MultiProcess mode on Android

README.md

@@ -108,12 +108,13 @@ See [Configuring App Groups](https://developer.apple.com/documentation/xcode/con
 #### Customize
 
 ```js
-import { MMKV } from 'react-native-mmkv'
+import { MMKV, MMKVMode } from 'react-native-mmkv'
 
 export const storage = new MMKV({
   id: `user-${userId}-storage`,
   path: `${USER_DIRECTORY}/storage`,
-  encryptionKey: 'hunter2'
+  encryptionKey: 'hunter2',
+  mode: MMKVMode.SingleProcess
 })
 ```
 
@@ -124,6 +125,8 @@ The following values can be configured:
 * `id`: The MMKV instance's ID. If you want to use multiple instances, use different IDs. For example, you can separate the global app's storage and a logged-in user's storage. (required if `path` or `encryptionKey` fields are specified, otherwise defaults to: `'mmkv.default'`)
 * `path`: The MMKV instance's root path. By default, MMKV stores file inside `$(Documents)/mmkv/`. You can customize MMKV's root directory on MMKV initialization (documentation: [iOS](https://github.com/Tencent/MMKV/wiki/iOS_advance#customize-location) / [Android](https://github.com/Tencent/MMKV/wiki/android_advance#customize-location))
 * `encryptionKey`: The MMKV instance's encryption/decryption key. By default, MMKV stores all key-values in plain text on file, relying on iOS's/Android's sandbox to make sure the file is encrypted. Should you worry about information leaking, you can choose to encrypt MMKV. (documentation: [iOS](https://github.com/Tencent/MMKV/wiki/iOS_advance#encryption) / [Android](https://github.com/Tencent/MMKV/wiki/android_advance#encryption))
+* `mode`:  *Android Only*: The MMKV mode. It is set to SingleProcess by default. You can set its value to MultiProcess to support simultaneous read-write access between processus at the cost of performance. This is useful when you want to share data between your react-native app and native extensions such as widgets. _Notice_: On iOS, this will automatically be set to MMKVMode.MultiProcess if you set an AppGroup in the plist configuration (more information on AppGroups [here](https://github.com/mrousavy/react-native-mmkv/tree/master#app-groups))
+
 
 ### Set
 

android/src/main/cpp/MmkvHostObject.cpp

@@ -14,14 +14,14 @@
 #include <vector>
 
 MmkvHostObject::MmkvHostObject(const std::string& instanceId, std::string path,
-                               std::string cryptKey) {
+                               std::string cryptKey, MMKVMode mmkvMode) {
   bool hasEncryptionKey = cryptKey.size() > 0;
   __android_log_print(ANDROID_LOG_INFO, "RNMMKV",
                       "Creating MMKV instance \"%s\"... (Path: %s, Encrypted: %b)",
                       instanceId.c_str(), path.c_str(), hasEncryptionKey);
   std::string* pathPtr = path.size() > 0 ? &path : nullptr;
   std::string* cryptKeyPtr = cryptKey.size() > 0 ? &cryptKey : nullptr;
-  instance = MMKV::mmkvWithID(instanceId, mmkv::DEFAULT_MMAP_SIZE, MMKV_SINGLE_PROCESS, cryptKeyPtr,
+  instance = MMKV::mmkvWithID(instanceId, mmkv::DEFAULT_MMAP_SIZE, mmkvMode, cryptKeyPtr,
                               pathPtr);
 
   if (instance == nullptr) {

android/src/main/cpp/MmkvHostObject.h

@@ -15,7 +15,7 @@ using namespace facebook;
 
 class JSI_EXPORT MmkvHostObject : public jsi::HostObject {
 public:
-  MmkvHostObject(const std::string& instanceId, std::string path, std::string cryptKey);
+  MmkvHostObject(const std::string& instanceId, std::string path, std::string cryptKey, MMKVMode mmkvMode);
 
 public:
   jsi::Value get(jsi::Runtime&, const jsi::PropNameID& name) override;

android/src/main/cpp/cpp-adapter.cpp

@@ -13,6 +13,22 @@ std::string getPropertyAsStringOrEmptyFromObject(jsi::Object& object,
   return value.isString() ? value.asString(runtime).utf8(runtime) : "";
 }
 
+MMKVMode getPropertyAsMMKVModeFromObject(jsi::Object& object,
+                           const std::string& propertyName,
+                           jsi::Runtime& runtime) {
+  jsi::Value value = object.getProperty(runtime, propertyName.c_str());
+
+  // Checks that the value is a number without any fractional part
+  double integralPart;
+  if (!value.isNumber() || modf(value.asNumber(), &integralPart) != 0) {
+      // The value is not an integer which does not make sense. Return a default value
+      return MMKV_SINGLE_PROCESS;
+  }
+
+  // Cast to uint32_t value
+  return static_cast<MMKVMode>(integralPart);
+}
+
 void install(jsi::Runtime& jsiRuntime) {
   // MMKV.createNewInstance()
   auto mmkvCreateNewInstance = jsi::Function::createFromHostFunction(
@@ -28,8 +44,9 @@ void install(jsi::Runtime& jsiRuntime) {
         std::string path = getPropertyAsStringOrEmptyFromObject(config, "path", runtime);
         std::string encryptionKey =
             getPropertyAsStringOrEmptyFromObject(config, "encryptionKey", runtime);
+        MMKVMode mode = getPropertyAsMMKVModeFromObject(config, "mode", runtime);
 
-        auto instance = std::make_shared<MmkvHostObject>(instanceId, path, encryptionKey);
+        auto instance = std::make_shared<MmkvHostObject>(instanceId, path, encryptionKey, mode);
         return jsi::Object::createFromHostObject(runtime, instance);
       });
   jsiRuntime.global().setProperty(jsiRuntime, "mmkvCreateNewInstance",

src/MMKV.ts

@@ -6,6 +6,14 @@ interface Listener {
   remove: () => void;
 }
 
+/**
+ * All the possible MMKV modes. The values are extracted from [MMKV.h](https://github.com/Tencent/MMKV/blob/a8d3cdd2a43a8e5c5ab5043dfad111c96a4963bf/Core/MMKV.h#L41)
+ */
+export enum MMKVMode {
+  SingleProcess = 1 << 0,
+  MultiProcess = 1 << 1,
+}
+
 /**
  * Used for configuration of a single MMKV instance.
  */
@@ -46,6 +54,20 @@ export interface MMKVConfiguration {
    * ```
    */
   encryptionKey?: string;
+  /**
+   * *Android Only*: The MMKV mode. It is set to SingleProcess by default. You can set its value to MultiProcess to support simultaneous read-write access between processus at the cost of performance.
+   *
+   * This is useful when you want to share data between your react-native app and native extensions such as widgets.
+   *
+   * @example
+   * ```ts
+   * const extensionStorage = new MMKV({ mode: MMKVMode.MultiProcess })
+   * ```
+   *
+   * _Notice_: On iOS, this will automatically be set to MMKVMode.MultiProcess if you set an AppGroup in the plist configuration.
+   * More information on AppGroups [here](https://github.com/mrousavy/react-native-mmkv/tree/master#app-groups)
+   */
+  mode?: MMKVMode;
 }
 
 /**