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c语言压缩文件详细讲解

时间:2021-12-31 15:01     来源/作者:micDavid

c语言压缩文件

话说当今压缩市场三足鼎立,能叫上名号的有zip、rar、7z。其中zip是压缩界的鼻祖,在各大平台上的流行度最广,rar是商业软件,压缩率和效率都是很高的,对个人用户没有限制。7z是开源的,属于后起之秀,也有着不凡的压缩率,但在内存占有率的问题上,稍逊风骚。今天,主要总结下,windows平台下,zip的压缩与解压的方法,用ICSharpCode组件。

一、单文件压缩

      场景,文件可能比较大,需要压缩传输,比如上传和下载

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/// <summary>
 /// 单文件压缩
/// </summary>
  /// <param name="sourceFile">源文件</param>
  /// <param name="zipedFile">zip压缩文件</param>
  /// <param name="blockSize">缓冲区大小</param>
  /// <param name="compressionLevel">压缩级别</param>
 public static void ZipFile(string sourceFile, string zipedFile, int blockSize = 1024, int compressionLevel = 6)
 {
     if (!File.Exists(sourceFile))
    {
        throw new System.IO.FileNotFoundException("The specified file " + sourceFile + " could not be found.");
     }
     var fileName = System.IO.Path.GetFileNameWithoutExtension(sourceFile);
 
    FileStream streamToZip = new FileStream(sourceFile, FileMode.Open, FileAccess.Read);
     FileStream zipFile = File.Create(zipedFile);
    ZipOutputStream zipStream = new ZipOutputStream(zipFile);
 
     ZipEntry zipEntry = new ZipEntry(fileName);
     zipStream.PutNextEntry(zipEntry);
 
    //存储、最快、较快、标准、较好、最好  0-9
   zipStream.SetLevel(compressionLevel);
 
     byte[] buffer = new byte[blockSize];
 
     int size = streamToZip.Read(buffer, 0, buffer.Length);
     zipStream.Write(buffer, 0, size);
     try
     {
         while (size < streamToZip.Length)
         {
           int sizeRead = streamToZip.Read(buffer, 0, buffer.Length);
            zipStream.Write(buffer, 0, sizeRead);
            size += sizeRead;
        }
    }
     catch (Exception ex)
     {
        throw ex;
     }
    zipStream.Finish();
    zipStream.Close();
     streamToZip.Close();
 }

说明:26行,blocksize为缓存区大小,不能设置太大,如果太大也会报异常。26-38行,把文件通过FileStream流,读取到缓冲区中,再写入到ZipOutputStream流。你可以想象,两个管道,一个读,另一个写,中间是缓冲区,它们的工作方式是同步的方式。想一下,能不能以异步的方式工作,读的管道只管读,写的管道只管写?如果是这样一个场景,读的特别快,写的比较慢,比如,不是本地写,而是要经过网络传输,就可以考虑异步的方式。怎么做,读者可以自行改造。关键一点,流是有顺序的,所以要保证顺序的正确性即可。

二、多文件压缩

      这种场景也是比较多见,和单文件压缩类似,无非就是多循环几次。

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/// <summary>
 /// 多文件压缩
/// </summary>
/// <param name="zipfile">zip压缩文件</param>
/// <param name="filenames">源文件集合</param>
/// <param name="password">压缩加密</param>
public void ZipFiles(string zipfile, string[] filenames, string password = "")
{
     ZipOutputStream s = new ZipOutputStream(System.IO.File.Create(zipfile));
 
   s.SetLevel(6);
     if (password != "")
        s.Password = Md5Help.Encrypt(password);
 
    foreach (string file in filenames)
    {
       //打开压缩文件
       FileStream fs = File.OpenRead(file);
 
       byte[] buffer = new byte[fs.Length];
        fs.Read(buffer, 0, buffer.Length);
 
        var name = Path.GetFileName(file);
 
        ZipEntry entry = new ZipEntry(name);
        entry.DateTime = DateTime.Now;
        entry.Size = fs.Length;
       fs.Close();
        s.PutNextEntry(entry);
        s.Write(buffer, 0, buffer.Length);
    }
    s.Finish();
    s.Close();
}

说明:21行,缓冲区大小直接为文件大小,所以一次读完,没有循环读写。这种情况下,单个文件不能太大,比如超过1G。14行,可以为压缩包设置密码,

MD5的生成方法如下:

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public class Md5Help
{
    /// <summary>
    ///32位 MD5加密
    /// </summary>
    /// <param name="str">加密字符</param>
    /// <returns></returns>
    public static string Encrypt(string str)
    {
        MD5 md5 = new MD5CryptoServiceProvider();
 
        byte[] encryptdata = md5.ComputeHash(Encoding.UTF8.GetBytes(str));
 
        return Convert.ToBase64String(encryptdata);
    }
}

三、多文件异步压缩

      上面同步的压缩的前提是,假设文件不大,而且文件数不多,但是现实是,不光文件大,而且文件数比较多。这种情况,就要考虑异步方法了。否则会阻塞主线程,就是我们平常说的卡死。

