c4-11.cs

一本很好的教材.C#开发者必备.内容全面,很难得哦.

// 批量图像处理器的同步实现。
using System;
using System.IO;
using System.Threading;
using System.Runtime.InteropServices;

public class BulkImageProcSync
{
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 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 ProcessImage(byte[] pixels, int imageNum)
{
Console.WriteLine("处理图像"+imageNum);
// 在图象上执行耗费CPU的操作
for(int i=0; i<processImageRepeats; i++)
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("图像处理中...  ");
long t0 = Environment.TickCount;
byte[] pixels = new byte[numPixels];
for(int i=0; i<numImages; i++) 
{
FileStream input = new FileStream(ImageBaseName+i+".tmp", FileMode.Open,
   FileAccess.Read, FileShare.Read, 4196, false);
input.Read(pixels, 0, numPixels);
input.Close();
ProcessImage(pixels, i);
FileStream output = new FileStream(ImageBaseName+i+".done", 
   FileMode.Create, FileAccess.Write, FileShare.None, 4196, false);
output.Write(pixels, 0, numPixels);
output.Close();
}
long t1 = Environment.TickCount;
Console.WriteLine("处理图像总的时间: {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()
{
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("使用同步I/O处理图像的示例");
Console.WriteLine("模拟简单图像输出到 "+numImages+" \"images\"");
Console.WriteLine("(同步文件流)");
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);
}