[C#]Stream.Write Extension Method

2011-07-12

14104
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C#

在處理Stream型態時常會使用到Stream.Write這個方法，每次都會有種疑問就是，大多數的處理都是要將Buffer整個寫入，為何偏偏每次都要將索引帶0，長度帶為Buffer的大小呢?另外在處理Stream時，若要顯示其處理進度，是否能有更為簡單的方法?這邊將我為了解決這些問題所寫的擴充方法整裡如下：


using System.Reflection;
using System.ComponentModel;
using System.Linq;
using System.IO;

public static class StreamExtension
{
    public static void Write(this Stream targetStream, byte[] buffer)
    {
        if (!targetStream.CanWrite)
            throw new ArgumentException("targetStream", "Unwritable stream");

        targetStream.Write(buffer, 0, buffer.Length);
    }

    public static void Write(this Stream targetStream, Stream sourceStream)
    {
        if (!targetStream.CanWrite)
            throw new ArgumentException("targetStream", "Unwritable stream");

        if (sourceStream == null)
            throw new ArgumentNullException("sourceStream");

        if (!sourceStream.CanRead)
            throw new ArgumentException("sourceStream", "Unreadable stream");

        targetStream.Write(sourceStream, 1024, null);
    }

    public static void Write(this Stream targetStream, Stream sourceStream, int bufferSize, Action<object, System.ComponentModel.ProgressChangedEventArgs> progressChangedCallBack)
    {
        if (sourceStream == null)
            throw new ArgumentNullException("sourceStream");

        if (!sourceStream.CanRead)
            throw new ArgumentException("sourceStream", "Unreadable stream");

        if (!targetStream.CanWrite)
            throw new ArgumentException("targetStream", "Unwritable stream");

        if (bufferSize < 1024)
            throw new ArgumentOutOfRangeException("bufferSize", "Must bigger than 1024");

        byte[] buffer = new byte[bufferSize];

        int offset = 0;
        int readByteCount = 0;
        int percent = 0;

        while ((readByteCount = sourceStream.Read(buffer, 0, bufferSize)) > 0)
        {
            targetStream.Write(buffer, 0, readByteCount);

            if (progressChangedCallBack != null)
            {
                offset += readByteCount;

                var currentPercent = (int)(((double)offset) / sourceStream.Length * 100);
                if (currentPercent == percent)
                    continue;

                percent = currentPercent;
                progressChangedCallBack(targetStream, new System.ComponentModel.ProgressChangedEventArgs(percent, null));
            }
        }
    }
}

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。


targetStream.Write(sourceStream);
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。


using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication11
{
    class Program
    {
        static void Main(string[] args)
        {            
                using (FileStream targetStream = File .Create (@"c:\test_copy.dat"))
                {
                    using (FileStream sourceStream= File.Open (@"c:\test.dat", FileMode.Open))
                    {
                        targetStream.Write(sourceStream, 1024, (sender, e) => { Console.WriteLine(e.ProgressPercentage.ToString()); });
                    }
                }
        }
    }
}

運行結果如下：

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