Is there any way to bind the 2 for loops in one for loop in c#-CodePudding

I am writing a code where it reads Messages from MCU, and stores them in an array of 8 bytes[0]~[7], specifically storing the first 4 values in the first half[0] ~[3] and the next four values in the next half[4] ~[7], Is there any way to bind the two for loops into one for loop, coz I have to run 7 cases in the switch with 2 for loops in each, all the for loops has the same syntax.

halfbytelength = 4;
bytelength =8;

case 0:

 for (index = 0; index <halfbytelength; index  = 1)
 {
    Array1[index] = msg[index];
 }
 for (index = halfbytelength; index < bytelength; index  = 1)
 {
   Array2[index - halfbytelength] = msg[index];
 }
 MainArray[0] = ASCIIEncoding.ASCII.GetString(Array1);
 MainArray[1] = ASCIIEncoding.ASCII.GetString(Array2);

CodePudding user response：

Assuming that bytelength stays even, you can do the following to replace your 2 loops with 1:

for (int index = 0; index < halfbytelength;   index)
{
    Array1[index] = msg[index];
    Array2[index] = msg[index   halfbytelength];
}

Note: as @JeremyLakeman commented below, using Array.Copy might be faster.
Your code will also be shorter (1 line per array, with no loops).
(assuming that msg,Array1,Array2 are of array type - which you didn't specify in your question).

CodePudding user response：

There should be no need to write the loop to copy bytes yourself. You for example use spans to slice the array.

var array1 = msg.AsSpan().Slice(0, 4).ToArray();
var array2 = msg.AsSpan().Slice(4, 8).ToArray();

I would say that it is significantly easier to read. Or add an extension method to convert a span to string directly.

Or you could use Array.Copy

Array.Copy(msg, 0, array1, 0, 4);
Array.Copy(msg, 4, array2, 0, 4);

But I find that less easy to read.

With regards to performance I would not expect a huge difference. I would expect converting the array to a string to take more time than copying a few bytes. But any method that avoid allocations might have some advantage if it is run in a tight loop.