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esp-idf/components/nvs_flash/include/nvs.h
Aditya Patwardhan 163d5f314a nvs_flash: fix nvs initialization API documentation
2020-12-15 08:11:49 +05:30

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// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef ESP_NVS_H
#define ESP_NVS_H
#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#include "esp_attr.h"
#include "esp_err.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* Opaque pointer type representing non-volatile storage handle
*/
typedef uint32_t nvs_handle_t;
/*
* Pre-IDF V4.0 uses nvs_handle, so leaving the original typedef here for compatibility.
*/
typedef nvs_handle_t nvs_handle IDF_DEPRECATED("Replace with nvs_handle_t");
#define ESP_ERR_NVS_BASE 0x1100 /*!< Starting number of error codes */
#define ESP_ERR_NVS_NOT_INITIALIZED (ESP_ERR_NVS_BASE + 0x01) /*!< The storage driver is not initialized */
#define ESP_ERR_NVS_NOT_FOUND (ESP_ERR_NVS_BASE + 0x02) /*!< Id namespace doesn’t exist yet and mode is NVS_READONLY */
#define ESP_ERR_NVS_TYPE_MISMATCH (ESP_ERR_NVS_BASE + 0x03) /*!< The type of set or get operation doesn't match the type of value stored in NVS */
#define ESP_ERR_NVS_READ_ONLY (ESP_ERR_NVS_BASE + 0x04) /*!< Storage handle was opened as read only */
#define ESP_ERR_NVS_NOT_ENOUGH_SPACE (ESP_ERR_NVS_BASE + 0x05) /*!< There is not enough space in the underlying storage to save the value */
#define ESP_ERR_NVS_INVALID_NAME (ESP_ERR_NVS_BASE + 0x06) /*!< Namespace name doesn’t satisfy constraints */
#define ESP_ERR_NVS_INVALID_HANDLE (ESP_ERR_NVS_BASE + 0x07) /*!< Handle has been closed or is NULL */
#define ESP_ERR_NVS_REMOVE_FAILED (ESP_ERR_NVS_BASE + 0x08) /*!< The value wasn’t updated because flash write operation has failed. The value was written however, and update will be finished after re-initialization of nvs, provided that flash operation doesn’t fail again. */
#define ESP_ERR_NVS_KEY_TOO_LONG (ESP_ERR_NVS_BASE + 0x09) /*!< Key name is too long */
#define ESP_ERR_NVS_PAGE_FULL (ESP_ERR_NVS_BASE + 0x0a) /*!< Internal error; never returned by nvs API functions */
#define ESP_ERR_NVS_INVALID_STATE (ESP_ERR_NVS_BASE + 0x0b) /*!< NVS is in an inconsistent state due to a previous error. Call nvs_flash_init and nvs_open again, then retry. */
#define ESP_ERR_NVS_INVALID_LENGTH (ESP_ERR_NVS_BASE + 0x0c) /*!< String or blob length is not sufficient to store data */
#define ESP_ERR_NVS_NO_FREE_PAGES (ESP_ERR_NVS_BASE + 0x0d) /*!< NVS partition doesn't contain any empty pages. This may happen if NVS partition was truncated. Erase the whole partition and call nvs_flash_init again. */
#define ESP_ERR_NVS_VALUE_TOO_LONG (ESP_ERR_NVS_BASE + 0x0e) /*!< String or blob length is longer than supported by the implementation */
#define ESP_ERR_NVS_PART_NOT_FOUND (ESP_ERR_NVS_BASE + 0x0f) /*!< Partition with specified name is not found in the partition table */
#define ESP_ERR_NVS_NEW_VERSION_FOUND (ESP_ERR_NVS_BASE + 0x10) /*!< NVS partition contains data in new format and cannot be recognized by this version of code */
#define ESP_ERR_NVS_XTS_ENCR_FAILED (ESP_ERR_NVS_BASE + 0x11) /*!< XTS encryption failed while writing NVS entry */
#define ESP_ERR_NVS_XTS_DECR_FAILED (ESP_ERR_NVS_BASE + 0x12) /*!< XTS decryption failed while reading NVS entry */
