C# の Stream 変換検証

Class1.cpp

#include "pch.h"
#include "Class1.h"

using namespace Concurrency;
using namespace Platform;
using namespace Windows::Foundation;
using namespace Windows::Storage::Streams;
using namespace StreamTestFactory;

IBuffer^ Class1::GetBuffer()
{
	return ref new Buffer( 1024 * 1024 );
}

IAsyncOperation<IInputStream^>^ Class1::GetInputStreamAsync()
{
	return create_async( []
	{
		auto buffer = ref new Buffer( 1024 * 1024 );
		auto ms = ref new InMemoryRandomAccessStream();
		return create_task( ms->WriteAsync( buffer ) ).then( [ms]( uint32 length )
		{
			return ms->GetInputStreamAt( 0 );
		} );
	} );
}

Class1.h

#pragma once

namespace StreamTestFactory
{
	public ref class Class1 sealed
	{
	public:
		static Windows::Storage::Streams::IBuffer^ GetBuffer();
		static Windows::Foundation::IAsyncOperation<Windows::Storage::Streams::IInputStream^>^ GetInputStreamAsync();
	};
}

MainPage.xaml.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace StreamTest
{
	public sealed partial class MainPage: Page
	{
		public MainPage()
		{
			this.InitializeComponent();
		}

		private async void Page_Loaded( object sender, RoutedEventArgs e )
		{
			var c = 100000000;

			var ary = new byte[1024 * 1024];
			var stream = new MemoryStream( 1024 * 1024 );
			stream.Write( ary, 0, ary.Length );
			var inputStream = stream.AsInputStream();
			var buffer = stream.GetWindowsRuntimeBuffer();

			var start = DateTimeOffset.Now;
			for( var i = 0; i < c; ++i )
			{
				inputStream.AsStreamForRead();
			}
			var end = DateTimeOffset.Now;
			var offset = end - start;

			var start2 = DateTimeOffset.Now;
			for( var i = 0; i < c; ++i )
			{
				buffer.AsStream();
			}
			var end2 = DateTimeOffset.Now;
			var offset2 = end2 - start2;

			var inputStreamPP = await StreamTestFactory.Class1.GetInputStreamAsync();
			var start3 = DateTimeOffset.Now;
			for( var i = 0; i < c; ++i )
			{
				inputStreamPP.AsStreamForRead();
			}
			var end3 = DateTimeOffset.Now;
			var offset3 = end3 - start3;

			var bufferPP = StreamTestFactory.Class1.GetBuffer();
			var start4 = DateTimeOffset.Now;
			for( var i = 0; i < c; ++i )
			{
				bufferPP.AsStream();
			}
			var end4 = DateTimeOffset.Now;
			var offset4 = end4 - start4;

			Debug.WriteLine( "{0}, {1}, {2}, {3}", offset, offset2, offset3, offset4 );
		}
	}
}

result.txt

+		offset	{00:00:00.8987264}	System.TimeSpan
+		offset2	{00:00:05.8384010}	System.TimeSpan
+		offset3	{00:00:06.6026362}	System.TimeSpan
+		offset4	{00:00:58.0481722}	System.TimeSpan