1 files changed, 98 insertions, 0 deletions
diff --git a/crates/common/tedge_utils/src/fs.rs b/crates/common/tedge_utils/src/fs.rs
new file mode 100644
index 00000000..197c6b8a
--- /dev/null
+++ b/crates/common/tedge_utils/src/fs.rs
@@ -0,0 +1,98 @@
+use std::{fs as std_fs, io::Write, path::Path};
+
+use tokio::{fs as tokio_fs, io::AsyncWriteExt};
+
+/// Write file to filesystem atomically using std::fs synchronously.
+pub fn atomically_write_file_sync(
+    tempfile: impl AsRef<Path>,
+    dest: impl AsRef<Path>,
+    content: &[u8],
+) -> std::io::Result<()> {
+    let mut file = std_fs::OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(tempfile.as_ref())?;
+
+    if let Err(err) = file.write_all(content) {
+        let _ = std_fs::remove_file(tempfile);
+        return Err(err);
+    }
+
+    if let Err(err) = std_fs::rename(tempfile.as_ref(), dest) {
+        let _ = std_fs::remove_file(tempfile);
+        return Err(err);
+    }
+
+    Ok(())
+}
+
+/// Write file to filesystem atomically using tokio::fs asynchronously.
+pub async fn atomically_write_file_async(
+    tempfile: impl AsRef<Path>,
+    dest: impl AsRef<Path>,
+    content: &[u8],
+) -> std::io::Result<()> {
+    let mut file = tokio_fs::OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(tempfile.as_ref())
+        .await?;
+
+    if let Err(err) = file.write_all(content).await {
+        let () = tokio_fs::remove_file(tempfile).await?;
+        return Err(err);
+    }
+
+    if let Err(err) = tokio_fs::rename(tempfile.as_ref(), dest).await {
+        let () = tokio_fs::remove_file(tempfile).await?;
+        return Err(err);
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::fs::{atomically_write_file_async, atomically_write_file_sync};
+
+    use tempfile::tempdir;
+
+    #[tokio::test]
+    async fn atomically_write_file_file_async() {
+        let temp_dir = tempdir().unwrap();
+        let temp_path = temp_dir.path().join("test1");
+        let destination_path = temp_dir.path().join("test2");
+
+        let content = "test_data";
+
+        let () = atomically_write_file_async(&temp_path, &destination_path, content.as_bytes())
+            .await
+            .unwrap();
+
+        std::fs::File::open(&temp_path).unwrap_err();
+        if let Ok(destination_content) = std::fs::read(&destination_path) {
+            assert_eq!(destination_content, content.as_bytes());
+        } else {
+            panic!("failed to read the new file");
+        }
+    }
+
+    #[test]
+    fn atomically_write_file_file_sync() {
+        let temp_dir = tempdir().unwrap();
+        let temp_path = temp_dir.path().join("test1");
+        let destination_path = temp_dir.path().join("test2");
+
+        let content = "test_data";
+
+        let () =
+            atomically_write_file_sync(&temp_path, &destination_path, content.as_bytes()).unwrap();
+
+        std::fs::File::open(&temp_path).unwrap_err();
+        if let Ok(destination_content) = std::fs::read(&destination_path) {
+            assert_eq!(destination_content, content.as_bytes());
+        } else {
+            panic!("failed to read the new file");
+        }
+    }
+}