chematic-inchi 0.4.27

Pure Rust InChI/InChIKey generation (WASM-compatible) + optional IUPAC-standard InChI via native-inchi feature
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196

// Minimal pure-software SHA-256 — replaces the sha2 crate (~56 KB WASM code).
// Saves ~15 KB gzip in the WASM build. Output is identical to sha2::Sha256.
#[rustfmt::skip]
const K: [u32; 64] = [
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
];

fn sha256(data: &[u8]) -> [u8; 32] {
    let mut h: [u32; 8] = [
        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab,
        0x5be0cd19,
    ];
    let bit_len = (data.len() as u64).wrapping_mul(8);
    let mut padded = data.to_vec();
    padded.push(0x80);
    while padded.len() % 64 != 56 {
        padded.push(0);
    }
    padded.extend_from_slice(&bit_len.to_be_bytes());
    for chunk in padded.chunks_exact(64) {
        let mut w = [0u32; 64];
        for i in 0..16 {
            w[i] = u32::from_be_bytes([
                chunk[4 * i],
                chunk[4 * i + 1],
                chunk[4 * i + 2],
                chunk[4 * i + 3],
            ]);
        }
        for i in 16..64 {
            let s0 = w[i - 15].rotate_right(7) ^ w[i - 15].rotate_right(18) ^ (w[i - 15] >> 3);
            let s1 = w[i - 2].rotate_right(17) ^ w[i - 2].rotate_right(19) ^ (w[i - 2] >> 10);
            w[i] = w[i - 16]
                .wrapping_add(s0)
                .wrapping_add(w[i - 7])
                .wrapping_add(s1);
        }
        let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut hh] = h;
        for i in 0..64 {
            let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
            let ch = (e & f) ^ (!e & g);
            let t1 = hh
                .wrapping_add(s1)
                .wrapping_add(ch)
                .wrapping_add(K[i])
                .wrapping_add(w[i]);
            let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
            let maj = (a & b) ^ (a & c) ^ (b & c);
            let t2 = s0.wrapping_add(maj);
            (a, b, c, d, e, f, g, hh) = (t1.wrapping_add(t2), a, b, c, d.wrapping_add(t1), e, f, g);
        }
        h[0] = h[0].wrapping_add(a);
        h[1] = h[1].wrapping_add(b);
        h[2] = h[2].wrapping_add(c);
        h[3] = h[3].wrapping_add(d);
        h[4] = h[4].wrapping_add(e);
        h[5] = h[5].wrapping_add(f);
        h[6] = h[6].wrapping_add(g);
        h[7] = h[7].wrapping_add(hh);
    }
    let mut out = [0u8; 32];
    for (i, &hi) in h.iter().enumerate() {
        out[4 * i..4 * i + 4].copy_from_slice(&hi.to_be_bytes());
    }
    out
}

/// Generate InChIKey (27-character identifier) from an InChI string.
///
/// Format: `XXXXXXXXXXXXXX-XXXXXXXXXX-N` where N is the version flag.
pub fn inchi_key(inchi_str: &str) -> String {
    // Remove "InChI=1S/" prefix
    let inchi_content = if let Some(pos) = inchi_str.find("/") {
        &inchi_str[pos..]
    } else {
        inchi_str
    };

    // Split into parts: /c.../h... is connectivity+hydrogen, rest is charge/isotope
    let parts: Vec<&str> = inchi_content.split('/').collect();

    // First block: hash connectivity and hydrogen layers (/c and /h)
    let connectivity_input = if parts.len() >= 3 {
        // /c...../h..... format
        format!("{}/{}", parts[1], parts[2])
    } else if parts.len() >= 2 {
        // Just /c.....
        parts[1].to_string()
    } else {
        inchi_content.to_string()
    };

    // Second block: hash remaining layers (charge, isotope, stereo)
    let remaining_input = if parts.len() > 3 {
        parts[3..].join("/")
    } else {
        String::new()
    };

    // Compute SHA-256 hashes
    let hash1_bytes = sha256_hash(&connectivity_input);
    let hash2_bytes = sha256_hash(&remaining_input);

    // Convert to base-26 (A-Z) representation
    let block1 = bytes_to_base26(&hash1_bytes[..12]); // 12 bytes → ~14 chars
    let block2 = bytes_to_base26(&hash2_bytes[..9]); // 9 bytes → ~10 chars

    // Ensure block1 is exactly 14 chars and block2 is exactly 9 chars
    let block1_padded = format!("{:<14}", block1);
    let block2_padded = format!("{:<9}", block2);

    // Take only first 14 and 10 chars respectively, then truncate to exact size
    let block1_final = &block1_padded[..14];
    let block2_final = &block2_padded[..10];

    format!("{}-{}-N", block1_final, block2_final)
}

fn sha256_hash(input: &str) -> Vec<u8> {
    sha256(input.as_bytes()).to_vec()
}

fn bytes_to_base26(bytes: &[u8]) -> String {
    let mut result = String::new();
    for &byte in bytes {
        // Convert byte to 2 base-26 digits
        let d1 = (byte / 26) % 26;
        let d2 = byte % 26;
        result.push((b'A' + d1) as char);
        result.push((b'A' + d2) as char);
    }
    result
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn sha256_abc() {
        // RFC 4634 test vector: SHA-256("abc")
        let got = sha256(b"abc");
        let expected: [u8; 32] = [
            0xba, 0x78, 0x16, 0xbf, 0x8f, 0x01, 0xcf, 0xea, 0x41, 0x41, 0x40, 0xde, 0x5d, 0xae,
            0x22, 0x23, 0xb0, 0x03, 0x61, 0xa3, 0x96, 0x17, 0x7a, 0x9c, 0xb4, 0x10, 0xff, 0x61,
            0xf2, 0x00, 0x15, 0xad,
        ];
        assert_eq!(got, expected);
    }

    #[test]
    fn sha256_empty() {
        // SHA-256("")
        let got = sha256(b"");
        let expected: [u8; 32] = [
            0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14, 0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f,
            0xb9, 0x24, 0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c, 0xa4, 0x95, 0x99, 0x1b,
            0x78, 0x52, 0xb8, 0x55,
        ];
        assert_eq!(got, expected);
    }

    #[test]
    fn test_inchi_key_format() {
        let inchi = "InChI=1S/C6H6/c1-2-3-4-5-6-1/h1-6H";
        let key = inchi_key(inchi);
        assert_eq!(key.len(), 27);
        assert_eq!(&key[14..15], "-");
        assert_eq!(&key[25..26], "-");
        assert_eq!(&key[26..27], "N");
    }

    #[test]
    fn test_inchi_key_deterministic() {
        let inchi = "InChI=1S/C6H6/c1-2-3-4-5-6-1/h1-6H";
        let key1 = inchi_key(inchi);
        let key2 = inchi_key(inchi);
        assert_eq!(key1, key2);
    }

    #[test]
    fn test_inchi_key_different_for_different_inchi() {
        let inchi1 = "InChI=1S/CH4/h1H4";
        let inchi2 = "InChI=1S/C2H6/c1-2/h1-2H3";
        let key1 = inchi_key(inchi1);
        let key2 = inchi_key(inchi2);
        assert_ne!(key1, key2);
    }
}