crc32fast 1.5.1

Fast, SIMD-accelerated CRC32 (IEEE) checksum computation
Documentation 
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use std::{env, process::Command};

fn main() {
    if let Some(minor_version) = minor_rustc_version() {
        // rustc 1.80 stabilized ARM CRC32 intrinsics:
        // https://doc.rust-lang.org/nightly/core/arch/aarch64/fn.__crc32d.html
        if minor_version >= 80 {
            println!("cargo:rustc-check-cfg=cfg(stable_arm_crc32_intrinsics)");
            println!("cargo:rustc-check-cfg=cfg(stable_vpclmulqdq)");
            println!("cargo:rustc-cfg=stable_arm_crc32_intrinsics");
        }

        // rustc 1.89 stabilized the x86 VPCLMULQDQ intrinsics (256-bit AVX2 and 512-bit AVX-512):
        // https://doc.rust-lang.org/core/arch/x86_64/fn._mm256_clmulepi64_epi128.html
        // Gating the wide fold paths on this keeps the crate MSRV unchanged on older toolchains.
        if minor_version >= 89 {
            println!("cargo:rustc-cfg=stable_vpclmulqdq");
        }
    }
}

fn minor_rustc_version() -> Option<u32> {
    Command::new(env::var_os("RUSTC")?)
        .arg("--version")
        .output()
        .ok()
        .and_then(|output| {
            std::str::from_utf8(&output.stdout).ok().and_then(|output| {
                output
                    .split('.')
                    .nth(1)
                    .and_then(|minor_version| minor_version.parse().ok())
            })
        })
}