rawfile-guidelines.md

# Raw File Development

 

## When to Use

This document describes how to use the native Rawfile APIs to manage raw file directories and files in OpenHarmony. The table below describes the APIs.

## Available APIs

| API                                                      | Description                                    |
| :----------------------------------------------------------- | :--------------------------------------- |
| NativeResourceManager *OH_ResourceManager_InitNativeResourceManager(napi_env env, napi_value jsResMgr) | Initializes the native resource manager.         |
| RawDir *OH_ResourceManager_OpenRawDir(const NativeResourceManager *mgr, const char *dirName) | Opens a raw file directory.                   |
| int OH_ResourceManager_GetRawFileCount(RawDir *rawDir)       | Obtains the number of raw files in the specified directory.|
| const char *OH_ResourceManager_GetRawFileName(RawDir *rawDir, int index) | Obtains the name of a raw file.                       |
| RawFile *OH_ResourceManager_OpenRawFile(const NativeResourceManager *mgr, const char *fileName) | Opens a raw file.                   |
| long OH_ResourceManager_GetRawFileSize(RawFile *rawFile)     | Obtains the size of a raw file.                   |
| int OH_ResourceManager_SeekRawFile(const RawFile *rawFile, long offset, int whence) | Seeks a data read/write position in a raw file based on the specified offset.                   |
| long OH_ResourceManager_GetRawFileOffset(const RawFile *rawFile) | Obtains the offset.                     |
| int OH_ResourceManager_ReadRawFile(const RawFile *rawFile, void *buf, size_t length) | Reads a raw file.                   |
| void OH_ResourceManager_CloseRawFile(RawFile *rawFile)       | Closes a raw file to release resources.               |
| void OH_ResourceManager_CloseRawDir(RawDir *rawDir)          | Closes a raw file directory to release resources.               |
| bool OH_ResourceManager_GetRawFileDescriptor(const RawFile *rawFile, RawFileDescriptor &descriptor) | Obtains the file description (FD) of a raw file.                       |
| bool OH_ResourceManager_ReleaseRawFileDescriptor(const RawFileDescriptor &descriptor) | Releases the FD of a raw file.                       |
| void OH_ResourceManager_ReleaseNativeResourceManager(NativeResourceManager *resMgr) | Releases native resource manager resources.   |

## How to Develop

1. Add the header file.

    ```c++
    #include "raw_file_manager.h"
    ```
    
    

2. Call **OH_ResourceManager_InitNativeResourceManager(napi_env env, napi_value jsResMgr)** to obtain a **NativeResourceManager** instance.

    ```js
    // Call the JS API to pass the JS resource manager.
    import resManager from '@ohos.resourceManager'
    import rawfileTest from 'librawFileTest.so'
    resManager.getResourceManager().then(resmgr => {
        rawfileTest.testRawFile("test", resmgr, (error, value) => {
            console.log("test rawFile");
        })
    });
    ```

    ```c++
    // The C++ API obtains and parses the parameters passed by the JS API.
    NativeResourceManager* nativeResourceManager = nullptr;
    std::string path;
    if (i == 0 && valueType == napi_string) {
        // Parse the first parameter, which is the file or directory path relative to the raw file directory.
        ......
        path = buf.data();
    } else if (i == 1 && valueType == napi_object) {
        // Parse the second parameter, which is the resource manager.
        nativeResourceManager = OH_ResourceManager_InitNativeResourceManager(env, argv[i]);
    }
    ```

    

3. Call **OH_ResourceManager_OpenRawDir** to obtain a **RawDir** instance based on the **NativeResourceManager** instance.

    ```c++
    RawDir* rawDir = OH_ResourceManager_OpenRawDir(nativeResourceManager, path.c_str());
    ```
    
    
    
4. Call **OH_ResourceManager_GetRawFileCount** to obtain the total number of raw files in the directory based on the **RawDir** instance.

    ```c++
    int count = OH_ResourceManager_GetRawFileCount(rawDir);
    ```
    
    
    
5. Call **OH_ResourceManager_GetRawFileName** to obtain the name of the raw file based on the specified index.

    ```c++
    for (int index = 0; index < count; index++) {
        std::string fileName = OH_ResourceManager_GetRawFileName(rawDir, index);
    }
    ```

    

6. Call **OH_ResourceManager_OpenRawFile** to obtain a **RawFile** instance based on the specified file name.

    ```c++
    RawFile* rawFile = OH_ResourceManager_OpenRawFile(nativeResourceManager, fileName.c_str());
    ```
    
    
    
7. Call **OH_ResourceManager_GetRawFileSize** to obtain the size of the raw file.

    ```c++
    long rawFileSize = OH_ResourceManager_GetRawFileSize(rawFile);
    ```
    
    

8. Call **OH_ResourceManager_SeekRawFile** to seek a data read/write position in the raw file based on the specified offset.

    ```c++
    int position = OH_ResourceManager_SeekRawFile(rawFile, 10, 0);
    int position = OH_ResourceManager_SeekRawFile(rawFile, 0 , 1);
    int position = OH_ResourceManager_SeekRawFile(rawFile, -10, 2);
    ```
    
    

9. Call **OH_ResourceManager_GetRawFileOffset** to obtain the raw file offset.

    ```c++
    long rawFileOffset = OH_ResourceManager_GetRawFileOffset(rawFile)
    ```
    
    

10. Call **OH_ResourceManager_ReadRawFile** to read a raw file.

    ```c++
    std::unique_ptr<char[]> mediaData = std::make_unique<char[]>(rawFileSize);
    long rawFileOffset = OH_ResourceManager_ReadRawFile(rawFile, mediaData.get(), rawFileSize);
    ```

    

11. Call **OH_ResourceManager_CloseRawFile** to close the file to release resources.

    ```c++
    OH_ResourceManager_CloseRawFile(rawFile);
    ```
    
    

12. Call **OH_ResourceManager_CloseRawDir** to close the raw file directory.

    ```c++
    OH_ResourceManager_CloseRawDir(rawDir);
    ```
    
    

13. Call **OH_ResourceManager_GetRawFileDescriptor** to obtain **RawFileDescriptor** of the raw file.

    ```c++
    RawFileDescriptor descriptor;
    bool result = OH_ResourceManager_GetRawFileDescriptor(rawFile, descriptor);
    ```

    

14. Call **OH_ResourceManager_ReleaseRawFileDescriptor** to release the FD of the raw file.

    ```c++
    OH_ResourceManager_ReleaseRawFileDescriptor(descriptor);
    ```



15. Call **OH_ResourceManager_ReleaseNativeResourceManager** to release the native resource manager.

    ```c++
    OH_ResourceManager_ReleaseNativeResourceManager(nativeResourceManager);
    ```