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?

• Snixtor: I'm conscious that neither your existing code, nor the code in Jesse's answer is thread-safe because of the use of Stream.Position. If you can be assured that it's only ever a MemoryStream that you'll be working with, you could produce a thread-safe implementation by working with the byte array (MemoryStream.GetBuffer()) and using BitConverter to read values.

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;
 }
}