How can I get the standard form of a parity check matrix?

I have a binary parity check matrix (a matrix whose null space is a finite vector space). Actually I want to obtain the generator matrix (the matrix whose row space is the vector space) and then see the vectors spanned by its row. There is a command already which converts the parity check matrix to the generator matrix gen2par. However my parity check matrix isn't in the standard form and the command is valid for only matrix having standard form. Is there a way to achieve this? I think there sholud be but I couldn't find.

A generator matrix is of the standard form if it is of the form [I|A] i.e. the id matrix appears on le left

A parity-check matrix is of the standard form if it is [B|I] i.e. the id matrix appears on le right