How to get little endian data from big endian in c# using bitConverter.ToInt32 method?

Question

I am making application in C# which has a byte array containing hex values.

I am getting data as a big-endian but I want it as a little-endian and I am using Bitconverter.toInt32 method for converting that value to integer.

My problem is that before converting the value, I have to copy that 4 byte data into temporary array from source byte array and then reverse that temporary byte array.

I can't reverse source array because it also contains other data.

Because of that my application becomes slow.

In the code I have one source array of byte as waveData[] which contains a lot of data.

byte[] tempForTimestamp=new byte[4]; tempForTimestamp[0] = waveData[290]; tempForTimestamp[1] = waveData[289]; tempForTimestamp[2] = waveData[288]; tempForTimestamp[3] = waveData[287]; int number = BitConverter.ToInt32(tempForTimestamp, 0); 

Is there any other method for that conversion?

Answer 1

In modern-day Linq the one-liner and easiest to understand version would be:

int number = BitConverter.ToInt32(waveData.Skip(286).Take(4).Reverse().ToArray(), 0); 

You could also...

byte[] tempForTimestamp = new byte[4]; Array.Copy(waveData, 287, tempForTimestamp, 0, 4); Array.Reverse(tempForTimestamp); int number = BitConverter.ToInt32(tempForTimestamp); 

:)

Answer 2

If you know the data is big-endian, perhaps just do it manually:

int value = (buffer[i++] << 24) | (buffer[i++] << 16)           | (buffer[i++] << 8) | buffer[i++]; 

this will work reliably on any CPU, too. Note i is your current offset into the buffer.

Another approach would be to shuffle the array:

byte tmp = buffer[i+3]; buffer[i+3] = buffer[i]; buffer[i] = tmp; tmp = buffer[i+2]; buffer[i+2] = buffer[i+1]; buffer[i+1] = tmp; int value = BitConverter.ToInt32(buffer, i); i += 4; 

I find the first immensely more readable, and there are no branches / complex code, so it should work pretty fast too. The second could also run into problems on some platforms (where the CPU is already running big-endian).