Author: admin

In my previous post, I introduced the SharpExt4 .Net library. In this post, I will show how to use SharpExt4 to access the Raspberry Pi SD card from Windows OS.

• Take out the Raspberry Pi SD card and insert it into a USB card reader

• Run “diskpart” from Windows command prompt and find out the SD card disk number and partition number. In my case, the disk number is 3 and the partition is 2.

• Clone the SharpExt4 from GitHub, and open Visual Studio as Admin

Note: If you want to access physical drive, you must run application in admin permission

• Open SharpExt4 and edit the Program.cs from the Sample project

static void Main(string[] args)
{
    //Open Raspberry Pi SD card, see diskpart disk number
    var disk = ExtDisk.Open(3);
    //Get the file system, see diskpart partition number
    var fs = ExtFileSystem.Open(disk.Parititions[1]);
    //List all directories in root folder
    foreach (var file in fs.GetDirectories("/", "*", SearchOption.TopDirectoryOnly))
    {
        Console.WriteLine(file);
    }
}

Run the Sample project and see the result to list all the folders in Raspberry Pi root folder.

Follow my previous post: https://www.nickdu.com/?p=896

Open Ext4 file system.

 //Get the file system
 var fs = ExtFileSystem.Open(disk.Parititions[0]);

Sample code to open a file for read

//Open a file for read
var file = fs.OpenFile("/etc/shells", FileMode.Open, FileAccess.Read);
//Check the file length
var filelen = file.Length;
var buf = new byte[filelen];
//Read the file content
var count = file.Read(buf, 0, (int)filelen);
file.Close();
var content = Encoding.Default.GetString(buf);
Console.WriteLine(content);

Sample code for listing all files in a folder

//List all files in /etc folder
foreach (var file in fs.GetFiles("/etc", "*", SearchOption.AllDirectories))
{
    Console.WriteLine(file);
}

Sample code for file creation

//Open a file for write
var file = fs.OpenFile("/etc/test", FileMode.Create, FileAccess.Write);
var hello = "Hello World";
var buf = Encoding.ASCII.GetBytes(hello);
//Write to file
file.Write(buf, 0, buf.Length);
file.Close();

Full ExtDisk APIs

public sealed class ExtDisk : IDisposable
{
    public IList<Partition> Parititions { get; }
    public Geometry Geometry { get; }
    public ulong Capacity { get; }

    public static ExtDisk Open(string imagePath);
    public static ExtDisk Open(int DiskNumber);
    public sealed override void Dispose();
    public byte[] GetMasterBootRecord();

}

Full ExtFileSystem APIs

public sealed class ExtFileSystem : IDisposable
{
    public static string MountPoint { get; }
    public string Name { get; }
    public string VolumeLabel { get; }
    public bool CanWrite { get; }
    public string Description { get; }

    public static ExtFileSystem Open(Partition partition);
    public void CopyFile(string sourceFile, string destinationFile, bool overwrite);
    public void CreateDirectory(string path);
    public void CreateHardLink(string target, string path);
    public void CreateSymLink(string target, string path);
    public void DeleteDirectory(string path);
    public void DeleteFile(string path);
    public bool DirectoryExists(string path);
    public sealed override void Dispose();
    public bool FileExists(string path);
    public ValueType GetCreationTime(string path);
    public string[] GetDirectories(string path, string searchPattern, SearchOption searchOption);
    public ulong GetFileLength(string path);
    public string[] GetFiles(string path, string searchPattern, SearchOption searchOption);
    public DateTime GetLastAccessTime(string path);
    public DateTime GetLastWriteTime(string path);
    public uint GetMode(string path);
    public Tuple<uint, uint> GetOwner(string path);
    public void MoveDirectory(string sourceDirectoryName, string destinationDirectoryName);
    public ExtFileStream OpenFile(string path, FileMode mode, FileAccess access);
    public string ReadSymLink(string path);
    public void RenameFile(string sourceFileName, string destFileName);
    public void SetCreationTime(string path, DateTime newTime);
    public void SetLastAccessTime(string path, DateTime newTime);
    public void SetLastWriteTime(string path, DateTime newTime);
    public void SetMode(string path, uint mode);
    public void SetOwner(string path, uint uid, uint gid);
    public sealed override string ToString();
    public void Truncate(string path, ulong size);
}

Full ExtFileStream APIs

public class ExtFileStream : Stream
{
    public ExtFileStream(ExtFileSystem fs, string path, FileMode mode, FileAccess access);

    public override long Position { get; set; }
    public override long Length { get; }
    public override bool CanWrite { get; }
    public override bool CanRead { get; }
    public override bool CanSeek { get; }

    public override void Close();
    public override void Flush();
    public override int Read(byte[] array, int offset, int count);
    public override long Seek(long offset, SeekOrigin origin);
    public override void SetLength(long value);
    public override void Write(byte[] array, int offset, int count);

}

The full SharpExt4 library can be found at my GitHub.

https://github.com/nickdu088/SharpExt4

Follow my last post SharpExt4, a .Net library, provides read/write Linux ext2/3/4 file system from Windows application.

The lwext4 is a great start point for me (thanks the author of lwext4), and it provides the core implementation of Linux ext2/3/4 filesystem.

What I need to do:

1. To port the entire lwext4 project over to Visual Studio C/C++ (MSVC) environment, and compile it as a static library.
2. To create a clr wrapper around the lwext4 static library and compiled as a .Net assembly DLL.
3. To provide a .Net friendly interface for .Net Application to use.

When creating this .Net library, I would like to access not only physical Linux disk directly, but also Linux disk image file.

SharpExt4 provides two open disk APIs:

//Open physical Linux disk
ExtDisk SharpExt4.ExtDisk.Open(int DiskNumber);
//Open Linux disk image file
ExtDisk SharpExt4.ExtDisk.Open(String imagePath);

Open Linux disk image allows developer to directly manipulate the saved Linux disk image file, e.g. Raspberry Pi OS image or Debian OS image. The saved Linux disk image must be raw format. This API doesn’t support Virtual Machine disk files (VHD, VDI, XVA, VMDK, etc).

This API also support open USB/Hard drive as physical disk by giving disk number. If you have a USB disk or hard drive formatted as ext2/3/4 file system, this API allows the developer to read/write directly.

To be continue…

Next post: https://www.nickdu.com/?p=912