# Utils Development ## Available APIs **Table 1** APIs for file operations

Function

Description

int UtilsFileOpen(const char* path, int oflag, int mode)

Opens or creates a file.

int UtilsFileClose(int fd)

Closes a file with a specified file descriptor.

int UtilsFileRead(int fd, char *buf, unsigned int len)

Reads a specified length of data from a file with the specified file descriptor and writes the data into the buffer.

int UtilsFileWrite(int fd, const char *buf, unsigned int len)

Writes a specified length of data into a file with the specified file descriptor.

int UtilsFileDelete(const char *path)

Deletes a specified file.

int UtilsFileStat(const char *path, unsigned int *fileSize)

Obtains the file size.

int UtilsFileSeek(int fd, int offset, unsigned int whence)

Adjusts the read and write position offset in a file.

int UtilsFileCopy(const char* src, const char* dest)

Copies the source file to a target file.

int UtilsFileMove(const char* src, const char* dest)

Moves the source file into a target file.
Sample code for file operations: ``` // Open a file and write data. char fileName[] = "testfile"; static const char def[] = "utils_file_operation implement."; 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); // Adjust the position offset in the file. ret = UtilsFileSeek(fd, 5, SEEK_SET_FS); printf("lseek ret = %d\n", ret); // Read data and close the file. char buf[64] = {0}; int readLen = UtilsFileRead(fd, buf, 64); ret = UtilsFileClose(fd); printf("read len = %d : buf = %s\n", readLen, buf); // Obtain the file size. int fileLen = 0; ret = UtilsFileStat(fileName, &fileLen); printf("file size = %d\n", fileLen); // Delete the file. ret = UtilsFileDelete(fileName); printf("delete ret = %d\n", ret); ``` **Table 2** APIs for KV store operations

Function

Description

int UtilsGetValue(const char* key, char* value, unsigned int len)

Obtains the value matching a specified key from the file system or cache.

int UtilsSetValue(const char* key, const char* value)

Adds or updates the value matching a specified key in the file system or cache.

int UtilsDeleteValue(const char* key)

Deletes the value matching a specified key from the file system or cache.
Sample code for the KV store: ``` // Set the value matching the specified key. char key[] = "rw.sys.version_100"; char value[] = "Hello kv operation implement!"; int ret = UtilsSetValue(key, value); printf("UtilsSetValue set ret = %d\n", ret); // Obtain the value matching the specified key. char temp[128] = {0}; ret = UtilsGetValue(key, temp, 128); printf("UtilsGetValue get ret = %d, temp = %s\n", ret, temp); // Delete the value matching the specified key. ret = UtilsDeleteValue(key); printf("UtilsDeleteValue delete ret = %d\n", ret); ``` ## How to Develop ### Developing a Native Application for the KV Store That Uses the LiteOS Cortex-A Kernel \(Hi3516 or Hi3518\) 1. Develop the native application for the KV store using **AbilityKit** APIs. - Write the user program by calling the APIs provided by the KV store and compile the **libLauncher.so** file. ``` // Set the value matching the specified key. char key[] = "rw.sys.version_100"; char value[] = "Hello kv operation implement!"; int ret = UtilsSetValue(key, value); printf("UtilsSetValue set ret = %d\n", ret); // Obtain the value matching the specified key. char temp[128] = {0}; ret = UtilsGetValue(key, temp, 128); printf("UtilsGetValue get ret = %d, temp = %s\n", ret, temp); // Delete the value matching the specified key. ret = UtilsDeleteValue(key); printf("UtilsDeleteValue delete ret = %d\n", ret); ``` - Edit the **config.json** file as follows: ``` { "app": { "bundleName": "com.example.launcher", "vendor": "example, "version": { "code": 1, "name": "1.0" } }, "deviceConfig": { "default": { "reqSdk": { "compatible": "zsdk 1.0.0", "target": "zsdk 1.0.1" }, "keepAlive": false }, "smartCamera": { "reqSdk": { "compatible": "zsdk 1.0.0", "target": "zsdk 1.0.1" }, "keepAlive": false } }, "module": { "package": "com.example.launcher", "name": ".MyHarmonyAbilityPackage", "deviceType": [ "phone", "tv","tablet", "pc","car","smartWatch","sportsWatch","smartCamera" ], "distro": { "deliveryWithInstall": true, "moduleName": "Launcher", "moduleType": "entry" }, "abilities": [{ "name": "MainAbility", "icon": "res/drawable/phone.png", "label": "test app 1", "launchType": "standard", "type": "page" }, { "name": "SecondAbility", "icon": "res/drawable/phone.png", "label": "test app 2", "launchType": "standard", "type": "page" }, { "name": "ServiceAbility", "icon": "res/drawable/phone.png", "label": "test app 2", "launchType": "standard", "type": "service" } ] } } ``` - Generate a HAP file. - Add resource files in the **res/drawable** directory based on the following directory structure. ![](figure/unnaming.png) - Compress the **libLauncher.so**, **config.json**, and resource files into a ZIP package and change the file name extension to **.hap**, for example, **Launcher.hap**. 2. Connect the development board and send the command for installing the native KV store application to the board through the serial port. ``` ./nfs/dev_tools/bin/bm install -p /nfs/Launcher.hap ``` 3. Send the command for running the native KV store application to the board through the serial port. ``` ./nfs/dev_tools/bin/aa start -p com.example.launcher -n ServiceAbility ``` ### Dumping System Attributes on the Platform That Uses the LiteOS Cortex-M Kernel 1. Connect the development board and send the **AT+SYSPARA** command to the board through the serial port. ``` AT+SYSPARA ``` **Figure 1** Output of the system attribute dumping command for the LiteOS Cortex-M kernel ![](figure/output-of-the-system-attribute-dumping-command-for-the-liteos-cortex-m-kernel.png "output-of-the-system-attribute-dumping-command-for-the-liteos-cortex-m-kernel") ### Dumping System Attributes on the Platform That Uses the LiteOS Cortex-A Kernel 1. Connect the development board and run the **os\_dump --help** command in the **bin** directory to view the **os\_dump** help information. ``` ./bin/os_dump --help ``` 2. Run the **os\_dump -l** command in the **bin** directory to view system modules that support attribute dumping. ``` ./bin/os_dump -l ``` 3. Run the **os\_dump syspara** command in the **bin** directory to dump the current system attributes. ``` ./bin/os_dump syspara ``` **Figure 2** Output of the system attribute dumping command for the LiteOS Cortex-A kernel ![](figure/output-of-the-system-attribute-dumping-command-for-the-liteos-cortex-a-kernel.png "output-of-the-system-attribute-dumping-command-for-the-liteos-cortex-a-kernel")