#define ESP_ERR_NVS_XTS_CFG_FAILED (ESP_ERR_NVS_BASE + 0x13) /*!< XTS configuration setting failed */
#define ESP_ERR_NVS_XTS_CFG_NOT_FOUND (ESP_ERR_NVS_BASE + 0x14) /*!< XTS configuration not found */
#define ESP_ERR_NVS_ENCR_NOT_SUPPORTED (ESP_ERR_NVS_BASE + 0x15) /*!< NVS encryption is not supported in this version */
#define ESP_ERR_NVS_KEYS_NOT_INITIALIZED (ESP_ERR_NVS_BASE + 0x16) /*!< NVS key partition is uninitialized */
#define ESP_ERR_NVS_CORRUPT_KEY_PART (ESP_ERR_NVS_BASE + 0x17) /*!< NVS key partition is corrupt */
#define ESP_ERR_NVS_WRONG_ENCRYPTION (ESP_ERR_NVS_BASE + 0x19) /*!< NVS partition is marked as encrypted with generic flash encryption. This is forbidden since the NVS encryption works differently. */
#define ESP_ERR_NVS_CONTENT_DIFFERS (ESP_ERR_NVS_BASE + 0x18) /*!< Internal error; never returned by nvs API functions. NVS key is different in comparison */
#define NVS_DEFAULT_PART_NAME "nvs" /*!< Default partition name of the NVS partition in the partition table */
#define NVS_PART_NAME_MAX_SIZE 16 /*!< maximum length of partition name (excluding null terminator) */
#define NVS_KEY_NAME_MAX_SIZE 16 /*!< Maximal length of NVS key name (including null terminator) */
/**
* @brief Mode of opening the non-volatile storage
*/
typedef enum {
NVS_READONLY, /*!< Read only */
NVS_READWRITE /*!< Read and write */
} nvs_open_mode_t;
/*
* Pre-IDF V4.0 uses nvs_open_mode, so leaving the original typedef here for compatibility.
*/
typedef nvs_open_mode_t nvs_open_mode IDF_DEPRECATED("Replace with nvs_open_mode_t");
/**
* @brief Types of variables
*
*/
typedef enum {
NVS_TYPE_U8 = 0x01, /*!< Type uint8_t */
NVS_TYPE_I8 = 0x11, /*!< Type int8_t */
NVS_TYPE_U16 = 0x02, /*!< Type uint16_t */
NVS_TYPE_I16 = 0x12, /*!< Type int16_t */
NVS_TYPE_U32 = 0x04, /*!< Type uint32_t */
NVS_TYPE_I32 = 0x14, /*!< Type int32_t */
NVS_TYPE_U64 = 0x08, /*!< Type uint64_t */
NVS_TYPE_I64 = 0x18, /*!< Type int64_t */
NVS_TYPE_STR = 0x21, /*!< Type string */
NVS_TYPE_BLOB = 0x42, /*!< Type blob */
NVS_TYPE_ANY = 0xff /*!< Must be last */
} nvs_type_t;
/**
* @brief information about entry obtained from nvs_entry_info function
*/
typedef struct {
char namespace_name[16]; /*!< Namespace to which key-value belong */
char key[16]; /*!< Key of stored key-value pair */
nvs_type_t type; /*!< Type of stored key-value pair */
} nvs_entry_info_t;
/**
* Opaque pointer type representing iterator to nvs entries
*/
typedef struct nvs_opaque_iterator_t *nvs_iterator_t;
/**
* @brief Open non-volatile storage with a given namespace from the default NVS partition
*
* Multiple internal ESP-IDF and third party application modules can store
* their key-value pairs in the NVS module. In order to reduce possible
* conflicts on key names, each module can use its own namespace.
* The default NVS partition is the one that is labelled "nvs" in the partition
* table.
*
* @param[in] name Namespace name. Maximal length is (NVS_KEY_NAME_MAX_SIZE-1) characters. Shouldn't be empty.
* @param[in] open_mode NVS_READWRITE or NVS_READONLY. If NVS_READONLY, will
* open a handle for reading only. All write requests will
* be rejected for this handle.
* @param[out] out_handle If successful (return code is zero), handle will be
* returned in this argument.
