在几秒钟内用 C# 创建一个巨大的虚拟文件
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原文地址: http://stackoverflow.com/questions/1881050/
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Creating a Huge Dummy File in a Matter of Seconds in C#
提问by Seyed Vahid Hashemi
I want to create a huge dummy file say 1~2 GBs in matter of seconds. here is what I've written in C# :
我想在几秒钟内创建一个巨大的虚拟文件，比如 1~2 GB。这是我用 C# 写的：
file.writeallbytes("filename",new byte[a huge number]);
and another way with indicating the status, was like following :
以及指示状态的另一种方式，如下所示：
long FSS = din.TotalFreeSpace;
long segments = FSS / 10000;
long last_seg = FSS % 10000;
BinaryWriter br = new BinaryWriter(fs);
for (long i = 0; i < segments; i++)
{
br.Write(new byte[10000]);
this.label2.Text = "segments write :" + i.ToString() + "\r\n" + "segments remain :" + ((segments-i)+1).ToString();
Application.DoEvents();
}
br.Write(new byte[last_seg]);
this.label2.Text += "\r\nDone!";
br.Close();
where din is Disk Information object
其中 din 是磁盘信息对象
well with these two approach it takes something like 2 or more minutes to write such a big but dummy file. is there any other faster way for doing so?
使用这两种方法，编写如此大但虚拟的文件需要 2 分钟或更长时间。还有其他更快的方法吗？
regards.
问候。
采纳答案by mdb
Simply create the file, seek to a suitably large offset, and write a single byte:
只需创建文件，寻找合适的大偏移量，然后写入一个字节：
FileStream fs = new FileStream(@"c:\tmp\huge_dummy_file", FileMode.CreateNew);
fs.Seek(2048L * 1024 * 1024, SeekOrigin.Begin);
fs.WriteByte(0);
fs.Close();
This will yield a 2GB file with basically unpredictable contents, which should be fine for your purposes.
这将产生一个 2GB 的文件，其内容基本上是不可预测的，这对您来说应该没问题。
回答by Kane
I could be wrong but you will probably find that it's impossible to create a file that large that quickly as there will be a bottleneck in the I/O writing process.
我可能是错的，但您可能会发现不可能这么快地创建一个这么大的文件，因为 I/O 写入过程中会出现瓶颈。
However in your code above the Applciation.DoEvents will be slowing things down. Also any repainting of the screenthis.label2.Text =will cause a slight slow down.
但是，在您上面的代码中， Applciation.DoEvents 会减慢速度。此外，对screenthis.label2.Text = 的任何重绘都会导致速度稍慢。
回答by John Feminella
If you just need a FileStream, you could use FileStream.SetLength. That will get you a stream which is 2 GB long. Then you can write the final byte at an arbitrary position of your choice. But the contents will be undefined.
如果你只需要一个FileStream，你可以使用FileStream.SetLength. 这将为您提供一个 2 GB 长的流。然后您可以在您选择的任意位置写入最后一个字节。但内容将是未定义的。
If you're trying to actually create a file on the disk, yes, you'll need to actually write its contents. And yes, hard disks are going to be slow; something like a 1 GB/min write speed isn't totally ridiculous. Sorry -- that's physics!
如果您尝试在磁盘上实际创建文件，是的，您需要实际写入其内容。是的，硬盘会变慢。像 1 GB/min 的写入速度并不是完全荒谬的。对不起——那是物理学！
回答by Rob Levine
If you don't care about the contents, then by far the fastest way I know of is this - it is practically instant:
如果你不关心内容，那么到目前为止我所知道的最快的方法是这个 - 它实际上是即时的：
private void CreateDummyFile(string fileName, long length)
{
using (var fileStream = new FileStream(fileName, FileMode.Create, FileAccess.Write, FileShare.None))
{
fileStream.SetLength(length);
}
}
回答by t0mm13b
Why did you not use the BackgroundWorkerclass to achieve this, as you can pass anything into the method ReportProgressto indicate the status report. See the example below:
为什么不使用BackgroundWorker类来实现这一点，因为您可以将任何内容传递到方法中ReportProgress以指示状态报告。请参阅下面的示例：
private BackgroundWorker bgWorker;
public Form1()
{
InitializeComponent();
bgWorker = new BackgroundWorker();
bgWorker.DoWork += new DoWorkEventHandler(bgWorker_DoWork);
bgWorker.ProgressChanged += new ProgressChangedEventHandler(bgWorker_ProgressChanged);
bgWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bgWorker_RunWorkerCompleted);
bgWorker.RunWorkerAsync();
}
void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
this.label2.Text = "Done";
}
void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
MyStatus myProgressStatus = (MyStatus)e.UserState;
this.label2.Text = string.Format("segments write : {0}" + Environment.Newline + "Segments Remain: {1}", myProgressStatus.iWritten, myProgressStatus.iRemaining);
}
void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
long FSS = din.TotalFreeSpace;
long segments = FSS / 10000;
long last_seg = FSS % 10000;
BinaryWriter br = new BinaryWriter(fs);
for (long i = 0; i < segments; i++)
{
br.Write(new byte[10000]);
bgWorker.ReportProgress(i.ToString(), new MyStatus(i, ((segments-i) + 1)));
}
br.Write(new byte[last_seg]);
br.Close();
}
public class MyStatus{
public int iWritten;
public int iRemaining;
public MyStatus(int iWrit, int iRem){
this.iWritten = iWrit;
this.iRemaining = iRem;
}
}
}
This is a rough draft...
这是一个草稿...
