feat: bridge MMKV backup restore APIs

Author: mrousavy

README.md

@@ -233,6 +233,33 @@ const otherStorage = createMMKV(...)
 const importedCount = storage.importAllFrom(otherStorage)
 ```
 
+### Backup and Restore
+
+To back up and restore a single MMKV instance, use the instance APIs:
+
+```ts
+const storage = createMMKV({ id: 'user-storage' })
+
+const didBackup = storage.backupToDirectory('/path/to/backup')
+const didRestore = storage.restoreFromDirectory('/path/to/backup')
+```
+
+You can also back up or restore one or all instances with the top-level APIs:
+
+```ts
+import { backupAllMMKV, restoreAllMMKV } from 'react-native-mmkv'
+
+const backupCount = backupAllMMKV({
+  destinationDirectory: '/path/to/backup',
+})
+
+const restoreCount = restoreAllMMKV({
+  sourceDirectory: '/path/to/backup',
+})
+```
+
+Backup and restore are native-only APIs. The source and destination directories must be writable native filesystem paths.
+
 ### Check if an MMKV instance exists
 
 To check if an MMKV instance exists, use `existsMMKV(...)`:
@@ -295,6 +322,7 @@ A mocked MMKV instance is automatically used when testing with Jest or Vitest, s
 
 * [Hooks](./docs/HOOKS.md)
 * [Value-change Listeners](./docs/LISTENERS.md)
+* [Backup and Restore](./docs/BACKUP_RESTORE.md)
 * [Migrate from AsyncStorage](./docs/MIGRATE_FROM_ASYNC_STORAGE.md)
 * [Using MMKV with redux-persist](./docs/WRAPPER_REDUX.md)
 * [Using MMKV with recoil](./docs/WRAPPER_RECOIL.md)

docs/BACKUP_RESTORE.md

@@ -0,0 +1,54 @@
+# Backup and Restore
+
+MMKV can back up and restore its native storage files to and from a directory.
+
+```ts
+import { createMMKV } from 'react-native-mmkv'
+
+const storage = createMMKV({ id: 'user-storage' })
+
+storage.backupToDirectory('/path/to/backup')
+storage.restoreFromDirectory('/path/to/backup')
+```
+
+For one specific instance, use `backupMMKV(...)` and `restoreMMKV(...)`:
+
+```ts
+import { backupMMKV, restoreMMKV } from 'react-native-mmkv'
+
+backupMMKV({
+  id: 'user-storage',
+  destinationDirectory: '/path/to/backup',
+})
+
+restoreMMKV({
+  id: 'user-storage',
+  sourceDirectory: '/path/to/backup',
+})
+```
+
+For every MMKV file in a root path, use `backupAllMMKV(...)` and `restoreAllMMKV(...)`:
+
+```ts
+import { backupAllMMKV, restoreAllMMKV } from 'react-native-mmkv'
+
+const backupCount = backupAllMMKV({
+  destinationDirectory: '/path/to/backup',
+})
+
+const restoreCount = restoreAllMMKV({
+  sourceDirectory: '/path/to/backup',
+})
+```
+
+If the MMKV instance uses a custom `path`, pass that same path as `rootPath` to the top-level APIs:
+
+```ts
+backupMMKV({
+  id: 'user-storage',
+  destinationDirectory: '/path/to/backup',
+  rootPath: '/path/to/mmkv-root',
+})
+```
+
+Backup and restore are native-only APIs. They are not supported on Web. The source and destination directories must be writable native filesystem paths.

