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diff --git a/src/regex/regex_internal.h b/src/regex/regex_internal.h
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+/*
+     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.h
+ * @brief common internal definitions for regex library.
+ * @author Maximilian Szengel
+ */
+#ifndef REGEX_INTERNAL_H
+#define REGEX_INTERNAL_H
+
+#include "gnunet_regex_lib.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+/**
+ * char array of literals that are allowed inside a regex (apart from the
+ * operators)
+ */
+#define ALLOWED_LITERALS "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+
+/**
+ * Transition between two states. Transitions are stored at the states from
+ * which they origin ('from_state'). Each state can have 0-n transitions.
+ * If label is NULL, this is considered to be an epsilon transition.
+ */
+struct GNUNET_REGEX_Transition
+{
+  /**
+   * This is a linked list.
+   */
+  struct GNUNET_REGEX_Transition *prev;
+
+  /**
+   * This is a linked list.
+   */
+  struct GNUNET_REGEX_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;
+};
+
+
+/**
+ * A state. Can be used in DFA and NFA automatons.
+ */
+struct GNUNET_REGEX_State;
+
+
+/**
+ * Set of states.
+ */
+struct GNUNET_REGEX_StateSet
+{
+  /**
+   * Array of states.
+   */
+  struct GNUNET_REGEX_State **states;
+
+  /**
+   * Number of entries in *use* in the 'states' array.
+   */
+  unsigned int off;
+
+  /**
+   * Length of the 'states' array.
+   */
+  unsigned int size;
+};
+
+
+/**
+ * A state. Can be used in DFA and NFA automatons.
+ */
+struct GNUNET_REGEX_State
+{
+  /**
+   * This is a linked list to keep states in an automaton.
+   */
+  struct GNUNET_REGEX_State *prev;
+
+  /**
+   * This is a linked list to keep states in an automaton.
+   */
+  struct GNUNET_REGEX_State *next;
+
+  /**
+   * This is a multi DLL for StateSet_MDLL.
+   */
+  struct GNUNET_REGEX_State *prev_SS;
+
+  /**
+   * This is a multi DLL for StateSet_MDLL.
+   */
+  struct GNUNET_REGEX_State *next_SS;
+
+  /**
+   * This is a multi DLL for StateSet_MDLL Stack.
+   */
+  struct GNUNET_REGEX_State *prev_ST;
+
+  /**
+   * This is a multi DLL for StateSet_MDLL Stack.
+   */
+  struct GNUNET_REGEX_State *next_ST;
+
+  /**
+   * Unique state id.
+   */
+  unsigned int id;
+
+  /**
+   * Unique state id that is used for traversing the automaton. It is guaranteed
+   * to be > 0 and < state_count.
+   */
+  unsigned int traversal_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 state. Used for debugging and graph
+   * creation.
+   */
+  char *name;
+
+  /**
+   * Hash of the state.
+   */
+  struct GNUNET_HashCode hash;
+
+  /**
+   * Linear state ID accquired by depth-first-search. This ID should be used for
+   * storing information about the state in an array, because the 'id' of the
+   * state is not guaranteed to be linear. The 'dfs_id' is guaranteed to be > 0
+   * and < 'state_count'.
+   */
+  unsigned int dfs_id;
+
+  /**
+   * Proof for this state.
+   */
+  char *proof;
+
+  /**
+   * Number of transitions from this state to other states.
+   */
+  unsigned int transition_count;
+
+  /**
+   * DLL of transitions.
+   */
+  struct GNUNET_REGEX_Transition *transitions_head;
+
+  /**
+   * DLL of transitions.
+   */
+  struct GNUNET_REGEX_Transition *transitions_tail;
+
+  /**
+   * Number of incoming transitions. Used for compressing DFA paths.
+   */
+  unsigned int incoming_transition_count;
+
+  /**
+   * 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;
+};
+
+
+/**
+ * Type of an automaton.
+ */
+enum GNUNET_REGEX_AutomatonType
+{
+  NFA,
+  DFA
+};
+
+
+/**
+ * Automaton representation.
