`BufferedStream`

With a buffer, we avoid executing writes and reads until a certain number of operations has been requested. Then we execute them all at once.

Buffering makes things faster—many bytes can be written at once, reducing overhead of each byte. The BufferedStream in C# can be used to optimize stream reads and writes.

Example program

Consider this program. It uses a MemoryStream and we want to write 5 million bytes to it. But we wrap the MemoryStream in a BufferedStream.

And We call WriteByte on the BufferedStream, which acts upon the MemoryStream. But it buffers operations.

Result The total time required for the 5 million buffered WriteByte calls is printed as the program exits.

using System;
using System.Diagnostics;
using System.IO;

class Program
{
    static void Main()
    {
        var t1 = Stopwatch.StartNew();
        // Use BufferedStream to buffer writes to a MemoryStream.
        using (MemoryStream memory = new MemoryStream())
        using (BufferedStream stream = new BufferedStream(memory))
        {
            // Write a byte 5 million times.
            for (int i = 0; i < 5000000; i++)
            {
                stream.WriteByte(5);
            }
        }
        t1.Stop();
        Console.WriteLine("BUFFEREDSTREAM TIME: " + t1.Elapsed.TotalMilliseconds);
    }
}
BUFFEREDSTREAM TIME: 20.6607

Benchmark, part 2

We must compare our BufferedStream benchmark to another one without BufferedStream. Here we use MemoryStream directly—no buffering is done.

Result The 5 million WriteByte calls in this program take an entire 5 milliseconds more than in the version that uses BufferedStream.

using System;
using System.Diagnostics;
using System.IO;

class Program
{
    static void Main()
    {
        var t1 = Stopwatch.StartNew();
        // Use MemoryStream directly with no buffering.
        using (MemoryStream memory = new MemoryStream())
        {
            // Write a byte 5 million times.
            for (int i = 0; i < 5000000; i++)
            {
                memory.WriteByte(5);
            }
        }
        t1.Stop();
        Console.WriteLine("MEMORYSTREAM TIME: " + t1.Elapsed.TotalMilliseconds);
    }
}
MEMORYSTREAM TIME: 26.2119

Notes, performance

By using BufferedStream, we achieved a performance boost. This would not be helpful on small streams or fewer writes.

Notes, continued

To achieve "optimal" performance, we need to always measure. But BufferedStream is a good option to try to improve stream read and write performance.

Tip Optimal performance is "undecidable" which means no program is optimal because another might someday exist that is faster.

Most programs will not benefit from BufferedStream. But it is good to know it exists. It can improve both reads and writes.