*
* @return
* - ESP_OK if storage handle was opened successfully
* - ESP_ERR_NVS_NOT_INITIALIZED if the storage driver is not initialized
* - ESP_ERR_NVS_PART_NOT_FOUND if the partition with label "nvs" is not found
* - ESP_ERR_NVS_NOT_FOUND id namespace doesn't exist yet and
* mode is NVS_READONLY
* - ESP_ERR_NVS_INVALID_NAME if namespace name doesn't satisfy constraints
* - ESP_ERR_NO_MEM in case memory could not be allocated for the internal structures
* - other error codes from the underlying storage driver
*/
esp_err_t nvs_open(const char* name, nvs_open_mode_t open_mode, nvs_handle_t *out_handle);
/**
* @brief Open non-volatile storage with a given namespace from specified partition
*
* The behaviour is same as nvs_open() API. However this API can operate on a specified NVS
* partition instead of default NVS partition. Note that the specified partition must be registered
* with NVS using nvs_flash_init_partition() API.
*
* @param[in] part_name Label (name) of the partition of interest for object read/write/erase
* @param[in] name Namespace name. Maximal length is (NVS_KEY_NAME_MAX_SIZE-1) characters. Shouldn't be empty.
* @param[in] open_mode NVS_READWRITE or NVS_READONLY. If NVS_READONLY, will
* open a handle for reading only. All write requests will
* be rejected for this handle.
* @param[out] out_handle If successful (return code is zero), handle will be
* returned in this argument.
*
* @return
* - ESP_OK if storage handle was opened successfully
* - ESP_ERR_NVS_NOT_INITIALIZED if the storage driver is not initialized
* - ESP_ERR_NVS_PART_NOT_FOUND if the partition with specified name is not found
* - ESP_ERR_NVS_NOT_FOUND id namespace doesn't exist yet and
* mode is NVS_READONLY
* - ESP_ERR_NVS_INVALID_NAME if namespace name doesn't satisfy constraints
* - ESP_ERR_NO_MEM in case memory could not be allocated for the internal structures
* - other error codes from the underlying storage driver
*/
esp_err_t nvs_open_from_partition(const char *part_name, const char* name, nvs_open_mode_t open_mode, nvs_handle_t *out_handle);
/**@{*/
/**
* @brief set 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.
*
* @param[in] handle Handle obtained from nvs_open function.
* Handles that were opened read only cannot be used.
* @param[in] key Key name. Maximal length is (NVS_KEY_NAME_MAX_SIZE-1) characters. Shouldn't be empty.
* @param[in] value The value to set.
* For strings, the maximum length (including null character) is
* 4000 bytes.
*
* @return
* - ESP_OK if value was set successfully
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL
* - ESP_ERR_NVS_READ_ONLY if storage handle was opened as read only
* - ESP_ERR_NVS_INVALID_NAME if key name doesn't satisfy constraints
* - ESP_ERR_NVS_NOT_ENOUGH_SPACE if there is not enough space in the
* underlying storage to save the value
* - ESP_ERR_NVS_REMOVE_FAILED if the value wasn't updated because flash
* write operation has failed. The value was written however, and
* update will be finished after re-initialization of nvs, provided that
* flash operation doesn't fail again.
* - ESP_ERR_NVS_VALUE_TOO_LONG if the string value is too long
*/
esp_err_t nvs_set_i8 (nvs_handle_t handle, const char* key, int8_t value);
esp_err_t nvs_set_u8 (nvs_handle_t handle, const char* key, uint8_t value);
esp_err_t nvs_set_i16 (nvs_handle_t handle, const char* key, int16_t value);
esp_err_t nvs_set_u16 (nvs_handle_t handle, const char* key, uint16_t value);
esp_err_t nvs_set_i32 (nvs_handle_t handle, const char* key, int32_t value);
esp_err_t nvs_set_u32 (nvs_handle_t handle, const char* key, uint32_t value);
esp_err_t nvs_set_i64 (nvs_handle_t handle, const char* key, int64_t value);
esp_err_t nvs_set_u64 (nvs_handle_t handle, const char* key, uint64_t value);
esp_err_t nvs_set_str (nvs_handle_t handle, const char* key, const char* value);
/**@}*/
/**
* @brief 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.
*
* @param[in] handle Handle obtained from nvs_open function.
* Handles that were opened read only cannot be used.
* @param[in] key Key name. Maximal length is (NVS_KEY_NAME_MAX_SIZE-1) characters. Shouldn't be empty.
* @param[in] value The value to set.
* @param[in] length length of binary value to set, in bytes; Maximum length is
* 508000 bytes or (97.6% of the partition size - 4000) bytes
* whichever is lower.
