+ {
+ /* R^{(k)}_{ij} = N | N */
+ *R_cur_ij = NULL;
+ return;
+ }
+
+ if ((NULL == R_last_ik) || (NULL == R_last_kk) || /* technically cannot happen, but looks saner */
+ (NULL == R_last_kj))
+ {
+ /* R^{(k)}_{ij} = R^{(k-1)}_{ij} | N */
+ *R_cur_ij = GNUNET_strdup (R_last_ij);
+ return;
+ }
+
+ // $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;
+ R_cur_l = NULL;
+
+ // cache results from strcmp, we might need these many times
+ ij_kj_cmp = nullstrcmp (R_last_ij, R_last_kj);
+ ij_ik_cmp = nullstrcmp (R_last_ij, R_last_ik);
+ ik_kk_cmp = nullstrcmp (R_last_ik, R_last_kk);
+ kk_kj_cmp = 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
+ R_temp_ik = remove_parentheses (remove_epsilon (R_last_ik));
+ R_temp_kk = remove_parentheses (remove_epsilon (R_last_kk));
+ R_temp_kj = remove_parentheses (remove_epsilon (R_last_kj));
+
+ clean_ik_kk_cmp = nullstrcmp (R_last_ik, R_temp_kk);
+ clean_kk_kj_cmp = nullstrcmp (R_temp_kk, R_last_kj);
+
+ // construct R_cur_l (and, if necessary R_cur_r)
+ if (NULL != R_last_ij)
+ {
+ // Assign R_temp_ij to R_last_ij and remove epsilon as well
+ // as parentheses, so we can better compare the contents
+ R_temp_ij = remove_parentheses (remove_epsilon (R_last_ij));
+
+ if (0 == strcmp (R_temp_ij, R_temp_ik) && 0 == strcmp (R_temp_ik, R_temp_kk)
+ && 0 == strcmp (R_temp_kk, R_temp_kj))
+ {
+ if (0 == strlen (R_temp_ij))
+ {
+ R_cur_r = GNUNET_strdup ("");
+ }
+ else if ((0 == strncmp (R_last_ij, "(|", 2)) ||
+ (0 == strncmp (R_last_ik, "(|", 2) &&
+ 0 == strncmp (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))
+ GNUNET_asprintf (&R_cur_r, "(%s)*", R_temp_ij);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s*", 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))
+ GNUNET_asprintf (&R_cur_r, "(%s)+", R_temp_ij);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s+", R_temp_ij);
+ }
+ }
+ else if (0 == ij_ik_cmp && 0 == clean_kk_kj_cmp && 0 != clean_ik_kk_cmp)
+ {
+ // a|ab*b = ab*
+ if (strlen (R_last_kk) < 1)
+ R_cur_r = GNUNET_strdup (R_last_ij);
+ else if (GNUNET_YES == needs_parentheses (R_temp_kk))
+ GNUNET_asprintf (&R_cur_r, "%s(%s)*", R_last_ij, R_temp_kk);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s%s*", R_last_ij, R_last_kk);
+
+ R_cur_l = NULL;
+ }
+ else if (0 == ij_kj_cmp && 0 == clean_ik_kk_cmp && 0 != clean_kk_kj_cmp)
+ {
+ // a|bb*a = b*a
+ if (strlen (R_last_kk) < 1)
+ R_cur_r = GNUNET_strdup (R_last_kj);
+ else if (GNUNET_YES == needs_parentheses (R_temp_kk))
+ GNUNET_asprintf (&R_cur_r, "(%s)*%s", R_temp_kk, R_last_kj);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s*%s", R_temp_kk, R_last_kj);
+
+ R_cur_l = NULL;
+ }
+ 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))
+ GNUNET_asprintf (&R_cur_r, "%s(%s)*", R_last_ij, R_temp_kk);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s%s*", R_last_ij, R_temp_kk);
+
+ R_cur_l = NULL;
+ }
+ 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))
+ GNUNET_asprintf (&R_cur_r, "(%s)*%s", R_temp_kk, R_last_ij);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s*%s", R_temp_kk, R_last_ij);
+
+ R_cur_l = NULL;
+ }
+ else
+ {
+ temp_a = (NULL == R_last_ij) ? NULL : GNUNET_strdup (R_last_ij);
+ temp_a = remove_parentheses (temp_a);
+ R_cur_l = temp_a;
+ }
+
+ GNUNET_free_non_null (R_temp_ij);
+ }
+ else
+ {
+ // we have no left side
+ R_cur_l = NULL;
+ }
+
+ // construct R_cur_r, if not already constructed
+ if (NULL == R_cur_r)
+ {
+ length = strlen (R_temp_kk) - strlen (R_last_ik);
+
+ // a(ba)*bx = (ab)+x
+ if (length > 0 && NULL != R_last_kk && 0 < strlen (R_last_kk) &&
+ NULL != R_last_kj && 0 < strlen (R_last_kj) && NULL != R_last_ik &&
+ 0 < strlen (R_last_ik) && 0 == strkcmp (R_temp_kk, R_last_ik, length) &&
+ 0 == strncmp (R_temp_kk, R_last_kj, length))
+ {
+ temp_a = GNUNET_malloc (length + 1);
+ temp_b = GNUNET_malloc ((strlen (R_last_kj) - length) + 1);
+
+ length_l = 0;
+ length_r = 0;
+
+ for (cnt = 0; cnt < strlen (R_last_kj); cnt++)
+ {
+ if (cnt < length)
+ {
+ temp_a[length_l] = R_last_kj[cnt];
+ length_l++;
+ }
+ else
+ {
+ temp_b[length_r] = R_last_kj[cnt];
+ length_r++;
+ }
+ }
+ temp_a[length_l] = '\0';
+ temp_b[length_r] = '\0';
+
+ // e|(ab)+ = (ab)*
+ if (NULL != R_cur_l && 0 == strlen (R_cur_l) && 0 == strlen (temp_b))
+ {
+ GNUNET_asprintf (&R_cur_r, "(%s%s)*", R_last_ik, temp_a);
+ GNUNET_free (R_cur_l);
+ R_cur_l = NULL;
+ }
+ else
+ {
+ GNUNET_asprintf (&R_cur_r, "(%s%s)+%s", R_last_ik, temp_a, temp_b);
+ }
+ GNUNET_free (temp_a);
+ GNUNET_free (temp_b);
+ }
+ else if (0 == strcmp (R_temp_ik, R_temp_kk) &&
+ 0 == 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))
+ GNUNET_asprintf (&R_cur_r, "(%s)*", R_temp_kk);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s*", 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))
+ GNUNET_asprintf (&R_cur_r, "(%s)+%s", R_temp_kk, R_temp_kk);
+ else
+ GNUNET_asprintf (&R_cur_r, "(%s)+%s", 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 (eps_check == 1)
+ {
+ if (needs_parentheses (R_temp_kk))
+ GNUNET_asprintf (&R_cur_r, "(%s)+", R_temp_kk);
+ else
+ GNUNET_asprintf (&R_cur_r, "%s+", R_temp_kk);
+ }
+ }