使用虛擬路徑提供程序和Amazon S3 SDK上載文件

Question

此問題的背景是基於我正在開發的虛擬文件系統。我使用的概念是不同類型存儲類型的虛擬路徑提供者，即本地文件系統，Dropbox和亞馬遜S3。我的虛擬文件的基類如下所示：

public abstract class CommonVirtualFile : VirtualFile { 
    public virtual string Url { 
     get { throw new NotImplementedException(); } 
    } 
    public virtual string LocalPath { 
     get { throw new NotImplementedException(); } 
    } 
    public override Stream Open() { 
     throw new NotImplementedException(); 
    } 
    public virtual Stream Open(FileMode fileMode) { 
     throw new NotImplementedException(); 
    } 
    protected CommonVirtualFile(string virtualPath) : base(virtualPath) { } 
} 

執行第二個Open方法是我的問題。如果我們看一下我的實現了本地文件系統，即節省了磁盤上的文件，它看起來像這樣：

public override Stream Open(FileMode fileMode) { 
    return new FileStream("The_Path_To_The_File_On_Disk"), fileMode); 
} 

如果我想保存在本地文件系統中的文件，這將是這個樣子：

const string virtualPath = "/assets/newFile.txt"; 
    var file = HostingEnvironment.VirtualPathProvider.GetFile(virtualPath) as CommonVirtualFile; 
    if (file == null) { 
     var virtualDir = VirtualPathUtility.GetDirectory(virtualPath); 
     var directory = HostingEnvironment.VirtualPathProvider.GetDirectory(virtualDir) as CommonVirtualDirectory; 
     file = directory.CreateFile(VirtualPathUtility.GetFileName(virtualPath)); 
    } 
    byte[] fileContent; 
    using (var fileStream = new FileStream(@"c:\temp\fileToCopy.txt", FileMode.Open, FileAccess.Read)) { 
     fileContent = new byte[fileStream.Length]; 
     fileStream.Read(fileContent, 0, fileContent.Length); 
    } 
    // write the content to the local file system 
    using (Stream stream = file.Open(FileMode.Create)) { 
     stream.Write(fileContent, 0, fileContent.Length); 
    } 

我想的是，如果我切換到我的Amazon S3的虛擬路徑提供我想要這個代碼直接沒有任何變化工作，以便總結的東西了，我怎麼能解決這個使用Amazon S3的SDK和如何應我在我的amazon s3虛擬路徑提供程序中實現我的Open（FileMode fileMode）方法？

Answer 1

嘿，我也代表這個問題，我解決它實現一個流。

這是我的方式，我做到了，也許它可以幫助：

public static Stream OpenStream(S3TransferUtility transferUtility, string key) 
    {      
     byte[] buffer = new byte[Buffersize + Buffersize/2]; 

     S3CopyMemoryStream s3CopyStream = 
      new S3CopyMemoryStream(key, buffer, transferUtility) 
      .WithS3CopyFileStreamEvent(CreateMultiPartS3Blob); 

     return s3CopyStream; 
    } 

我與構造流覆蓋接近和write（數組，偏移量計算）方法，並上傳流到Amazon S3部分。

public class S3CopyMemoryStream : MemoryStream 
    { 

     public S3CopyMemoryStream WithS3CopyFileStreamEvent(StartUploadS3CopyFileStreamEvent doing) 
     { 
      S3CopyMemoryStream s3CopyStream = new S3CopyMemoryStream(this._key, this._buffer, this._transferUtility); 

      s3CopyStream.StartUploadS3FileStreamEvent = new S3CopyMemoryStream.StartUploadS3CopyFileStreamEvent(CreateMultiPartS3Blob); 

      return s3CopyStream; 
     } 

     public S3CopyMemoryStream(string key, byte[] buffer, S3TransferUtility transferUtility) 
      : base(buffer) 
     { 
      if (buffer.LongLength > int.MaxValue) 
       throw new ArgumentException("The length of the buffer may not be longer than int.MaxValue", "buffer"); 

      InitiatingPart = true; 
      EndOfPart = false; 
      WriteCount = 1; 
      PartETagCollection = new List<PartETag>(); 

      _buffer = buffer; 
      _key = key; 
      _transferUtility = transferUtility; 
     } 

事件StartUploadS3FileStreamEvent調用啓動，uploadpart並完成上載的調用。

或者你可以實現一個FileStream這是容易得多，因爲你可以在被覆蓋的的FileStream的Close方法使用

TransferUtilityUploadRequest request = 
      new TransferUtilityUploadRequest() 
      .WithAutoCloseStream(false).WithBucketName(
       transferUtility.BucketName) 
       .WithKey(key) 
       .WithPartSize(stream.PartSize) 
       .WithInputStream(stream) as TransferUtilityUploadRequest; 

     transferUtility.Upload(request); 

。缺點是你必須先將整個數據寫入磁盤，然後才能上傳。