How to transpose a text file on character basis

There are some tools like datamesh to transpose a matrix in a csv file, but I want to exchange rows and columns character based. So a file abcde fghij klmn opqrs should become afko bglq chmq dinr ej s Note that as line 3 is shorter, a whitespace has to be inserted in the last row. Of source I could write some C program to do it, but I thought I once met a tool to do this, but my search engine doesn't help me find it.