I have a memory stream that contains a zip file in byte[] format. Is there any way I can unzip this memory stream, without any need of writing the file to disk?
In general I am using ICSharpCode.SharpZipLib.Zip.FastZip to unzip a file, but is there any way to unzip a memory stream, maybe by storing the files in another MemoryStream or in byte[] format according to the files/folders present in the zip?
Any way I can use the Memorymapped files feature in this scenario ?
Yes, .Net 4.5 now supports more Zip functionality.
Here is a code example based on your description.
In your project, right click on the References folder and add a reference to System.IO.Compression
using System.IO.Compression;
Stream data = new MemoryStream(); // The original data
Stream unzippedEntryStream; // Unzipped data from a file in the archive
ZipArchive archive = new ZipArchive(data);
foreach (ZipArchiveEntry entry in archive.Entries)
{
if(entry.FullName.EndsWith(".txt", StringComparison.OrdinalIgnoreCase))
{
unzippedEntryStream = entry.Open(); // .Open will return a stream
// Process entry data here
}
}
We use DotNetZip, and I can unzip the contents of a zip file from a Stream into memory. Here's the sample code for extracting a specifically named file from a stream (LocalCatalogZip) and returning a stream to read that file, but it'd be easy to expand on it.
private static MemoryStream UnZipCatalog()
{
MemoryStream data = new MemoryStream();
using (ZipFile zip = ZipFile.Read(LocalCatalogZip))
{
zip["ListingExport.txt"].Extract(data);
}
data.Seek(0, SeekOrigin.Begin);
return data;
}
It's not the library you're using now, but if you can change, you can get that functionality.
Here's a variation which would return a Dictionary<string,MemoryStream> of for the contents of every file of a zip file.
private static Dictionary<string,MemoryStream> UnZipToMemory()
{
var result = new Dictionary<string,MemoryStream>();
using (ZipFile zip = ZipFile.Read(LocalCatalogZip))
{
foreach (ZipEntry e in zip)
{
MemoryStream data = new MemoryStream();
e.Extract(data);
result.Add(e.FileName, data);
}
}
return result;
}
I've just had a similar issue and the answer I found which I think seems to be fairly elegant is to use #ZipLib (available using nuget) and do the following:
private byte[] GetUncompressedPayload(byte[] data)
{
using (var outputStream = new MemoryStream())
using (var inputStream = new MemoryStream(data))
{
using (var zipInputStream = new ZipInputStream(inputStream))
{
zipInputStream.GetNextEntry();
zipInputStream.CopyTo(outputStream);
}
return outputStream.ToArray();
}
}
This seems to have worked a treat. Hope this helps.
Yes, Change from using FastZip To new ZipFile(stream), but this only works if your stream can seek. (Just use your MemoryStream in new ZipFile(fs); instead of reading a file stream like the example.)
C#
using ICSharpCode.SharpZipLib.Core;
using ICSharpCode.SharpZipLib.Zip;
public void ExtractZipFile(string archiveFilenameIn, string password, string outFolder) {
ZipFile zf = null;
try {
FileStream fs = File.OpenRead(archiveFilenameIn);
zf = new ZipFile(fs);
if (!String.IsNullOrEmpty(password)) {
zf.Password = password; // AES encrypted entries are handled automatically
}
foreach (ZipEntry zipEntry in zf) {
if (!zipEntry.IsFile) {
continue; // Ignore directories
}
String entryFileName = zipEntry.Name;
// to remove the folder from the entry:- entryFileName = Path.GetFileName(entryFileName);
// Optionally match entrynames against a selection list here to skip as desired.
// The unpacked length is available in the zipEntry.Size property.
byte[] buffer = new byte[4096]; // 4K is optimum
Stream zipStream = zf.GetInputStream(zipEntry);
// Manipulate the output filename here as desired.
String fullZipToPath = Path.Combine(outFolder, entryFileName);
string directoryName = Path.GetDirectoryName(fullZipToPath);
if (directoryName.Length > 0)
Directory.CreateDirectory(directoryName);
// Unzip file in buffered chunks. This is just as fast as unpacking to a buffer the full size
// of the file, but does not waste memory.
// The "using" will close the stream even if an exception occurs.
using (FileStream streamWriter = File.Create(fullZipToPath)) {
StreamUtils.Copy(zipStream, streamWriter, buffer);
}
}
} finally {
if (zf != null) {
zf.IsStreamOwner = true; // Makes close also shut the underlying stream
zf.Close(); // Ensure we release resources
}
}
}
If you are using a non-seekable stream use ZipInputStream.
// Calling example:
WebClient webClient = new WebClient();
Stream data = webClient.OpenRead("http://www.example.com/test.zip");
// This stream cannot be opened with the ZipFile class because CanSeek is false.
UnzipFromStream(data, @"c:\temp");
public void UnzipFromStream(Stream zipStream, string outFolder) {
ZipInputStream zipInputStream = new ZipInputStream(zipStream);
ZipEntry zipEntry = zipInputStream.GetNextEntry();
while (zipEntry != null) {
String entryFileName = zipEntry.Name;
// to remove the folder from the entry:- entryFileName = Path.GetFileName(entryFileName);
// Optionally match entrynames against a selection list here to skip as desired.
// The unpacked length is available in the zipEntry.Size property.
byte[] buffer = new byte[4096]; // 4K is optimum
// Manipulate the output filename here as desired.
String fullZipToPath = Path.Combine(outFolder, entryFileName);
string directoryName = Path.GetDirectoryName(fullZipToPath);
if (directoryName.Length > 0)
Directory.CreateDirectory(directoryName);
// Unzip file in buffered chunks. This is just as fast as unpacking to a buffer the full size
// of the file, but does not waste memory.
// The "using" will close the stream even if an exception occurs.
using (FileStream streamWriter = File.Create(fullZipToPath)) {
StreamUtils.Copy(zipInputStream, streamWriter, buffer);
}
zipEntry = zipInputStream.GetNextEntry();
}
}
Examples taken from the ICSharpCode Wiki
