der_oid_macro/
lib.rs

1use proc_macro::TokenStream;
2
3fn encode_components(components: &[num_bigint::BigUint], relative: bool) -> Vec<u8> {
4    use num_traits::cast::ToPrimitive;
5
6    let mut enc = Vec::new();
7    let mut dec = components;
8    if !relative {
9        if dec.len() < 2 {
10            if dec.len() == 1 && dec[0] == 0u8.into() {
11                return vec![0];
12            }
13            panic!("Need at least two components for non-relative oid");
14        }
15        if dec[0] >= 7u8.into() || dec[1] >= 40u8.into() {
16            panic!("First components are too big");
17        }
18        enc.push(dec[0].to_u8().unwrap() * 40 + dec[1].to_u8().unwrap());
19        dec = &dec[2..];
20    }
21
22    for int in dec.iter() {
23        let mut bytes = int.to_bytes_be();
24        if bytes[0] == 0 {
25            enc.push(0u8);
26            continue;
27        }
28        let total_bits = (8 - bytes[0].leading_zeros()) as usize + (bytes.len() - 1) * 8;
29        let octects_needed = ((total_bits + 6) / 7).max(1);
30        enc.resize_with(enc.len() + octects_needed, Default::default);
31
32        let mut pos = enc.len() - 1;
33        let mut extra = 0u8;
34        let mut extra_size = 0u8;
35        bytes.reverse();
36        let mut bytes_stored = 0;
37        for byte in bytes.into_iter() {
38            if extra_size == 7 {
39                // there a seven bits in extra
40                enc[pos] = extra | (1 << 7);
41                bytes_stored += 1;
42                pos -= 1;
43                extra = 0;
44                extra_size = 0;
45            }
46            // make space for the extra bits
47            enc[pos] = (byte << extra_size) | extra | (1 << 7);
48            bytes_stored += 1;
49            if pos > 0 {
50                pos -= 1;
51                extra_size += 1;
52                extra = byte >> (8 - extra_size);
53            }
54        }
55        let last = enc.len() - 1;
56        if bytes_stored != octects_needed {
57            let first = last + 1 - octects_needed;
58            enc[first] = extra | (1 << 7);
59        }
60        enc[last] ^= 1 << 7;
61    }
62    enc
63}
64
65#[proc_macro]
66pub fn encode_oid(input: TokenStream) -> TokenStream {
67    let s = input.to_string();
68
69    let (rem, relative) = if s.starts_with("rel ") {
70        (&s[4..], true)
71    } else {
72        (s.as_ref(), false)
73    };
74
75    let ints: Vec<num_bigint::BigUint> = rem
76        .split('.')
77        .map(|segment| segment.trim())
78        .map(|s| s.parse().unwrap())
79        .collect();
80
81    let enc = encode_components(&ints, relative);
82
83    let mut s = String::with_capacity(2 + 6 * enc.len());
84    s.push('[');
85    for byte in enc.iter() {
86        s.insert_str(s.len(), &format!("0x{:02x}, ", byte));
87    }
88    s.push(']');
89    s.parse().unwrap()
90}
der_oid_macro/lib.rs

der_oid_macro/
lib.rs
