Re: CTFE Status

[Stefan Koch via Digitalmars-d]

After the bad news now a bit of good news.
I just finished the strCat algorithm;
The reason this took so much time is because of the 
representation the heap has in the elevator.
it is a uint[] meaning you are getting into trouble with offsets 
if the first string is not a multiple of 4 characters long:)
This is the code for strcat :

uint[] strcat(const uint[] a, const uint[] b, uint aLength = 0, 
uint bLength = 0)
{
  aLength = a[0];
  bLength = b[0];
  uint resultLength = a[0] + b[0];
  uint[] result;
  result.length = neededArraySize(resultLength);
  assert(result.length == (a.length + b.length) - 2);
  result[0] = resultLength;
  auto resultPosition = 1;

  auto aMinusOne = !(aLength & 3);
  foreach(p, ca; a[1 .. $ - aMinusOne])
  {
    result[resultPosition++] = ca;
  }
  // this one is easy we just copy
    auto bMinusOne = !(bLength & 3);

  uint offset = aLength & 3;
  if (offset)
  {
    assert(offset == 2);
    resultPosition--;
    foreach(p, cb; b[1 .. $])
    {
      result[resultPosition++] |= (cb & ((1U << (offset*8)) -1)) 
<< (offset*8);
      if (resultPosition == result.length) break;
      result[resultPosition++] |= (cb & ~((1U << (offset*8)) -1)) 
>> (offset*8);
      resultPosition--;
    }
  }
  else
  {
    foreach(p, cb; b[1 .. $ - bMinusOne])
    {
      result[resultPosition++] = cb;
    }
  }

  return result;
}

uint neededArraySize(uint size)
{
  return (((size - 1) / 4) + 2) + (!(size & 3));
}