What's the algorithm?

[ixaaxar]

I have only a pseudo code
I see that using XOR.

int __thiscall sub_BBB8F0(int this, unsigned __int8 a2, __int16 a3, int a4, int a5)
{
  int result; // eax@1
  signed int i; // [sp+4h] [bp-8h]@2


  result = a3;
  if ( a3 > 0 )
  {
    for ( i = 0; i < a3; ++i )
    {
      result = i + a5;
      *(_BYTE *)(i + a5) = *(_BYTE *)(*(_DWORD *)this + 2 * (255 - i % 256) + 1) ^ *(_BYTE *)(*(_DWORD *)this
                                                                                            + 2 * a2
                                                                                            + 1) ^ *(_BYTE *)(*(_DWORD *)this + 2 * *(_BYTE *)(this + 4)) ^ *(_BYTE *)(i + a4);
    }
  }
  return result;
}