Re-committing http://codereview.chromium.org/6803005/ after fixing multi-dll build:

third_party/libphonenumber/cpp/src/re2_cache.h

+// Copyright (C) 2011 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: Fredrik Roubert <roubert@google.com>
+
+// RE2Cache is a simple wrapper around hash_map<> to store RE2 objects.
+//
+// To get a cached RE2 object for a regexp pattern string, create a ScopedAccess
+// object with a pointer to the cache object and the pattern string itself as
+// constructor parameters. If an RE2 object corresponding to the pattern string
+// doesn't already exist, it will be created by the access object constructor.
+// The access object implements operator const RE& and can therefore be passed
+// as an argument to any function that expects an RE2 object.
+//
+// RE2Cache cache;
+// RE2Cache::ScopedAccess foo(&cache, "foo");
+// bool match = RE2::FullMatch("foobar", foo);
+
+#ifndef I18N_PHONENUMBERS_RE2_CACHE_H_
+#define I18N_PHONENUMBERS_RE2_CACHE_H_
+
+#ifdef __DEPRECATED
+#undef __DEPRECATED  // Don't warn for using <hash_map>.
+#endif
+
+#include <cstddef>
+#include <hash_map>
+#include <string>
+
+#include "base/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+
+namespace re2 {
+class RE2;
+}  // namespace re2
+
+namespace i18n {
+namespace phonenumbers {
+
+using re2::RE2;
+using std::string;
+using __gnu_cxx::hash_map;
+
+class RE2Cache {
+ private:
+  typedef hash_map<string, const RE2*> CacheImpl;
+
+ public:
+  explicit RE2Cache(size_t min_items);
+  ~RE2Cache();
+
+  class ScopedAccess {
+   public:
+    ScopedAccess(RE2Cache* cache, const string& pattern);
+    operator const RE2&() const { return *regexp_; }
+
+   private:
+    const RE2* regexp_;
+    friend class RE2CacheTest_AccessConstructor_Test;
+  };
+
+ private:
+  base::Lock lock_;  // protects cache_impl_
+  scoped_ptr<CacheImpl> cache_impl_;  // protected by lock_
+  friend class RE2CacheTest_CacheConstructor_Test;
+  friend class RE2CacheTest_AccessConstructor_Test;
+};
+
+}  // namespace phonenumbers
+}  // namespace i18n
+
+#endif  // I18N_PHONENUMBERS_RE2_CACHE_H_