zerocopy 0.8.56: zerocopy::Ref

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Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify zerocopy::Ref in pkg:cargo/zerocopy@0.8.56
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:cargo/zerocopy@0.8.56
Demonstrate these symbols/APIs:
  - zerocopy::Ref

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:c2c50e7a31bcd211681fe9b998413369ae5503e3337db7f803e6591d4801c8ec","contract":["Ref::from_bytes parses an exact-size byte slice into a typed Ref and provides access to fields via Deref","Ref::into_ref converts Ref into a native immutable reference of the target type","Ref::from_bytes on a mutable byte slice allows in-place mutation through DerefMut and Ref::into_mut","Ref::from_prefix and Ref::from_suffix split byte slices into a Ref and remaining unparsed byte slices","Ref::from_bytes returns CastError when the input slice length does not match the target type size"],"goal":"verify zerocopy::Ref in pkg:cargo/zerocopy@0.8.56","kind":"HOW","packages":["pkg:cargo/zerocopy@0.8.56"],"schemaVersion":1,"symbols":["zerocopy::Ref"]},"contractCommand":["cargo","run","--offline"],"environment":{"arch":"x64","distro":"alpine","ecosystem":"cargo","libc":"musl","os":"linux","packageManager":"cargo","schemaVersion":1},"license":"MIT-0","packages":["pkg:cargo/zerocopy@0.8.56"],"schemaVersion":1,"subject":"pkg:cargo/zerocopy@0.8.56","symbols":["zerocopy::Ref"],"verifierAdapter":"cargo@1"}

{
  "schemaVersion": 1,
  "goal": "verify zerocopy::Ref in pkg:cargo/zerocopy@0.8.56",
  "kind": "HOW",
  "packages": [
    "pkg:cargo/zerocopy@0.8.56"
  ],
  "symbols": [
    "zerocopy::Ref"
  ]
}

//! Clean-room verification sample for zerocopy.

pub use zerocopy::*;

use zerocopy::{FromBytes, Immutable, IntoBytes, KnownLayout, Ref, Unaligned};

#[derive(Clone, Copy, Debug, PartialEq, Eq, FromBytes, IntoBytes, KnownLayout, Immutable, Unaligned)]
#[repr(C)]
struct Header {
    magic: [u8; 4],
    version: u8,
    flags: u8,
    length: [u8; 2],
}

fn main() {
    let raw = [b'C', b'S', b'X', b'1', 1, 0, 0x00, 0x10];

    // 1. Ref::from_bytes parses an exact-size byte slice into a typed Ref and provides access to fields via Deref
    let r = Ref::<&[u8], Header>::from_bytes(&raw[..]).expect("from_bytes exact slice");
    assert_eq!(r.magic, *b"CSX1");
    assert_eq!(r.version, 1);
    assert_eq!(r.flags, 0);
    assert_eq!(r.length, [0x00, 0x10]);

    // 2. Ref::into_ref converts Ref into a native immutable reference of the target type
    let header_ref: &Header = Ref::into_ref(r);
    assert_eq!(header_ref.version, 1);
    assert_eq!(header_ref.length, [0x00, 0x10]);

    // 3. Ref::from_bytes on a mutable byte slice allows in-place mutation through DerefMut and Ref::into_mut
    let mut mut_buf = raw;
    {
        let mut r_mut = Ref::<&mut [u8], Header>::from_bytes(&mut mut_buf[..]).expect("from_bytes mut slice");
        r_mut.version = 2;
        let header_mut: &mut Header = Ref::into_mut(r_mut);
        header_mut.flags = 0xFF;
    }
    assert_eq!(mut_buf[4], 2);
    assert_eq!(mut_buf[5], 0xFF);

    // 4. Ref::from_prefix and Ref::from_suffix split byte slices into a Ref and remaining unparsed byte slices
    let extended = [b'C', b'S', b'X', b'1', 1, 0, 0, 0, 0xAA, 0xBB, 0xCC];
    let (r_prefix, suffix) = Ref::<&[u8], Header>::from_prefix(&extended[..]).expect("from_prefix");
    assert_eq!(r_prefix.magic, *b"CSX1");
    assert_eq!(suffix, &[0xAA, 0xBB, 0xCC]);

    let (prefix, r_suffix) = Ref::<&[u8], Header>::from_suffix(&extended[..]).expect("from_suffix");
    assert_eq!(prefix, &extended[..3]);
    assert_eq!(r_suffix.magic, [b'1', 1, 0, 0]);
    assert_eq!(r_suffix.version, 0);
    assert_eq!(r_suffix.flags, 0xAA);
    assert_eq!(r_suffix.length, [0xBB, 0xCC]);

    // 5. Ref::from_bytes returns CastError when the input slice length does not match the target type size
    let short = [0u8; 7];
    assert!(Ref::<&[u8], Header>::from_bytes(&short[..]).is_err());
    let long = [0u8; 9];
    assert!(Ref::<&[u8], Header>::from_bytes(&long[..]).is_err());

    println!("All zerocopy::Ref contract assertions passed successfully.");
}