*
* @return
* - ESP_OK if value was set successfully
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL
* - ESP_ERR_NVS_READ_ONLY if storage handle was opened as read only
* - ESP_ERR_NVS_INVALID_NAME if key name doesn't satisfy constraints
* - ESP_ERR_NVS_NOT_ENOUGH_SPACE if there is not enough space in the
* underlying storage to save the value
* - ESP_ERR_NVS_REMOVE_FAILED if the value wasn't updated because flash
* write operation has failed. The value was written however, and
* update will be finished after re-initialization of nvs, provided that
* flash operation doesn't fail again.
* - ESP_ERR_NVS_VALUE_TOO_LONG if the value is too long
*/
esp_err_t nvs_set_blob(nvs_handle_t handle, const char* key, const void* value, size_t length);
/**@{*/
/**
* @brief get value for given key
*
* These functions retrieve value for the key, given its name. 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.
*
* All functions expect out_value to be a pointer to an already allocated variable
* of the given type.
*
* \code{c}
* // Example of using nvs_get_i32:
* int32_t max_buffer_size = 4096; // default value
* esp_err_t err = nvs_get_i32(my_handle, "max_buffer_size", &max_buffer_size);
* assert(err == ESP_OK || err == ESP_ERR_NVS_NOT_FOUND);
* // if ESP_ERR_NVS_NOT_FOUND was returned, max_buffer_size will still
* // have its default value.
*
* \endcode
*
* @param[in] handle Handle obtained from nvs_open function.
* @param[in] key Key name. Maximal length is (NVS_KEY_NAME_MAX_SIZE-1) characters. Shouldn't be empty.
* @param out_value Pointer to the output value.
* May be NULL for nvs_get_str and nvs_get_blob, in this
* case required length will be returned in length argument.
*
* @return
* - ESP_OK if the value was retrieved successfully
* - ESP_ERR_NVS_NOT_FOUND if the requested key doesn't exist
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL
* - ESP_ERR_NVS_INVALID_NAME if key name doesn't satisfy constraints
* - ESP_ERR_NVS_INVALID_LENGTH if length is not sufficient to store data
*/
esp_err_t nvs_get_i8 (nvs_handle_t handle, const char* key, int8_t* out_value);
esp_err_t nvs_get_u8 (nvs_handle_t handle, const char* key, uint8_t* out_value);
esp_err_t nvs_get_i16 (nvs_handle_t handle, const char* key, int16_t* out_value);
esp_err_t nvs_get_u16 (nvs_handle_t handle, const char* key, uint16_t* out_value);
esp_err_t nvs_get_i32 (nvs_handle_t handle, const char* key, int32_t* out_value);
esp_err_t nvs_get_u32 (nvs_handle_t handle, const char* key, uint32_t* out_value);
esp_err_t nvs_get_i64 (nvs_handle_t handle, const char* key, int64_t* out_value);
esp_err_t nvs_get_u64 (nvs_handle_t handle, const char* key, uint64_t* out_value);
/**@}*/
/**
* @brief 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.
*
* All functions expect out_value to be a pointer to an already allocated variable
* of the given type.
*
* nvs_get_str and nvs_get_blob functions support WinAPI-style length queries.
* To get the size necessary to store the value, call nvs_get_str or nvs_get_blob
* with zero out_value and non-zero pointer to length. Variable pointed to
* by length argument will be set to the required length. For nvs_get_str,
* this length includes the zero terminator. When calling nvs_get_str and
* nvs_get_blob with non-zero out_value, length has to be non-zero and has to
* point to the length available in out_value.
* It is suggested that nvs_get/set_str is used for zero-terminated C strings, and
* nvs_get/set_blob used for arbitrary data structures.
*
* \code{c}
* // Example (without error checking) of using nvs_get_str to get a string into dynamic array:
* size_t required_size;
* nvs_get_str(my_handle, "server_name", NULL, &required_size);
* char* server_name = malloc(required_size);
* nvs_get_str(my_handle, "server_name", server_name, &required_size);
*
* // Example (without error checking) of using nvs_get_blob to get a binary data
* into a static array:
* uint8_t mac_addr[6];
* size_t size = sizeof(mac_addr);
* nvs_get_blob(my_handle, "dst_mac_addr", mac_addr, &size);
* \endcode
*
* @param[in] handle Handle obtained from nvs_open function.
* @param[in] key Key name. Maximal length is (NVS_KEY_NAME_MAX_SIZE-1) characters. Shouldn't be empty.
* @param out_value Pointer to the output value.
* May be NULL for nvs_get_str and nvs_get_blob, in this
* case required length will be returned in length argument.
