1 files changed, 97 insertions, 0 deletions
diff --git a/src/fileutil.rs b/src/fileutil.rs
new file mode 100644
index 0000000..0bbafc0
--- /dev/null
+++ b/src/fileutil.rs
@@ -0,0 +1,97 @@
+use std::ffi::OsString;
+#[cfg(unix)]
+use std::os::unix::fs::OpenOptionsExt;
+use std::path::{Path, PathBuf};
+use std::{fs, io, mem};
+
+#[repr(transparent)]
+pub struct Temp {
+    path: PathBuf,
+}
+
+impl Drop for Temp {
+    fn drop(&mut self) {
+        if self.path.as_os_str().is_empty() {
+            return;
+        }
+        fs::remove_file(&self.path).expect("Failed to clean up temporary file");
+    }
+}
+
+impl Temp {
+    #[inline]
+    pub fn path(&self) -> &Path {
+        &*self.path
+    }
+
+    #[inline]
+    pub fn leave(mut self) -> PathBuf {
+        mem::replace(&mut self.path, PathBuf::new())
+    }
+
+    #[inline]
+    pub fn rename_to(self, to: impl AsRef<Path>) -> io::Result<()> {
+        fs::rename(self.leave(), to)
+    }
+}
+
+pub struct Writer {
+    inner: Temp,
+    file: fs::File,
+}
+
+impl Writer {
+    pub fn new(path: PathBuf) -> io::Result<Self> {
+        let mut file = fs::OpenOptions::new();
+        file.create_new(true);
+        file.append(true);
+        #[cfg(unix)]
+        file.mode(0o0600);
+        let file = file.open(&path)?;
+
+        Ok(Self {
+            inner: Temp { path },
+            file,
+        })
+    }
+
+    #[inline]
+    pub fn file(&mut self) -> &mut fs::File {
+        &mut self.file
+    }
+
+    #[inline]
+    pub fn sync_done(self) -> io::Result<Temp> {
+        self.file.sync_data()?;
+        Ok(self.inner)
+    }
+
+    #[inline]
+    pub fn done(self) -> Temp {
+        self.inner
+    }
+}
+
+pub fn update(path: &Path, data: &[u8]) -> io::Result<()> {
+    let mut tmp = OsString::from(path);
+    tmp.push(".tmp");
+    let mut tmp = Writer::new(PathBuf::from(tmp))?;
+    io::Write::write_all(tmp.file(), data)?;
+    tmp.sync_done()?.rename_to(path)
+}
+
+pub fn load(path: &Path) -> io::Result<Option<Vec<u8>>> {
+    let mut file = match fs::File::open(&path) {
+        Ok(file) => file,
+        Err(e) => {
+            if e.kind() == io::ErrorKind::NotFound {
+                return Ok(None);
+            }
+            return Err(e);
+        }
+    };
+
+    let mut data = Vec::new();
+    io::Read::read_to_end(&mut file, &mut data)?;
+    Ok(Some(data))
+}