Support reading volume label from root directory

TODO.md

@@ -1,6 +1,5 @@
 TODO
 ====
-* support for a volume label file in the root directory
 * format volume API
 * add method for getting `DirEntry` from a path (possible names: metadata, lookup)
 * do not create LFN entries if the name fits in a SFN entry

src/dir.rs

@@ -106,11 +106,7 @@ impl<'a, T: ReadWriteSeek + 'a> Dir<'a, T> {
 
     /// Creates directory entries iterator.
     pub fn iter(&self) -> DirIter<'a, T> {
-        DirIter {
-            stream: self.stream.clone(),
-            fs: self.fs,
-            err: false,
-        }
+        DirIter::new(self.stream.clone(), self.fs, true)
     }
 
     fn find_entry(
@@ -138,6 +134,16 @@ impl<'a, T: ReadWriteSeek + 'a> Dir<'a, T> {
         Err(io::Error::new(ErrorKind::NotFound, "No such file or directory"))
     }
 
+    pub(crate) fn find_volume_entry(&self) -> io::Result<Option<DirEntry<'a, T>>> {
+        for r in DirIter::new(self.stream.clone(), self.fs, false) {
+            let e = r?;
+            if e.data.is_volume() {
+                return Ok(Some(e));
+            }
+        }
+        Ok(None)
+    }
+
     fn check_for_existence(&self, name: &str, is_dir: Option<bool>) -> io::Result<DirEntryOrShortName<'a, T>> {
         let mut short_name_gen = ShortNameGenerator::new(name);
         loop {
@@ -453,10 +459,28 @@ impl<'a, T: ReadWriteSeek> Clone for Dir<'a, T> {
 pub struct DirIter<'a, T: ReadWriteSeek + 'a> {
     stream: DirRawStream<'a, T>,
     fs: &'a FileSystem<T>,
+    skip_volume: bool,
     err: bool,
 }
 
 impl<'a, T: ReadWriteSeek> DirIter<'a, T> {
+    fn new(stream: DirRawStream<'a, T>, fs: &'a FileSystem<T>, skip_volume: bool) -> Self {
+        DirIter {
+            stream, fs, skip_volume,
+            err: false,
+        }
+    }
+
+    fn should_ship_entry(&self, raw_entry: &DirEntryData) -> bool {
+        if raw_entry.is_deleted() {
+            return true;
+        }
+        match raw_entry {
+            DirEntryData::File(sfn_entry) => self.skip_volume && sfn_entry.is_volume(),
+            _ => false,
+        }
+    }
+
     fn read_dir_entry(&mut self) -> io::Result<Option<DirEntry<'a, T>>> {
         #[cfg(feature = "alloc")]
         let mut lfn_buf = LongNameBuilder::new();
@@ -465,19 +489,19 @@ impl<'a, T: ReadWriteSeek> DirIter<'a, T> {
         loop {
             let raw_entry = DirEntryData::deserialize(&mut self.stream)?;
             offset += DIR_ENTRY_SIZE;
-            match raw_entry {
-                DirEntryData::File(data) => {
-                    // Check if this is end of dif
-                    if data.is_end() {
+            // Check if this is end of dir
+            if raw_entry.is_end() {
                 return Ok(None);
             }
             // Check if this is deleted or volume ID entry
-                    if data.is_deleted() || data.is_volume() {
+            if self.should_ship_entry(&raw_entry) {
                 #[cfg(feature = "alloc")]
                 lfn_buf.clear();
                 begin_offset = offset;
                 continue;
             }
+            match raw_entry {
+                DirEntryData::File(data) => {
                     // Get entry position on volume
                     let abs_pos = self.stream.abs_pos().map(|p| p - DIR_ENTRY_SIZE);
                     // Check if LFN checksum is valid
@@ -496,13 +520,6 @@ impl<'a, T: ReadWriteSeek> DirIter<'a, T> {
                     }));
                 },
                 DirEntryData::Lfn(data) => {
-                    // Check if this is deleted entry
-                    if data.is_deleted() {
-                        #[cfg(feature = "alloc")]
-                        lfn_buf.clear();
-                        begin_offset = offset;
-                        continue;
-                    }
                     // Append to LFN buffer
                     #[cfg(feature = "alloc")]
                     lfn_buf.process(&data);
@@ -519,6 +536,7 @@ impl<'a, T: ReadWriteSeek> Clone for DirIter<'a, T> {
             stream: self.stream.clone(),
             fs: self.fs,
             err: self.err,
+            skip_volume: self.skip_volume,
         }
     }
 }

src/fs.rs

@@ -494,11 +494,44 @@ impl<T: ReadWriteSeek> FileSystem<T> {
     /// Note: File with `VOLUME_ID` attribute in root directory is ignored by this library.
     /// Only label from BPB is used.
     pub fn volume_label_as_bytes(&self) -> &[u8] {
+        const PADDING: u8 = 0x20;
         let full_label_slice = &self.bpb.volume_label;
-        let len = full_label_slice.iter().rposition(|b| *b != 0x20).map(|p| p + 1).unwrap_or(0);
+        let len = full_label_slice.iter().rposition(|b| *b != PADDING).map(|p| p + 1).unwrap_or(0);
         &full_label_slice[..len]
     }
 
+    /// Returns a volume label from root directory as `String`.
+    ///
+    /// It finds file with `VOLUME_ID` attribute and returns its short name.
+    #[cfg(feature = "alloc")]
+    pub fn read_volume_label_from_root_dir(&self) -> io::Result<Option<String>> {
+        // Note: DirEntry::file_short_name() cannot be used because it interprets name as 8.3
+        // (adds dot before an extension)
+        let volume_label_opt = self.read_volume_label_from_root_dir_as_bytes()?;
+        if let Some(volume_label) = volume_label_opt {
+            const PADDING: u8 = 0x20;
+            // Strip label padding
+            let len = volume_label.iter().rposition(|b| *b != PADDING).map(|p| p + 1).unwrap_or(0);
+            let label_slice = &volume_label[..len];
+            // Decode volume label from OEM codepage
+            let volume_label_iter = label_slice.iter().cloned();
+            let char_iter = volume_label_iter.map(|c| self.options.oem_cp_converter.decode(c));
+            // Build string from character iterator
+            Ok(Some(String::from_iter(char_iter)))
+        } else {
+            Ok(None)
+        }
+    }
+
+    /// Returns a volume label from root directory as byte array.
+    ///
+    /// Label is encoded in the OEM codepage.
+    /// It finds file with `VOLUME_ID` attribute and returns its short name.
+    pub fn read_volume_label_from_root_dir_as_bytes(&self) -> io::Result<Option<[u8; 11]>> {
+        let entry_opt = self.root_dir().find_volume_entry()?;
+        Ok(entry_opt.map(|e| *e.raw_short_name()))
+    }
+
     /// Returns a root directory object allowing for futher penetration of a filesystem structure.
     pub fn root_dir<'b>(&'b self) -> Dir<'b, T> {
         let root_rdr = {

tests/read.rs

@@ -187,6 +187,7 @@ fn test_get_file_by_path_fat32() {
 fn test_volume_metadata(fs: FileSystem, fat_type: FatType) {
     assert_eq!(fs.volume_id(), 0x12345678);
     assert_eq!(fs.volume_label(), "Test!");
+    assert_eq!(&fs.read_volume_label_from_root_dir().unwrap().unwrap(), "Test!");
     assert_eq!(fs.fat_type(), fat_type);
 }