Function sled::sled_get

#[no_mangle]pub unsafe extern "C" fn sled_get(
    db: *mut Db, 
    key: *const c_char, 
    keylen: size_t, 
    vallen: *mut size_t
) -> *mut c_char

Get the value of a key. Caller is responsible for freeing the returned value with sled_free_buf if it's non-null.