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/// <summary>
/// 异步压缩文件为zip压缩包
/// </summary>
/// <param name="zipfile">压缩包存储路径</param>
/// <param name="filenames">文件集合</param>
public static async void ZipFilesAsync(string zipfile, string[] filenames)
{
    await Task.Run(() =>
    {
        ZipOutputStream s = null;
        try
        {
            s = new ZipOutputStream(System.IO.File.Create(zipfile));
 
            s.SetLevel(6); // 0 - store only to 9 - means best compression
 
            foreach (string file in filenames)
            {
                //打开压缩文件
                FileStream fs = System.IO.File.OpenRead(file);
 
                var name = Path.GetFileName(file);
                ZipEntry entry = new ZipEntry(name);
                entry.DateTime = DateTime.Now;
                entry.Size = fs.Length;
                s.PutNextEntry(entry);
 
                //如果文件大于1G
                long blockSize = 51200;
 
                var size = (int)fs.Length;
 
                var oneG = 1024 * 1024 * 1024;
 
                if (size > oneG)
                {
                    blockSize = oneG;
                }
                byte[] buffer = new byte[blockSize];
 
                size = fs.Read(buffer, 0, buffer.Length);
 
                s.Write(buffer, 0, size);
 
                while (size < fs.Length)
                {
                    int sizeRead = fs.Read(buffer, 0, buffer.Length);
                    s.Write(buffer, 0, sizeRead);
                    size += sizeRead;
                }
                s.Flush();
                fs.Close();
            }
 
        }
        catch (Exception ex)
        {
            Console.WriteLine("异步压缩文件出错:" + ex.Message);
        }
        finally
        {
            s?.Finish();
            s?.Close();
        }
    });
}

四、压缩文件夹

    实际的应用当中,是文件和文件夹一起压缩,所以这种情况,就干脆把要压缩的东西全部放到一个文件夹,然后进行压缩。

 主方法如下:

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/// <summary>
        /// 异步压缩文件夹为zip压缩包
        /// </summary>
        /// <param name="zipfile">压缩包存储路径</param>
        /// <param name="sourceFolder">压缩包存储路径</param>
        /// <param name="filenames">文件集合</param>
        public static async void ZipFolderAsync(string zipfile, string sourceFolder, string[] filenames)
        {
            await Task.Run(() =>
            {
                ZipOutputStream s = null;
                try
                {
                    s = new ZipOutputStream(System.IO.File.Create(zipfile));
 
                    s.SetLevel(6); // 0 - store only to 9 - means best compression
 
                    CompressFolder(sourceFolder, s, sourceFolder);
                }
                catch (Exception ex)
                {
                    Console.WriteLine("异步压缩文件出错:" + ex.Message);
                }
                finally
                {
                    s?.Finish();
                    s?.Close();
                }
            });
        }

压缩的核心方法:

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/// <summary>
       /// 压缩文件夹
    /// </summary>
      /// <param name="source">源目录</param>
     /// <param name="s">ZipOutputStream对象</param>
      /// <param name="parentPath">和source相同</param>
       public static void CompressFolder(string source, ZipOutputStream s, string parentPath)
       {
           string[] filenames = Directory.GetFileSystemEntries(source);
          foreach (string file in filenames)
         {
              if (Directory.Exists(file))                 {
                  CompressFolder(file, s, parentPath);  //递归压缩子文件夹
              }
              else
              {
                  using (FileStream fs = System.IO.File.OpenRead(file))
                  {
                      var writeFilePath = file.Replace(parentPath, "");
                      ZipEntry entry = new ZipEntry(writeFilePath);
                      entry.DateTime = DateTime.Now;
                     entry.Size = fs.Length;
 
                     s.PutNextEntry(entry);
 
                      //如果文件大于1G
                      long blockSize = 51200;
 
                     var size = (int)fs.Length;
 
                      var oneG = 1024 * 1024 * 1024;
 
                      if (size > oneG)
                      {
                          blockSize = oneG;
                      }
                      byte[] buffer = new byte[blockSize];
 
                      size = fs.Read(buffer, 0, buffer.Length);
 
                    s.Write(buffer, 0, size);
 
 
                      while (size < fs.Length)
                      {
                          int sizeRead = fs.Read(buffer, 0, buffer.Length);
                         s.Write(buffer, 0, sizeRead);
                          size += sizeRead;
                      }
 
                      s.Flush();   //清除流的缓冲区,使得所有缓冲数据都写入到文件中
                      fs.Close();
                  }
             }
          }
      }

唯一需要注意的地方,可能解压出来的目录结构和压缩前的文件目录不同,这时候检查parentPath参数,它在ZipEntry实体new的时候用,替换绝对路径为当前的相对路径,也就是相对压缩文件夹的路径。

上面的方法比较复杂,还有一种相对简单的方式,直接调用api:

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public static string ZipFolder(string sourceFolder, string zipFile)
  {
      string result = "";
      try
      {
          //创建压缩包
          if (!Directory.Exists(sourceFolder)) return result = "压缩文件夹不存在";
 
          DirectoryInfo d = new DirectoryInfo(sourceFolder);
          var files = d.GetFiles();
          if (files.Length == 0)
          {
              //找子目录
              var ds = d.GetDirectories();
              if (ds.Length > 0)
              {
                  files = ds[0].GetFiles();
              }
          }
          if (files.Length == 0) return result = "待压缩文件为空";
          System.IO.Compression.ZipFile.CreateFromDirectory(sourceFolder, zipFile);
      }
      catch (Exception ex)
      {
          result += "压缩出错:" + ex.Message;
      }
      return result;
  }

以上就是c语言压缩文件详细讲解的详细内容,更多关于c语言压缩文件的资料请关注服务器之家其它相关文章!希望大家以后多多支持服务器之家!

原文链接:https://www.cnblogs.com/wangqiang3311/p/14924111.html

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