@@ -8,9 +8,10 @@ USB devices are classified into two types: USB host and USB device. On OpenHarmo
**Figure 1** USB service architecture
The USB service architecture consists of three layers:
- USB API: a layer that provides JS APIs for the upper layer through NAPI.
- USB Service: a layer implemented by using the C++ programming language and logically divided into the Host, Device, and Port modules. HDI-based APIs provided by USB Service are mainly used to implement management of USB device list, USB functions, USB ports, and USB device access permissions.
- USB service: a layer implemented by using the C++ programming language and logically divided into the Host, Device, and Port modules. HDI-based APIs provided by USB Service are mainly used to implement management of USB device list, USB functions, USB ports, and USB device access permissions.
- USB HAL: a layer implemented by using the C programming language. Based on the Host Driver Development Kit (SDK) and Device DDK, USB HAL encapsulates basic USB device operations, provides C++ APIs for the upper layer, and receives information from the kernel through the Hardware Driver Foundation (HDF) framework.
## 1. Failure in running the KV store on the LiteOS Cortex-A kernel \(Hi3516 or Hi3518\) due to incorrect path setting for the KV store<a name="section2041345718513"></a>
## 1. Failed to run the KV store on the LiteOS Cortex-A kernel \(Hi3516 or Hi3518\) due to incorrect path setting for the KV store<a name="section2041345718513"></a>
**Problem**
**Symptom**
When the LiteOS Cortex-A kernel \(Hi3516 or Hi3518 platform\) directly calls the API provided by the KV store, the compiled executable program fails to run.
**Possible Causes**
The compiled executable program is run directly without being converted to an application using **AbilityKit** APIs. In this case, the Bundle Manager Service \(BMS\) cannot correctly set the path for storing application data during application installation. As a result, the KV store fails to run.
The compiled executable program is run directly without being converted to an application using **AbilityKit** APIs. In this case, the Bundle Manager Service \(BMS\) cannot correctly set the path for storing application data during application installation. As a result, the KV store fails to run.
**Solution**
Call the **UtilsSetEnv** function of the KV store to set the data storage path.
Call the **UtilsSetEnv** function of the KV store to set the data storage path.
<tbody><trid="row671818445506"><tdclass="cellrowborder"valign="top"width="45.540000000000006%"headers="mcps1.2.3.1.1 "><pid="p871814441501"><aname="p871814441501"></a><aname="p871814441501"></a>int UtilsFileOpen(const char* path, int oflag, int mode)</p>
</td>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p127181444165016"><aname="p127181444165016"></a><aname="p127181444165016"></a>Opens or creates a file.</p>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p1071884416504"><aname="p1071884416504"></a><aname="p1071884416504"></a>Closes a file with a specified file descriptor.</p>
</td>
</tr>
<trid="row6718744105017"><tdclass="cellrowborder"valign="top"width="45.540000000000006%"headers="mcps1.2.3.1.1 "><pid="p137181644145015"><aname="p137181644145015"></a><aname="p137181644145015"></a>int UtilsFileRead(int fd, char *buf, unsigned int len)</p>
</td>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p1171854410509"><aname="p1171854410509"></a><aname="p1171854410509"></a>Reads a specified length of data from a file with the specified file descriptor and writes the data into the buffer.</p>
</td>
</tr>
<trid="row2071817440509"><tdclass="cellrowborder"valign="top"width="45.540000000000006%"headers="mcps1.2.3.1.1 "><pid="p17718144465012"><aname="p17718144465012"></a><aname="p17718144465012"></a>int UtilsFileWrite(int fd, const char *buf, unsigned int len)</p>
</td>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p67191444145012"><aname="p67191444145012"></a><aname="p67191444145012"></a>Writes a specified length of data into a file with the specified file descriptor.</p>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p2071919446507"><aname="p2071919446507"></a><aname="p2071919446507"></a>Deletes a specified file.</p>
</td>
</tr>
<trid="row1071964425013"><tdclass="cellrowborder"valign="top"width="45.540000000000006%"headers="mcps1.2.3.1.1 "><pid="p20719114405010"><aname="p20719114405010"></a><aname="p20719114405010"></a>int UtilsFileStat(const char *path, unsigned int *fileSize)</p>
</td>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p8719144435015"><aname="p8719144435015"></a><aname="p8719144435015"></a>Obtains the file size.</p>
</td>
</tr>
<trid="row2071924417504"><tdclass="cellrowborder"valign="top"width="45.540000000000006%"headers="mcps1.2.3.1.1 "><pid="p57193447501"><aname="p57193447501"></a><aname="p57193447501"></a>int UtilsFileSeek(int fd, int offset, unsigned int whence)</p>
</td>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p1071934495014"><aname="p1071934495014"></a><aname="p1071934495014"></a>Adjusts the read and write position offset in a file.</p>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p113501041155511"><aname="p113501041155511"></a><aname="p113501041155511"></a>Copies the source file to a target file.</p>
<tdclass="cellrowborder"valign="top"width="54.459999999999994%"headers="mcps1.2.3.1.2 "><pid="p921744595517"><aname="p921744595517"></a><aname="p921744595517"></a>Moves the source file into a target file.</p>
</td>
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</tbody>
</table>
| 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:
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@@ -92,30 +50,12 @@ printf("delete ret = %d\n", ret);
<tbody><trid="row34145016535"><tdclass="cellrowborder"valign="top"width="57.38999999999999%"headers="mcps1.2.3.1.1 "><pid="p980953910190"><aname="p980953910190"></a><aname="p980953910190"></a>int UtilsGetValue(const char* key, char* value, unsigned int len)</p>
</td>
<tdclass="cellrowborder"valign="top"width="42.61%"headers="mcps1.2.3.1.2 "><pid="p13562171015712"><aname="p13562171015712"></a><aname="p13562171015712"></a>Obtains the value matching a specified key from the file system or cache.</p>
<tdclass="cellrowborder"valign="top"width="42.61%"headers="mcps1.2.3.1.2 "><pid="p2431455765"><aname="p2431455765"></a><aname="p2431455765"></a>Adds or updates the value matching a specified key in the file system or cache.</p>
<tdclass="cellrowborder"valign="top"width="42.61%"headers="mcps1.2.3.1.2 "><pid="p126575774517"><aname="p126575774517"></a><aname="p126575774517"></a>Deletes the value matching a specified key from the file system or cache.</p>
</td>
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</tbody>
</table>
| 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:
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@@ -280,5 +220,3 @@ printf("UtilsDeleteValue delete ret = %d\n", ret);
**Figure 2** Output of the system attribute dumping command for the LiteOS Cortex-A kernel<a name="fig2179718143018"></a>
The Utils library stores common basic components of OpenHarmony. These basic components can be used by OpenHarmony service subsystems and upper-layer applications.
The Utils library stores basic OpenHarmony components that are commonly used by OpenHarmony service subsystems and upper-layer applications.
The Utils library provides the following capabilities on different platforms:
This library provides the following capabilities on different platforms:
LiteOS Cortex-M \(Hi3861 platform\): KV store, file operations, IoT peripheral control, and system attribute dumping
-LiteOS Cortex-M \(Hi3861 platform\): KV store, file operations, IoT peripheral control, and system attribute dumping
LiteOS Cortex-A \(Hi3516 or Hi3518 platform\): KV store, timer, JavaScript APIs for data and file storage, and system attribute dumping
-LiteOS Cortex-A \(Hi3516 or Hi3518 platform\): KV store, timer, JavaScript APIs for data and file storage, and system attribute dumping