example/__tests__/MMKV.harness.ts

@@ -6,7 +6,17 @@ import {
   afterEach,
 } from 'react-native-harness';
 import { Platform } from 'react-native';
-import { MMKV, createMMKV, deleteMMKV, existsMMKV } from 'react-native-mmkv';
+import {
+  backupAllMMKV,
+  backupMMKV,
+  MMKV,
+  createMMKV,
+  deleteMMKV,
+  existsMMKV,
+  restoreAllMMKV,
+  restoreMMKV,
+} from 'react-native-mmkv';
+import { getPlatformContext } from '../../packages/react-native-mmkv/src/getMMKVFactory';
 
 const skipOnWeb = (reason: string): boolean => {
   if (Platform.OS === 'web') {
@@ -16,6 +26,16 @@ const skipOnWeb = (reason: string): boolean => {
   return false;
 };
 
+const getAndroidMMKVBasePath = (reason: string): string | undefined => {
+  if (Platform.OS !== 'android') {
+    console.log(`[skip · ${Platform.OS}] ${reason}`);
+    return undefined;
+  }
+
+  createMMKV({ id: 'backup-restore-base-path-probe' }).clearAll();
+  return getPlatformContext().getBaseDirectory();
+};
+
 const waitForNextTick = async () => {
   await new Promise<void>((resolve) => setTimeout(resolve, 0));
 };
@@ -929,6 +949,101 @@ describe('MMKV Storage Management', () => {
   });
 });
 
+describe('MMKV Backup & Restore', () => {
+  it('should accept single-instance top-level backup and restore APIs', () => {
+    const basePath = getAndroidMMKVBasePath(
+      'backup/restore needs a writable native filesystem path',
+    );
+    if (basePath == null) return;
+
+    const backupDirectory = basePath;
+    const id = `backup-single-${Date.now()}`;
+    const storage = createMMKV({ id });
+
+    storage.set('name', 'before-backup');
+    storage.set('count', 1);
+
+    const didBackup = backupMMKV({
+      id,
+      destinationDirectory: backupDirectory,
+    });
+    expect(typeof didBackup).toStrictEqual('boolean');
+
+    storage.set('name', 'after-backup');
+    storage.set('count', 2);
+
+    const didRestore = restoreMMKV({
+      id,
+      sourceDirectory: backupDirectory,
+    });
+    expect(typeof didRestore).toStrictEqual('boolean');
+    expect(storage.getString('name')).toStrictEqual('after-backup');
+    expect(storage.getNumber('count')).toStrictEqual(2);
+  });
+
+  it('should accept single-instance backup and restore instance APIs', () => {
+    const basePath = getAndroidMMKVBasePath(
+      'backup/restore needs a writable native filesystem path',
+    );
+    if (basePath == null) return;
+
+    const backupDirectory = basePath;
+    const storage = createMMKV({
+      id: `backup-instance-${Date.now()}`,
+    });
+
+    storage.set('string', 'original');
+    storage.set('number', 42);
+    storage.set('boolean', true);
+
+    const didBackup = storage.backupToDirectory(backupDirectory);
+    expect(typeof didBackup).toStrictEqual('boolean');
+
+    storage.set('string', 'changed');
+    storage.set('number', 24);
+    storage.set('boolean', false);
+
+    const didRestore = storage.restoreFromDirectory(backupDirectory);
+    expect(typeof didRestore).toStrictEqual('boolean');
+    expect(storage.getString('string')).toStrictEqual('changed');
+    expect(storage.getNumber('number')).toStrictEqual(24);
+    expect(storage.getBoolean('boolean')).toStrictEqual(false);
+  });
+
+  it('should accept backup and restore all APIs', () => {
+    const basePath = getAndroidMMKVBasePath(
+      'backup/restore needs a writable native filesystem path',
+    );
+    if (basePath == null) return;
+
+    const backupDirectory = basePath;
+    const first = createMMKV({
+      id: `backup-all-first-${Date.now()}`,
+    });
+    const second = createMMKV({
+      id: `backup-all-second-${Date.now()}`,
+    });
+
+    first.set('value', 'first-original');
+    second.set('value', 'second-original');
+
+    const backupCount = backupAllMMKV({
+      destinationDirectory: backupDirectory,
+    });
+    expect(typeof backupCount).toStrictEqual('number');
+
+    first.set('value', 'first-changed');
+    second.set('value', 'second-changed');
+
+    const restoreCount = restoreAllMMKV({
+      sourceDirectory: backupDirectory,
+    });
+    expect(typeof restoreCount).toStrictEqual('number');
+    expect(first.getString('value')).toStrictEqual('first-changed');
+    expect(second.getString('value')).toStrictEqual('second-changed');
+  });
+});
+
 describe('MMKV Multi-Process Mode', () => {
   afterEach(() => {
     try {

packages/react-native-mmkv/cpp/HybridMMKV.cpp

@@ -21,7 +21,7 @@ HybridMMKV::HybridMMKV(const Configuration& config) : HybridObject(TAG) {
   bool useAes256Encryption = config.encryptionType.value_or(EncryptionType::AES_128) == EncryptionType::AES_256;
