I'm working on a project where we need to extract a single file from a zip file and we would prefer to not write the file out to disk. In searching I found DNZ and it appears to be a very full functioning set of utilities that cover everything that\r\n we would need to process zip files.
\r\nThe code I am using is:
\r\nUsing zip1 As ZipFile = ZipFile.Read(ZipToUnpack)\r\n Dim i As ZipEntry\r\n For Each i In zip1\r\n If i.FileName.Contains(".NAR") Then\r\n Dim snar As System.IO.Stream\r\n i.Extract(snar)\r\n\r\n 'Process streamed file\r\n End If\r\n Next\r\nEnd Using\r\n\r\n
The error I get is "Invalid input. Paramter name: outstream" when the i.Extract is performed.
\r\nIn researching the issue, I have tried using the following example I found to use the i.OpenReader but it appears to not produce the same type of stream that I need:
\r\nUsing zip1 As ZipFile = ZipFile.Read(ZipToUnpack)\r\n Dim i As ZipEntry\r\n\r\n For Each i In zip1\r\n If i.FileName.Contains(".NAR") Then\r\n Using s As Ionic.Zlib.CrcCalculatorStream = i.OpenReader\r\n Dim n As Integer\r\n Dim buffer As Byte() = New Byte(4096) {}\r\n Dim totalBytesRead As Integer = 0\r\n Do\r\n n = s.Read(buffer, 0, buffer.Length)\r\n totalBytesRead = (totalBytesRead + n)\r\n Loop While (n > 0)\r\n If (s.Crc <> i.Crc) Then\r\n Throw New Exception(String.Format("The Zip Entry failed the CRC Check. (0x{0:X8}!=0x{1:X8})", s.Crc, i.Crc))\r\n End If\r\n If (totalBytesRead <> i.UncompressedSize) Then\r\n Throw New Exception(String.Format("We read an unexpected number of bytes. ({0}!={1})", totalBytesRead, i.UncompressedSize))\r\n End If\r\n\r\n 'Process docNarr = New Document(s)\r\n End Using\r\n End If\r\n Next\r\nEnd Using\r\n\r\n
If I could use the i.Extract(stream) it should solve all of my issues, but for some reason it won't work. Also, if I write the file out to the disk first and then bring it back in the process works as expected.
\r\nAny ideas?
\r\n\r\n
Thanks!
\r\n\r\n", "PostedDate": "2011-05-16T09:32:37.323-07:00", "UserRole": null, "MarkedAsAnswerDate": null }, { "Id": "615407", "ThreadId": "257805", "Html": "
You have defined snar as a Stream, but it's not assigned a value in your code, as far as I can tell.
\r\nYou could extract into a MemoryStream, a FileStream, or some other type of writable stream. To use a MemoryStream you'd do something like this:
\r\nUsing zip1 As ZipFile = ZipFile.Read(ZipToUnpack)\r\n Dim e As ZipEntry\r\n For Each e In zip1\r\n If e.FileName.Contains(\".NAR\") Then\r\n Using snar As new System.IO.MemoryStream\r\n e.Extract(snar)\r\n snar.Seek(0,System.IO.SeekOrigin.Begin)\r\n 'Process streamed file here\r\n End Using\r\n End If\r\n Next\r\nEnd Using\r\n\r\n\r\n
But I'm not sure what you want to do about \"processing\" the snar. You said you wanted to extract it but didn't say where you wanted the data to be placed.
\r\nI guess that part is up to you.
\r\nGood luck.
\r\n", "PostedDate": "2011-05-19T11:44:06.917-07:00", "UserRole": null, "MarkedAsAnswerDate": null }, { "Id": "615457", "ThreadId": "257805", "Html": "
In my code, snar is defined as a System.IO.Stream which is what the extract method expects.
\r\nWhen it comes to the processing, I am using a utility from ASPOSE which allows me to read the file (an RTF) and then grab text out of the file. It will accept a stream but I am having problems getting System.IO.Stream back from the Extract method.
\r\nAny ideas?
", "PostedDate": "2011-05-19T12:22:49.48-07:00", "UserRole": null, "MarkedAsAnswerDate": null }, { "Id": "615548", "ThreadId": "257805", "Html": "I'm not clear on ... System.IO.Stream is an abstract base class. You cannot ever construct one. The way it works: you instantiate a derived type - like a MemoryStream, FileStream, NetworkStream or something else. The System.IO.Stream is just an abstraction, a way to deal with all of those things via the same methods (Read, Seek, Write, etc). http://msdn.microsoft.com/en-us/library/system.io.stream.aspx
\r\nIn your code, you declare snar as a Stream. But it isn't initialized. Not in the code I saw. It needs to hold reference to an instance of a concrete class. You've only declared it.
\r\nI don't know what the ASPOSE thing has to do with it. I'm not clear how you want that to work with DotNetZip.
\r\nIf you want a readable stream for a ZipEntry - in other words, you want to read an entry out of a zip file (and decompress as you read) - then call ZipEntry.OpenReader() in lieu of ZipEntry.Extract(). OpenReader gives you a readable stream. Extract() writes content into a writable stream, that you must have previously opened.
\r\nIf you're not clear on that - think of a stream as a conduit, a pipe that carries liquid. Some pipes can emit output - you can draw liquid from them. Some streams cannot emit output, but instead can carry liquid away, in other words they can accept input. The former are like Readable streams, the latter like writeable streams. Which kind of stream do you want? If you want to suck output out of the zipfile, then call ZipEntry.OpenReader. Then invoke stream.Read() on what you get back (See the doc for full examples). If you already have a writable stream - something that accepts input like a MemoryStream or a FileStream opened for output - then call ZipEntry.Extract() , passing your writable stream.
\r\n", "PostedDate": "2011-05-19T14:20:11.727-07:00", "UserRole": null, "MarkedAsAnswerDate": null }, { "Id": "620934", "ThreadId": "257805", "Html": "
Thank you, zipentry.OpenReader() solved my problem! I was trying to extract a compressed XML file without using a memory stream or temp file.
\nThis is what worked for me:
\n\n
\n
\n \nusing (var zipfile = ZipFile.Read(fileName)) {\r\n foreach (var zipentry in zipfile) {\r\n var xmlDoc = XElement.Load(zipentry.OpenReader());\r\n ...\r\n }\r\n} \r\n
\n
I don't get what you mean by \"OpenReader gives you a readable stream.\"
\nI'm trying to extract a zip file that contains a single txt file, directly to the output stream to make it downloadable. I was able achieve it with the code:
\nusing (ZipFile zip = ZipFile.Read(path))\n{\n var OutputStream = new MemoryStream();\n zip[0].Extract(OutputStream);\n OutputStream.Seek(0, SeekOrigin.Begin);\n\n Response.AddHeader(\"content-disposition\", \"attachment; filename=\" + filename);\n return File(OutputStream, \"text/plain\");\n}\n
Nevertheless I thought I could do it (in a better way) like this:
\nusing (ZipFile zip = ZipFile.Read(path))\n{\n Response.AddHeader(\"content-disposition\", \"attachment; filename=\" + filename);\n return File(zip[0].OpenReader(), \"text/plain\");\n}\n\n
But this code raises the error \"The stream is not readable.\". Shoudn't it be exactly the opposite?
", "PostedDate": "2012-01-20T15:53:13.24-08:00", "UserRole": null, "MarkedAsAnswerDate": null } ]