datatables number of columns

How do i get the number of columns in a datatable?

I can get the number of rows by doing oTable.fnGetData().length but how do I get the number of columns so I can Iterate over each cell like this:

var numColumns = //How to get the number of columns?
    for(var r=0;r<oTable.fnGetData().length;r++){
        for(var c=0;c <= numColumns;c++){
            console.log("[R]: "+r+ "[C]: "+c+ " data: "+oTable.fnGetData(r,c));   
        }
    }