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|
//! The exhaustive differential check described in `PROOF.md`.
//!
//! This is separate from `tests/differential.rs` because it is a different
//! kind of claim. That runner asks whether a handful of hand-written cases
//! agree; this one enumerates *entire input domains* — every two-byte input
//! to the decoder, every two-byte input to the encoder, every single byte
//! through `encode_str` and `HexDisplay` — and compares the complete output
//! of both programs byte for byte.
//!
//! The driver in `proof/main.rs` references base16ct's own module files in
//! place, so this cannot drift from what `tests/cases/026-base16ct-crate/`
//! transpiles.
use std::fs;
use std::io::Write as _;
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};
const RUSTNIM: &str = env!("CARGO_BIN_EXE_rustnim");
fn find_nim() -> PathBuf {
if let Ok(p) = std::env::var("RUSTNIM_NIM") {
return PathBuf::from(p);
}
let mut dir: Option<&Path> = Some(Path::new(env!("CARGO_MANIFEST_DIR")));
while let Some(d) = dir {
let c = d.join(".nim-toolchain/bin/nim");
if c.is_file() {
return c;
}
dir = d.parent();
}
panic!("no .nim-toolchain/bin/nim found; set RUSTNIM_NIM");
}
fn sh(cmd: &mut Command, what: &str) -> Vec<u8> {
let out = cmd
.stdout(Stdio::piped())
.stderr(Stdio::piped())
.output()
.unwrap_or_else(|e| panic!("{what}: spawn: {e}"));
if !out.status.success() {
let mut msg = String::from_utf8_lossy(&out.stderr).into_owned();
if msg.trim().is_empty() {
msg = String::from_utf8_lossy(&out.stdout).into_owned();
}
panic!("{what} failed ({:?}):\n{}", out.status.code(), tail(&msg));
}
out.stdout
}
fn tail(s: &str) -> String {
let v: Vec<&str> = s.trim_end().lines().collect();
v[v.len().saturating_sub(25)..].join("\n")
}
/// Report the first differing line, and how many lines differ in total.
fn first_difference(a: &[u8], b: &[u8]) -> String {
let (sa, sb) = (String::from_utf8_lossy(a), String::from_utf8_lossy(b));
let (la, lb): (Vec<_>, Vec<_>) = (sa.lines().collect(), sb.lines().collect());
let mut first = None;
let mut count = 0usize;
for i in 0..la.len().max(lb.len()) {
if la.get(i) != lb.get(i) {
count += 1;
if first.is_none() {
first = Some(i);
}
}
}
match first {
None => format!("{} vs {} bytes, but every line matches", a.len(), b.len()),
Some(i) => format!(
"{count} line(s) differ; first at line {}:\n rustc: {:?}\n nim : {:?}",
i + 1,
la.get(i),
lb.get(i)
),
}
}
#[test]
fn base16ct_is_byte_identical_over_the_enumerated_domains() {
let root = Path::new(env!("CARGO_MANIFEST_DIR"));
let work = root.join("tests/.work/proof");
let _ = fs::remove_dir_all(&work);
fs::create_dir_all(&work).unwrap();
let driver = root.join("proof/main.rs");
let crate_dir = root.join("tests/cases/026-base16ct-crate");
let mut modules: Vec<PathBuf> = fs::read_dir(&crate_dir)
.unwrap()
.filter_map(|e| e.ok().map(|e| e.path()))
.filter(|p| {
p.extension().is_some_and(|x| x == "rs")
&& p.file_name().is_some_and(|f| f != "main.rs")
})
.collect();
modules.sort();
assert!(
modules.len() == 5,
"expected base16ct's five module files, found {:?}",
modules
);
// -- rustc: the oracle.
let rs_bin = work.join("rs");
sh(
Command::new("rustc")
.arg("--edition=2021")
.arg("--cfg")
.arg("feature=\"alloc\"")
.arg("-A")
.arg("warnings")
.arg(&driver)
.arg("-o")
.arg(&rs_bin)
.env("TMPDIR", &work),
"rustc",
);
let expected = sh(&mut Command::new(&rs_bin).env("TMPDIR", &work), "the Rust binary");
// -- rustnim, then Nim.
let nim_src = work.join("proof.nim");
let mut t = Command::new(RUSTNIM);
t.arg(&driver);
for m in &modules {
t.arg(m);
}
t.arg("--cfg")
.arg("feature=alloc")
.arg("-o")
.arg(&nim_src)
.env("TMPDIR", &work);
sh(&mut t, "rustnim");
let meta = fs::metadata(&nim_src).expect("rustnim wrote no output file");
assert!(meta.len() > 0, "rustnim wrote an empty output file");
let nim_bin = work.join("nim");
sh(
Command::new(find_nim())
.arg("c")
.arg("--hints:off")
.arg("--warnings:off")
.arg("--colors:off")
.arg(format!("--nimcache:{}", work.join("cache").display()))
.arg(format!("-o:{}", nim_bin.display()))
.arg(&nim_src)
.env("TMPDIR", &work),
"nim c",
);
let actual = sh(&mut Command::new(&nim_bin).env("TMPDIR", &work), "the Nim binary");
// The output must be substantial: an empty or truncated run agreeing with
// an empty or truncated run would otherwise read as success, which is the
// exact failure this project exists to avoid.
let lines = expected.iter().filter(|b| **b == b'\n').count();
assert!(
lines > 150_000 && expected.ends_with(b"done\n"),
"the oracle did not run to completion: {lines} lines, {} bytes",
expected.len()
);
assert!(
expected == actual,
"outputs differ.\n{}",
first_difference(&expected, &actual)
);
let _ = writeln!(
std::io::stderr(),
"proof: {} cases, {} bytes of output, byte-identical",
lines,
expected.len()
);
}
|