--- /dev/null
+! Copyright (C) 2019 John Benediktsson
+! See http://factorcode.org/license.txt for BSD license
+
+USING: base32 tools.test ;
+
+{ "16J" } [ 1234 base32> ] unit-test
+{ "16JD" } [ 1234 base32-checksum> ] unit-test
+{ "0" } [ 0 base32> ] unit-test
+{ "00" } [ 0 base32-checksum> ] unit-test
+[ -1 base32> ] must-fail
+[ 1.0 base32> ] must-fail
+
+{ 1234 } [ "16J" >base32 ] unit-test
+{ 1234 } [ "I6J" >base32 ] unit-test
+{ 1234 } [ "i6J" >base32 ] unit-test
+{ 1234 } [ "16JD" >base32-checksum ] unit-test
+{ 1234 } [ "I6JD" >base32-checksum ] unit-test
+{ 1234 } [ "i6JD" >base32-checksum ] unit-test
+{ 0 } [ "0" >base32 ] unit-test
+{ 0 } [ "00" >base32-checksum ] unit-test
--- /dev/null
+! Copyright (C) 2019 John Benediktsson
+! See http://factorcode.org/license.txt for BSD license
+
+USING: ascii assocs kernel literals math sequences ;
+
+IN: base32
+
+<PRIVATE
+
+<<
+CONSTANT: ALPHABET "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
+>>
+CONSTANT: CHECKSUM $[ ALPHABET "*~$=U" append ]
+
+: normalize-base32 ( seq -- seq' )
+ CHAR: - swap remove >upper H{
+ { CHAR: I CHAR: 1 }
+ { CHAR: L CHAR: 1 }
+ { CHAR: O CHAR: 0 }
+ } substitute ;
+
+: parse-base32 ( seq -- base32 )
+ 0 swap [ [ 32 * ] [ ALPHABET index + ] bi* ] each ;
+
+PRIVATE>
+
+: >base32 ( seq -- base32 )
+ normalize-base32 parse-base32 ;
+
+: base32> ( base32 -- seq )
+ dup 0 < [ non-negative-integer-expected ] when
+ [ dup 0 > ] [
+ 32 /mod ALPHABET nth
+ ] "" produce-as nip [ "0" ] when-empty reverse! ;
+
+: >base32-checksum ( seq -- base32 )
+ normalize-base32 unclip-last [ parse-base32 ] dip
+ CHECKSUM index over 37 mod assert= ;
+
+: base32-checksum> ( base32 -- seq )
+ [ base32> ] keep 37 mod CHECKSUM nth suffix ;