# Utils Library
## Overview
The Utils library stores basic components of OpenHarmony. These basic components are used by OpenHarmony service subsystems and upper-layer applications.
The Utils library provides the following capabilities on different platforms:
- LiteOS Cortex-M \(Hi3861 platform\): KV stores, file operations, timers, and IoT peripheral control
- LiteOS Cortex-A \(Hi3516 and Hi3518 platforms\): KV stores, timers, and ACE JavaScript APIs
## Directory Structure
```
utils/native/lite/ # Root directory of the Utils library
├── file # Implementation of the file interface
├── hals # HAL directory
│ └── file # Header files of the hardware abstraction layer for file operations
├── include # Files of external interfaces provided by the Utils library
├── js # ACE JavaScript API directory
│ └── builtin
│ ├── common
│ ├── deviceinfokit # Device information kit
│ ├── filekit # File kit
│ └── kvstorekit # KV store kit
├── kal # KAL directory
│ └── timer # KAL implementation of the timer
├── kv_store # KV store implementation
│ ├── innerkits # Internal KV store interfaces
│ └── src # KV store source file
└── timer_task # Timer implementation
base/iot_hardware # IoT peripheral control
├── frameworks
│ └── wifiiot_lite # Implementation of the IoT peripheral control module
├── hals
│ └── wifiiot_lite # HAL interfaces
└── interfaces
└── kits # Interfaces of the IoT peripheral control module
vendor/hisi/hi3861/hi3861_adapter/hals/iot_hardware # HAL for IoT peripheral control
└── wifiiot_lite # Implementation of the interfaces at the HAL
```
## Constraints
The Utils library is developed using the C language.
**Table 1** Capabilities and constraints of the Utils library
Component
Platform
Description
Constraint
KV store
LiteOS Cortex-M and LiteOS Cortex-A
Provides KV storage for applications.
N/A
File operation
LiteOS Cortex-M
Provides unified file operation interfaces that can be used on different underlying chip components.
N/A
Timer
LiteOS Cortex-M and LiteOS Cortex-A
Provides unified timer operation interfaces that can be used on different underlying chip components.
N/A
IoT peripheral control
LiteOS Cortex-M
Provides the capability of performing operations for peripherals.
## Usage
- **KV store**
```
Obtaining an interface
char key1[] = "rw.sys.version";
char value1[32] = {0};
int ret = UtilsGetValue(key1, value1, 32);
Setting the interface
char key14[] = "key_14";
ret = UtilsSetValue(key14, defValue);
```
- **File operation**
```
// open && write
char fileName[] = "testfile";
int fd = UtilsFileOpen(fileName, O_RDWR_FS | O_CREAT_FS | O_TRUNC_FS, 0);
printf("file handle = %d\n", fd);
int ret = UtilsFileWrite(fd, def, strlen(def));
printf("write ret = %d\n", ret);
// stat
int fileLen = 0;
ret = UtilsFileStat(fileName, &fileLen);
printf("file size = %d\n", fileLen);
// seek
int fd1 = UtilsFileOpen(fileName, O_RDWR_FS, 0);
ret = UtilsFileSeek(fd1, 5, SEEK_SET_FS);
printf("lseek ret = %d\n", ret);
char buf[32] = {0};
int readLen = UtilsFileRead(fd1, buf, 32);
ret = UtilsFileClose(fd1);
printf("read len = %d : buf = %s\n", readLen, buf);
// delete
ret = UtilsFileDelete(fileName);
printf("delete ret = %d\n", ret);
```
## Repositories Involved
iothardware\_frameworks\_wifiiot\_lite
iothardware\_hals\_wifiiot\_lite
iothardware\_interfaces\_kits\_wifiiot\_lite
utils\_native\_lite