c4-10.cs

一本很好的教材.C#开发者必备.内容全面,很难得哦.

// 批量图像处理器的异步实现
using System;
using System.IO;
using System.Threading;
using System.Runtime.InteropServices;

public class BulkImageProcAsync
{
public const String ImageBaseName = "tmpImage-";
public const int numImages = 200;
public const int numPixels = 512*512;
// 循环次数可以改变，让应用程序占用更多的CPU和I/O带宽
public static int processImageRepeats = 20;
public static int NumImagesToFinish = numImages;
public static Object NumImagesMutex = new Object[0];
// WaitObject在图形处理完成后被告知.
public static Object WaitObject = new Object[0];

public class ImageStateObject
{
public byte[] pixels;
public int imageNum;
public FileStream fs;
}

public static void MakeImageFiles()
{
int sides = (int) Math.Sqrt(numPixels);
Console.Write("正在生成 "+numImages+" "+sides+"x"+sides+" 图像： ");
byte[] pixels = new byte[numPixels];
for(int i=0; i<numPixels; i++)
pixels[i] = (byte) i;

for(int i=0; i<numImages; i++) 
{
FileStream fs = new FileStream(ImageBaseName+i+".tmp", FileMode.Create,
   FileAccess.Write, FileShare.None, 8192, false);
   fs.Write(pixels, 0, pixels.Length);
   FlushFileBuffers(fs.Handle);
   fs.Close();
   }
   Console.WriteLine("完成");
}

public static void ReadInImageCallback(IAsyncResult asyncResult)
{
ImageStateObject state = (ImageStateObject) asyncResult.AsyncState;
Stream stream = state.fs;
int bytesRead = stream.EndRead(asyncResult);
if (bytesRead != numPixels)
throw new Exception("在ReadInImageCallback函数中从图像中得到错误的字节数: "+bytesRead);
ProcessImage(state.pixels, state.imageNum);
stream.Close();
// 输出图像 
// 在这里使用异步I/O并不是最好的方式
FileStream fs = new FileStream(ImageBaseName+state.imageNum+".done", 
   FileMode.Create, FileAccess.Write, FileShare.None, 4096, false);
fs.Write(state.pixels, 0, numPixels);
fs.Close();

// 这个程序会占用许多内存，因此需要及时释放内存
state.pixels = null;

// 记录现在已经处理了一个图像
lock(NumImagesMutex) 
{
NumImagesToFinish--;
if (NumImagesToFinish==0) 
   {
      Monitor.Enter(WaitObject);
      Monitor.Pulse(WaitObject);
      Monitor.Exit(WaitObject);
      }
   }
}

public static void ProcessImage(byte[] pixels, int imageNum)
{
Console.WriteLine("处理图像 "+imageNum);

// 强制CPU处理图像
   for(int j=0; j<numPixels; j++)
      pixels[j] += 1;
Console.WriteLine("处理图像 "+imageNum+" 完成");
}

public static void ProcessImagesInBulk()
{
Console.WriteLine("正在处理图像...  ");
long t0 = Environment.TickCount;
NumImagesToFinish = numImages;
AsyncCallback readImageCallback = new AsyncCallback(ReadInImageCallback);
   for(int i=0; i<numImages; i++) 
   {
      ImageStateObject state = new ImageStateObject();
      state.pixels = new byte[numPixels];
      state.imageNum = i;
      // 大量数据只是被读入了一次，这样你就可使文件流缓冲变得很小，这样就可以节省内存
      FileStream fs = new FileStream(ImageBaseName+i+".tmp", 
         FileMode.Open, FileAccess.Read, FileShare.Read, 1, true);
      state.fs = fs;
      fs.BeginRead(state.pixels, 0, numPixels, readImageCallback, state);
   }
// 判断是否所有的图像都被处理了  
// 如果不是就阻塞进程直到被处理
bool mustBlock = false;
lock (NumImagesMutex) 
{
   if (NumImagesToFinish > 0)
      mustBlock = true;
}
   if (mustBlock) 
{
Console.WriteLine("所有的线程都已经排入队列...现在将阻塞直到所有线程结束。剩下的数量："+NumImagesToFinish);
Monitor.Enter(WaitObject);
Monitor.Wait(WaitObject);
Monitor.Exit(WaitObject);
}
long t1 = Environment.TickCount;
Console.WriteLine("处理图像一共花了: {0} ms", (t1-t0));
}

public static void Cleanup()
{
   for(int i=0; i<numImages; i++) 
   {
      File.Delete(ImageBaseName+i+".tmp");
      File.Delete(ImageBaseName+i+".done");
   }
}

public static void TryToClearDiskCache()
{
// 强迫所有未决数据写入磁盘，并且清空磁盘缓存
byte[] bytes = new byte[100*(1<<20)];
for(int i=0; i<bytes.Length; i++)
bytes[i] = 0;
bytes = null;
GC.Collect();
Thread.Sleep(2000);
}
   public static void Main(String[] args)
   {
      Console.WriteLine("使用异步I/O处理图像的示例");
      Console.WriteLine("模拟简单图像输出到"+numImages+" \"images\"");
      Console.WriteLine("(异步文件流)");
      Console.WriteLine("警告 - 这个测试需要 "+(numPixels * numImages * 2)+" 字节的临时空间");
      if (args.Length==1) 
      {
         processImageRepeats = Int32.Parse(args[0]);
         Console.WriteLine("ProcessImage 的内部循环 - "+processImageRepeats);
      }
      MakeImageFiles();
      TryToClearDiskCache();
      ProcessImagesInBulk();
      Cleanup();
   }
   [DllImport("KERNEL32", SetLastError=true)]
   private static extern void FlushFileBuffers(IntPtr handle);
}