使用 DotNetZip 时，是否可以在调用 Save(stream) 之前获得最终的 zip 文件大小？我有一个应用程序（窗口服务），其中包流大小超过 100MB，然后将保存包并将即将到来的文件添加到新包中。
我收到了same question for web application 但不明白答案。在保存到 I/O 系统之前，有什么方法可以在 DotnetZip 中找到 zip 流的大小？
【问题讨论】：
我得到了解决方案。这是代码。现在我将创建一个小于 100MB 的包。
using System;
using System.Collections;
using System.IO;
using Ionic.Zip;
using Ionic.Zlib;
namespace ZipFileSize1
{
/// <summary>
/// This source code is generate the specified size Packages from the directory.
/// </summary>
class Program
{
/// <summary>
/// The size of Package(100MB).
/// </summary>
public static long m_packageSize = 1024 * 1024 * 100;
/// <summary>
/// Main method of program class.
/// </summary>
/// <param name="args">Command line argument</param>
static void Main(string[] args)
{
Console.WriteLine("Enter Directory Full Name for Compression : ");
var dir = Console.ReadLine();
Console.WriteLine("Zip File saved Location Directory Name : ");
var savedir = Console.ReadLine();
//generate the random zip files.
var zipFile = Path.Combine(savedir, DateTime.Now.Ticks + ".zip");
ZipFiles(dir, savedir);
Console.ReadLine();
}
/// <summary>
/// This method generate the package as per the <c>PackageSize</c> declare.
/// Currently <c>PackageSize</c> is 100MB.
/// </summary>
/// <param name="inputFolderPath">Input folder Path.</param>
/// <param name="outputFolderandFile">Output folder Path.</param>
public static void ZipFiles(string inputFolderPath, string outputFolderandFile)
{
ArrayList ar = GenerateFileList(inputFolderPath); // generate file list
int trimLength = (Directory.GetParent(inputFolderPath)).ToString().Length;
// find number of chars to remove // from original file path
trimLength += 1; //remove '\'
// Output file stream of package.
FileStream ostream;
byte[] obuffer;
// Output Zip file name.
string outPath = Path.Combine(outputFolderandFile, DateTime.Now.Ticks + ".zip");
ZipOutputStream oZipStream = new ZipOutputStream(File.Create(outPath), true); // create zip stream
// Compression level of zip file.
oZipStream.CompressionLevel = CompressionLevel.Default;
// Initialize the zip entry object.
ZipEntry oZipEntry = new ZipEntry();
// numbers of files in file list.
var counter = ar.Count;
try
{
using (ZipFile zip = new ZipFile())
{
Array.Sort(ar.ToArray()); // Sort the file list array.
foreach (string Fil in ar.ToArray()) // for each file, generate a zip entry
{
if (!Fil.EndsWith(@"/")) // if a file ends with '/' its a directory
{
if (!zip.ContainsEntry(Path.GetFullPath(Fil.ToString())))
{
oZipEntry = zip.AddEntry(Path.GetFullPath(Fil.ToString()), Fil.Remove(0, trimLength));
counter--;
try
{
if (counter > 0)
{
if (oZipStream.Position < m_packageSize)
{
oZipStream.PutNextEntry(oZipEntry.FileName);
ostream = File.OpenRead(Fil);
obuffer = new byte[ostream.Length];
ostream.Read(obuffer, 0, obuffer.Length);
oZipStream.Write(obuffer, 0, obuffer.Length);
}
if (oZipStream.Position > m_packageSize)
{
zip.RemoveEntry(oZipEntry);
oZipStream.Flush();
oZipStream.Close(); // close the zip stream.
outPath = Path.Combine(outputFolderandFile, DateTime.Now.Ticks + ".zip"); // create new output zip file when package size.
oZipStream = new ZipOutputStream(File.Create(outPath), true); // create zip stream
}
}
else
{
Console.WriteLine("No more file existed in directory");
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
zip.RemoveEntry(oZipEntry.FileName);
}
}
else
{
Console.WriteLine("File Existed {0} in Zip {1}", Path.GetFullPath(Fil.ToString()), outPath);
}
}
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
oZipStream.Flush();
oZipStream.Close();// close stream
Console.WriteLine("Remain Files{0}", counter);
}
}
/// <summary>
/// This method return the list of files from the directory
/// Also read the child directory also, but not add the 0 length file.
/// </summary>
/// <param name="Dir">Name of directory.</param>
/// <returns>return the list of all files including into subdirectory files </returns>
private static ArrayList GenerateFileList(string Dir)
{
ArrayList fils = new ArrayList();
foreach (string file in Directory.GetFiles(Dir, "*.*", SearchOption.AllDirectories)) // add each file in directory
{
if (File.ReadAllBytes(file).Length > 0)
fils.Add(file);
}
return fils; // return file list
}
}
}
【讨论】：
不明白答案
答案很清楚，但需要对压缩有一些基本的了解。举个例子，看看LZW。
归结为：压缩引擎在压缩所有源数据之前并不知道压缩数据的最终大小。而且您不希望这样做两次。
正如 dotnetzip 的documentation 中所述，压缩仅在调用ZipFile.Save() 时开始。
【讨论】：
ZipFile.MaxOutputSegmentSize ...虽然保存到流时这不起作用。