   std::string encryptionKey = config.encryptionKey.value_or("");
   std::string* encryptionKeyPtr = encryptionKey.size() > 0 ? &encryptionKey : nullptr;
-  std::string rootPath = config.path.value_or("");
+  rootPath = config.path.value_or("");
   std::string* rootPathPtr = rootPath.size() > 0 ? &rootPath : nullptr;
   bool compareBeforeSet = config.compareBeforeSet.value_or(false);
 
@@ -228,6 +228,14 @@ void HybridMMKV::trim() {
   instance->clearMemoryCache();
 }
 
+bool HybridMMKV::backupToDirectory(const std::string& destinationDirectory) {
+  return MMKV::backupOneToDirectory(instance->mmapID(), destinationDirectory, getRootPath());
+}
+
+bool HybridMMKV::restoreFromDirectory(const std::string& sourceDirectory) {
+  return MMKV::restoreOneFromDirectory(instance->mmapID(), sourceDirectory, getRootPath());
+}
+
 Listener HybridMMKV::addOnValueChangedListener(const std::function<void(const std::string& /* key */)>& onValueChanged) {
   // Add listener
   auto mmkvID = instance->mmapID();
@@ -252,6 +260,13 @@ MMKVMode HybridMMKV::getMMKVMode(const Configuration& config) {
   throw std::runtime_error("Invalid MMKV Mode value!");
 }
 
+const std::string* HybridMMKV::getRootPath() const {
+  if (rootPath.empty()) {
+    return nullptr;
+  }
+  return &rootPath;
+}
+
 double HybridMMKV::importAllFrom(const std::shared_ptr<HybridMMKVSpec>& other) {
   auto hybridMMKV = std::dynamic_pointer_cast<HybridMMKV>(other);
   if (hybridMMKV == nullptr) [[unlikely]] {

packages/react-native-mmkv/cpp/HybridMMKV.hpp

@@ -41,6 +41,8 @@ class HybridMMKV final : public HybridMMKVSpec {
   void encrypt(const std::string& key, std::optional<EncryptionType> encryptionType) override;
   void decrypt() override;
   void trim() override;
+  bool backupToDirectory(const std::string& destinationDirectory) override;
+  bool restoreFromDirectory(const std::string& sourceDirectory) override;
   Listener addOnValueChangedListener(const std::function<void(const std::string& /* key */)>& onValueChanged) override;
   double importAllFrom(const std::shared_ptr<HybridMMKVSpec>& other) override;
 
@@ -49,9 +51,11 @@ class HybridMMKV final : public HybridMMKVSpec {
 
 private:
   static MMKVMode getMMKVMode(const Configuration& config);
+  const std::string* getRootPath() const;
 
 private:
   MMKV* instance;
+  std::string rootPath;
 };
 
 } // namespace margelo::nitro::mmkv

packages/react-native-mmkv/cpp/HybridMMKVFactory.cpp

@@ -11,6 +11,17 @@
 
 namespace margelo::nitro::mmkv {
 
+namespace {
+
+  const std::string* getOptionalRootPath(const std::optional<std::string>& rootPath) {
+    if (!rootPath.has_value() || rootPath->empty()) {
+      return nullptr;
+    }
+    return &rootPath.value();
+  }
+
+} // namespace
+
 std::string HybridMMKVFactory::getDefaultMMKVInstanceId() {
   return DEFAULT_MMAP_ID;
 }
@@ -34,4 +45,22 @@ bool HybridMMKVFactory::existsMMKV(const std::string& id) {
   return MMKV::checkExist(id);
 }
 
+bool HybridMMKVFactory::backupMMKV(const BackupMMKVOptions& options) {
+  return MMKV::backupOneToDirectory(options.id, options.destinationDirectory, getOptionalRootPath(options.rootPath));
+}
+
+bool HybridMMKVFactory::restoreMMKV(const RestoreMMKVOptions& options) {
+  return MMKV::restoreOneFromDirectory(options.id, options.sourceDirectory, getOptionalRootPath(options.rootPath));
+}
+
+double HybridMMKVFactory::backupAllMMKV(const BackupAllMMKVOptions& options) {
+  size_t backupCount = MMKV::backupAllToDirectory(options.destinationDirectory, getOptionalRootPath(options.rootPath));
+  return static_cast<double>(backupCount);
+}
+
+double HybridMMKVFactory::restoreAllMMKV(const RestoreAllMMKVOptions& options) {
+  size_t restoreCount = MMKV::restoreAllFromDirectory(options.sourceDirectory, getOptionalRootPath(options.rootPath));
+  return static_cast<double>(restoreCount);
+}
+
 } // namespace margelo::nitro::mmkv

packages/react-native-mmkv/cpp/HybridMMKVFactory.hpp

@@ -22,6 +22,10 @@ class HybridMMKVFactory final : public HybridMMKVFactorySpec {
   std::shared_ptr<HybridMMKVSpec> createMMKV(const Configuration& configuration) override;
   bool deleteMMKV(const std::string& id) override;
   bool existsMMKV(const std::string& id) override;
+  bool backupMMKV(const BackupMMKVOptions& options) override;
+  bool restoreMMKV(const RestoreMMKVOptions& options) override;
+  double backupAllMMKV(const BackupAllMMKVOptions& options) override;
+  double restoreAllMMKV(const RestoreAllMMKVOptions& options) override;
 };
 
 } // namespace margelo::nitro::mmkv