bcf/io/reader/record: Return EOF when site length signals EOF

Fixes #255.

noodles-bcf/CHANGELOG.md

@@ -6,6 +6,12 @@
 
   * bcf/record/samples: Implement series selector (`Samples::select`).
 
+### Fixed
+
+  * bcf/io/reader/record: Return EOF when site length signals EOF ([#255]).
+
+[#255]: https://github.com/zaeleus/noodles/issues/255
+
 ## 0.50.0 - 2024-04-11
 
 ### Changed

noodles-bcf/src/async/io/reader/record.rs

@@ -8,7 +8,11 @@ pub(super) async fn read_record<R>(reader: &mut R, record: &mut Record) -> io::R
 where
     R: AsyncRead + Unpin,
 {
-    let l_shared = read_site_length(reader).await?;
+    let l_shared = match read_site_length(reader).await? {
+        0 => return Ok(0),
+        n => n,
+    };
+
     let l_indiv = read_samples_length(reader).await?;
 
     let site_buf = record.fields_mut().site_buf_mut();
@@ -240,6 +244,15 @@ mod tests {
         Ok(())
     }
 
+    #[tokio::test]
+    async fn test_read_record_at_eof() -> io::Result<()> {
+        let data = [];
+        let mut reader = &data[..];
+        let mut record = Record::default();
+        assert_eq!(read_record(&mut reader, &mut record).await?, 0);
+        Ok(())
+    }
+
     #[tokio::test]
     async fn test_read_site_length() -> io::Result<()> {
         let data = [0x08, 0x00, 0x00, 0x00];

noodles-bcf/src/io/reader/record.rs

@@ -11,7 +11,11 @@ pub fn read_record<R>(reader: &mut R, record: &mut Record) -> io::Result<usize>
 where
     R: Read,
 {
-    let l_shared = read_site_length(reader)?;
+    let l_shared = match read_site_length(reader)? {
+        0 => return Ok(0),
+        n => n,
+    };
+
     let l_indiv = read_samples_length(reader)?;
 
     let site_buf = record.fields_mut().site_buf_mut();
@@ -312,6 +316,15 @@ pub(crate) mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_read_record_at_eof() -> io::Result<()> {
+        let data = [];
+        let mut reader = &data[..];
+        let mut record = Record::default();
+        assert_eq!(read_record(&mut reader, &mut record)?, 0);
+        Ok(())
+    }
+
     #[test]
     fn test_read_site_length() -> io::Result<()> {
         let data = [0x08, 0x00, 0x00, 0x00];