Fix multiple corner cases and simplify code.

src/dir.rs

@@ -74,7 +74,7 @@ pub(crate) struct DirFileEntryData {
     modify_time: u16,
     modify_date: u16,
     first_cluster_lo: u16,
-    pub(crate) size: u32,
+    size: u32,
 }
 
 impl DirFileEntryData {
@@ -93,6 +93,10 @@ impl DirFileEntryData {
         self.size
     }
     
+    pub(crate) fn set_size(&mut self, size: u32) {
+        self.size = size;
+    }
+    
     pub fn is_dir(&self) -> bool {
         self.attrs.contains(FileAttributes::DIRECTORY)
     }
@@ -107,7 +111,7 @@ impl DirFileEntryData {
     }
     
     pub(crate) fn serialize(&self, wrt: &mut Write) -> io::Result<()> {
-        wrt.write(&self.name)?;
+        wrt.write_all(&self.name)?;
         wrt.write_u8(self.attrs.bits())?;
         wrt.write_u8(self.reserved_0)?;
         wrt.write_u8(self.create_time_0)?;
@@ -150,7 +154,7 @@ pub struct Date {
 }
 
 impl Date {
-    pub(crate) fn from_word(dos_date: u16) -> Self {
+    pub(crate) fn from_u16(dos_date: u16) -> Self {
         let (year, month, day) = ((dos_date >> 9) + 1980, (dos_date >> 5) & 0xF, dos_date & 0x1F);
         Date { year, month, day }
     }
@@ -168,7 +172,7 @@ pub struct Time {
 }
 
 impl Time {
-    pub(crate) fn from_word(dos_time: u16) -> Self {
+    pub(crate) fn from_u16(dos_time: u16) -> Self {
         let (hour, min, sec) = (dos_time >> 11, (dos_time >> 5) & 0x3F, (dos_time & 0x1F) * 2);
         Time { hour, min, sec }
     }
@@ -185,10 +189,10 @@ pub struct DateTime {
 }
 
 impl DateTime {
-    pub(crate) fn from_words(dos_date: u16, dos_time: u16) -> Self {
+    pub(crate) fn from_u16(dos_date: u16, dos_time: u16) -> Self {
         DateTime {
-            date: Date::from_word(dos_date),
+            date: Date::from_u16(dos_date),
-            time: Time::from_word(dos_time),
+            time: Time::from_u16(dos_time),
         }
     }
 }
@@ -256,11 +260,11 @@ impl <'a, 'b> DirEntry<'a, 'b> {
     }
     
     pub fn is_dir(&self) -> bool {
-        self.data.attrs.contains(FileAttributes::DIRECTORY)
+        self.data.is_dir()
     }
     
     pub fn is_file(&self) -> bool {
-        !self.is_dir()
+        self.data.is_file()
     }
     
     pub(crate) fn first_cluster(&self) -> Option<u32> {
@@ -295,15 +299,15 @@ impl <'a, 'b> DirEntry<'a, 'b> {
     }
     
     pub fn created(&self) -> DateTime {
-        DateTime::from_words(self.data.create_date, self.data.create_time_1)
+        DateTime::from_u16(self.data.create_date, self.data.create_time_1)
     }
     
     pub fn accessed(&self) -> Date {
-        Date::from_word(self.data.access_date)
+        Date::from_u16(self.data.access_date)
     }
     
     pub fn modified(&self) -> DateTime {
-        DateTime::from_words(self.data.modify_date, self.data.modify_time)
+        DateTime::from_u16(self.data.modify_date, self.data.modify_time)
     }
 }
 

src/file.rs

@@ -8,11 +8,15 @@ use dir::{FileEntryInfo, DateTime};
 
