scrypt_opt_derive/
lib.rs

1use std::fmt::Write;
2
3use proc_macro::TokenStream;
4
5// multiversion crate doesn't work with trait methods and can't bring your own feature detection
6// so here is a contraption there will generate a suffixed variant of the function for each feature
7
8#[proc_macro_attribute]
9pub fn generate_target_variant(attrs: TokenStream, input: TokenStream) -> TokenStream {
10    let attrs = attrs.to_string();
11
12    let feature = attrs
13        .trim()
14        .strip_prefix("\"")
15        .unwrap()
16        .strip_suffix("\"")
17        .unwrap()
18        .split(",")
19        .collect::<Vec<_>>();
20
21    let mut comments = Vec::new();
22
23    let input_str = input.to_string();
24    let mut input_str = input_str.lines();
25
26    let mut def_line = input_str.next().unwrap();
27
28    while def_line.trim().starts_with("//")
29        || def_line
30            .trim()
31            .strip_prefix("#")
32            .map_or(false, |s| s.trim().starts_with("["))
33    {
34        comments.push(def_line.trim().to_string());
35        let Some(def_line_next) = input_str.next() else {
36            return "".parse().unwrap();
37        };
38        def_line = def_line_next;
39    }
40
41    let rest = if def_line.trim().starts_with("pub") {
42        let trimmed = def_line.trim();
43        let split = trimmed
44            .char_indices()
45            .filter(|(_, c)| c.is_whitespace())
46            .next()
47            .unwrap()
48            .0;
49        &trimmed[split..]
50    } else {
51        def_line
52    };
53
54    let Some(rest) = rest.trim().strip_prefix("fn ") else {
55        panic!("Expected a function definition, got {}", rest);
56    };
57
58    let name = rest
59        .chars()
60        .take_while(|c| c.is_alphanumeric() || *c == '_')
61        .collect::<String>();
62
63    let def_line_mutated =
64        def_line.replace(&name, format!("{}_{}", name, feature.join("_")).as_str());
65
66    let rest_lines = input_str.collect::<Vec<_>>();
67
68    let mut output = String::new();
69    for comment in comments.iter() {
70        writeln!(&mut output, "{}", comment).unwrap();
71    }
72    writeln!(&mut output, "{}", def_line).unwrap();
73    for line in rest_lines.iter() {
74        writeln!(&mut output, "{}", line).unwrap();
75    }
76
77    for comment in comments.iter() {
78        writeln!(&mut output, "{}", comment).unwrap();
79    }
80    writeln!(
81        &mut output,
82        "// This is a generated function for CPU target {}",
83        feature.join(", ")
84    )
85    .unwrap();
86    for feature in feature.iter() {
87        writeln!(&mut output, "#[target_feature(enable = \"{}\")]", feature).unwrap();
88    }
89    writeln!(&mut output, "{}", def_line_mutated).unwrap();
90    output.extend(rest_lines);
91
92    output.parse().unwrap()
93}
scrypt_opt_derive/lib.rs

scrypt_opt_derive/
lib.rs
