fdb - kv Database, power failure does not lose data

Adapted Air780E Air780EP Air780EPS

Note

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Tip

This library has its own demo,click this link to view the demo example of fdb

Example

-- This library has been abandoned, fskv library is recommended.

fdb.kvdb_init(name, partition)

Initialize the kv database

Parameters

Incoming Value Type	Explanation
string	Database name, currently only supported env
string	FAL Partition name, currently only supported onchip_fdb

Return Value

return value type	explanation
boolean	Returns true on success, otherwise false

Examples

-- fdb Library based on flashdb, thanks again.
if fdb.kvdb_init("env", "onchip_fdb") then
    log.info("fdb", "kv Database initialization successful")
end

-- About emptying the fdb library
-- The download tool does not provide a way to directly clear fdb data, but there are ways to solve it.
-- Write a main.lua, execute fdb.kvdb_init and then execute fdb.clear() to clear fdb data..

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fdb.kv_set(key, value)

set a pair of kv data

Parameters

Incoming Value Type	Explanation
string	key Name of, required, cannot be empty string
string	User data, required, cannot be nil, supports string/value/table/boolean, data length up to 255 bytes

Return Value

return value type	explanation
boolean	Returns true on success, otherwise false
number	The second returns the detailed status for the fdb_kv_set_blob returned as flashdb, 0: no error 1: erase error 2: read error 3: write error 4: not found 5:kv name error 6:kv name exists 7: saved 8: initialization error

Examples

if fdb.kvdb_init("env", "onchip_fdb") then
    log.info("fdb", fdb.kv_set("wendal", "goodgoodstudy"))
end

---

fdb.kv_get(key, skey)

Obtain the corresponding data according to the key.

Parameters

Incoming Value Type	Explanation
string	key Name of, required, cannot be empty string
string	Optional secondary key, valid only when the original value is table, equivalent fdb.kv_get(key)[skey]

Return Value

return value type	explanation
any	Returns data if it exists, otherwise nil

Examples

if fdb.kvdb_init("env", "onchip_fdb") then
    log.info("fdb", fdb.kv_get("wendal"))
end

---

fdb.kv_del(key)

Delete data based on key

Parameters

Incoming Value Type	Explanation
string	key Name of, required, cannot be empty string

Return Value

return value type	explanation
bool	Returns true on success, otherwise false

Examples

if fdb.kvdb_init("env", "onchip_fdb") then
    log.info("fdb", fdb.kv_del("wendal"))
end

---

fdb.kv_clr()

empty the entire kv database

Parameters

None

Return Value

return value type	explanation
bool	Returns true on success, otherwise false

Examples

-- Empty
fdb.kv_clr()

---

fdb.kv_iter()

kv Database Iterators

Parameters

None

Return Value

return value type	explanation
userdata	Returns an iterator pointer on success, otherwise nil

Examples

-- Empty
local iter = fdb.kv_iter()
if iter then
    while 1 do
        local k = fdb.kv_next(iter)
        if not k then
            break
        end
        log.info("fdb", k, "value", fdb.kv_get(k))
    end
end

---

fdb.kv_next(iter)

kv Iterator to get the next key

Parameters

Incoming Value Type	Explanation
userdata	fdb.kv_iter()Pointer returned

Return Value

return value type	explanation
string	Returns the string key value on success, otherwise nil

Examples

-- Empty
local iter = fdb.kv_iter()
if iter then
    while 1 do
        local k = fdb.kv_next(iter)
        if not k then
            break
        end
        log.info("fdb", k, "value", fdb.kv_get(k))
    end
end

---

fdb.kv_stat()

obtain kv database status

Parameters

None

Return Value

return value type	explanation
int	Space used in bytes
int	Total available space in bytes
int	total number of kv key-value pairs, units

Examples

-- This API was added on 2022.07.23
local used,maxs,kv_count = fdb.kv_stat()
log.info("fdb", "kv", used,maxs,kv_count)

---