re2/prefilter.h

// Copyright 2009 The RE2 Authors.  All Rights Reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Prefilter is the class used to extract string guards from regexps.
// Rather than using Prefilter class directly, use FilteredRE2.
// See filtered_re2.h

#ifndef RE2_PREFILTER_H_
#define RE2_PREFILTER_H_

#include "util/util.h"

namespace re2 {

class RE2;

class Regexp;

class Prefilter {
  // Instead of using Prefilter directly, use FilteredRE2; see filtered_re2.h
 public:
  enum Op {
    ALL = 0,  // Everything matches
    NONE,  // Nothing matches
    ATOM,  // The string atom() must match
    AND,   // All in subs() must match
    OR,   // One of subs() must match
  };

  explicit Prefilter(Op op);
  ~Prefilter();

  Op op() { return op_; }
  const string& atom() const { return atom_; }
  void set_unique_id(int id) { unique_id_ = id; }
  int unique_id() const { return unique_id_; }

  // The children of the Prefilter node.
  vector<Prefilter*>* subs() {
    CHECK(op_ == AND || op_ == OR);
    return subs_;
  }

  // Set the children vector. Prefilter takes ownership of subs and
  // subs_ will be deleted when Prefilter is deleted.
  void set_subs(vector<Prefilter*>* subs) { subs_ = subs; }

  // Given a RE2, return a Prefilter. The caller takes ownership of
  // the Prefilter and should deallocate it. Returns NULL if Prefilter
  // cannot be formed.
  static Prefilter* FromRE2(const RE2* re2);

  // Returns a readable debug string of the prefilter.
  string DebugString() const;

 private:
  class Info;

  // Combines two prefilters together to create an AND. The passed
  // Prefilters will be part of the returned Prefilter or deleted.
  static Prefilter* And(Prefilter* a, Prefilter* b);

  // Combines two prefilters together to create an OR. The passed
  // Prefilters will be part of the returned Prefilter or deleted.
  static Prefilter* Or(Prefilter* a, Prefilter* b);

  // Generalized And/Or
  static Prefilter* AndOr(Op op, Prefilter* a, Prefilter* b);

  static Prefilter* FromRegexp(Regexp* a);

  static Prefilter* FromString(const string& str);

  static Prefilter* OrStrings(set<string>* ss);

  static Info* BuildInfo(Regexp* re);

  Prefilter* Simplify();

  // Kind of Prefilter.
  Op op_;

  // Sub-matches for AND or OR Prefilter.
  vector<Prefilter*>* subs_;

  // Actual string to match in leaf node.
  string atom_;

  // If different prefilters have the same string atom, or if they are
  // structurally the same (e.g., OR of same atom strings) they are
  // considered the same unique nodes. This is the id for each unique
  // node. This field is populated with a unique id for every node,
  // and -1 for duplicate nodes.
  int unique_id_;

  // Used for debugging, helps in tracking memory leaks.
  int alloc_id_;

  DISALLOW_EVIL_CONSTRUCTORS(Prefilter);
};

}  // namespace re2

#endif  // RE2_PREFILTER_H_