Binary-reading code

Question

I'm currently writing a binary reader that reads a value from a BinaryReader at a given position. For that I have to store the current position of the MemoryStream so I can restore it afterwards.

public byte GetByte(int position)
{
   long oldPosition = this.memoryStream.Position;
   this.memoryStream.Position = position;

   byte value = this.ReadByte();

   this.memoryStream.Position = oldPosition;

   return value;
}

EDIT: As requested, more similar functions:

public byte[] GetByteArray(int position, int length)
{
    long oldPosition = this.memoryStream.Position;
    this.memoryStream.Position = position;

    byte[] value = this.ReadByteArray(length);

    this.memoryStream.Position = oldPosition;

    return value;
}

public bool GetBoolean(int position)
{
    long oldPosition = this.memoryStream.Position;
    this.memoryStream.Position = position;

    bool value = this.ReadBoolean();

    this.memoryStream.Position = oldPosition;

    return value;
}

public ushort GetUInt16(int position)
{
    long oldPosition = this.memoryStream.Position;
    this.memoryStream.Position = position;

    ushort value = this.ReadUInt16();

    this.memoryStream.Position = oldPosition;

    return value;
}

and so on..

Is there any way to shorten this process and avoid doubled-code since I have many functions similar to that?

Answer 1

Try a pair of methods like this:

public T GetValue<T>(int position, Func<T> readFunc)
{
    long oldPosition = this.memoryStream.Position;
    this.memoryStream.Position = position;

    T value = readFunc();

    this.memoryStream.Position = oldPosition;

    return value;
}

public T GetValue<T>(int position, Func<int, T> readFunc, int length)
{
    long oldPosition = this.memoryStream.Position;
    this.memoryStream.Position = position;

    T value = readFunc(length);

    this.memoryStream.Position = oldPosition;

    return value;
}

then they can be called as such:

byte b = GetValue(position, ReadByte);
byte[] ba = GetValue(position, ReadByteArray, length);
// etc.

ETA: I might write the methods like this to ensure the stream's position gets reset properly, even in the event of an exception:

public T GetValue<T>(int position, Func<T> readFunc)
{
    var oldPosition = this.memoryStream.Position;

    this.memoryStream.Position = position;
    try
    {
        return readFunc();
    }
    finally
    {
        this.memoryStream.Position = oldPosition;
    }
}

public T GetValue<T>(int position, Func<int, T> readFunc, int length)
{
    var oldPosition = this.memoryStream.Position;

    this.memoryStream.Position = position;
    try
    {
        return readFunc(length);
    }
    finally
    {
        this.memoryStream.Position = oldPosition;
    }
}