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use std::{
ops::{Deref, DerefMut},
path::{Path, PathBuf},
};
use talpid_types::ErrorExt;
use tokio::{fs, io};
/// Stores content in a temporary file before moving it to the
/// final destination, ensuring that consumers of the file never
/// end up with partial content. Must be moved with `finalize`.
pub struct AtomicFile {
file: Option<fs::File>,
temp_path: PathBuf,
target_path: PathBuf,
}
impl AtomicFile {
pub async fn new<P: Into<PathBuf>>(target_path: P) -> io::Result<Self> {
let target_path = target_path.into();
let temp_path = target_path.with_file_name(uuid::Uuid::new_v4().to_string());
Ok(Self {
file: Some(fs::File::create(&temp_path).await?),
temp_path,
target_path,
})
}
/// Flushes and moves the file to `self.target_path`, replacing it if it exists.
pub async fn finalize(mut self) -> io::Result<()> {
let result = async {
let file = self.file.take().unwrap();
file.sync_all().await?;
let std_file = file.into_std().await;
let _ = tokio::task::spawn_blocking(move || drop(std_file)).await;
fs::rename(&self.temp_path, &self.target_path).await
}
.await;
if result.is_err() {
let _ = tokio::task::spawn_blocking(move || try_remove_file(&self.temp_path)).await;
}
result
}
}
impl Drop for AtomicFile {
fn drop(&mut self) {
if self.file.is_some() {
log::error!("{} was not finalized", self.target_path.display());
try_remove_file(&self.temp_path);
}
}
}
fn try_remove_file(temp_path: &Path) {
if let Err(error) = std::fs::remove_file(temp_path) {
let msg = format!("Failed to delete temp file: {}", temp_path.display());
log::warn!("{}", error.display_chain_with_msg(&msg));
}
}
impl Deref for AtomicFile {
type Target = fs::File;
fn deref(&self) -> &Self::Target {
self.file.as_ref().unwrap()
}
}
impl DerefMut for AtomicFile {
fn deref_mut(&mut self) -> &mut Self::Target {
self.file.as_mut().unwrap()
}
}
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