壓縮到流

Question

我試圖壓縮一個文件到流，通過wcf發送和解壓縮。但是，使用下面的代碼，我在嘗試執行解壓縮的exe文件時得不到有效的exe文件。任何解壓縮的exe文件大約比原文低211-212字節。

Sub Main() 

    Dim strm As Stream = CompressToStream("c:\rje\Launcher.exe") 

    DecompressToFile(strm) 

End Sub 

壓縮例程

Private Function CompressToStream(ByVal strFullFilename As String) As Stream 

    If File.Exists(strFullFilename) Then 

     Dim uncompressedfile As New MemoryStream(File.ReadAllBytes(strFullFilename)) 

     Dim compressedStream As New MemoryStream 
     Dim compressionStream As New GZipStream(compressedStream, CompressionMode.Compress) 

     uncompressedfile.CopyToStream(compressionStream) 
     compressionStream.Flush() 
     compressedStream.Position = 0 
     Return compressedStream 

    End If 

    Return Nothing 
End Function 

擴展方法複製流作爲使用.NET3.5

<System.Runtime.CompilerServices.Extension()> _ 
Private Sub CopyToStream(ByVal input As Stream, ByRef output As Stream) 

    Dim Buffer(4096) As Byte 
    Dim numRead As Integer = input.Read(Buffer, 0, Buffer.Length) 
    Do While numRead <> 0 
     output.Write(Buffer, 0, numRead) 
     numRead = input.Read(Buffer, 0, Buffer.Length) 
    Loop 
End Sub 

最後減壓

Private Sub DecompressToFile(ByVal strmDownload As Stream) 

    Dim spath As String = "c:\rje\text.exe" 

    Using outFile As FileStream = File.Create(spath) 
     Using Decompress As GZipStream = New GZipStream(strmDownload, CompressionMode.Decompress) 
      ' Copy the compressed file into the decompression stream. 

      Dim buffer(4096) As Byte 
      Dim numRead As Integer = Decompress.Read(buffer, 0, buffer.Length) 
      Do While numRead <> 0 
       outFile.Write(buffer, 0, numRead) 
       numRead = Decompress.Read(buffer, 0, buffer.Length) 
      Loop 
     End Using 
     outFile.Close() 
    End Using 
End Sub 

如果有人能指出我哪裏「M出錯了，那會很好。

Answer 1

錯誤是與CompressToStream，修改爲正確如下功能

Private Function CompressToStream(ByVal strFullFilename As String) As Stream 

    If File.Exists(strFullFilename) Then 
     Dim compressedStream As New MemoryStream() 
     Using uncompressedfile As New MemoryStream(File.ReadAllBytes(strFullFilename)) 
      Using compressionStream As New GZipStream(compressedStream, CompressionMode.Compress, True) 
       uncompressedfile.CopyToStream(compressionStream) 
      End Using 
     End Using 
     compressedStream.Seek(0, SeekOrigin.Begin) 
     Return compressedStream 
    End If 

    Return Nothing 
End Function 

我還沒有一個答案，爲什麼我不應該使用File.Exists（）？

Answer 2

以下是改編自於我張貼在我的評論鏈接樣本壓縮（）/解壓縮（）方法：

Private Function Compress(ByVal strFullFilename As FileInfo) As Stream 
    ' Get the stream of the source file. 
    Dim fi as New FileInfo(strFullFilename) 
    Dim result As New MemoryStream() 
    Using inFile As FileStream = fi.OpenRead() 
     ' Compressing: 
     ' Prevent compressing hidden and already compressed files. 

     If (File.GetAttributes(fi.FullName) And FileAttributes.Hidden) _ 
      <> FileAttributes.Hidden And fi.Extension <> ".gz" Then 
      ' Create the compressed file. 
      Using Compress As GZipStream = New GZipStream(result, CompressionMode.Compress) 
       ' Copy the source file into the compression stream. 
       Dim buffer As Byte() = New Byte(4096) {} 
       Dim numRead As Integer = inFile.Read(buffer, 0, buffer.Length) 
       Do While numRead <> 0 
        Compress.Write(buffer, 0, numRead) 
        numRead = inFile.Read(buffer, 0, buffer.Length) 
       Loop 

       'Console.WriteLine("Compressed {0} from {1} to {2} bytes.", fi.Name, fi.Length.ToString(), result.Length.ToString()) 

      End Using 
     End If 
    End Using 
    Return result 
End Sub 

' Method to decompress. 
Private Sub Decompress(ByVal strmDownload As Stream, ByVal resultFileName As String)   

     ' Create the decompressed file. 
     Using outFile As FileStream = File.Create(resultFileName) 
      Using Decomp As GZipStream = New GZipStream(strmDownload, CompressionMode.Decompress) 
       ' Copy the compressed file into the decompression stream. 
       Dim buffer As Byte() = New Byte(4096) {} 
       Dim numRead As Integer = Decompress.Read(buffer, 0, buffer.Length) 

       Do While numRead <> 0 
        outFile.Write(buffer, 0, numRead) 
        numRead = Decomp.Read(buffer, 0, buffer.Length) 
       Loop 
       'Console.WriteLine("Decompressed: {0}", fi.Name) 

      End Using 
     End Using 
    End Using 
End Sub