Enhance NVSStorageHandler with filtering capabilities and update constructor to accept namespace

main/io/nvs_handler.h

@@ -5,17 +5,61 @@
 
 class NVSStorageHandler : public KVStorageHandler {
 public:
-  NVSStorageHandler() = default;
+  NVSStorageHandler(
+    const char* name_space
+  );
   ~NVSStorageHandler() override;
 
   void init(const EventGroupHandle_t& system_event_group) override;
 
-  void put(const char*& key, const char*& value) override;
+  void put(const char* const& key, const char* const& value) override;
 
-  char* get(const char*& key) const override;
+  char* get(const char* const& key) const override;
+  esp_err_t process_all(KeyValueProcessor processor, void* arg) const override;
+  esp_err_t process_filtered(const char* const& key_prefix, KeyValueProcessor processor, void* arg) const override;
+  esp_err_t process_filtered(FilterFunc filter_func, KeyValueProcessor processor, void* arg) const override;
 
-  void remove(const char*& key) override;
+  void remove(const char* const& key) override;
 
 private:
+  NVSIteratorGuard create_iterator() const;
+
   nvs_handle_t nvsHandle = 0;
+  const char* name_space;
+};
+
+struct NVSIteratorGuard {
+public:
+  ~NVSIteratorGuard() {
+    if (iterator) {
+      nvs_release_iterator(iterator);
+    }
+  }
+  const nvs_iterator_t const& get_iterator() const {
+    return iterator;
+  }
+  void advance_iter() {
+    if (iterator) {
+      // advance the iterator and update the internal state
+      esp_err_t err = nvs_entry_next(&iterator);
+      if (err != ESP_OK) {
+        error = err;
+        iterator = nullptr;
+      }
+    }
+  }
+
+  esp_err_t get_error() const {
+    return error;
+  }
+  bool is_valid() const {
+    return iterator != nullptr && error == ESP_OK;
+  }
+  friend class NVSStorageHandler;
+private:
+  NVSIteratorGuard(nvs_iterator_t it
+    , esp_err_t err
+  ) : iterator(it), error(err) { }
+  nvs_iterator_t iterator;
+  esp_err_t error;
 };