Convert int to different size of byte array

Question

I have a byte array result. I would like to convert my type called Info which are all int to the byte array but all of them are in different size.

a = 4 bytes

b = 3 bytes

c = 2 bytes

d = 1 bytes

This is the code I've tried.

private byte[] getInfoByteArray(Info data)
{
    byte[] result = new byte[10];
    BitConverter.GetBytes((data.a)).CopyTo(result, 0);
    BitConverter.GetBytes((data.b)).CopyTo(result, 4);
    BitConverter.GetBytes((data.c)).CopyTo(result, 7);
    result [9] = Convert.ToByte(data.d);

    return result;
    }

However, I found out that BitConverter.GetBytes returns 4 bytes.

Are there any general solutions that can get different size of bytes to a byte array?

int is always stored as 4 bytes. GetBytes() doesn't always only return byte arrays that are 4 long, it's only doing that because you're using the int data type. You could use this answer to calculate the minimum number of bytes needed to hold your integer values (presumable returning the 4, 3, 2, and 1 sizes as listed), then trim the result of .GetBytes() to that length before copying to your final byte array. — Cᴏʀʏ
– Cᴏʀʏ, Commented Sep 7, 2016 at 2:23
It's not clear why you want different byte lengths for your fields, especially if they are all actually int types. If you are sure you really only need 3, 2, or 1 byte for b, c, and d, then c and d can be short and byte, giving you exactly what you need. Your result for b depends on endianness, but you can truncate the array, e.g. Array.Copy(BitConverter.GetBytes(data.b), 0, result, 4, 3). I.e. if you don't want all the bytes, then don't copy all the bytes. — Peter Duniho
– Peter Duniho, Commented Sep 7, 2016 at 2:24

Cᴏʀʏ · Accepted Answer · 2016-09-07 02:32:30Z

1

Use Array.Copy(Array, Int32, Array, Int32, Int32) method:

byte[] result = new byte[10];
Array.Copy(BitConverter.GetBytes(data.a), 0, result, 0, 4);
Array.Copy(BitConverter.GetBytes(data.b), 0, result, 4, 3);
Array.Copy(BitConverter.GetBytes(data.c), 0, result, 7, 2);
Array.Copy(BitConverter.GetBytes(data.d), 0, result, 9, 1);

This assumes little endian hardware. If your hardware is big endian, use

byte[] result = new byte[10];
Array.Copy(BitConverter.GetBytes(data.a), 0, result, 0, 4);
Array.Copy(BitConverter.GetBytes(data.b), 1, result, 4, 3);
Array.Copy(BitConverter.GetBytes(data.c), 2, result, 7, 2);
Array.Copy(BitConverter.GetBytes(data.d), 3, result, 9, 1);

edited Sep 7, 2016 at 2:32

Cᴏʀʏ

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answered Sep 7, 2016 at 2:28

Sergey Kalinichenko

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