FinishDecoding is a procedure used to ensure that unused characters in the internal buffer for TIdDecoderMIMELineByLine are padded with the value specified in FillChar and decoded. 

FinishDecoding ensure that the number of pending characters is always a multiple of 4 (for the 4-byte to 3-byte decoding operation). 

FinishDecoding calls the inherited Decode method. 

Use Clear to discard and ignore any unused characters from prior calls to the Decode method.

Decode 

Clear