[core] expose an option to change the db file path in runtime

include/mbgl/storage/default_file_source.hpp

@@ -47,6 +47,8 @@ public:
 
     void setResourceTransform(optional<ActorRef<ResourceTransform>>&&);
 
+    void setResourceCachePath(const std::string&);
+
     std::unique_ptr<AsyncRequest> request(const Resource&, Callback) override;
 
     /*

platform/android/scripts/exclude-activity-gen.json

@@ -46,5 +46,7 @@
   "GridSourceActivity",
   "AnimatedImageSourceActivity",
   "EspressoTestActivity",
+  "ChangeResourcesCachePathActivity",
+  "EspressoTestActivity",
   "FragmentBackStackActivity"
 ]

platform/default/include/mbgl/storage/offline_database.hpp

@@ -43,6 +43,10 @@ public:
     OfflineDatabase(std::string path, uint64_t maximumCacheSize = util::DEFAULT_MAX_CACHE_SIZE);
     ~OfflineDatabase();
 
+    void changePath(const std::string&);
+
+    void cleanup();
+
     optional<Response> get(const Resource&);
 
     // Return value is (inserted, stored size)
@@ -112,7 +116,7 @@ private:
     std::pair<int64_t, int64_t> getCompletedResourceCountAndSize(int64_t regionID);
     std::pair<int64_t, int64_t> getCompletedTileCountAndSize(int64_t regionID);
 
-    const std::string path;
+    std::string path;
     std::unique_ptr<mapbox::sqlite::Database> db;
     std::unordered_map<const char *, const std::unique_ptr<mapbox::sqlite::Statement>> statements;
 

platform/default/src/mbgl/storage/default_file_source.cpp

@@ -45,6 +45,10 @@ public:
         onlineFileSource.setResourceTransform(std::move(transform));
     }
 
+    void setResourceCachePath(const std::string& path) {
+        offlineDatabase->changePath(path);
+    }
+
     void listRegions(std::function<void (expected<OfflineRegions, std::exception_ptr>)> callback) {
         callback(offlineDatabase->listRegions());
     }
@@ -243,6 +247,10 @@ void DefaultFileSource::setResourceTransform(optional<ActorRef<ResourceTransform
     impl->actor().invoke(&Impl::setResourceTransform, std::move(transform));
 }
 
+void DefaultFileSource::setResourceCachePath(const std::string& path) {
+    impl->actor().invoke(&Impl::setResourceCachePath, path);
+}
+
 std::unique_ptr<AsyncRequest> DefaultFileSource::request(const Resource& resource, Callback callback) {
     auto req = std::make_unique<FileSourceRequest>(std::move(callback));
 

platform/default/src/mbgl/storage/offline_database.cpp

@@ -27,16 +27,7 @@ OfflineDatabase::OfflineDatabase(std::string path_, uint64_t maximumCacheSize_)
 }
 
 OfflineDatabase::~OfflineDatabase() {
-    // Deleting these SQLite objects may result in exceptions, but we're in a destructor, so we
-    // can't throw anything.
-    try {
-        statements.clear();
-        db.reset();
-    } catch (const util::IOException& ex) {
-        handleError(ex, "close database");
-    } catch (const mapbox::sqlite::Exception& ex) {
-        handleError(ex, "close database");
-    }
+    cleanup();
 }
 
 void OfflineDatabase::initialize() {
@@ -78,6 +69,25 @@ void OfflineDatabase::initialize() {
     }
 }
 
+void OfflineDatabase::changePath(const std::string& path_) {
+    Log::Info(Event::Database, "Changing the database path.");
+    cleanup();
+    path = path_;
+    initialize();
+}
+
+void OfflineDatabase::cleanup() {
+    // Deleting these SQLite objects may result in exceptions
+    try {
+        statements.clear();
+        db.reset();
+    } catch (const util::IOException& ex) {
+        handleError(ex, "close database");
+    } catch (const mapbox::sqlite::Exception& ex) {
+        handleError(ex, "close database");
+    }
+}
+
 void OfflineDatabase::handleError(const mapbox::sqlite::Exception& ex, const char* action) {
     if (ex.code == mapbox::sqlite::ResultCode::NotADB ||
         ex.code == mapbox::sqlite::ResultCode::Corrupt ||

test/storage/offline_database.test.cpp

@@ -1352,3 +1352,11 @@ TEST(OfflineDatabase, TEST_REQUIRES_WRITE(MergeDatabaseWithDiskFull)) {
 }
 #endif // __QT__
 
+TEST(OfflineDatabse, ChangePath) {
+    std::string newPath("test/fixtures/offline_database/test.db");
+    OfflineDatabase db(":memory:");
+    db.changePath(newPath);
+    mapbox::sqlite::Database::open(newPath, mapbox::sqlite::ReadOnly);
+    util::deleteFile(newPath);
+}
+