c# Combine byte array and convert to a 16-bit Integer

Question

Lets say I have a byte array defined like this:

byte[] byteArray = { 0x08, 0x00 };

I need to combine the elements in the array to create:

0x0800

Then convert that to an int:

Something like this:

    private static int GetMessageType(byte[] byteArray)
    {
        if(byteArray.Length != 2)
            throw new ArgumentOutOfRangeException("byteArray");

        throw new NotImplementedException();
    }

Two bytes does not make an Int32... What rules do you want for the conversion here? — Reed Copsey
– Reed Copsey, Commented Jul 5, 2012 at 22:29
bits 0 through 15 would be the Int16 and bits 16 through 31 would be zero. So 0x0800 would be: 0000 0000 0000 0000 0000 1000 0000 0000 — aelstonjones
– aelstonjones, Commented Jul 5, 2012 at 22:42

score 4 · Accepted Answer · 2012-07-05 23:00:52Z

4

Why not just use simple bitwise operators? e.g.

byte hiByte = byteArray[0];  // or as appropriate
byte lowByte = byteArray[1];
short val = (short)((hiByte << 8) | lowByte);

In this case the bitwise result is treated as a [signed] short (following the title?) and could result in a negative value, but that can be altered as needed by just removing the cast ..

edited Jul 5, 2012 at 23:00

answered Jul 5, 2012 at 22:44

user166390

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Comments

Ben Voigt · Accepted Answer · 2012-07-05 22:30:58Z

1

You should use BitConverter.ToInt16, except it appears that you want a BigEndian conversion. So use Jon Skeet's EndianBitConverter: http://www.yoda.arachsys.com/csharp/miscutil/

answered Jul 5, 2012 at 22:30

Ben Voigt

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2 Comments

aelstonjones Over a year ago

I used a decompiler on Jon Skeets .dll and it looks like his EndianBitConverter uses the same bitwise operations pst suggested.

Ben Voigt Over a year ago

@aelstonjones: Right, but one is more self-explanatory when you see it again.

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