zerocopy 0.8.42

Zerocopy makes zero-cost memory manipulation effortless. We write "unsafe" so you don't have to.
Documentation 
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// Copyright 2026 The Fuchsia Authors
//
// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
// This file may not be copied, modified, or distributed except according to
// those terms.

#![cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)]

use std::{path::PathBuf, process::Command};

enum Directive {
    Asm,
    Mca,
}

impl Directive {
    fn arg(&self) -> &'static str {
        match self {
            Directive::Asm => "--asm",
            Directive::Mca => "--mca",
        }
    }

    fn ext(&self) -> &'static str {
        match self {
            Directive::Asm => "",
            Directive::Mca => ".mca",
        }
    }
}

fn run_codegen_test(bench_name: &str, target_cpu: &str, bless: bool) {
    println!("Testing {bench_name}.{target_cpu}");

    let manifest_path = env!("CARGO_MANIFEST_PATH");
    let target_dir = env!("CARGO_TARGET_DIR");

    let cargo_asm = |directive: &Directive| {
        Command::new("cargo")
            .args([
                "asm",
                "-p",
                "zerocopy",
                "--manifest-path",
                manifest_path,
                "--target-dir",
                target_dir,
                "--bench",
                bench_name,
                "--target-cpu",
                target_cpu,
                "--simplify",
                directive.arg(),
                &format!("bench_{bench_name}"),
            ])
            .output()
            .expect("failed to execute process")
    };

    let test_directive = |directive: Directive| {
        let output = cargo_asm(&directive);
        let actual_result = output.stdout;

        if !(output.status.success()) {
            panic!(
                "{}\n{}",
                String::from_utf8_lossy(&actual_result),
                String::from_utf8_lossy(&output.stderr)
            );
        }

        let expected_file_path = {
            let ext = directive.ext();
            let mut path: PathBuf = env!("CARGO_MANIFEST_DIR").into();
            path.push("benches");
            let file_name = format!("{bench_name}.{target_cpu}{ext}",);
            path.push(file_name);
            path
        };

        if bless {
            std::fs::write(expected_file_path, &actual_result).unwrap();
        } else {
            let expected_result = std::fs::read(expected_file_path).unwrap_or_default();
            if actual_result != expected_result {
                let expected = String::from_utf8_lossy(&expected_result[..]);
                panic!("Bless codegen tests with BLESS=1\nGot unexpected output:\n{}", expected);
            }
        }
    };

    test_directive(Directive::Asm);
    test_directive(Directive::Mca);
}

#[test]
#[cfg_attr(miri, ignore)]
fn codegen() {
    let bless = std::env::var("BLESS").is_ok();
    let paths = std::fs::read_dir("benches").unwrap();
    for path in paths {
        let path = path.unwrap().path();
        if !path.extension().map(|s| s == "rs").unwrap_or(false) {
            continue;
        }
        let path = path.file_stem().unwrap().to_str().unwrap();
        run_codegen_test(path, "x86-64", bless);
    }
}