 #[derive(Clone)]
 pub struct File<'a, 'b: 'a> {
+    // Note first_cluster is None if file is empty
     first_cluster: Option<u32>,
     // Note: if offset points between clusters current_cluster is the previous cluster
     current_cluster: Option<u32>,
+    // current position in this file
     offset: u32,
+    // file dir entry - None for root dir
     entry: Option<FileEntryInfo>,
+    // should file dir entry be flushed?
     entry_dirty: bool,
     fs: FileSystemRef<'a, 'b>,
 }
@@ -31,7 +35,7 @@ impl <'a, 'b> File<'a, 'b> {
         match self.entry {
             Some(ref mut e) => {
                 if self.offset > e.data.size() {
-                    e.data.size = self.offset;
+                    e.data.set_size(self.offset);
                     self.entry_dirty = true;
                 }
             },
@@ -42,11 +46,11 @@ impl <'a, 'b> File<'a, 'b> {
     pub fn truncate(&mut self) -> io::Result<()> {
         match self.entry {
             Some(ref mut e) => {
-                if e.data.size == self.offset {
+                if e.data.size() == self.offset {
                     return Ok(());
                 }
                 
-                e.data.size = self.offset;
+                e.data.set_size(self.offset);
                 if self.offset == 0 {
                     e.data.set_first_cluster(None);
                 }
@@ -55,15 +59,21 @@ impl <'a, 'b> File<'a, 'b> {
             _ => {},
         }
         if self.offset > 0 {
-            self.fs.cluster_iter(self.current_cluster.unwrap()).truncate()
+            debug_assert!(self.current_cluster.is_some());
+            self.fs.cluster_iter(self.current_cluster.unwrap()).truncate() // safe
         } else {
-            self.fs.cluster_iter(self.first_cluster.unwrap()).free()?;
+            debug_assert!(self.current_cluster.is_none());
+            match self.first_cluster {
+                Some(n) => self.fs.cluster_iter(n).free()?,
+                _ => {},
+            }
             self.first_cluster = None;
             Ok(())
         }
     }
     
     pub(crate) fn global_pos(&self) -> Option<u64> {
+        // Returns current position relative to filesystem start
         // Note: when between clusters it returns position after previous cluster
         match self.current_cluster {
             Some(n) => {
@@ -78,11 +88,13 @@ impl <'a, 'b> File<'a, 'b> {
     
     pub(crate) fn flush_dir_entry(&self) -> io::Result<()> {
         if self.entry_dirty {
-            self.entry.iter().next().unwrap().write(self.fs)
+            match self.entry {
-        } else {
+                Some(ref e) => e.write(self.fs)?,
-            Ok(())
+                _ => {},
             }
         }
+        Ok(())
+    }
     
     pub fn set_modified(&mut self, date_time: DateTime) {
         match self.entry {
@@ -98,7 +110,7 @@ impl <'a, 'b> File<'a, 'b> {
         match self.entry {
             Some(ref e) => {
                 if e.data.is_file() {
-                    Some((e.data.size - self.offset) as usize)
+                    Some((e.data.size() - self.offset) as usize)
                 } else {
                     None
                 }
@@ -127,9 +139,7 @@ impl<'a, 'b> Drop for File<'a, 'b> {
 