* @param[inout] length A non-zero pointer to the variable holding the length of out_value.
* In case out_value a zero, will be set to the length
* required to hold the value. In case out_value is not
* zero, will be set to the actual length of the value
* written. For nvs_get_str this includes zero terminator.
*
* @return
* - ESP_OK if the value was retrieved successfully
* - ESP_ERR_NVS_NOT_FOUND if the requested key doesn't exist
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL
* - ESP_ERR_NVS_INVALID_NAME if key name doesn't satisfy constraints
* - ESP_ERR_NVS_INVALID_LENGTH if length is not sufficient to store data
*/
/**@{*/
esp_err_t nvs_get_str (nvs_handle_t handle, const char* key, char* out_value, size_t* length);
esp_err_t nvs_get_blob(nvs_handle_t handle, const char* key, void* out_value, size_t* length);
/**@}*/
/**
* @brief Erase key-value pair with given key name.
*
* Note that actual storage may not be updated until nvs_commit function is called.
*
* @param[in] handle Storage handle obtained with nvs_open.
* Handles that were opened read only cannot be used.
*
* @param[in] key Key name. Maximal length is (NVS_KEY_NAME_MAX_SIZE-1) characters. Shouldn't be empty.
*
* @return
* - ESP_OK if erase operation was successful
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL
* - ESP_ERR_NVS_READ_ONLY if handle was opened as read only
* - ESP_ERR_NVS_NOT_FOUND if the requested key doesn't exist
* - other error codes from the underlying storage driver
*/
esp_err_t nvs_erase_key(nvs_handle_t handle, const char* key);
/**
* @brief Erase all key-value pairs in a namespace
*
* Note that actual storage may not be updated until nvs_commit function is called.
*
* @param[in] handle Storage handle obtained with nvs_open.
* Handles that were opened read only cannot be used.
*
* @return
* - ESP_OK if erase operation was successful
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL
* - ESP_ERR_NVS_READ_ONLY if handle was opened as read only
* - other error codes from the underlying storage driver
*/
esp_err_t nvs_erase_all(nvs_handle_t handle);
/**
* @brief Write any pending changes to non-volatile storage
*
* After setting any values, nvs_commit() must be called to ensure changes are written
* to non-volatile storage. Individual implementations may write to storage at other times,
* but this is not guaranteed.
*
* @param[in] handle Storage handle obtained with nvs_open.
* Handles that were opened read only cannot be used.
*
* @return
* - ESP_OK if the changes have been written successfully
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL
* - other error codes from the underlying storage driver
*/
esp_err_t nvs_commit(nvs_handle_t handle);
/**
* @brief Close the storage handle and free any allocated resources
*
* This function should be called for each handle opened with nvs_open once
* the handle is not in use any more. Closing the handle may not automatically
* write the changes to nonvolatile storage. This has to be done explicitly using
* nvs_commit function.
* Once this function is called on a handle, the handle should no longer be used.
*
* @param[in] handle Storage handle to close
*/
void nvs_close(nvs_handle_t handle);
/**
* @note Info about storage space NVS.
*/
typedef struct {
size_t used_entries; /**< Amount of used entries. */
size_t free_entries; /**< Amount of free entries. */
size_t total_entries; /**< Amount all available entries. */
size_t namespace_count; /**< Amount name space. */
} nvs_stats_t;
/**
* @brief Fill structure nvs_stats_t. It provides info about used memory the partition.
*
* This function calculates to runtime the number of used entries, free entries, total entries,
* and amount namespace in partition.
*
* \code{c}
* // Example of nvs_get_stats() to get the number of used entries and free entries:
* nvs_stats_t nvs_stats;
* nvs_get_stats(NULL, &nvs_stats);
* printf("Count: UsedEntries = (%d), FreeEntries = (%d), AllEntries = (%d)\n",
nvs_stats.used_entries, nvs_stats.free_entries, nvs_stats.total_entries);
* \endcode
*
* @param[in] part_name Partition name NVS in the partition table.
* If pass a NULL than will use NVS_DEFAULT_PART_NAME ("nvs").
*
* @param[out] nvs_stats Returns filled structure nvs_states_t.
* It provides info about used memory the partition.
*
*
* @return
* - ESP_OK if the changes have been written successfully.
* Return param nvs_stats will be filled.
* - ESP_ERR_NVS_PART_NOT_FOUND if the partition with label "name" is not found.
