Final release of open source Data Shredder that called "Eliminator", supports 4 type of shredding and added free space wipe feature.
tested with several 1 & 2 TB hard disk to wipe information and attempt to recovery, all of test was unsuccessful in data recovery.
I changed "grinder" name to "eliminator" because there is some app with name similarity that have porno uses !
access full source code
https://github.com/NIKJOO/FastShredder