How to read data from a zip file without having to unzip the entire file

问题

Is there anyway in .Net (C#) to extract data from a zip file without decompressing the complete file?

Simply I possibly want to extract data (file) from the start of a zip file, obviously this depends if the compression algorithm compress the file in a deterministic order.

回答1:

DotNetZip is your friend here.

As easy as:

using (ZipFile zip = ZipFile.Read(ExistingZipFile))
{
  ZipEntry e = zip["MyReport.doc"];
  e.Extract(OutputStream);
}

(you can also extract to a file or other destinations).

Reading the zip file's table of contents is as easy as:

using (ZipFile zip = ZipFile.Read(ExistingZipFile))
{
  foreach (ZipEntry e in zip)
  {
    if (header)
    {
      System.Console.WriteLine("Zipfile: {0}", zip.Name);
      if ((zip.Comment != null) && (zip.Comment != "")) 
        System.Console.WriteLine("Comment: {0}", zip.Comment);
      System.Console.WriteLine("\n{1,-22} {2,8}  {3,5}   {4,8}  {5,3} {0}",
                               "Filename", "Modified", "Size", "Ratio", "Packed", "pw?");
      System.Console.WriteLine(new System.String('-', 72));
      header = false;
    }
    System.Console.WriteLine("{1,-22} {2,8} {3,5:F0}%   {4,8}  {5,3} {0}",
                             e.FileName,
                             e.LastModified.ToString("yyyy-MM-dd HH:mm:ss"),
                             e.UncompressedSize,
                             e.CompressionRatio,
                             e.CompressedSize,
                             (e.UsesEncryption) ? "Y" : "N");

  }
}

Edited To Note: DotNetZip used to live at Codeplex. Codeplex has been shut down. The old archive is still available at Codeplex. It looks like the code has migrated to Github:

https://github.com/DinoChiesa/DotNetZip. Looks to be the original author's repo.
https://github.com/haf/DotNetZip.Semverd. This looks to be the currently maintained version. It's also packaged up an available via Nuget at https://www.nuget.org/packages/DotNetZip/

回答2:

With .Net Framework 4.5 (using ZipArchive):

using (ZipArchive zip = ZipFile.Open(zipfile, ZipArchiveMode.Read))
    foreach (ZipArchiveEntry entry in zip.Entries)
        if(entry.Name == "myfile")
            entry.ExtractToFile("myfile");

Find "myfile" in zipfile and extract it.

回答3:

Something like this will list and extract the files one by one, if you want to use SharpZipLib:

var zip = new ZipInputStream(File.OpenRead(@"C:\Users\Javi\Desktop\myzip.zip"));
var filestream = new FileStream(@"C:\Users\Javi\Desktop\myzip.zip", FileMode.Open, FileAccess.Read);
ZipFile zipfile = new ZipFile(filestream);
ZipEntry item;
while ((item = zip.GetNextEntry()) != null)
{
     Console.WriteLine(item.Name);
     using (StreamReader s = new StreamReader(zipfile.GetInputStream(item)))
     {
      // stream with the file
          Console.WriteLine(s.ReadToEnd());
     }
 }

Based on this example: content inside zip file

回答4:

Here is how a UTF8 text file can be read from a zip archive into a string variable (.NET Framework 4.5 and up):

string zipFileFullPath = "{{TypeYourZipFileFullPathHere}}";
string targetFileName = "{{TypeYourTargetFileNameHere}}";
string text = new string(
            (new System.IO.StreamReader(
             System.IO.Compression.ZipFile.OpenRead(zipFileFullPath)
             .Entries.Where(x => x.Name.Equals(targetFileName,
                                          StringComparison.InvariantCulture))
             .FirstOrDefault()
             .Open(), Encoding.UTF8)
             .ReadToEnd())
             .ToArray());

回答5:

Zip files have a table of contents. Every zip utility should have the ability to query just the TOC. Or you can use a command line program like 7zip -t to print the table of contents and redirect it to a text file.

回答6:

In such case you will need to parse zip local header entries. Each file, stored in zip file, has preceding Local File Header entry, which (normally) contains enough information for decompression, Generally, you can make simple parsing of such entries in stream, select needed file, copy header + compressed file data to other file, and call unzip on that part (if you don't want to deal with the whole Zip decompression code or library).

来源：https://stackoverflow.com/questions/5967864/how-to-read-data-from-a-zip-file-without-having-to-unzip-the-entire-file

标签

compression

zip

data-compression