 impl<'a, 'b> Read for File<'a, 'b> {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        let mut buf_offset: usize = 0;
         let cluster_size = self.fs.get_cluster_size();
-        loop {
         let current_cluster_opt = if self.offset % cluster_size == 0 {
             // next cluster
             match self.current_cluster {
@@ -148,49 +158,44 @@ impl<'a, 'b> Read for File<'a, 'b> {
         };
         let current_cluster = match current_cluster_opt {
             Some(n) => n,
-                None => break,
+            None => return Ok(0),
         };
         let offset_in_cluster = self.offset % cluster_size;
         let bytes_left_in_cluster = (cluster_size - offset_in_cluster) as usize;
         let bytes_left_in_file = self.bytes_left_in_file().unwrap_or(bytes_left_in_cluster);
-            let bytes_left_in_buf = buf.len() - buf_offset;
+        let read_size = cmp::min(cmp::min(buf.len(), bytes_left_in_cluster), bytes_left_in_file);
-            let read_size = cmp::min(cmp::min(bytes_left_in_buf, bytes_left_in_cluster), bytes_left_in_file);
         if read_size == 0 {
-                break;
+            return Ok(0);
         }
         //println!("read c {} n {}", current_cluster, read_size);
         let offset_in_fs = self.fs.offset_from_cluster(current_cluster) + (offset_in_cluster as u64);
         let read_bytes = {
             let mut disk = self.fs.disk.borrow_mut();
             disk.seek(SeekFrom::Start(offset_in_fs))?;
-                disk.read(&mut buf[buf_offset..buf_offset+read_size])?
+            disk.read(&mut buf[..read_size])?
         };
         if read_bytes == 0 {
-                break;
+            return Ok(0);
         }
         self.offset += read_bytes as u32;
         self.current_cluster = Some(current_cluster);
-            buf_offset += read_bytes;
+        Ok(read_bytes)
-        }
-        Ok(buf_offset)
     }
 }
 
 impl<'a, 'b> Write for File<'a, 'b> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        let mut buf_offset: usize = 0;
         let cluster_size = self.fs.get_cluster_size();
-        loop {
         let offset_in_cluster = self.offset % cluster_size;
         let bytes_left_in_cluster = (cluster_size - offset_in_cluster) as usize;
-            let bytes_left_in_buf = buf.len() - buf_offset;
+        let write_size = cmp::min(buf.len(), bytes_left_in_cluster);
-            let write_size = cmp::min(bytes_left_in_buf, bytes_left_in_cluster);
         //println!("write {:?}", write_size);
+        // Exit early if we are going to write no data
         if write_size == 0 {
-                break;
+            return Ok(0);
         }
-            
+        // Get cluster for write possibly allocating new one
-            let current_cluster_opt = if self.offset % cluster_size == 0 {
+        let current_cluster = if self.offset % cluster_size == 0 {
             // next cluster
             let next_cluster = match self.current_cluster {
                 None => self.first_cluster,
@@ -204,37 +209,36 @@ impl<'a, 'b> Write for File<'a, 'b> {
                 },
             };
             match next_cluster {
-                    Some(_) => next_cluster,
+                Some(n) => n,
                 None => {
+                    // end of chain reached - allocate new cluster
                     let new_cluster = self.fs.alloc_cluster(self.current_cluster)?;
                     if self.first_cluster.is_none() {
                         self.set_first_cluster(new_cluster);
                     }
-                        Some(new_cluster)
+                    new_cluster
                 },
             }
         } else {
-                self.current_cluster
+            // self.current_cluster should be a valid cluster
-            };
+            match self.current_cluster {
-            let current_cluster = match current_cluster_opt {
                 Some(n) => n,
-                None => panic!("Offset inside cluster but no cluster allocated"), // FIXME
+                None => panic!("Offset inside cluster but no cluster allocated"),
+            }
         };
         let offset_in_fs = self.fs.offset_from_cluster(current_cluster) + (offset_in_cluster as u64);
         let written_bytes = {
             let mut disk = self.fs.disk.borrow_mut();
             disk.seek(SeekFrom::Start(offset_in_fs))?;
-                disk.write(&buf[buf_offset..buf_offset+write_size])?
+            disk.write(&buf[..write_size])?
         };
         if written_bytes == 0 {
-                break;
+            return Ok(0);
         }
         self.offset += written_bytes as u32;
         self.current_cluster = Some(current_cluster);
-            buf_offset += written_bytes;
-        }
         self.update_size();
-        Ok(buf_offset)
+        Ok(written_bytes)
     }
     
     fn flush(&mut self) -> io::Result<()> {
@@ -246,33 +250,49 @@ impl<'a, 'b> Write for File<'a, 'b> {
 
