bottleneck.rb

        builder.c %{
          void increment_C(
            VALUE _count_ary,   // Count ary.
            VALUE _nodes_ary,   // Nodes ary.
            VALUE _length       // Nodes ary length.
          )
          {
            int *count_ary  = (int *) StringValuePtr(_count_ary);
            int *nodes_ary  = (int *) StringValuePtr(_nodes_ary);
            int  length     = FIX2INT(_length);
            int  i          = 0;

            for (i = length - 1; i >= 0; i--)
            {
              count_ary[nodes_ary[i]]++;
            }
          }
        }