opthash 0.10.2

Rust implementations of Elastic Hashing and Funnel Hashing
Documentation 
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fn main() {
    println!("cargo:rerun-if-env-changed=CARGO_CFG_TARGET_ARCH");
    println!("cargo:rerun-if-env-changed=CARGO_CFG_TARGET_FEATURE");
    println!("cargo:rerun-if-env-changed=CARGO_FEATURE_NIGHTLY");

    for cfg in [
        "opthash_avx512_group",
        "opthash_wide_group",
        "opthash_neon_group",
        "opthash_x86_16_group",
        "opthash_scalar_group",
        "opthash_avx2",
        "opthash_eq_bits_16",
    ] {
        println!("cargo:rustc-check-cfg=cfg({cfg})");
    }

    let nightly = std::env::var_os("CARGO_FEATURE_NIGHTLY").is_some();
    let arch = std::env::var("CARGO_CFG_TARGET_ARCH").unwrap_or_default();
    let features = std::env::var("CARGO_CFG_TARGET_FEATURE").unwrap_or_default();
    let has_feature = |feature: &str| features.split(',').any(|f| f == feature);

    // Only nightly AVX-512 builds use the 64-byte control-group layout.
    let avx512_group =
        nightly && arch == "x86_64" && has_feature("avx512f") && has_feature("avx512bw");
    let avx2 = arch == "x86_64" && has_feature("avx2");

    if avx512_group {
        println!("cargo:rustc-cfg=opthash_avx512_group");
        println!("cargo:rustc-cfg=opthash_wide_group");
    }
    if arch == "aarch64" {
        println!("cargo:rustc-cfg=opthash_neon_group");
    }
    if arch == "x86_64" && !avx512_group {
        println!("cargo:rustc-cfg=opthash_x86_16_group");
    }
    // AVX2 only widens the cold linear scan to 32 bytes.
    if avx2 {
        println!("cargo:rustc-cfg=opthash_avx2");
    }
    if !(avx512_group && avx2) {
        println!("cargo:rustc-cfg=opthash_eq_bits_16");
    }
    if arch != "x86_64" && arch != "aarch64" {
        println!("cargo:rustc-cfg=opthash_scalar_group");
    }
}