In engineering practice, analog signal that is transformed with Fourier Transform has to be periodic. If signal is not periodic, but limited to certain time interval, signal can be repeated, so formally can be treated as periodic one.
Read more:

http://www.cirvirlab.com/index.php/electric/183-fourier-transform-and-dft-discrete-fourier-transform.html

and also online calculate DFT coefficients of an arbitrary signal:

http://www.cirvirlab.com/simulation/DFT-Discrete-Fourier-Transform-sin-cos-calculator-online.php

http://www.cirvirlab.com/index.php/electric/183-fourier-transform-and-dft-discrete-fourier-transform.html

and also online calculate DFT coefficients of an arbitrary signal:

http://www.cirvirlab.com/simulation/DFT-Discrete-Fourier-Transform-sin-cos-calculator-online.php