#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void* memorycopy (void *des, const void *src, size_t count)
{

  size_t n = (count + 7) / 8;
  char* destination = (char *) des;
  char* source = (char *) src;

  switch (count % 8)
  {
      case 0:  do{  *destination++ = *source++;
      case 7:  *destination++ = *source++;
      case 6:  *destination++ = *source++;
      case 5:  *destination++ = *source++;
      case 4:  *destination++ = *source++;
      case 3:  *destination++ = *source++;
      case 2:  *destination++ = *source++;
      case 1:  *destination++ = *source++;

    } while (--n > 0);
  }

  return des;
}


void tworegistervarswap (int *x, int *y)
{
  if (x != y)
  {
    *x = *x ^ *y;
    *y = *x ^ *y;
    *x = *x ^ *y;
  }
}


int bigintegeraverage (int x, int y)
{
  return (x & y) + ((x ^ y) >> 1);
}


int main (void) 
{
  char *testArray = "This is a test.";
  char buffer[50];
  int x = 10;
  int y = 20;
  int m = 2000000000;
  int n = 1000000000;
 
  printf ("\nmemorycopy test before: %s", testArray);
  memorycopy (buffer, testArray, strlen(testArray) + 1);
  printf ("\nmemorycopy test after: %s", buffer);
  printf ("\n");

  printf ("\ntworegistervarswap test before: %d %d", x, y);
  tworegistervarswap (&x, &y);
  printf ("\ntworegistervarswap test after: %d %d", x, y);
  printf ("\n");

  printf ("\nbigintegeraverage regular code test: %d ", (m + n) / 2);
  printf ("\nbigintegeraverage function test: %d", bigintegeraverage (m, n) );
  printf ("\n");

  return 0;
}