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. You can use the APIs to traverse, open, search for, read, and close raw files.

Available APIs

How to Develop

1. Add the header file.

   #include "raw_file_manager.h"
   

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

   // Import the JS resource manager from the JS head file and pass it to the C++ file.
   import resManager from '@ohos.resourceManager'
   import rawfileTest from 'librawFileTest.so'
   resManager.getResourceManager().then(resmgr => {
       rawfileTest.testRawFile("test", resmgr, (error, value) => {
           console.log("test rawFile");
       })
   });
   

   // Obtain and parse the parameters in the C++ file.
   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 JS resource manager.
       nativeResourceManager = OH_ResourceManager_InitNativeResourceManager(env, argv[i]);
   }
   

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

   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.

   int count = OH_ResourceManager_GetRawFileCount(rawDir);
   

5. Call OH_ResourceManager_GetRawFileName to obtain the name of the raw file with the specified index.

   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 with the specified file name.

   RawFile* rawFile = OH_ResourceManager_OpenRawFile(nativeResourceManager, fileName.c_str());
   

7. Call OH_ResourceManager_GetRawFileSize to obtain the size of the raw file.

   long rawFileSize = OH_ResourceManager_GetRawFileSize(rawFile);
   

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

   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.

   long rawFileOffset = OH_ResourceManager_GetRawFileOffset(rawFile)
   

10. Call OH_ResourceManager_ReadRawFile to read the raw file.

    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.

    OH_ResourceManager_CloseRawFile(rawFile);
    

12. Call OH_ResourceManager_CloseRawDir to close the raw file directory.

    OH_ResourceManager_CloseRawDir(rawDir);
    

13. Call OH_ResourceManager_GetRawFileDescriptor to obtain the FD of the raw file.

    RawFileDescriptor descriptor;
    bool result = OH_ResourceManager_GetRawFileDescriptor(rawFile, descriptor);
    

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

    OH_ResourceManager_ReleaseRawFileDescriptor(descriptor);
    

15. Call OH_ResourceManager_ReleaseNativeResourceManager to release the native resource manager.

    OH_ResourceManager_ReleaseNativeResourceManager(nativeResourceManager);