The ENCODERS/DECODERS library consists of the following 3 generic components :

decN	:	N input decoder. The input word selects which output bit is asserted.
decNen	:	N input decoder. The input word selects which output bit is asserted if allowed by enable. This module can be used as a demultiplexer.
encN	:	N input MSB-priority encoder. When no input is asserted the output of the module is 1 (0-), where the number of '0's is log2(N)

The ENC_DECs library can be verified with this testbench : test_encoders_decoders