reverse tool path

[a71sa]

Hi every one
there is something that used in plasma cnc machines it's for when for some reason plasma get cut off or no cutting is done so the solution for correct continue is to pause cnc and get back to edge of place that plasma got off then continue from there
it called reverse tool path, i think but i'm not sure.
i want to add this feature but i can't find good doc or something to start with code (i'm not very pro with java )
so any idea of what can i do ? or something helpful ?
thanks