Convert byte array to short array in C#

Question

I'm currently reading a file and wanted to be able to convert the array of bytes obtained from the file into a short array.

How would I go about doing this?

Do you want to convert 1 byte to 1 short, or 2 bytes to 1 short? — maxwellb
– maxwellb, Commented Jul 9, 2009 at 15:27

Peter Mortensen · Accepted Answer · 2016-07-01 13:57:46Z

70

Use Buffer.BlockCopy.

Create the short array at half the size of the byte array, and copy the byte data in:

short[] sdata = new short[(int)Math.Ceiling(data.Length / 2)];
Buffer.BlockCopy(data, 0, sdata, 0, data.Length);

It is the fastest method by far.

edited Jul 1, 2016 at 13:57

Peter Mortensen

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answered Oct 30, 2010 at 18:27

steppenwolfe

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2 Comments

DaMachk Over a year ago

The solution i don't deserve, but the one i need right now!

Hagbard Over a year ago

Thanks! Great answer but I had to change the code slightly to: short[] sdata = new short[(int)Math.Ceiling(data.Length / 2.0)];. Otherwise, I would have gotten the following error: "The call is ambiguous between the following methods or properties: 'Math.Ceiling(decimal)' and 'Math.Ceiling(double)' "

jason · Accepted Answer · 2009-07-09 15:25:38Z

16

One possibility is using Enumerable.Select:

byte[] bytes;
var shorts = bytes.Select(b => (short)b).ToArray();

Another is to use Array.ConvertAll:

byte[] bytes;
var shorts = Array.ConvertAll(bytes, b => (short)b);

answered Jul 9, 2009 at 15:25

jason

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4 Comments

Philippe Leybaert Over a year ago

Your original suggestion (before you added the second one later on) is rather inefficient

Joel Mueller Over a year ago

Another option would be bytes.Cast<short>().ToArray();

jason Over a year ago

Actually, this results in a InvalidCastException. The short explanation is that this code implicitly causes an boxed byte to be unboxed to a short which is not a valid unboxing operation. For details, see stackoverflow.com/questions/445471/….

user18443 Over a year ago

When I used var shorts[] = Array.ConvertAll(bytes, b => (short)b); I got each byte converted to a short not each pair of bytes converted.

Peter Mortensen · Accepted Answer · 2016-07-01 13:56:08Z

6

A shorthard is a compound of two bytes. If you are writing all the shorts to the file as true shorts then those conversions are wrong. You must use two bytes to get the true short value, using something like:

short s = (short)(bytes[0] | (bytes[1] << 8))

edited Jul 1, 2016 at 13:56

Peter Mortensen

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answered Aug 9, 2009 at 0:31

Gusman

2 Comments

DaveN59 Over a year ago

This doesn't work. You have to do it like this to make it work: short s = (short)((bytes[0] << 8) | bytes[1]);

Indy9000 Over a year ago

Assuming little endian, this should be: short s = (short)(bytes[0] | (bytes[1] << 8))

Gabriel · Accepted Answer · 2010-04-30 12:52:05Z

2

short value = BitConverter.ToInt16(bytes, index);

answered Apr 30, 2010 at 12:52

Gabriel

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2 Comments

Nazar Over a year ago

This one uses index as LSB and index+1 as MSB. Is there one that follows BigEndian to use index as the MSB?

Kishan Vaishnav Over a year ago

Did you even read the question? It is about byte[] to short[] not short.

Wolfgang Roth · Accepted Answer · 2016-11-15 09:59:24Z

1

I dont know, but I would have expected another aproach to this question. When converting a sequence of bytes into a sequence of shorts, i would have it done like @Peter did

short s = (short)(bytes[0] | (bytes[1] << 8))

or

short s = (short)((bytes[0] << 8) | bytes[1])

depending on endianess of the bytes in the file.

But the OP didnt mention his usage of the shorts or the definition of the shorts in the file. In his case it would make no sense to convert the byte array to a short array, because it would take twice as much memory, and i doubt if a byte would be needed to be converted to a short when used elsewhere.

answered Nov 15, 2016 at 9:59

Wolfgang Roth

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Comments

Philippe Leybaert · Accepted Answer · 2009-07-09 15:26:06Z

0

 short[] wordArray = Array.ConvertAll(byteArray, (b) => (short)b);

answered Jul 9, 2009 at 15:26

Philippe Leybaert

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1 Comment

Tobias Raphael Dieckmann Over a year ago

In my opinion, this would convert every byte into a short, which might not be the expected result als two bytes would represent a short ;-)

Jhonny D. Cano -Leftware- · Accepted Answer · 2009-07-09 15:29:05Z

-2

byte[] bytes;
var shorts = bytes.Select(n => System.Convert.ToInt16(n)).ToArray();

edited Jul 9, 2009 at 15:29

Jhonny D. Cano -Leftware-

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answered Jul 9, 2009 at 15:28

Muad'Dib

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3 Comments

Philippe Leybaert Over a year ago

That's extremely inefficient: Calling convert.ToInt16() for every element, storing it in a temporary list, and then copying it to an new array.

Muad'Dib Over a year ago

yes, it is inefficient. I'm thinking that it's safer, tho, then casting.

Philippe Leybaert Over a year ago

Safer than casting? A cast of byte to short always works. It can never throw an exception

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