Improve EOF processing for potential re-reading

Author: Evgeny Khramtsov

src/reading.rs

@@ -761,7 +761,21 @@ impl<T :io::Read + io::Seek> PacketReader<T> {
 			if let Some(pck) = self.base_pck_rdr.read_packet() {
 				return Ok(Some(pck));
 			}
-			let page = tri!(self.read_ogg_page());
+			// Save the current position to rewind if EOF is reached.
+			let pos = tri!(self.rdr.stream_position());
+			let page = tri!(match self.read_ogg_page() {
+				Err(OggReadError::ReadError(e)) if e.kind() == ErrorKind::UnexpectedEof => {
+					// Rewind to the saved position to allow for potential re-reading.
+					self.rdr.seek(SeekFrom::Start(pos))?;
+					Err(OggReadError::ReadError(e))
+				}
+				Ok(None) => {
+					// Rewind to the saved position to allow for potential re-reading.
+					self.rdr.seek(SeekFrom::Start(pos))?;
+					Ok(None)
+				}
+				ret => ret,
+			});
 			match page {
 				Some(page) => tri!(self.base_pck_rdr.push_page(page)),
 				None => return Ok(None),
@@ -818,7 +832,8 @@ impl<T :io::Read + io::Seek> PacketReader<T> {
 		let header_buf :[u8; 27] = match tri!(self.read_until_pg_header()) {
 			Some(s) => s,
 			None if self.read_some_pg => return Ok(None),
-			None => return Err(OggReadError::NoCapturePatternFound)
+			None => tri!(Err(Error::new(ErrorKind::UnexpectedEof,
+                                "Expected ogg packet but found end of physical stream"))),
 		};
 		let (mut pg_prs, page_segments) = tri!(PageParser::new(header_buf));
 

src/test.rs

@@ -542,6 +542,8 @@ fn test_issue_14() {
 // data is treated as invalid.
 #[test]
 fn test_issue_7() {
+	use std::io::ErrorKind::UnexpectedEof;
+
 	let mut c = Cursor::new(Vec::new());
 	let test_arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
 	let test_arr_2 = [2, 4, 8, 16, 32, 64, 128, 127, 126, 125, 124];
@@ -564,17 +566,19 @@ fn test_issue_7() {
 		assert!(r.read_packet().unwrap().is_none());
 	}
 
-	// Non-Ogg data should return an error.
+	// Truncated data should return the UnexpectedEof error.
 	let c = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
 	{
 		let mut r = PacketReader::new(c);
-		assert!(matches!(r.read_packet(), Err(OggReadError::NoCapturePatternFound)));
+		assert!(matches!(r.read_packet(),
+			Err(OggReadError::ReadError(e)) if e.kind() == UnexpectedEof));
 	}
 
-	// Empty data is considered non-Ogg data.
+	// Empty data should return the UnexpectedEof error.
 	let c = Cursor::new(&[]);
 	{
 		let mut r = PacketReader::new(c);
-		assert!(matches!(r.read_packet(), Err(OggReadError::NoCapturePatternFound)));
+		assert!(matches!(r.read_packet(),
+			Err(OggReadError::ReadError(e)) if e.kind() == UnexpectedEof));
 	}
 }