C# BinaryReader notably slower. Alternative?

Question

For my project I need to write UInt16, UInt32, Bytes and Strings from a file. I started with a simple class I wrote like this:

    public FileReader(string path)  //constructor
    {
        if (!System.IO.File.Exists(path))
            throw new Exception("FileReader::File not found.");

        m_byteFile = System.IO.File.ReadAllBytes(path);
        m_readPos = 0;
    }
    public UInt16 getU16()   // basic function for reading
    {
        if (m_readPos + 1 >= m_byteFile.Length)
            return 0;

        UInt16 ret = (UInt16)((m_byteFile[m_readPos + 0])
                            + (m_byteFile[m_readPos + 1] << 8));
        m_readPos += 2;
        return ret;
    }

I thought it might be better to use the already existing BinaryReader though and so I tried it, but I noticed that it is slower than my approach. Can somebody explain why this is and if there is another already existing class I could use to load a file and read from it?

~Adura

Answer 1

You have all the data upfront in an array in memory whereas BinaryReader streams the bytes in one at a time from the source which I guess is a file on disk. I guess you could speed it up by passing it a stream that reads from an in-memory array:

Stream stream = new MemoryStream(byteArray);
//Pass the stream to BinaryReader

Note that with this approach you need to fill the entire file in memory at once but I guess that's ok for you.