src/net/instaweb/util/public/statistics_template.h

/**
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Author: jmarantz@google.com (Joshua Marantz)

#ifndef NET_INSTAWEB_UTIL_PUBLIC_STATISTICS_TEMPLATE_H_
#define NET_INSTAWEB_UTIL_PUBLIC_STATISTICS_TEMPLATE_H_

#include <map>
#include <vector>
#include "net/instaweb/util/public/statistics.h"
#include "net/instaweb/util/public/stl_util.h"
#include <string>
#include "net/instaweb/util/public/string_util.h"

namespace net_instaweb {

// This class makes it easier to define new Statistics implementations
// by providing a templatized implementation of variable registration and
// management.
template<class Var> class StatisticsTemplate : public Statistics {
 public:
  StatisticsTemplate() {}
  virtual ~StatisticsTemplate() {
    STLDeleteContainerPointers(variables_.begin(), variables_.end());
  }

  // Add a new variable, or returns an existing one of that name.
  // The Variable* is owned by the Statistics class -- it should
  // not be deleted by the caller.
  virtual Variable* AddVariable(const StringPiece& name) {
    return AddVariableInternal(name);
  }

  // Find a variable from a name, returning NULL if not found.
  virtual Variable* FindVariable(const StringPiece& name) const {
    return FindVariableInternal(name);
  }

 protected:
  // Adds a variable, returning as the template class Var type, rather
  // than its base class, as AddVariable does.
  virtual Var* AddVariableInternal(const StringPiece& name) {
    Var* var = FindVariableInternal(name);
    if (var == NULL) {
      var = NewVariable(name, variables_.size());
      variables_.push_back(var);
      variable_map_[std::string(name.data(), name.size())] = var;
    }
    return var;
  }

  // Finds a variable, returning as the template class Var type, rather
  // than its base class, as FindVariable does.
  virtual Var* FindVariableInternal(const StringPiece& name) const {
    typename VarMap::const_iterator p = variable_map_.find(name.as_string());
    Var* var = NULL;
    if (p != variable_map_.end()) {
      var = p->second;
    }
    return var;
  }

  virtual Var* NewVariable(const StringPiece& name, int index) = 0;

 protected:
  typedef std::vector<Var*> VarVector;
  typedef std::map<std::string, Var*> VarMap;
  VarVector variables_;
  VarMap variable_map_;

  DISALLOW_COPY_AND_ASSIGN(StatisticsTemplate);
};

}  // namespace net_instaweb

#endif  // NET_INSTAWEB_UTIL_PUBLIC_STATISTICS_TEMPLATE_H_