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[C#]Stream.Write Extension Method

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11/28
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在处理Stream型态时常会使用到Stream.Write这个方法，每次都会有种疑问就是，大多数的处理都是要将Buffer整个写入，為何偏偏每次都要将索引带0，长度带為Buffer的大小呢?另外在处理Stream时，若要显示其处理进度，是否能有更為简单的方法?这边将我為了解决这些问题所写的扩充方法整裡如下：

using System;
02 using System.Reflection;
03 using System.ComponentModel;
04 using System.Linq;
05 using System.IO;
06
07 public static class StreamExtension
08 {
09 public static void Write( this Stream targetStream, byte [] buffer)
10 {
11 if (!targetStream.CanWrite)
12 throw new ArgumentException( "targetStream" , "Unwritable stream" );
13
14 targetStream.Write(buffer, 0, buffer.Length);
15 }
16
17 public static void Write( this Stream targetStream, Stream sourceStream)
18 {
19 if (!targetStream.CanWrite)
20 throw new ArgumentException( "targetStream" , "Unwritable stream" );
21
22 if (sourceStream == null )
23 throw new ArgumentNullException( "sourceStream" );
24
25 if (!sourceStream.CanRead)
26 throw new ArgumentException( "sourceStream" , "Unreadable stream" );
27
28 targetStream.Write(sourceStream, 1024, null );
29 }
30
31 public static void Write( this Stream targetStream, Stream sourceStream, int bufferSize, Action< object , System.ComponentModel.ProgressChangedEventArgs> progressChangedCallBack)
32 {
33 if (sourceStream == null )
34 throw new ArgumentNullException( "sourceStream" );
35
36 if (!sourceStream.CanRead)
37 throw new ArgumentException( "sourceStream" , "Unreadable stream" );
38
39 if (!targetStream.CanWrite)
40 throw new ArgumentException( "targetStream" , "Unwritable stream" );
41
42 if (bufferSize < 1024)
43 throw new ArgumentOutOfRangeException( "bufferSize" , "Must bigger than 1024" );
44
45 byte [] buffer = new byte [bufferSize];
46
47 int offset = 0;
48 int readByteCount = 0;
49 int percent = 0;
50
51 while ((readByteCount = sourceStream.Read(buffer, 0, bufferSize)) > 0)
52 {
53 targetStream.Write(buffer, 0, readByteCount);
54
55 if (progressChangedCallBack != null )
56 {
57 offset += readByteCount;
58
59 var currentPercent = ( int )((( double )offset) / sourceStream.Length * 100);
60 if (currentPercent == percent)
61 continue ;
62
63 percent = currentPercent;
64 progressChangedCallBack(targetStream, new System.ComponentModel.ProgressChangedEventArgs(percent, null ));
65 }
66 }
67 }
68 }

使用上Write方法會多三個多載版本，一個是將buffer整個寫入、一個是將stream的內容整個讀出並寫入、一個則是用來寫入整個stream內容，並可帶入處理的Buffer大小，與處理進度回報的Callback，用以處理進度的顯示。

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1 targetStream.Write(buffer);
2 targetStream.Write(sourceStream);
3 targetStream.Write(sourceStream, 1024, (sender, e) => { Console.WriteLine(e.ProgressPercentage.ToString ()); });

這邊針對進度處理的擴充方法示範個較為詳細的範例，這邊我會讀取C槽下的test.data檔案，檔案大小為5MB多，開啟後將其寫入c槽下的test_copy.data。處理的buffer大小為1024，每當在處理時偵測到進度改變時會顯示出當前處理的進度比例。

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01 using System;
02 using System.Collections.Generic;
03 using System.Linq;
04 using System.Text;
05 using System.IO;
06
07 namespace ConsoleApplication11
08 {
09 class Program
10 {
11 static void Main( string [] args)
12 {
13 using (FileStream targetStream = File .Create ( @"c:\test_copy.dat" ))
14 {
15 using (FileStream sourceStream= File.Open ( @"c:\test.dat" , FileMode.Open))
16 {
17 targetStream.Write(sourceStream, 1024, (sender, e) => { Console.WriteLine(e.ProgressPercentage.ToString()); });
18 }
19 }
20 }
21 }
22 }

運行結果如下：

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