+ */
+struct GNUNET_REGEX_Automaton
+{
+  /**
+   * Linked list of NFAs used for partial NFA creation.
+   */
+  struct GNUNET_REGEX_Automaton *prev;
+
+  /**
+   * Linked list of NFAs used for partial NFA creation.
+   */
+  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 partial NFA. This is undefined for DFAs
+   */
+  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_AutomatonType type;
+
+  /**
+   * Regex
+   */
+  char *regex;
+
+  /**
+   * Canonical regex (result of RX->NFA->DFA->RX)
+   */
+  char *canonical_regex;
+
+  /**
+   * GNUNET_YES, if multi strides have been added to the Automaton.
+   */
+  int is_multistrided;
+};
+
+
+/**
+ * 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_automaton_destroy.
+ */
+struct GNUNET_REGEX_Automaton *
+GNUNET_REGEX_construct_nfa (const char *regex, const size_t len);
+
+
+/**
+ * Function that get's passed to automaton traversal and is called before each
+ * next traversal from state 's' using transition 't' to check if traversal
+ * should proceed. Return GNUNET_NO to stop traversal or GNUNET_YES to continue.
+ *
+ * @param cls closure for the check.
+ * @param s current state in the traversal.
+ * @param t current transition from state 's' that will be used for the next
+ *          step.
+ *
+ * @return GNUNET_YES to proceed traversal, GNUNET_NO to stop.
+ */
+typedef int (*GNUNET_REGEX_traverse_check) (void *cls,
+                                            struct GNUNET_REGEX_State * s,
+                                            struct GNUNET_REGEX_Transition * t);
+
+
+/**
+ * Function that is called with each state, when traversing an automaton.
+ *
+ * @param cls closure.
+ * @param count current count of the state, from 0 to a->state_count -1.
+ * @param s state.
+ */
+typedef void (*GNUNET_REGEX_traverse_action) (void *cls,
+                                              const unsigned int count,
+                                              struct GNUNET_REGEX_State * s);
+
+
+/**
+ * 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
+GNUNET_REGEX_automaton_traverse (const struct GNUNET_REGEX_Automaton *a,
+                                 struct GNUNET_REGEX_State *start,
+                                 GNUNET_REGEX_traverse_check check,
+                                 void *check_cls,
+                                 GNUNET_REGEX_traverse_action action,
+                                 void *action_cls);
+
+/**
+ * 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 canonical regex string.
+ */
+const char *
+GNUNET_REGEX_get_canonical_regex (struct GNUNET_REGEX_Automaton *a);
+
+
+/**
+ * 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
+GNUNET_REGEX_get_transition_count (struct GNUNET_REGEX_Automaton *a);
+
+
+/**
+ * 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;
+
+  /**
+   * 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;
+};
+
+
+/**
+ * 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
+GNUNET_REGEX_dfa_add_multi_strides (struct GNUNET_REGEX_Context *regex_ctx,
+                                    struct GNUNET_REGEX_Automaton *dfa,
+                                    const unsigned int stride_len);
+
+
+/**
+ * Generate a (pseudo) random regular expression of length 'rx_length', as well
+ * as a (optional) string that will be matched by the generated regex. The
+ * returned regex needs to be freed.
+ *
+ * @param rx_length length of the random regex.
+ * @param matching_str (optional) pointer to a string that will contain a string
+ *                     that will be matched by the generated regex, if
+ *                     'matching_str' pointer was not NULL.
+ *
+ * @return NULL if 'rx_length' is 0, a random regex of length 'rx_length', which
+ *         needs to be freed, otherwise.
+ */
+char *
+GNUNET_REGEX_generate_random_regex (size_t rx_length, char *matching_str);
+
+
+/**
+ * Generate a random string of maximum length 'max_len' that only contains literals allowed
+ * in a regular expression. The string might be 0 chars long but is garantueed
+ * to be shorter or equal to 'max_len'.
+ *
+ * @param max_len maximum length of the string that should be generated.
+ *
+ * @return random string that needs to be freed.
+ */
+char *
+GNUNET_REGEX_generate_random_string (size_t max_len);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+#endif