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, Jul 09 '09 at 15:27

score 66 · Answer 1 · edited Jul 01 '16 at 13:57

66

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 01 '16 at 13:57

Peter Mortensen

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answered Oct 30 '10 at 18:27

steppenwolfe

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The solution i don't deserve, but the one i need right now! – DaMachk Apr 16 '16 at 18:26
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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)' " – Hagbard Dec 19 '18 at 12:18

score 15 · Accepted Answer · answered Jul 09 '09 at 15:25

15

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 09 '09 at 15:25

jason

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Your original suggestion (before you added the second one later on) is rather inefficient – Philippe Leybaert Jul 09 '09 at 15:35
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Another option would be bytes.Cast().ToArray(); – Joel Mueller Aug 09 '09 at 04:04
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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 http://stackoverflow.com/questions/445471/puzzling-enumerable-cast-invalidcastexception. – jason Aug 19 '09 at 06:56
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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. – Nov 29 '15 at 22:57

score 6 · Answer 3 · edited Jul 01 '16 at 13:56

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 01 '16 at 13:56

Peter Mortensen

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answered Aug 09 '09 at 00:31

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This doesn't work. You have to do it like this to make it work: short s = (short)((bytes[0] << 8) | bytes[1]); – DaveN59 Dec 03 '09 at 21:12
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Assuming little endian, this should be: short s = (short)(bytes[0] | (bytes[1] << 8)) – Indy9000 May 31 '11 at 16:45

score 2 · Answer 4 · answered Apr 30 '10 at 12:52

2

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

answered Apr 30 '10 at 12:52

Gabriel

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This one uses _index_ as LSB and _index+1_ as MSB. Is there one that follows BigEndian to use _index_ as the MSB? – Nazar Sep 12 '18 at 20:40
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Did you even read the question? It is about byte[] to short[] not short. – Kishan Vaishnav May 02 '19 at 11:53

score 1 · Answer 5 · answered Nov 15 '16 at 09:59

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.

score 0 · Answer 6 · answered Jul 09 '09 at 15:26

0

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

answered Jul 09 '09 at 15:26

Philippe Leybaert

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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 ;-) – Tobias Raphael Dieckmann Jan 25 '21 at 08:20

score -2 · Answer 7 · edited Jul 09 '09 at 15:29

-2

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

edited Jul 09 '09 at 15:29

Jhonny D. Cano -Leftware-

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answered Jul 09 '09 at 15:28

Muad'Dib

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That's extremely inefficient: Calling convert.ToInt16() for every element, storing it in a temporary list, and then copying it to an new array. – Philippe Leybaert Jul 09 '09 at 15:30
yes, it is inefficient. I'm thinking that it's safer, tho, then casting. – Muad'Dib Jul 09 '09 at 16:09
Safer than casting? A cast of byte to short always works. It can never throw an exception – Philippe Leybaert Jul 09 '09 at 16:24

Convert byte array to short array in C#

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