Base32🔗ℹ

James Alexander Feldman-Crough <alex@fldcr.com>

This library provides utilities for converting byte-strings to and from an encoding based on Crockford’s Base32 encoding.

Compared to similar Base32 encodings like RFC 4648, Crockford’s encoding has a few desirable characteristics which make it especially appealing for user-facing use:

Potentially ambiguous characters, like i, I, l, and L are treated as synonyms.
The digits 0 through F have the same value as their hexadecimal counterparts.
The letter U is invalid, lowering the surface area for obscene encodings.

This library deviates from Crockford’s encoding by encoding strings as lower-case by default. Hyphens are also disallowed as spacing and check characters are unimplemented, although this is a shortcoming of the implementation.

1 API🔗ℹ

(require base32)

package: base32

1.1 Encoding and decoding byte-strings🔗ℹ

procedure
(base32? x) → boolean?
x : any/c

Determines whether or not a value is a valid Base32 encoding.

procedure
(base32-decode-bytes b32) → bytes?
b32 : base32?

Encodes bs as a base32 encoded string.

procedure
(base32-encode-bytes bs) → base32?
bs : bytes?

Encodes bs as a base32 encoded string.

1.2 Encoding and decoding ports🔗ℹ

procedure
(base32-decode in [#:close? close?]) → input-port?
in : input-port?
close? : boolean? = #t

Create a new input port that reads bytes from in after decoding them. If in is not base32 encoded, read will raise an exn:fail:contract upon encountering an invalid character.

If close? is #t, in will be closed once eof is reached.

procedure
(base32-encode in [#:close? close?]) → input-port?
in : input-port?
close? : boolean? = #t

Create a new input port that reads base64-encoded bytes from in.

If close? is #t, in will be closed once eof is reached.

1.3 Comparing base32 strings🔗ℹ

Because some characters are synonymous, two Base32 encodings may be representationally equivalent but not structurally equivalent.

Examples:

> (define-values (x y)
(values "ABC0123"
"abcoi23"))
> (equal? x y)
#f
> (base32=? x y)
#t
> (string<? x y)
#t
> (base32<? x y)
#f

procedure
(base32=? x y) → boolean?
x : base32?
y : base32?

Determine if two base32 strings are equivalent after normalizing synonymous characters.

procedure
(base32<? x y) → boolean?
x : base32?
y : base32?

Determine if two base32 strings are ordered lexicographically after normalizing synonymous characters.

2 Conversion table🔗ℹ

The following table shows the decimal value for each valid base32 character. When encoding, this library always chooses the first base32 representation in the table below.

base 10	base 32
0	0 o O =
1	1 i I l L
2	2
3	3
4	4
5	5
6	6
7	7
8	8
9	9
10	a A
11	b B
12	c C
13	d D
14	e E
15	f F
16	g G
17	h H
18	j J
19	k K
20	m M
21	n N
22	p P
23	q Q
24	r R
25	s S
26	t T
27	v V
28	w W
29	x X
30	y Y
31	z Z