1 // This is a modification of base32 from https://crates.io/crates/base32(v0.4.0),
2 // copied from rust-lightning.
3 // The original portions of this software are Copyright (c) 2015 The base32 Developers
4 // The remainder is copyright rust-lightning developers, as viewable in version control at
5 // https://github.com/lightningdevkit/rust-lightning/
7 // This file is licensed under either of
8 // Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0) or
9 // MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT) at your option.
13 /// RFC4648 "extended hex" encoding table
15 const RFC4648_ALPHABET: &'static [u8] = b"0123456789ABCDEFGHIJKLMNOPQRSTUV";
17 /// RFC4648 "extended hex" decoding table
18 const RFC4648_INV_ALPHABET: [i8; 39] = [
19 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13,
20 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
23 /// Encode bytes into a base32 string.
25 pub fn encode(data: &[u8]) -> alloc::string::String {
26 // output_length is calculated as follows:
27 // / 5 divides the data length by the number of bits per chunk (5),
28 // * 8 multiplies the result by the number of characters per chunk (8).
29 // + 4 rounds up to the nearest character.
30 let output_length = (data.len() * 8 + 4) / 5;
31 let mut ret = encode_data(data, RFC4648_ALPHABET);
32 ret.truncate(output_length);
35 assert_eq!(ret.capacity(), (data.len() + 4) / 5 * 8);
37 alloc::string::String::from_utf8(ret).expect("Invalid UTF-8")
40 /// Decode a base32 string into a byte vector.
41 pub fn decode(data: &str) -> Result<Vec<u8>, ()> {
42 let data = data.as_bytes();
43 // If the string has more characters than are required to alphabet_encode the number of bytes
44 // decodable, treat the string as invalid.
45 match data.len() % 8 { 1|3|6 => return Err(()), _ => {} }
46 decode_data(data, RFC4648_INV_ALPHABET)
49 /// Encode a byte slice into a base32 string.
51 fn encode_data(data: &[u8], alphabet: &'static [u8]) -> Vec<u8> {
52 // cap is calculated as follows:
53 // / 5 divides the data length by the number of bits per chunk (5),
54 // * 8 multiplies the result by the number of characters per chunk (8).
55 // + 4 rounds up to the nearest character.
56 let cap = (data.len() + 4) / 5 * 8;
57 let mut ret = Vec::with_capacity(cap);
58 for chunk in data.chunks(5) {
59 let mut buf = [0u8; 5];
60 for (i, &b) in chunk.iter().enumerate() {
63 ret.push(alphabet[((buf[0] & 0xF8) >> 3) as usize]);
64 ret.push(alphabet[(((buf[0] & 0x07) << 2) | ((buf[1] & 0xC0) >> 6)) as usize]);
65 ret.push(alphabet[((buf[1] & 0x3E) >> 1) as usize]);
66 ret.push(alphabet[(((buf[1] & 0x01) << 4) | ((buf[2] & 0xF0) >> 4)) as usize]);
67 ret.push(alphabet[(((buf[2] & 0x0F) << 1) | (buf[3] >> 7)) as usize]);
68 ret.push(alphabet[((buf[3] & 0x7C) >> 2) as usize]);
69 ret.push(alphabet[(((buf[3] & 0x03) << 3) | ((buf[4] & 0xE0) >> 5)) as usize]);
70 ret.push(alphabet[(buf[4] & 0x1F) as usize]);
73 assert_eq!(ret.capacity(), cap);
78 fn decode_data(data: &[u8], alphabet: [i8; 39]) -> Result<Vec<u8>, ()> {
79 // cap is calculated as follows:
80 // / 8 divides the data length by the number of characters per chunk (8),
81 // * 5 multiplies the result by the number of bits per chunk (5),
82 // + 7 rounds up to the nearest byte.
83 let cap = (data.len() + 7) / 8 * 5;
84 let mut ret = Vec::with_capacity(cap);
85 for chunk in data.chunks(8) {
86 let mut buf = [0u8; 8];
87 for (i, &c) in chunk.iter().enumerate() {
88 match alphabet.get(c.to_ascii_uppercase().wrapping_sub(b'0') as usize) {
89 Some(&-1) | None => return Err(()),
90 Some(&value) => buf[i] = value as u8,
93 ret.push((buf[0] << 3) | (buf[1] >> 2));
94 ret.push((buf[1] << 6) | (buf[2] << 1) | (buf[3] >> 4));
95 ret.push((buf[3] << 4) | (buf[4] >> 1));
96 ret.push((buf[4] << 7) | (buf[5] << 2) | (buf[6] >> 3));
97 ret.push((buf[6] << 5) | buf[7]);
99 let output_length = data.len() * 5 / 8;
100 for c in ret.drain(output_length..) {
102 // If the original string had any bits set at positions outside of the encoded data,
103 // treat the string as invalid.
108 // Check that our capacity calculation doesn't under-shoot in fuzzing
110 assert_eq!(ret.capacity(), cap);
119 fn test_encode_decode() {
120 let mut bytes = [0u8; 256 * 5];
122 bytes[i as usize + 256*0] = i;
123 bytes[i as usize + 256*1] = i.wrapping_add(1);
124 bytes[i as usize + 256*2] = i.wrapping_add(2);
125 bytes[i as usize + 256*3] = i.wrapping_add(3);
126 bytes[i as usize + 256*4] = i.wrapping_add(4);
128 assert_eq!(decode(&encode(&bytes)).unwrap(), bytes);