cxx_build/
cargo.rs

1use crate::gen::{CfgEvaluator, CfgResult};
2use std::borrow::Borrow;
3use std::cmp::Ordering;
4use std::collections::{BTreeMap as Map, BTreeSet as Set};
5use std::env;
6use std::sync::OnceLock;
7
8static ENV: OnceLock<CargoEnv> = OnceLock::new();
9
10struct CargoEnv {
11    features: Set<Name>,
12    cfgs: Map<Name, String>,
13}
14
15pub(super) struct CargoEnvCfgEvaluator;
16
17impl CfgEvaluator for CargoEnvCfgEvaluator {
18    fn eval(&self, name: &str, query_value: Option<&str>) -> CfgResult {
19        let env = ENV.get_or_init(CargoEnv::load);
20        if name == "feature" {
21            return if let Some(query_value) = query_value {
22                CfgResult::from(env.features.contains(Lookup::new(query_value)))
23            } else {
24                let msg = "expected `feature = \"...\"`".to_owned();
25                CfgResult::Undetermined { msg }
26            };
27        }
28        if name == "test" && query_value.is_none() {
29            let msg = "cfg(test) is not supported because Cargo runs your build script only once across the lib and test build of the same crate".to_owned();
30            return CfgResult::Undetermined { msg };
31        }
32        if let Some(cargo_value) = env.cfgs.get(Lookup::new(name)) {
33            return if let Some(query_value) = query_value {
34                CfgResult::from(cargo_value.split(',').any(|value| value == query_value))
35            } else {
36                CfgResult::True
37            };
38        }
39        if name == "debug_assertions" && query_value.is_none() {
40            return CfgResult::from(cfg!(debug_assertions));
41        }
42        CfgResult::False
43    }
44}
45
46impl CargoEnv {
47    fn load() -> Self {
48        const CARGO_FEATURE_PREFIX: &str = "CARGO_FEATURE_";
49        const CARGO_CFG_PREFIX: &str = "CARGO_CFG_";
50
51        let mut features = Set::new();
52        let mut cfgs = Map::new();
53        for (k, v) in env::vars_os() {
54            let Some(k) = k.to_str() else {
55                continue;
56            };
57            let Ok(v) = v.into_string() else {
58                continue;
59            };
60            if let Some(feature_name) = k.strip_prefix(CARGO_FEATURE_PREFIX) {
61                let feature_name = Name(feature_name.to_owned());
62                features.insert(feature_name);
63            } else if let Some(cfg_name) = k.strip_prefix(CARGO_CFG_PREFIX) {
64                let cfg_name = Name(cfg_name.to_owned());
65                cfgs.insert(cfg_name, v);
66            }
67        }
68        CargoEnv { features, cfgs }
69    }
70}
71
72struct Name(String);
73
74impl Ord for Name {
75    fn cmp(&self, rhs: &Self) -> Ordering {
76        Lookup::new(&self.0).cmp(Lookup::new(&rhs.0))
77    }
78}
79
80impl PartialOrd for Name {
81    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
82        Some(self.cmp(rhs))
83    }
84}
85
86impl Eq for Name {}
87
88impl PartialEq for Name {
89    fn eq(&self, rhs: &Self) -> bool {
90        Lookup::new(&self.0).eq(Lookup::new(&rhs.0))
91    }
92}
93
94#[repr(transparent)]
95struct Lookup(str);
96
97impl Lookup {
98    fn new(name: &str) -> &Self {
99        unsafe { &*(name as *const str as *const Self) }
100    }
101}
102
103impl Borrow<Lookup> for Name {
104    fn borrow(&self) -> &Lookup {
105        Lookup::new(&self.0)
106    }
107}
108
109impl Ord for Lookup {
110    fn cmp(&self, rhs: &Self) -> Ordering {
111        self.0
112            .bytes()
113            .map(CaseAgnosticByte)
114            .cmp(rhs.0.bytes().map(CaseAgnosticByte))
115    }
116}
117
118impl PartialOrd for Lookup {
119    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
120        Some(self.cmp(rhs))
121    }
122}
123
124impl Eq for Lookup {}
125
126impl PartialEq for Lookup {
127    fn eq(&self, rhs: &Self) -> bool {
128        self.0
129            .bytes()
130            .map(CaseAgnosticByte)
131            .eq(rhs.0.bytes().map(CaseAgnosticByte))
132    }
133}
134
135struct CaseAgnosticByte(u8);
136
137impl Ord for CaseAgnosticByte {
138    fn cmp(&self, rhs: &Self) -> Ordering {
139        self.0.to_ascii_lowercase().cmp(&rhs.0.to_ascii_lowercase())
140    }
141}
142
143impl PartialOrd for CaseAgnosticByte {
144    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
145        Some(self.cmp(rhs))
146    }
147}
148
149impl Eq for CaseAgnosticByte {}
150
151impl PartialEq for CaseAgnosticByte {
152    fn eq(&self, rhs: &Self) -> bool {
153        self.cmp(rhs) == Ordering::Equal
154    }
155}
cxx_build/cargo.rs

cxx_build/
cargo.rs
