base_62/
base62.rs

1// Copyright 2019 KryptCo, Inc
2//
3// Licensed under the MIT license <LICENSE-MIT or http://opensource.org/licenses/MIT>.
4// This file may not be copied, modified, or distributed except according to those terms.
5
6use num_bigint::{BigUint};
7use num_traits::{Zero, One, ToPrimitive};
8use num_integer::Integer;
9use failure::Fail;
10
11/// Convert a byte buffer into a Base62 String
12pub fn encode(bytes: &[u8]) -> String {
13    if bytes.is_empty() { return "".into() }
14
15    let mut input = vec![1u8];
16    input.extend_from_slice(bytes);
17
18    let mut result = String::new();
19    let mut val = BigUint::from_bytes_be(&input);
20    let base:BigUint = (BASE.to_owned() as u64).into();
21
22    while val > BigUint::zero() {
23        let remainder = val.mod_floor(&base).to_usize().unwrap_or(0);
24        result.push(ALPHABET[remainder]);
25        val /= &base;
26    }
27
28    result
29}
30
31/// Convert a Base62 String into a byte buffer
32pub fn decode(input: &str) -> Result<Vec<u8>, Error> {
33    let mut val:BigUint = BigUint::zero();
34    let mut base_mul = BigUint::one();
35    let base:BigUint = (BASE.to_owned() as u64).into();
36
37    for c in input.chars().into_iter() {
38        let remainder:BigUint = char_to_remainder(c)?.into();
39        val += remainder*&base_mul;
40        base_mul *= &base;
41    }
42
43    Ok(val.to_bytes_be()[1..].to_vec())
44}
45
46#[derive(Debug, Fail)]
47pub enum Error {
48    #[fail(display = "Invalid character '{}'", character)]
49    BadCharacter { character: char}
50}
51
52// Alphabet Mapping
53const BASE: usize = 62;
54const ALPHABET: [char; BASE] = [
55    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
56    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
57    'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
58    'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
59    'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
60    'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
61    'y', 'z',
62];
63
64/// Reverse map a char to its "remainder" (its index in `ALPHABET`)
65fn char_to_remainder(c: char) -> Result<u64, Error> {
66    let i = match c {
67        '0'...'9' => ((c as u64) % ('0' as u64)),
68        'A'...'Z' => ((c as u64) % ('A' as u64)) + 10,
69        'a'...'z' => ((c as u64) % ('a' as u64)) + 36,
70        _ => return Err(Error::BadCharacter { character: c })
71    };
72
73    Ok(i)
74}
75
76#[test]
77fn test_encode() {
78    let cases:Vec<Vec<u8>> = vec![
79        vec![],
80        vec![0u8],
81        vec![1u8],
82        vec![0u8,0u8],
83        vec![0u8,1u8],
84        vec![1u8,0u8],
85        vec![1u8,1u8],
86        vec![0, 0, 0, 1],
87        [62u8; 10].to_vec(),
88        [63u8; 10].to_vec(),
89        [1u8; 10].to_vec(),
90        [0u8; 10].to_vec(),
91        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt".as_bytes().to_vec(),
92        vec![0xDE, 0xAD, 0xBE, 0xEF],
93    ];
94
95    cases.into_iter().enumerate().for_each(|(case, input)| {
96        let encoded = encode(&input);
97        let decoded = decode(&encoded).expect("error decoding base62 input");
98        assert_eq!(input, decoded, "\nCase {}:\nbase62({})\nmismatch: \nencoded({:?}) != \ndecoded({:?})", case, encoded, input, decoded);
99    })
100}
101
102#[test]
103fn test_invalid() {
104    decode("abc-").expect_err("expected invalid '-'");
105    decode("wSBzv9UB5PeI/26").expect_err("expected invalid '/'");
106    decode("jSO+uL8").expect_err("expected invalid '+");
107}
base_62/base62.rs

base_62/
base62.rs
