nvs::NVSHandle class

A handle allowing nvs-entry related operations on the NVS.

Syntax

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Summary

Declaration

from nvs_handle.hpp:53

class NVSHandle { public: virtual ~NVSHandle() { } template<typename T> esp_err_t set_item(const char *key, T value); virtual esp_err_t set_string(const char *key, const char* value) = 0; template<typename T> esp_err_t get_item(const char *key, T &value); virtual esp_err_t set_blob(const char *key, const void* blob, size_t len) = 0; virtual esp_err_t get_string(const char *key, char* out_str, size_t len) = 0; virtual esp_err_t get_blob(const char *key, void* out_blob, size_t len) = 0; virtual esp_err_t get_item_size(ItemType datatype, const char *key, size_t &size) = 0; virtual esp_err_t find_key(const char* key, nvs_type_t &nvstype) = 0; virtual esp_err_t erase_item(const char* key) = 0; virtual esp_err_t erase_all() = 0; virtual esp_err_t commit() = 0; virtual esp_err_t get_used_entry_count(size_t& usedEntries) = 0; protected: virtual esp_err_t set_typed_item(ItemType datatype, const char *key, const void* data, size_t dataSize) = 0; virtual esp_err_t get_typed_item(ItemType datatype, const char *key, void* data, size_t dataSize) = 0; };

Methods

set_item()

set_string()

get_item()

erase_all()

Erases all entries in the scope of this handle. The scope may vary, depending on the implementation. @not If you want to erase the whole nvs flash (partition), refer to.

commit()

Commits all changes done through this handle so far. Currently, NVS writes to storage right after the set and get functions, but this is not guaranteed.

get_used_entry_count()

Calculate all entries in the scope of the handle.

set_typed_item()

get_typed_item()

set_blob()

set variable length binary value for given key This family of functions set value for the key, given its name. Note that actual storage will not be updated until nvs_commit function is called.

get_string()

get value for given key These functions retrieve the data of an entry, given its key. If key does not exist, or the requested variable type doesn't match the type which was used when setting a value, an error is returned. In case of any error, out_value is not modified. Both functions expect out_value to be a pointer to an already allocated variable of the given type. It is suggested that nvs_get/set_str is used for zero-terminated short C strings, and nvs_get/set_blob is used for arbitrary data structures and long C strings.