Add exists method on Dir (#33)

embedded-fatfs/src/dir.rs

@@ -194,6 +194,43 @@ impl<'a, IO: ReadWriteSeek, TP: TimeProvider, OCC: OemCpConverter> Dir<'a, IO, T
         }
     }
 
+    /// Check to see if a file or directory with the given name exists
+    pub async fn exists(&self, path: &str) -> Result<bool, Error<IO::Error>> {
+        self.exists_internal(path, None).await
+    }
+
+    /// Check to see if a file with the given name exists
+    pub async fn file_exists(&self, path: &str) -> Result<bool, Error<IO::Error>> {
+        self.exists_internal(path, Some(false)).await
+    }
+
+    /// Check to see if a directory with the given name exists
+    pub async fn dir_exists(&self, path: &str) -> Result<bool, Error<IO::Error>> {
+        self.exists_internal(path, Some(true)).await
+    }
+
+    async fn exists_internal(&self, mut path: &str, is_dir: Option<bool>) -> Result<bool, Error<IO::Error>> {
+        let mut dir = self.clone();
+        // traverse path
+        while let (name, Some(rest)) = split_path(path) {
+            dir = dir.find_entry(name, Some(true), None).await?.to_dir();
+            path = rest;
+        }
+        let (name, _rest) = split_path(path);
+
+        // check if name exists and matches the is_dir flag
+        match dir.find_entry(name, None, None).await {
+            Ok(e) => match is_dir {
+                None => Ok(true),
+                Some(is_dir) => Ok(e.is_dir() == is_dir),
+            },
+            Err(e) => match e {
+                Error::NotFound => Ok(false),
+                _ => Err(e),
+            },
+        }
+    }
+
     /// Opens existing subdirectory.
     ///
     /// `path` is a '/' separated directory path relative to self directory.

embedded-fatfs/tests/read.rs

@@ -247,6 +247,46 @@ async fn test_get_file_by_path_fat32() {
     test_get_file_by_path(create_fs(FAT32_IMG).await).await
 }
 
+async fn test_exists(fs: FileSystem) {
+    let root_dir = fs.root_dir();
+
+    // check for existence of existing dir
+    assert_eq!(root_dir.exists("very/long/path").await.unwrap(), true);
+    assert_eq!(root_dir.file_exists("very/long/path").await.unwrap(), false);
+    assert_eq!(root_dir.dir_exists("very/long/path").await.unwrap(), true);
+    // check for existence of existing file
+    assert_eq!(root_dir.exists("very/long/path/test.txt").await.unwrap(), true);
+    assert_eq!(root_dir.file_exists("very/long/path/test.txt").await.unwrap(), true);
+    assert_eq!(root_dir.dir_exists("very/long/path/test.txt").await.unwrap(), false);
+    // check for existence of non existing file
+    assert_eq!(root_dir.exists("very/long/path/missing.txt").await.unwrap(), false);
+    assert_eq!(root_dir.file_exists("very/long/path/missing.txt").await.unwrap(), false);
+    assert_eq!(root_dir.dir_exists("very/long/path/missing.txt").await.unwrap(), false);
+    // check for existence of invalid path
+    assert!(root_dir.exists("very/missing/path/test.txt").await.is_err());
+    assert!(root_dir.file_exists("very/missing/path/test.txt").await.is_err());
+    assert!(root_dir.dir_exists("very/missing/path/test.txt").await.is_err());
+    // check for existence of invalid path containing file as non-last component
+    assert!(root_dir.exists("very/missing/path/test.txt/abc").await.is_err());
+    assert!(root_dir.file_exists("very/missing/path/test.txt/abc").await.is_err());
+    assert!(root_dir.dir_exists("very/missing/path/test.txt/abc").await.is_err());
+}
+
+#[tokio::test]
+async fn test_exists_fat12() {
+    test_exists(create_fs(FAT12_IMG).await).await
+}
+
+#[tokio::test]
+async fn test_exists_fat16() {
+    test_exists(create_fs(FAT16_IMG).await).await
+}
+
+#[tokio::test]
+async fn test_exists_fat32() {
+    test_exists(create_fs(FAT32_IMG).await).await
+}
+
 async fn test_volume_metadata(fs: FileSystem, fat_type: FatType) {
     assert_eq!(fs.volume_id(), 0x1234_5678);
     assert_eq!(fs.volume_label(), "Test!");