 impl<'a, 'b> Seek for File<'a, 'b> {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
-        let new_offset = match pos {
+        let mut new_pos = match pos {
             SeekFrom::Current(x) => self.offset as i64 + x,
             SeekFrom::Start(x) => x as i64,
             SeekFrom::End(x) => self.entry.iter().next().expect("cannot seek from end if size is unknown").data.size() as i64 + x,
         };
-        if new_offset < 0 {
+        if new_pos < 0 {
             return Err(io::Error::new(ErrorKind::InvalidInput, "invalid seek"));
         }
+        new_pos = match self.entry {
+            Some(ref e) => cmp::min(new_pos, e.data.size() as i64),
+            _ => new_pos,
+        };
         let cluster_size = self.fs.get_cluster_size();
-        let cluster_count = ((new_offset + cluster_size as i64 - 1) / cluster_size as i64 - 1) as isize;
+        let new_cluster = if new_pos == 0 {
-        let new_cluster = if cluster_count == -1 {
             None
-        } else if cluster_count == 0 {
-            self.first_cluster
         } else {
+            // get number of clusters to seek (favoring previous cluster in corner case)
+            let cluster_count = ((new_pos - 1) / cluster_size as i64) as isize;
             match self.first_cluster {
                 Some(n) => {
-                    match self.fs.cluster_iter(n).skip(cluster_count as usize - 1).next() {
+                    let mut cluster = n;
+                    let mut iter = self.fs.cluster_iter(n);
+                    for i in 0..cluster_count {
+                        cluster = match iter.next() {
                             Some(Err(err)) => return Err(err),
-                        Some(Ok(n)) => Some(n),
+                            Some(Ok(n)) => n,
-                        None => None,
+                            None => {
-                    }
+                                // chain ends before new position - seek to end of last cluster
+                                new_pos = (i + 1) as i64 * cluster_size as i64;
+                                break;
+                            },
+                        };
+                    }
+                    Some(cluster)
+                },
+                None => {
+                    // empty file - always seek to 0
+                    new_pos = 0;
+                    None
                 },
-                None => None,
             }
         };
-        self.offset = new_offset as u32;
+        self.offset = new_pos as u32;
         self.current_cluster = new_cluster;
         Ok(self.offset as u64)
     }

tests/read.rs

@@ -58,7 +58,7 @@ fn test_read_seek_short_file(fs: FileSystem) {
     short_file.read_exact(&mut buf2).unwrap();
     assert_eq!(str::from_utf8(&buf2).unwrap(), &TEST_TEXT[5..10]);
     
-    assert_eq!(short_file.seek(SeekFrom::Start(1000)).unwrap(), 1000);
+    assert_eq!(short_file.seek(SeekFrom::Start(1000)).unwrap(), TEST_TEXT.len() as u64);
     let mut buf2 = [0; 5];
     assert_eq!(short_file.read(&mut buf2).unwrap(), 0);
 }

tests/write.rs

@@ -33,7 +33,7 @@ fn test_write_short_file(fs: FileSystem) {
     let mut root_dir = fs.root_dir();
     let mut file = root_dir.open_file("short.txt").expect("open file");
     file.truncate().unwrap();
-    assert_eq!(TEST_STR.len(), file.write(&TEST_STR.as_bytes()).unwrap());
+    file.write_all(&TEST_STR.as_bytes()).unwrap();
     file.seek(io::SeekFrom::Start(0)).unwrap();
     let mut buf = Vec::new();
     file.read_to_end(&mut buf).unwrap();
@@ -60,7 +60,7 @@ fn test_write_long_file(fs: FileSystem) {
     let mut file = root_dir.open_file("long.txt").expect("open file");
     file.truncate().unwrap();
     let test_str = TEST_STR.repeat(100);
-    assert_eq!(test_str.len(), file.write(&test_str.as_bytes()).unwrap());
+    file.write_all(&test_str.as_bytes()).unwrap();
     file.seek(io::SeekFrom::Start(0)).unwrap();
     let mut buf = Vec::new();
     file.read_to_end(&mut buf).unwrap();