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|
//! This module implements (temporary) compatibility shims between
//! Tvix and C++ Nix.
//!
//! These are not intended to be long-lived, but should bootstrap Tvix
//! by piggybacking off functionality that already exists in Nix and
//! is still being implemented in Tvix.
use std::collections::HashMap;
use std::path::Path;
use std::process::Command;
use std::sync::RwLock;
use std::{io, path::PathBuf};
use smol_str::SmolStr;
use tvix_eval::{EvalIO, FileType, StdIO};
/// Compatibility implementation of [`EvalIO`] that uses C++ Nix to
/// write files to the Nix store.
pub struct NixCompatIO {
/// Most IO requests are tunneled through to [`tvix_eval::StdIO`]
/// instead.
underlying: StdIO,
/// Cache paths for identical files being imported to the store.
// TODO(tazjin): This could be done better by having a thunk cache
// for these calls on the eval side, but that is a little more
// complex.
import_cache: RwLock<HashMap<PathBuf, PathBuf>>,
}
impl EvalIO for NixCompatIO {
fn store_dir(&self) -> Option<String> {
Some("/nix/store".into())
}
// Pass path imports through to `nix-store --add`
fn import_path(&mut self, path: &Path) -> Result<PathBuf, io::Error> {
let path = path.to_owned();
if let Some(path) = self
.import_cache
.read()
.map_err(|e| io::Error::new(io::ErrorKind::Other, e.to_string()))?
.get(&path)
{
return Ok(path.to_path_buf());
}
let store_path = self.add_to_store(&path)?;
self.import_cache
.write()
.map_err(|e| io::Error::new(io::ErrorKind::Other, e.to_string()))?
.insert(path, store_path.clone());
Ok(store_path)
}
// Pass the rest of the functions through to `Self::underlying`
fn path_exists(&mut self, path: &Path) -> Result<bool, io::Error> {
if path.starts_with("/__corepkgs__") {
return Ok(true);
}
self.underlying.path_exists(path)
}
fn read_to_string(&mut self, path: &Path) -> Result<String, io::Error> {
// Bundled version of corepkgs/fetchurl.nix. This workaround
// is similar to what cppnix does for passing the path
// through.
//
// TODO: this comparison is bad and allocates, we should use
// the sane path library.
if path.starts_with("/__corepkgs__/fetchurl.nix") {
return Ok(include_str!("fetchurl.nix").to_string());
}
self.underlying.read_to_string(path)
}
fn read_dir(&mut self, path: &Path) -> Result<Vec<(SmolStr, FileType)>, io::Error> {
self.underlying.read_dir(path)
}
}
impl NixCompatIO {
pub fn new() -> Self {
NixCompatIO {
underlying: StdIO,
import_cache: RwLock::new(HashMap::new()),
}
}
/// Add a path to the Nix store using the `nix-store --add`
/// functionality from C++ Nix.
fn add_to_store(&self, path: &Path) -> Result<PathBuf, io::Error> {
if !path.try_exists()? {
return Err(io::Error::from(io::ErrorKind::NotFound));
}
let mut cmd = Command::new("nix-store");
cmd.arg("--add");
cmd.arg(path);
let out = cmd.output()?;
if !out.status.success() {
return Err(io::Error::new(
io::ErrorKind::Other,
String::from_utf8_lossy(&out.stderr).trim().to_owned(),
));
}
let out_path_str = String::from_utf8(out.stdout)
.map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err))?;
let out_path_trimmed = out_path_str.trim();
let mut out_path = PathBuf::new();
out_path.push(out_path_trimmed);
Ok(out_path)
}
}
|
