refactor: DbPool for managing shared db files

src/rime/dict/db_pool.h

@@ -0,0 +1,25 @@
+#ifndef RIME_DB_POOL_H_
+#define RIME_DB_POOL_H_
+
+#include <rime/common.h>
+#include <rime/resource.h>
+
+namespace rime {
+
+class ResourceResolver;
+
+template <class T>
+class DbPool {
+ public:
+  explicit DbPool(the<ResourceResolver> resource_resolver);
+
+  an<T> GetDb(const string& db_name);
+
+ protected:
+  the<ResourceResolver> resource_resolver_;
+  map<string, weak<T>> db_pool_;
+};
+
+}  // namespace rime
+
+#endif  // RIME_DB_POOL_H_

src/rime/dict/db_pool_impl.h

@@ -0,0 +1,26 @@
+#ifndef RIME_DB_POOL_IMPL_H_
+#define RIME_DB_POOL_IMPL_H_
+
+#include "db_pool.h"
+#include <rime/resource.h>
+
+namespace rime {
+
+template <class T>
+DbPool<T>::DbPool(the<ResourceResolver> resource_resolver)
+    : resource_resolver_(std::move(resource_resolver)) {}
+
+template <class T>
+an<T> DbPool<T>::GetDb(const string& db_name) {
+  auto db = db_pool_[db_name].lock();
+  if (!db) {
+    auto file_path = resource_resolver_->ResolvePath(db_name).string();
+    db = New<T>(file_path);
+    db_pool_[db_name] = db;
+  }
+  return db;
+};
+
+}  // namespace rime
+
+#endif  // RIME_DB_POOL_IMPL_H_

src/rime/dict/reverse_lookup_dictionary.cc

@@ -14,6 +14,7 @@
 #include <rime/schema.h>
 #include <rime/service.h>
 #include <rime/ticket.h>
+#include <rime/dict/db_pool_impl.h>
 #include <rime/dict/dict_settings.h>
 #include <rime/dict/reverse_lookup_dictionary.h>
 
@@ -235,17 +236,13 @@ static const ResourceType kReverseDbResourceType = {"reverse_db", "",
                                                     ".reverse.bin"};
 
 ReverseLookupDictionaryComponent::ReverseLookupDictionaryComponent()
-    : resource_resolver_(Service::instance().CreateDeployedResourceResolver(
-          kReverseDbResourceType)) {}
+    : DbPool(the<ResourceResolver>(
+          Service::instance().CreateDeployedResourceResolver(
+              kReverseDbResourceType))) {}
 
 ReverseLookupDictionary* ReverseLookupDictionaryComponent::Create(
     const string& dict_name) {
-  auto db = db_pool_[dict_name].lock();
-  if (!db) {
-    auto file_path = resource_resolver_->ResolvePath(dict_name).string();
-    db = New<ReverseDb>(file_path);
-    db_pool_[dict_name] = db;
-  }
+  auto db = GetDb(dict_name);
   return new ReverseLookupDictionary(db);
 };
 

src/rime/dict/reverse_lookup_dictionary.h

@@ -11,6 +11,7 @@
 #include <stdint.h>
 #include <rime/common.h>
 #include <rime/component.h>
+#include <rime/dict/db_pool.h>
 #include <rime/dict/mapped_file.h>
 #include <rime/dict/string_table.h>
 #include <rime/dict/vocabulary.h>
@@ -75,15 +76,12 @@ class ReverseLookupDictionary
 class ResourceResolver;
 
 class ReverseLookupDictionaryComponent
-    : public ReverseLookupDictionary::Component {
+    : public ReverseLookupDictionary::Component,
+      protected DbPool<ReverseDb> {
  public:
   ReverseLookupDictionaryComponent();
   ReverseLookupDictionary* Create(const Ticket& ticket);
   ReverseLookupDictionary* Create(const string& dict_name);
-
- private:
-  map<string, weak<ReverseDb>> db_pool_;
-  the<ResourceResolver> resource_resolver_;
 };
 
 }  // namespace rime