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//! This selects the curve25519_dalek_bits either by default from target_pointer_width or explicitly set
#![deny(clippy::unwrap_used, dead_code)]
#[allow(non_camel_case_types)]
enum DalekBits {
Dalek32,
Dalek64,
}
fn main() {
let curve25519_dalek_bits = match std::env::var("CARGO_CFG_CURVE25519_DALEK_BITS").as_deref() {
Ok("32") => DalekBits::Dalek32,
Ok("64") => DalekBits::Dalek64,
_ => deterministic::determine_curve25519_dalek_bits(),
};
match curve25519_dalek_bits {
DalekBits::Dalek64 => println!("cargo:rustc-cfg=curve25519_dalek_bits=\"64\""),
DalekBits::Dalek32 => println!("cargo:rustc-cfg=curve25519_dalek_bits=\"32\""),
}
}
// Deterministic cfg(curve25519_dalek_bits) when this is not explicitly set.
mod deterministic {
use super::*;
// Standard Cargo TARGET environment variable of triplet is required
static ERR_MSG_NO_TARGET: &str = "Standard Cargo TARGET environment variable is not set";
// Custom Non-Rust standard target platforms require explicit settings.
static ERR_MSG_NO_PLATFORM: &str = "Unknown Rust target platform.";
// Warning when the curve25519_dalek_bits cannot be determined
fn determine_curve25519_dalek_bits_warning(cause: &str) {
println!("cargo:warning=\"Defaulting to curve25519_dalek_bits=32: {cause}\"");
}
// Determine the curve25519_dalek_bits based on Rust standard TARGET triplet
pub(super) fn determine_curve25519_dalek_bits() -> DalekBits {
use platforms::target::PointerWidth;
// TARGET environment is supplied by Cargo
// https://doc.rust-lang.org/cargo/reference/environment-variables.html
let target_triplet = match std::env::var("TARGET") {
Ok(t) => t,
Err(_) => {
determine_curve25519_dalek_bits_warning(ERR_MSG_NO_TARGET);
return DalekBits::Dalek32;
}
};
// platforms crate is the source of truth used to determine the platform
let platform = match platforms::Platform::find(&target_triplet) {
Some(p) => p,
None => {
determine_curve25519_dalek_bits_warning(ERR_MSG_NO_PLATFORM);
return DalekBits::Dalek32;
}
};
#[allow(clippy::match_single_binding)]
match platform.target_arch {
//Issues: 449 and 456
//TODO(Arm): Needs tests + benchmarks to back this up
//platforms::target::Arch::Arm => DalekBits::Dalek64,
//TODO(Wasm32): Needs tests + benchmarks to back this up
//platforms::target::Arch::Wasm32 => DalekBits::Dalek64,
_ => match platform.target_pointer_width {
PointerWidth::U64 => DalekBits::Dalek64,
PointerWidth::U32 => DalekBits::Dalek32,
// Intended default solely for non-32/64 target pointer widths
// Otherwise known target platforms only.
_ => DalekBits::Dalek32,
},
}
}
}