Calculate redirect hash in drupal 7?
Usually there is always a module that can help out. 

In your case I recommend Path Redirect Import. It has a bulk import mechanism for redirects via CSV. It supports the Drupal 7 redirect module.

To get the redirects exported from D6 in the right format, check the Path Redirect Export module.

I believe that should do the trick for you.

I hope this helps you.