Move deduping_factory files.

chrome/browser/extensions/api/declarative/deduping_factory.h

-// Copyright (c) 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CHROME_BROWSER_EXTENSIONS_API_DECLARATIVE_DEDUPING_FACTORY_H__
-#define CHROME_BROWSER_EXTENSIONS_API_DECLARATIVE_DEDUPING_FACTORY_H__
-
-#include <list>
-#include <string>
-
-#include "base/compiler_specific.h"
-#include "base/containers/hash_tables.h"
-#include "base/logging.h"
-#include "base/memory/ref_counted.h"
-#include "base/stl_util.h"
-
-namespace base {
-class Value;
-}  // namespace base
-
-namespace extensions {
-
-// Factory class that stores a cache of the last |N| created objects of each
-// kind. These objects need to be immutable, refcounted objects that are derived
-// from BaseClassT. The objects do not need to be RefCountedThreadSafe. If a new
-// instance of an object is created that is identical to a pre-existing object,
-// it is discarded and the pre-existing object is recycled.
-//
-// BaseClassT needs to provide a comparison operations. Like the following:
-//
-// class BaseClassT {
-//   virtual bool Equals(const BaseClassT* other) const;
-// };
-//
-// The unit test shows an example.
-template<typename BaseClassT>
-class DedupingFactory {
- public:
-  // Factory methods for BaseClass instances. |value| contains e.g. the json
-  // dictionary that describes the object to be instantiated. |error| is used
-  // to return error messages in case the extension passed an action that was
-  // syntactically correct but semantically incorrect. |bad_message| is set to
-  // true in case |dict| does not confirm to the validated JSON specification.
-  typedef scoped_refptr<const BaseClassT>
-      (* FactoryMethod)(const std::string& instance_type,
-                        const base::Value* /* value */ ,
-                        std::string* /* error */,
-                        bool* /* bad_message */);
-
-  enum Parameterized {
-    // Two instantiated objects may be different and we need to check for
-    // equality to see whether we can recycle one.
-    IS_PARAMETERIZED,
-    // The objects are not parameterized, i.e. all created instances are the
-    // same and it is sufficient to create a single one.
-    IS_NOT_PARAMETERIZED
-  };
-
-  // Creates a DedupingFactory with a MRU cache of size |max_number_prototypes|
-  // per instance_type. If we find a match within the cache, the factory reuses
-  // that instance instead of creating a new one. The cache size should not be
-  // too large because we probe linearly whether an element is in the cache.
-  explicit DedupingFactory(size_t max_number_prototypes);
-  ~DedupingFactory();
-
-  void RegisterFactoryMethod(const std::string& instance_type,
-                             Parameterized parameterized,
-                             FactoryMethod factory_method);
-
-  scoped_refptr<const BaseClassT> Instantiate(const std::string& instance_type,
-                                              const base::Value* value,
-                                              std::string* error,
-                                              bool* bad_message);
-
-  void ClearPrototypes();
-
- private:
-  typedef std::string InstanceType;
-  // Cache of previous prototypes in most-recently-used order. Most recently
-  // used objects are at the end.
-  typedef std::list<scoped_refptr<const BaseClassT> > PrototypeList;
-  typedef base::hash_map<InstanceType, PrototypeList> ExistingPrototypes;
-  typedef base::hash_map<InstanceType, FactoryMethod> FactoryMethods;
-  typedef base::hash_set<InstanceType> ParameterizedTypes;
-
-  const size_t max_number_prototypes_;
-  ExistingPrototypes prototypes_;
-  FactoryMethods factory_methods_;
-  ParameterizedTypes parameterized_types_;
-
-  DISALLOW_COPY_AND_ASSIGN(DedupingFactory);
-};
-
-template<typename BaseClassT>
-DedupingFactory<BaseClassT>::DedupingFactory(size_t max_number_prototypes)
-    : max_number_prototypes_(max_number_prototypes) {}
-
-template<typename BaseClassT>
-DedupingFactory<BaseClassT>::~DedupingFactory() {}
-
-template<typename BaseClassT>
-void DedupingFactory<BaseClassT>::RegisterFactoryMethod(
-    const std::string& instance_type,
-    typename DedupingFactory<BaseClassT>::Parameterized parameterized,
-    FactoryMethod factory_method) {
-  DCHECK(!ContainsKey(factory_methods_, instance_type));
-  factory_methods_[instance_type] = factory_method;
-  if (parameterized == IS_PARAMETERIZED)
-    parameterized_types_.insert(instance_type);
-}
-
-template<typename BaseClassT>
-scoped_refptr<const BaseClassT> DedupingFactory<BaseClassT>::Instantiate(
-    const std::string& instance_type,
-    const base::Value* value,
-    std::string* error,
-    bool* bad_message) {
-  typename FactoryMethods::const_iterator factory_method_iter =
-      factory_methods_.find(instance_type);
-  if (factory_method_iter == factory_methods_.end()) {
-    *error = "Invalid instance type " + instance_type;
-    *bad_message = true;
-    return scoped_refptr<const BaseClassT>();
-  }
-
-  FactoryMethod factory_method = factory_method_iter->second;
-
-  PrototypeList& prototypes = prototypes_[instance_type];
-
-  // We can take a shortcut for objects that are not parameterized. For those
-  // only a single instance may ever exist so we can simplify the creation
-  // logic.
-  if (!ContainsKey(parameterized_types_, instance_type)) {
-    if (prototypes.empty()) {
-      scoped_refptr<const BaseClassT> new_object =
-          (*factory_method)(instance_type, value, error, bad_message);
-      if (!new_object.get() || !error->empty() || *bad_message)
-        return scoped_refptr<const BaseClassT>();
-      prototypes.push_back(new_object);
-    }
-    return prototypes.front();
-  }
-
-  // Handle parameterized objects.
-  scoped_refptr<const BaseClassT> new_object =
-      (*factory_method)(instance_type, value, error, bad_message);
-  if (!new_object.get() || !error->empty() || *bad_message)
-    return scoped_refptr<const BaseClassT>();
-
-  size_t length = 0;
-  for (typename PrototypeList::iterator i = prototypes.begin();
-       i != prototypes.end();
-       ++i) {
-    if ((*i)->Equals(new_object.get())) {
-      // Move the old object to the end of the queue so that it gets
-      // discarded later.
-      scoped_refptr<const BaseClassT> old_object = *i;
-      prototypes.erase(i);
-      prototypes.push_back(old_object);
-      return old_object;
-    }
-    ++length;
-  }
-
-  if (length >= max_number_prototypes_)
-    prototypes.pop_front();
-  prototypes.push_back(new_object);
-
-  return new_object;
-}
-
-template<typename BaseClassT>
-void DedupingFactory<BaseClassT>::ClearPrototypes() {
-  prototypes_.clear();
-}
-
-}  // namespace extensions
-
-#endif  // CHROME_BROWSER_EXTENSIONS_API_DECLARATIVE_DEDUPING_FACTORY_H__