* Return param nvs_stats will be filled 0.
* - ESP_ERR_NVS_NOT_INITIALIZED if the storage driver is not initialized.
* Return param nvs_stats will be filled 0.
* - ESP_ERR_INVALID_ARG if nvs_stats equal to NULL.
* - ESP_ERR_INVALID_STATE if there is page with the status of INVALID.
* Return param nvs_stats will be filled not with correct values because
* not all pages will be counted. Counting will be interrupted at the first INVALID page.
*/
esp_err_t nvs_get_stats(const char *part_name, nvs_stats_t *nvs_stats);
/**
* @brief Calculate all entries in a namespace.
*
* Note that to find out the total number of records occupied by the namespace,
* add one to the returned value used_entries (if err is equal to ESP_OK).
* Because the name space entry takes one entry.
*
* \code{c}
* // Example of nvs_get_used_entry_count() to get amount of all key-value pairs in one namespace:
* nvs_handle_t handle;
* nvs_open("namespace1", NVS_READWRITE, &handle);
* ...
* size_t used_entries;
* size_t total_entries_namespace;
* if(nvs_get_used_entry_count(handle, &used_entries) == ESP_OK){
* // the total number of records occupied by the namespace
* total_entries_namespace = used_entries + 1;
* }
* \endcode
*
* @param[in] handle Handle obtained from nvs_open function.
*
* @param[out] used_entries Returns amount of used entries from a namespace.
*
*
* @return
* - ESP_OK if the changes have been written successfully.
* Return param used_entries will be filled valid value.
* - ESP_ERR_NVS_NOT_INITIALIZED if the storage driver is not initialized.
* Return param used_entries will be filled 0.
* - ESP_ERR_NVS_INVALID_HANDLE if handle has been closed or is NULL.
* Return param used_entries will be filled 0.
* - ESP_ERR_INVALID_ARG if used_entries equal to NULL.
* - Other error codes from the underlying storage driver.
* Return param used_entries will be filled 0.
*/
esp_err_t nvs_get_used_entry_count(nvs_handle_t handle, size_t* used_entries);
/**
* @brief Create an iterator to enumerate NVS entries based on one or more parameters
*
* \code{c}
* // Example of listing all the key-value pairs of any type under specified partition and namespace
* nvs_iterator_t it = nvs_entry_find(partition, namespace, NVS_TYPE_ANY);
* while (it != NULL) {
* nvs_entry_info_t info;
* nvs_entry_info(it, &info);
* it = nvs_entry_next(it);
* printf("key '%s', type '%d' \n", info.key, info.type);
* };
* // Note: no need to release iterator obtained from nvs_entry_find function when
* // nvs_entry_find or nvs_entry_next function return NULL, indicating no other
* // element for specified criteria was found.
* }
* \endcode
*
* @param[in] part_name Partition name
*
* @param[in] namespace_name Set this value if looking for entries with
* a specific namespace. Pass NULL otherwise.
*
* @param[in] type One of nvs_type_t values.
*
* @return
* Iterator used to enumerate all the entries found,
* or NULL if no entry satisfying criteria was found.
* Iterator obtained through this function has to be released
* using nvs_release_iterator when not used any more.
*/
nvs_iterator_t nvs_entry_find(const char *part_name, const char *namespace_name, nvs_type_t type);
/**
* @brief Returns next item matching the iterator criteria, NULL if no such item exists.
*
* Note that any copies of the iterator will be invalid after this call.
*
* @param[in] iterator Iterator obtained from nvs_entry_find function. Must be non-NULL.
*
* @return
* NULL if no entry was found, valid nvs_iterator_t otherwise.
*/
nvs_iterator_t nvs_entry_next(nvs_iterator_t iterator);
/**
* @brief Fills nvs_entry_info_t structure with information about entry pointed to by the iterator.
*
* @param[in] iterator Iterator obtained from nvs_entry_find or nvs_entry_next function. Must be non-NULL.
*
* @param[out] out_info Structure to which entry information is copied.
*/
void nvs_entry_info(nvs_iterator_t iterator, nvs_entry_info_t *out_info);
/**
* @brief Release iterator
*
* @param[in] iterator Release iterator obtained from nvs_entry_find function. NULL argument is allowed.
*
*/
void nvs_release_iterator(nvs_iterator_t iterator);
#ifdef __cplusplus
} // extern "C"
#endif
#endif //ESP_NVS_H
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