C# in Depth

Life before extension methods257System.IO.Stream. The Stream class is the bedrock of binary communications in .NET.Stream itself is an abstract class with several concrete derived classes, such as Network-Stream, FileStream, and MemoryStream. Unfortunately, there are a few pieces of functionalitythat would have been handy to include in Stream but that just aren’t there.The “missing features” I come across most often are the ability to read the whole ofa stream into memory as a byte array, and the ability to copy 1 the contents of onestream into another. Both of these are frequently implemented badly, making assumptionsabout streams that just aren’t valid (the most common is that Stream.Read willcompletely fill the given buffer if the data doesn’t run out first).It would be nice to have the functionality in a single place, rather than duplicatingit in several projects. That’s why I wrote the StreamUtil class in my miscellaneous utilitylibrary. The real code contains a fair amount of error checking and other functionality,but listing 10.1 shows a cut-down version that is more than adequate for our needs.Listing 10.1A simple utility class to provide extra functionality for streamsusing System.IO;public static class StreamUtil{const int BufferSize = 8192;}public static void Copy(Stream input,Stream output){byte[] buffer = new byte[BufferSize];int read;while ((read = input.Read(buffer, 0, buffer.Length)) > 0){output.Write(buffer, 0, read);}}public static byte[] ReadFully(Stream input){using (MemoryStream tempStream = new MemoryStream()){Copy(input, tempStream);return tempStream.ToArray();}}The implementation details don’t matter much, although it’s worth noting that theReadFully method calls the Copy method—that will be useful to demonstrate a pointabout extension methods later. The class is easy to use—listing 10.2 shows how we canwrite a web response to disk, for example.1Due to the nature of streams, this “copying” doesn’t necessarily duplicate the data—it just reads it from onestream and writes it to another. Although “copy” isn’t a strictly accurate term in this sense, the difference isusually irrelevant.Licensed to Rhona Hadida