esp-idf/components/nvs_flash/include/nvs.h

// 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_err.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * Opaque pointer type representing non-volatile storage handle
 */
typedef uint32_t nvs_handle;

#define ESP_ERR_NVS_BASE                0x1100
#define ESP_ERR_NVS_NOT_INITIALIZED     (ESP_ERR_NVS_BASE + 0x01)
#define ESP_ERR_NVS_NOT_FOUND           (ESP_ERR_NVS_BASE + 0x02)
#define ESP_ERR_NVS_TYPE_MISMATCH       (ESP_ERR_NVS_BASE + 0x03)
#define ESP_ERR_NVS_READ_ONLY           (ESP_ERR_NVS_BASE + 0x04)
#define ESP_ERR_NVS_NOT_ENOUGH_SPACE    (ESP_ERR_NVS_BASE + 0x05)
#define ESP_ERR_NVS_INVALID_NAME        (ESP_ERR_NVS_BASE + 0x06)
#define ESP_ERR_NVS_INVALID_HANDLE      (ESP_ERR_NVS_BASE + 0x07)
#define ESP_ERR_NVS_REMOVE_FAILED       (ESP_ERR_NVS_BASE + 0x08)
#define ESP_ERR_NVS_KEY_TOO_LONG        (ESP_ERR_NVS_BASE + 0x09)
#define ESP_ERR_NVS_PAGE_FULL           (ESP_ERR_NVS_BASE + 0x0a)
#define ESP_ERR_NVS_INVALID_STATE       (ESP_ERR_NVS_BASE + 0x0b)
#define ESP_ERR_NVS_INVALID_LENGTH      (ESP_ERR_NVS_BASE + 0x0c)

typedef enum {
	NVS_READONLY,
	NVS_READWRITE
} nvs_open_mode;

/**
 * @brief      Open non-volatile storage with a given namespace
 *
 * 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.
 *
 * @param[in]  name        Namespace name. Maximal length is determined by the
 *                         underlying implementation, but is guaranteed to be
 *                         at least 16 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_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
 *             - other error codes from the underlying storage driver
 */
esp_err_t nvs_open(const char* name, nvs_open_mode open_mode, nvs_handle *out_handle);

/**
 * @brief      nvs_set_X - 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. If the handle was
 *                     opened with read_only set to true, nvs_set_X functions will
 *                     fail with ESP_ERR_NVS_READONLY.
 * @param[in]  key     Key name. Maximal length is determined by the underlying
 *                     implementation, but is guaranteed to be at least
 *                     16 characters. Shouldn't be empty.
 * @param[in]  value   The value to set.
 * @param[in]  length  For nvs_set_blob: length of binary value to set, in 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_t nvs_set_i8  (nvs_handle handle, const char* key, int8_t value);
esp_err_t nvs_set_u8  (nvs_handle handle, const char* key, uint8_t value);
esp_err_t nvs_set_i16 (nvs_handle handle, const char* key, int16_t value);
esp_err_t nvs_set_u16 (nvs_handle handle, const char* key, uint16_t value);
esp_err_t nvs_set_i32 (nvs_handle handle, const char* key, int32_t value);
esp_err_t nvs_set_u32 (nvs_handle handle, const char* key, uint32_t value);
esp_err_t nvs_set_i64 (nvs_handle handle, const char* key, int64_t value);
esp_err_t nvs_set_u64 (nvs_handle handle, const char* key, uint64_t value);
esp_err_t nvs_set_str (nvs_handle handle, const char* key, const char* value);
esp_err_t nvs_set_blob(nvs_handle handle, const char* key, const void* value, size_t length);

/**
 * @brief      nvs_get_X - 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.
 * Additionally, nvs_get_str and nvs_get_blob 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.
 *
 * 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.
 *
 * 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);
 *
 * @param[in]     handle     Handle obtained from nvs_open function.
 * @param[in]     key        Key name. Maximal length is determined by the underlying
 *                           implementation, but is guaranteed to be at least
 *                           16 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     For nvs_get_str and nvs_get_blob, 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_i8  (nvs_handle handle, const char* key, int8_t* out_value);
esp_err_t nvs_get_u8  (nvs_handle handle, const char* key, uint8_t* out_value);
esp_err_t nvs_get_i16 (nvs_handle handle, const char* key, int16_t* out_value);
esp_err_t nvs_get_u16 (nvs_handle handle, const char* key, uint16_t* out_value);
esp_err_t nvs_get_i32 (nvs_handle handle, const char* key, int32_t* out_value);
esp_err_t nvs_get_u32 (nvs_handle handle, const char* key, uint32_t* out_value);
esp_err_t nvs_get_i64 (nvs_handle handle, const char* key, int64_t* out_value);
esp_err_t nvs_get_u64 (nvs_handle handle, const char* key, uint64_t* out_value);
esp_err_t nvs_get_str (nvs_handle handle, const char* key, char* out_value, size_t* length);
esp_err_t nvs_get_blob(nvs_handle handle, const char* key, void* out_value, size_t* length);

/**
 * @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. If handle has to be
 *                     opened as not read only for this call to succeed.
 *
 * @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 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 handle);


#ifdef __cplusplus
} // extern "C"
#endif

#endif //ESP_NVS_H