Cant figure it out.

Is there a fast way to set 2 unsigned char arrays equal to eachother?

Right now im just running a for loop which sets x[i] = y[i] but is there a way to do


unsigned char Xarray[4];
unsigned char Yarray[4];

Xarray = Yarray;

?

Quote:

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Originally Posted by Coder87C

Is there a fast way to set 2 unsigned char arrays equal to eachother?

Right now im just running a for loop which sets x[i] = y[i] but is there a way to do


unsigned char Xarray[4];
unsigned char Yarray[4];

Xarray = Yarray;

?

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It is more C'ish but you can use memcpy or memset.


Mezzano

memcpy(Xarray,YArray,sizeof(YArray));
beware that if Yarray is a pointer and not an array you'll need so specify the size of the contained buffer on memcpy last paramater

Works like a charmed ANgel

If you're looking for all-out speed, then unroll the loop (some compilers will do this for you)

Code:

---

Xarray[0] = Yarray[0];
Xarray[1] = Yarray[1];
Xarray[2] = Yarray[2];
Xarray[3] = Yarray[3];

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The problem with say memcpy() is that it is likely to be a function call, which can get expensive in comparison if you're only copying small blocks of data.

Something like this can be amusing.

Code:

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  struct block
  {
      unsigned char array[4];
  };
  *(struct block *)Xarray = *(struct block *)Yarray;

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[edit]Hmm. For a Win32 console app using BC55, it makes pretty tiny assembly code; copying all 4 characters at once via a 4-byte register:

Code:

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        mov      eax,dword ptr [_Yarray]
        mov      dword ptr [_Xarray],eax

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It might seem ridiculous for a large array, but your loop idea is fine. The CPU's little brain can only handle one variable (one element of the array) at a time. ...No matter what technique you use, the machine code has to step-thru the array.

EDIT-
Oh, with character arrays (null-terminated C-style strings) you can use the strcpy() or strncpy() functions in the <cstring> header to copy one character array into another. These functions do the looping for you. :)