Function fs_write_atomic

crates/cache/src/lib.rs:324–333

Assumption: path inside cache directory. Then, we don't have to use sound OS-specific exclusive file access. Note: there's no need to remove temporary file here - cleanup task will do it later.

(path: &Path, reason: &str, contents: &[u8])

// Then, we don't have to use sound OS-specific exclusive file access.
// Note: there's no need to remove temporary file here - cleanup task will do it later.
fn fs_write_atomic(path: &Path, reason: &str, contents: &[u8]) -> io::Result<()> {
    let lock_path = path.with_extension(format!("wip-atomic-write-{reason}"));
    fs::OpenOptions::new()
        .create_new(true) // atomic file creation (assumption: no one will open it without this flag)
        .write(true)
        .open(&lock_path)
        .and_then(|mut file| file.write_all(contents))
        // file should go out of scope and be closed at this point
        .and_then(|()| fs::rename(&lock_path, &path)) // atomic file rename
}

#[cfg(test)]
mod tests;