Base32 Encoder and Decoder in J

base32.ijs

NB. ENCODER
NB. information about algorithm came from https://herongyang.com/Encoding/Base32-Encoding-Algorithm.html

NB. RFC 4648 character set
cs =: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'

NB. interval array
ia =: {{0 = 5 | i. # y}}

NB. padded length value
pl =: {{5 * >. 5 %~ # y}}

pad =: (pl $!.(0{a.) ])&.>

NB. split stream, pad, and unbox
ss =: > @ pad @ <;.1~ ia

NB. bit groups
bgs =: [: (8,5)&($,)"2 (8#2) #: a. i. ]

NB. override count
oc =: [: {&(0 6 4 3 1 0) # - ([: -&5 pl)

map =: [: {&cs #.

NB. override
o =: (-@[ }. ,@]) , #&'='@[

NB. encode
e =: oc o map@bgs@ss


NB. DECODER

NB. dyadic: count x in y
c =: +/@:=

NB. dyadic: remove all x from y
sc =: -@:c }. ]

NB. convert to bgs and add null rows
conv =: {{ (#: cs i. '=' sc y) , (5,~ '=' c y) $ 0 }}

NB. calculate new shape to go from shape (n 5) to (m 8) 
ns =: {{8 ,~ 5 * 8 %~ # y}}

NB. reshape
rs =: ns ($,) ]

NB. decode
d =: {{ u: 0 sc #. rs conv y }}